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1.  Multiple mechanisms support oligoclonal T cell expansion in rheumatoid synovitis. 
Molecular Medicine  1997;3(7):452-465.
BACKGROUND: The synovial T cell infiltrate in rheumatoid arthritis (RA) is diverse but contains clonally expanded CD4+ populations. Recent reports have emphasized that RA patients have a tendency to develop CD4+ T cell oligoclonality which also manifests in the peripheral blood. Clonal dominance in the tissue may thus result from antigen specific stimulation in the synovial membrane or may reflect the infiltration of expanded clonotypes present throughout the lymphoid system. We have explored to what extent clonal populations amongst tissue CD4+ T cells display joint specificity as defined by their restriction to the joint, their persistence over time, and their expression of markers indicative for local activation. MATERIALS AND METHODS: Matched samples of peripheral blood and synovial fluid or synovial tissue were collected from 14 patients with active RA and CD4+ IL-2R+ and CD4+ IL-2R- T cells from both compartments were purified. Clonal populations of CD4+ T cells were detected by RT-PCR amplification of T cell receptor (TCR) transcripts with BV and BJ specific primers followed by size fractionation and direct sequencing of dominant size classes of TCR transcripts. RESULTS: Clonal CD4+ T cells were detected in the synovial fluid and synovial tissue of all patients. All patients carried synovial clonotypes that were undetectable in the blood but were present in independent joints or at several non-adjacent areas of the same joint. These joint restricted CD4+ clonotypes were generally small in size, were preferentially found in the IL-2R+ subpopulation, and persisted over time. A second type of clonogenic T cells in the synovial infiltrate had an unrestricted tissue distribution and was present at similar frequencies amongst activated and nonactivated T cells in the blood and affected joints. Ubiquitous clonotypes isolated from two different patients expressed sequence homologies of the TCR beta chain. CONCLUSIONS: Two types of expanded CD4+ clonotypes contribute to the T cell infiltrate in rheumatoid synovitis. Differences in the distribution pattern and in molecular features suggest that distinct mechanisms are supporting the clonal outgrowth of these two groups of clonotypes. Clonally expanded T cells restricted to the joint but present in several independent joints appear to respond to locally residing antigens. Clonogenic cells with an unrestricted distribution pattern and widespread activation in the blood and tissue may react to a different class of antigens which appear to be shared by multiple patients. T cell recognition in RA may be involved at several different levels and may be related to more than one pathomechanism.
PMCID: PMC2230222  PMID: 9260157
2.  Specificity of T cells in synovial fluid: high frequencies of CD8+ T cells that are specific for certain viral epitopes 
Arthritis Research  2000;2(2):154-164.
CD8+ T cells dominate the lymphocyte population in synovial fluid in chronic inflammatory arthritis. It is known that these CD8+ T cells are often clonally or oligoclonally expanded, but their specificity and their relevance to the pathogenesis of joint disease has remained unclear. We found that as many as 15.5% of synovial CD8+ T cells may be specific for a single epitope from an Epstein-Barr virus lytic cycle protein. The virus-specific T cells within the joint showed increased expression of markers of activation and differentiation compared with those in the periphery, and retained their functional capacity to secrete proinflammatory cytokines on stimulation. These activated, virus-specific CD8+ T cells could therefore interact with synoviocytes, either by cell-cell contact or by a cytokine network, and play a 'bystander' role in the maintenance of inflammation in patients with arthritis.
Epstein-Barr virus (EBV) is transmitted orally, replicates in the oropharynx and establishes life-long latency in human B lymphocytes. T-cell responses to latent and lytic/replicative cycle proteins are readily detectable in peripheral blood from healthy EBV-seropositive individuals. EBV has also been detected within synovial tissue, and T-cell responses to EBV lytic proteins have been reported in synovial fluid from a patient with rheumatoid arthritis (RA). This raises the question regarding whether T cells specific for certain viruses might be present at high frequencies within synovial fluid and whether such T cells might be activated or able to secrete cytokines. If so, they might play a 'bystander' role in the pathogenesis of inflammatory joint disease.
To quantify and characterize T cells that are specific for epitopes from EBV, cytomegalovirus (CMV) and influenza in peripheral blood and synovial fluid from patients with arthritis.
Peripheral blood mononuclear cells (PBMCs) and synovial fluid mononuclear cells (SFMCs) were obtained from patients with inflammatory arthritis (including those with RA, osteoarthritis, psoriatic arthritis and reactive arthritis). Samples from human leucocyte antigen (HLA)-A2-positive donors were stained with fluorescent-labelled tetramers of HLA-A2 complexed with the GLCTLVAML peptide epitope from the EBV lytic cycle protein BMLF1, the GILGFVFTL peptide epitope from the influenza A matrix protein, or the NLVPMVATV epitope from the CMV pp65 protein. Samples from HLA-B8-positive donors were stained with fluorescent-labelled tetramers of HLA-B8 complexed with the RAKFKQLL peptide epitope from the EBV lytic protein BZLF1 or the FLRGRAYGL peptide epitope from the EBV latent protein EBNA3A. All samples were costained with an antibody specific for CD8. CD4+ T cells were not analyzed. Selected samples were costained with antibodies specific for cell-surface glycoproteins, in order to determine the phenotype of the T cells within the joint and the periphery. Functional assays to detect release of IFN-γ or tumour necrosis factor (TNF)-α were also performed on some samples.
The first group of 15 patients included 10 patients with RA, one patient with reactive arthritis, one patient with psoriatic arthritis and three patients with osteoarthritis. Of these, 11 were HLA-A2 positive and five were HLA-B8 positive. We used HLA-peptide tetrameric complexes to analyze the frequency of EBV-specific T cells in PBMCs and SFMCs (Figs 1 and 2). Clear enrichment of CD8+ T cells specific for epitopes from the EBV lytic cycle proteins was seen within synovial fluid from almost all donors studied, including patients with psoriatic arthritis and osteoarthritis and those with RA. In donor RhA6, 9.5% of CD8+ SFMCs were specific for the HLA-A2 restricted GLCTLVAML epitope, compared with 0.5% of CD8+ PBMCs. Likewise in a donor with osteoarthritis (NR4), 15.5% of CD8+ SFMCs were specific for the HLA-B8-restricted RAKFKQLL epitope, compared with 0.4% of CD8+ PBMCs. In contrast, we did not find enrichment of T cells specific for the HLA-B8-restricted FLRGRAYGL epitope (from the latent protein EBNA3A) within SFMCs compared with PBMCs in any donors. In selected individuals we performed ELISpot assays to detect IFN-γ secreted by SFMCs and PBMCs after a short incubation in vitro with peptide epitopes from EBV lytic proteins. These assays confirmed enrichment of T cells specific for epitopes from EBV lytic proteins within synovial fluid and showed that subpopulations of these cells were able to secrete proinflammatory cytokines after short-term stimulation.
We used a HLA-A2/GILGFVFTL tetramer to stain PBMCs and SFMCs from six HLA-A2-positive patients. The proportion of T cells specific for this influenza epitope was low (<0.2%) in all donors studied, and we did not find any enrichment within SFMCs.
We had access to SFMCs only from a second group of four HLA-A2-positive patients with RA. A tetramer of HLA-A2 complexed to the NLVPMVATV epitope from the CMV pp65 protein reacted with subpopulations of CD8+ SFMCs in all four donors, with frequencies of 0.2, 0.5, 2.3 and 13.9%. SFMCs from all four donors secreted TNF after short-term incubation with COS cells transfected with HLA-A2 and pp65 complementary DNA. We analyzed the phenotype of virus-specific cells within PBMCs and SFMCs in three donors. The SFMC virus-specific T cells were more highly activated than those in PBMCs, as evidenced by expression of high levels of CD69 and HLA-DR. A greater proportion of SFMCs were CD38+, CD62L low, CD45RO bright, CD45RA dim, CD57+ and CD28- when compared with PBMCs.
This work shows that T cells specific for certain epitopes from viral proteins are present at very high frequencies (up to 15.5% of CD8+ T cells) within SFMCs taken from patients with inflammatory joint disease. This enrichment does not reflect a generalized enrichment for the 'memory pool' of T cells; we did not find enrichment of T cells specific for the GILGFVFTL epitope from influenza A or for the FLRGRAYGL epitope from the EBV latent protein EBNA3A, whereas we found clear enrichment of T cells specific for the GLCTLVAML epitope from the EBV lytic protein BMLF1 and for the RAKFKQLL epitope from the EBV lytic protein BZLF1.
The enrichment might reflect preferential recruitment of subpopulations of virus-specific T cells, perhaps based on expression of selectins, chemokine receptors or integrins. Alternatively, T cells specific for certain viral epitopes may be stimulated to proliferate within the joint, by viral antigens themselves or by cross-reactive self-antigens. Finally, it is theoretically possible that subpopulations of T cells within the joint are preferentially protected from apoptotic cell death. Whatever the explanation, the virus-specific T cells are present at high frequency, are activated and are able to secrete proinflammatory cytokines. They could potentially interact with synoviocytes and contribute to the maintenance of inflammation within joints in many different forms of inflammatory arthritis.
PMCID: PMC17809  PMID: 11062606
CD8+ T cell; Epstein-Barr virus lytic cycle; human leucocyte antigen peptide tetrameric complex; rheumatoid arthritis; viral immunity
3.  Ectopic Lymphoid Structures Support Ongoing Production of Class-Switched Autoantibodies in Rheumatoid Synovium 
PLoS Medicine  2009;6(1):e1.
Follicular structures resembling germinal centres (GCs) that are characterized by follicular dendritic cell (FDC) networks have long been recognized in chronically inflamed tissues in autoimmune diseases, including the synovium of rheumatoid arthritis (RA). However, it is debated whether these ectopic structures promote autoimmunity and chronic inflammation driving the production of pathogenic autoantibodies. Anti-citrullinated protein/peptide antibodies (ACPA) are highly specific markers of RA, predict a poor prognosis, and have been suggested to be pathogenic. Therefore, the main study objectives were to determine whether ectopic lymphoid structures in RA synovium: (i) express activation-induced cytidine deaminase (AID), the enzyme required for somatic hypermutation and class-switch recombination (CSR) of Ig genes; (ii) support ongoing CSR and ACPA production; and (iii) remain functional in a RA/severe combined immunodeficiency (SCID) chimera model devoid of new immune cell influx into the synovium.
Methods and Findings
Using immunohistochemistry (IHC) and quantitative Taqman real-time PCR (QT-PCR) in synovial tissue from 55 patients with RA, we demonstrated that FDC+ structures invariably expressed AID with a distribution resembling secondary lymphoid organs. Further, AID+/CD21+ follicular structures were surrounded by ACPA+/CD138+ plasma cells, as demonstrated by immune reactivity to citrullinated fibrinogen. Moreover, we identified a novel subset of synovial AID+/CD20+ B cells outside GCs resembling interfollicular large B cells. In order to gain direct functional evidence that AID+ structures support CSR and in situ manufacturing of class-switched ACPA, 34 SCID mice were transplanted with RA synovium and humanely killed at 4 wk for harvesting of transplants and sera. Persistent expression of AID and Iγ-Cμ circular transcripts (identifying ongoing IgM-IgG class-switching) was observed in synovial grafts expressing FDCs/CD21L. Furthermore, synovial mRNA levels of AID were closely associated with circulating human IgG ACPA in mouse sera. Finally, the survival and proliferation of functional B cell niches was associated with persistent overexpression of genes regulating ectopic lymphoneogenesis.
Our demonstration that FDC+ follicular units invariably express AID and are surrounded by ACPA-producing plasma cells provides strong evidence that ectopic lymphoid structures in the RA synovium are functional and support autoantibody production. This concept is further confirmed by evidence of sustained AID expression, B cell proliferation, ongoing CSR, and production of human IgG ACPA from GC+ synovial tissue transplanted into SCID mice, independently of new B cell influx from the systemic circulation. These data identify AID as a potential therapeutic target in RA and suggest that survival of functional synovial B cell niches may profoundly influence chronic inflammation, autoimmunity, and response to B cell–depleting therapies.
Costantino Pitzalis and colleagues show that lymphoid structures in synovial tissue of patients with rheumatoid arthritis support production of anti-citrullinated peptide antibodies, which continues following transplantation into SCID mice.
Editors' Summary
More than 1 million people in the United States have rheumatoid arthritis, an “autoimmune” condition that affects the joints. Normally, the immune system provides protection against infection by responding to foreign antigens (molecules that are unique to invading organisms) while ignoring self-antigens present in the body's own tissues. In autoimmune diseases, this ability to discriminate between self and non-self fails for unknown reasons and the immune system begins to attack human tissues. In rheumatoid arthritis, the lining of the joints (the synovium) is attacked, it becomes inflamed and thickened, and chemicals are released that damage all the tissues in the joint. Eventually, the joint may become so scarred that movement is no longer possible. Rheumatoid arthritis usually starts in the small joints in the hands and feet, but larger joints and other tissues (including the heart and blood vessels) can be affected. Its symptoms, which tend to fluctuate, include early morning joint pain, swelling, and stiffness, and feeling generally unwell. Although the disease is not always easy to diagnose, the immune systems of many people with rheumatoid arthritis make “anti-citrullinated protein/peptide antibodies” (ACPA). These “autoantibodies” (which some experts believe can contribute to the joint damage in rheumatoid arthritis) recognize self-proteins that contain the unusual amino acid citrulline, and their detection on blood tests can help make the diagnosis. Although there is no cure for rheumatoid arthritis, the recently developed biologic drugs, often used together with the more traditional disease-modifying therapies, are able to halt its progression by specifically blocking the chemicals that cause joint damage. Painkillers and nonsteroidal anti-inflammatory drugs can reduce its symptoms, and badly damaged joints can sometimes be surgically replaced.
Why Was This Study Done?
Before scientists can develop a cure for rheumatoid arthritis, they need to know how and why autoantibodies are made that attack the joints in this common and disabling disease. B cells, the immune system cells that make antibodies, mature in structures known as “germinal centers” in the spleen and lymph nodes. In the germinal centers, immature B cells are exposed to antigens and undergo two genetic processes called “somatic hypermutation” and “class-switch recombination” that ensure that each B cell makes an antibody that sticks as tightly as possible to just one antigen. The B cells then multiply and enter the bloodstream where they help to deal with infections. Interestingly, the inflamed synovium of many patients with rheumatoid arthritis contains structures that resemble germinal centers. Could these ectopic (misplaced) lymphoid structures, which are characterized by networks of immune system cells called follicular dendritic cells (FDCs), promote autoimmunity and long-term inflammation by driving the production of autoantibodies within the joint itself? In this study, the researchers investigate this possibility.
What Did the Researchers Do and Find?
The researchers collected synovial tissue from 55 patients with rheumatoid arthritis and used two approaches, called immunohistochemistry and real-time PCR, to investigate whether FDC-containing structures in synovium expressed an enzyme called activation-induced cytidine deaminase (AID), which is needed for both somatic hypermutation and class-switch recombination. All the FDC-containing structures that the researchers found in their samples expressed AID. Furthermore, these AID-containing structures were surrounded by mature B cells making ACPAs. To test whether these B cells were derived from AID-expressing cells resident in the synovium rather than ACPA-expressing immune system cells coming into the synovium from elsewhere in the body, the researchers transplanted synovium from patients with rheumatoid arthritis under the skin of a special sort of mouse that largely lacks its own immune system. Four weeks later, the researchers found that the transplanted human lymphoid tissue was still making AID, that the level of AID expression correlated with the amount of human ACPA in the blood of the mice, and that the B cells in the transplant were proliferating.
What Do These Findings Mean?
These findings show that the ectopic lymphoid structures present in the synovium of some patients with rheumatoid arthritis are functional and are able to make ACPA. Because ACPA may be responsible for joint damage, the survival of these structures could, therefore, be involved in the development and progression of rheumatoid arthritis. More experiments are needed to confirm this idea, but these findings may explain why drugs that effectively clear B cells from the bloodstream do not always produce a marked clinical improvement in rheumatoid arthritis. Finally, they suggest that AID might provide a new target for the development of drugs to treat rheumatoid arthritis.
Additional Information.
Please access these Web sites via the online version of this summary at
This study is further discussed in a PLoS Medicine Perspective by Rene Toes and Tom Huizinga
The MedlinePlus Encyclopedia has a page on rheumatoid arthritis (in English and Spanish). MedlinePlus provides links to other information on rheumatoid arthritis (in English and Spanish)
The UK National Health Service Choices information service has detailed information on rheumatoid arthritis
The US National Institute of Arthritis and Musculoskeletal and Skin Diseases provides Fast Facts, an easy to read publication for the public, and a more detailed Handbook on rheumatoid arthritis
The US Centers for Disease Control and Prevention has an overview on rheumatoid arthritis that includes statistics about this disease and its impact on daily life
PMCID: PMC2621263  PMID: 19143467
4.  Cytokine, activation marker, and chemokine receptor expression by individual CD4+ memory T cells in rheumatoid arthritis synovium 
Arthritis Research  2000;2(5):415-423.
IL-10, IL-13, IFN-γ, tumor necrosis factor (TNF)-α, LT-α, CD154, and TNF-related activation-induced cytokine (TRANCE) were expressed by 2-20% of rheumatoid arthritis (RA) synovial tissue CD4+ memory T cells, whereas CD4+ cells that produced IL-2, IL-4, or IL-6 were not detected. Expression of none of these molecules by individual CD4+ cells correlated with the exception of TRANCE and IL-10, and TRANCE and TNF-α . A correlation between expression of IL-10 and CCR7, LT-α and CCR6, IFN-γ and CCR5, and TRANCE and CXCR4 was also detected.
In RA large numbers of CD4+ memory T cells infiltrate the inflamed synovium [1,2,3]. The accumulated CD4+ memory T cells in the RA synovium appear to be activated, because they express cytokines and activation markers [4,5,6,7,8]. Expressed cytokines and activation markers should play important roles in the pathogenesis of RA. However, the frequency of cytokine expression by RA synovial CD4+ T cells has not been analyzed accurately. Recently, the roles of chemokine and chemokine receptor interactions in T-cell migration have been intensively examined. Interactions of chemokine and chemokine receptors might therefore be important in the accumulation of the CD4+ T cells in the RA synovium. Accordingly, correlation of cytokine and chemokine receptor expression might be important in delineating the function and potential means of accumulation of individual CD4+ memory T cells in the RA synovium.
In the present study we analyzed cytokine (IL-2, IL-4, IL-6, IL-10, IL-13, IFN-γ , TNF-α , and LT-α ), activation marker (CD154 [CD40 ligand] and TRANCE - also called receptor activator of nuclear factor κ B ligand [RANKL] or osteoclast differentiation factor [ODF]), and chemokine receptor expression by individual CD4+ memory T cells isolated from rheumatoid synovium and blood. To achieve this we employed a single-cell reverse transcription (RT) polymerase chain reaction (PCR) technique. This technique made it possible to correlate mRNAs expressed by individual CD4+ memory T cells in the synovium and blood.
Materials and method:
Synovial tissues from three RA patients and peripheral blood mononuclear cells from two RA patients and a normal donor were analyzed.
Cytokine (IL-2, IL-4, IL-6, IL-10, IL-13, IFN-γ, TNF-α, and LT-α ) and activation marker (CD154 and TRANCE) expression by individual CD4+CD45RO+ T cells from RA synovium or blood were analyzed using a single-cell RT-PCR. In brief, single CD4+CD45RO+T cells was sorted into each well of a 96-well PCR plate using a flow cytometer. cDNA from individual cells was prepared, and then the cDNA was nonspecifically amplified. The product was then amplified by PCR using gene-specific primers to analyze cytokine and activation marker expression.
Cytokine and activation marker expression by individual CD4+CD45RO+T cells from RA synovial tissues was analyzed using a single-cell RT-PCR method. Expression of mRNAs was analyzed in 152 individual synovial tissue CD4+CD45RO+ T cells sorted from three RA patients in which T-cell receptor (TCR) Cβ mRNA was detected. Frequencies of CD4+ memory T cells expressing cytokine and activation marker mRNA in RA synovium are shown in Table 1. IL-2, IL-4, and IL-6 were not expressed by the synovial tissue CD4+CD45RO+ T cells, whereas 2-20% of cells expressed the other cytokine mRNAs.
Few correlations between cytokine and activation marker mRNAs were observed. Notably, no cells contained both IFN-γ and LT-α mRNAs, cytokines that are thought to define the T-helper (Th)1 phenotype [9]. However, the frequency of TRANCE-positive cells in IL-10-positive cells was significantly higher than that in IL-10-negative cells (Table 2). Moreover, the frequency of TRANCE-positive cells in TNF-α-positive cells was also significantly higher than that in TNF-α-negative cells.
Varying percentages of CD4+ memory T cells expressed CC and CXC chemokine receptors. The frequency of CCR5-positive cells in IFN-γ-positive cells was significantly higher than that in IFN-γ-negative cells, whereas the frequency of CCR6-positive cells in LT-α-positive cells was significantly higher than that in LT-α-negative cells, and the frequency of CCR7-positive cells in IL-10-positive cells was significantly higher than that in IL-10-negative cells. Furthermore, the frequency of CXCR4-positive cells in TRANCE-positive cells was significantly higher than that in TRANCE-negative cells.
Expression of cytokine and activation marker mRNAs was also analyzed in 48 individual peripheral blood CD4+CD45RO+ T cells from two RA patients. IL-2, IL-4, IL-6, and LT-α were not expressed by the peripheral CD4+CD45RO+ T cells, whereas 4-17% of cells expressed the other markers. The most striking difference between synovial tissue and peripheral blood CD4+ memory T cells was the presence of LT-α expression in the former, but not in the latter. IFN-γ and TNF-α were not expressed by normal peripheral blood CD4+ memory T cells, although they were expressed by RA peripheral blood CD4+ memory T cells.
The present study employed a single-cell PCR technology to analyze cytokine expression by unstimulated RA synovial tissue CD4+ memory T cells immediately after isolation, without in vitro manipulation. The results confirm the Th1 nature of rheumatoid inflammation. It is noteworthy that no individual synovial CD4+ memory T cells expressed both IFN-γ and LT-α mRNAs, even though these are the prototypic Th1 cytokines [9]. These results imply that, in the synovium, regulation of IFN-γ and LT-α must vary in individual cells, even though both Th1 cytokines can be produced.
The present data showed that CCR5 expression correlated with IFN-γ but not with LT-α expression by synovial CD4+ memory T cells. It has been reported that CCR5 expression is upregulated in RA synovial fluid and synovial tissue T cells [10,11,12] and that CCR5 Δ 32 deletion may have an influence on clinical manifestations of RA [13], suggesting that CCR5 might play an important role in RA. Recently, it has been claimed that CCR5 was preferentially expressed by Th1 cell lines [14,15]. However, in the present study CCR5 was not expressed by all IFN-γ-expressing cells. Moreover, CCR5 expression did not correlate with expression of LT-α by RA synovial CD4+ memory T cells. Therefore, it is unclear whether CCR5 is a marker of Th1 cells in RA synovium.
IL-10 expression correlated with CCR7 expression by RA synovial CD4+ memory T cells. Recently, it was reported [16] that in the blood CCR7+CD4+ memory T cells express lymph-node homing receptors and lack immediate effector function, but efficiently stimulate dendritic cells. These cells may play a unique role in the synovium as opposed to in the blood. By producing IL-10, they might have an immunoregulatory function. In addition, IL-10 expression also correlated with expression of TRANCE. Although it is possible that IL-10 produced by these cells inhibited T-cell activation in the synovium, TRANCE expressed by these same cells might function to activate dendritic cells and indirectly stimulate T cells, mediating inflammation in the synovium. These results imply that individual T cells in the synovium might have different, and sometimes opposite functional activities.
LT-α expression correlated with CCR6 expression by synovial CD4+ memory T cells. It has been reported that CCR6 is expressed by resting peripheral memory T cells [17], whereas LT-α expression is associated with the presence of lymphocytic aggregates in synovial tissue [7]. The correlation between the expression of these two markers therefore suggests the possibility that CCR6 may play a role in the development of aggregates of CD4+ T cells that are characteristically found in rheumatoid synovium.
TRANCE is known to be expressed by activated T cells, and can stimulate dendritic cells and osteoclasts [18]. Of note, TRANCE-mediated activation of osteoclasts has recently been shown [19] to play an important role in the damage to bone that is found in experimental models of inflammatory arthritis. It is therefore of interest that TRANCE was expressed by 3-16% of the RA synovial CD4+ memory T cells. Of note, 67% of TNF-α-positive cells expressed TRANCE. In concert, TNF-α and TRANCE expressed by this subset of CD4+ memory T cells might make them particularly important in mediating the bony erosions that are characteristic of RA.
Interestingly, there was a correlation between expression of IFN-γ and IL-10 in RA peripheral blood CD4+ memory T cells. In RA peripheral blood, CD154 expression correlated with that of CXCR3 by CD4+ memory T cells. It has been claimed [15] that CXCR3 is preferentially expressed by in vitro generated Th1 cells. However, in the present study CXCR3 did not correlate with IFN-γ expression. Although IFN-γ and TNF-α mRNAs were expressed in vivo by peripheral blood CD4+ T cells from RA patients, LT-α mRNA was not detected, whereas IFN-γ , TNF-α , and LT-α were not detected in samples from healthy donors. These findings indicate that RA peripheral blood CD4+ memory T cells are stimulated in vivo, although they do not express LT-α mRNA. The present studies indicate that the frequencies of CD4+ memory T cells that expressed IFN-γ in the blood and in the synovium are comparable. These results imply that activated CD4+ memory T cells migrate between blood and synovium, although the direction of the trafficking is unknown. The presence of LT-α mRNA in synovium, but not in blood, indicates that CD4+ memory cells are further activated in the synovium, and that these activated CD4+ memory T cells are retained in the synovium until LT-α mRNA decreases.
In conclusion, CD4+ memory T cells are biased toward Th1 cells in RA synovium and peripheral blood. In the synovium, IFN-γ and LT-α were produced by individual cells, whereas in the rheumatoid blood no LT-α-producing cells were detected. Furthermore, there were modest correlations between individual cells that expressed particular cytokines, such as IL-10, and certain chemokine receptor mRNAs.
PMCID: PMC17818  PMID: 11056676
chemokine receptor; cytokine; rheumatoid arthritis; T lymphocyte
5.  CDR3 sequence motifs shared by oligoclonal rheumatoid arthritis synovial T cells. Evidence for an antigen-driven response. 
Journal of Clinical Investigation  1994;94(6):2525-2531.
T lymphocytes reactive with as yet undefined joint-localized foreign or autoantigens may be important in the pathogenesis of RA. Molecular studies demonstrating skewed T cell antigen receptor (TCR) variable gene usage and selective expansion of particular T cell clones within the synovial compartment support this view. Based on our recent study documenting selective expansion of V beta 17+ T cells in RA, we have pursued the identification of T cells relevant to the disease process, in an informative patient, by combining molecular analysis of freshly explanted RA synovial tissue V beta 17 TCR transcripts with in vitro expansion of V beta 17+ synovial tissue T cell clones. Peripheral blood V beta 17 cDNA transcripts proved heterogeneous. In contrast, two closely related sequences, not found in the peripheral blood, dominated synovial tissue V beta 17 transcripts, suggesting selective localization and oligoclonal expansion at the site of pathology. CD4+, V beta 17+ synovial tissue-derived T cell clones, isolated and grown in vitro, were found to express TCR beta chain transcripts homologous to the dominant V beta 17 synovial tissue sequences. One clone shares with a dominant synovial tissue sequence a conserved cluster of 4/5 amino acids (IGQ-N) in the highly diverse antigen binding CDR3 region, suggesting that the T cells from which these transcripts derive may recognize the same antigen. These findings have permitted a complete characterization of the alpha/beta TCR expressed by putatively pathogenic T cell clones in RA. Functional analysis suggests that the conserved CDR3 sequence may confer specificity for, or restriction by, the MHC class II antigen, DR4.
PMCID: PMC330088  PMID: 7989613
6.  T cell receptor V beta gene bias in rheumatoid arthritis. 
Journal of Clinical Investigation  1993;92(6):2688-2701.
Polymerase chain reaction (PCR) technology was employed to examine peripheral blood and synovial T cells in patients with rheumatoid arthritis (RA) for biased utilization of T cell receptor (TCR) variable region (V) genes. Oligonucleotide primers specific for individual TCR V beta gene families were used to amplify TCR gene products in a semiquantitative assay of their relative utilization in unselected T cell populations. Mean V beta expression in 24 RA peripheral blood samples was very similar to that in a panel of 15 normal subjects, except for a slight decrease in V beta 13.2 expression. V beta utilization in 8 RA synovial tissue samples and 13 synovial fluid samples was compared to simultaneously obtained blood samples. Although heterogeneous patterns of skewed V beta utilization were observed, several significant trends emerged. By a number of approaches to data analysis, a statistically significant increase in expression of V beta 6 and V beta 15 in synovial T cells was documented. In addition, increased synovial expression of V beta 14 was found, but only in the synovial fluid samples. Reduced expression of V beta 1, V beta 4, V beta 5.1, V beta 10, V beta 16, and V beta 19 was also observed in synovial T cells. These results indicate that biased V beta gene utilization in different peripheral compartments of RA patients can be observed in unselected T cell populations, and are consistent with the conclusion that populations of T cells expressing these V beta gene products may be involved in the pathogenesis of the disease.
PMCID: PMC288467  PMID: 8254025
7.  FcgammaR expression on macrophages is related to severity and chronicity of synovial inflammation and cartilage destruction during experimental immune-complex-mediated arthritis (ICA) 
Arthritis Research  2000;2(6):489-503.
We investigated the role of Fcγ receptors (FcγRs) on synovial macrophages in immune-complex-mediated arthritis (ICA). ICA elicited in knee joints of C57BL/6 mice caused a short-lasting, florid inflammation and reversible loss of proteoglycans (PGs), moderate chondrocyte death, and minor erosion of the cartilage. In contrast, when ICA was induced in knee joints of Fc receptor (FcR) γ-chain-/- C57BL/6 mice, which lack functional FcγRI and RIII, inflammation and cartilage destruction were prevented. When ICA was elicited in DBA/1 mice, a very severe, chronic inflammation was observed, and significantly more chondrocyte death and cartilage erosion than in arthritic C57BL/6 mice. The synovial lining and peritoneal macrophages of naïve DBA/1 mice expressed a significantly higher level of FcγRs than was seen in C57BL/6 mice. Moreover, elevated and prolonged expression of IL-1 was found after stimulation of these cells with immune complexes. Zymosan or streptococcal cell walls caused comparable inflammation and only mild cartilage destruction in all strains. We conclude that FcγR expression on synovial macrophages may be related to the severity of synovial inflammation and cartilage destruction during ICA.
Fcγ receptors (FcγRs) present on cells of the haematopoietic lineage communicate with IgG-containing immune complexes that are abundant in the synovial tissue of patients with rheumatoid arthritis (RA). In mice, three classes of FcγR (RI, RII, and RIII) have been described. Binding of these receptors leads to either activation (FcγRI and RIII) or deactivation (FcγRII) of intracellular transduction pathways. Together, the expression of activating and inhibitory receptors is thought to drive immune-complex-mediated diseases.
Earlier studies in our laboratory showed that macrophages of the synovial lining are of utmost importance in the onset and propagation of immune-complex-driven arthritic diseases. Selective depletion of macrophages in the joint downregulated both inflammation and cartilage destruction. As all three classes of FcγR are expressed on synovial macrophages, these cells are among the first that come in contact with immune complexes deposited in the joint. Recently, we observed that when immune complexes were injected into the knee joints of mice, strains susceptible to collagen-type-II arthritis (DBA/1, B10.RIII) developed more severe arthritis than nonsusceptible strains did, or even developed chronic arthritis. One reason why these strains are more susceptible might be their higher levels of FcγRs on macrophage membranes. To test this hypothesis, we investigated the role of FcγRs in inflammation and cartilage damage during immune-complex-mediated arthritis (ICA). First, we studied arthritis and subsequent cartilage damage in mice lacking functional FcγRI and RIII (FcR γ-chain-/- mice). Next, DBA/1 mice, which are prone to develop collagen-type-II arthritis (`collagen-induced arthritis'; CIA) and are hypersensitive to immune complexes, were compared with control C57BL/6 mice as regards cartilage damage and the expression and function of FcγRs on their macrophages.
To examine whether FcγR expression on macrophages is related to severity of synovial inflammation and cartilage destruction during immune-complex-mediated joint inflammation.
ICA was induced in three strains of mice (FcR γ-chain-/-, C57BL/6, and DBA/1, which have, respectively, no functional FcγRI and RIII, intermediate basal expression of FcγRs, and high basal expression of FcγRs) by passive immunisation using rabbit anti-lysozyme antibodies, followed by poly-L-lysine lysozyme injection into the right knee joint 1 day later. In other experiments, streptococcal-cell-wall (SCW)- or zymosan-induced arthritis was induced by injecting SCW (25 μg) or zymosan (180 μg) directly into the knee joint. At several time points after arthritis induction, knee joints were dissected and studied either histologically (using haematoxylin/eosin or safranin O staining) or immuno-histochemically. The arthritis severity and the cartilage damage were scored separately on an arbitrary scale of 0-3.
FcγRs were immunohistochemically detected using the monoclonal antibody 2.4G2, which detects both FcγRII and RIII. Deposition of IgG and C3c in the arthritic joint tissue was also detected immunohistochemically. Expression of FcγRs by murine peritoneal macrophages was measured using a fluorescence-activated cell sorter (FACS).
Peritoneal macrophages were stimulated using heat-aggregated gamma globulins (HAGGs), and production of IL-1 was measured using a bioassay. To assess the levels of IL-1 and its receptor antagonist (IL-1Ra) during arthritis, tissue was dissected and washed in RPMI medium. Washouts were tested for levels of IL-1 and IL-1Ra using radioimmunoassay and enzyme-linked immunosorbent assay. mRNA was isolated from the tissue, and levels of macrophage inflammatory protein (MIP)-2, monocyte chemoattractant protein (MCP)-1, IL-1, and IL-1Ra were determined using semiquantitative reverse-transcription polymerase chain reaction (RT-PCR).
ICA induced in knee joints of C57BL/6 mice caused a florid inflammation at day 3 after induction. To investigate whether this arthritis was FcγR-mediated, ICA was induced in FcR γ-chain-/- mice, which lack functional FcγRI and RIII. At day3, virtually no inflammatory cells were found in their knee joints. Levels of mRNA of IL-1, IL-1Ra, MCP-1, and MIP-2, which are involved in the onset of this arthritis, were significantly lower in FcR γ-chain-/- mice than in control C57BL/6 mice. Levels of IL-1 protein were also measured. At 6 h after ICA induction, FcR γ-chain-/- mice and control C57BL/6 mice showed similar IL-1 production as measured by protein level. By 24 h after induction, however, IL-1 production in the FcR γ-chain-/- mice was below the detection limit, whereas the controls were still producing a significant amount. To investigate whether the difference in reaction to immune complexes between the DBA/1 and C57BL/6 mice might be due to variable expression of FcγRs in the knee joint, expression in situ of FcγRs in naïve knee joints of these mice was determined. The monoclonal antibody 2.4G2, which detects both FcγRII and RIII, stained macrophages from the synovial lining of DBA/1 mice more intensely than those from C57BL/6 mice. This finding suggests a higher constitutive expression of FcγRs by macrophages of the autoimmune-prone DBA/1 mice. To quantify the difference in FcγR expression on macrophages of the two strains, we determined the occurrence of FcγRs on peritoneal macrophages by FACS analysis. The levels of FcγR expressed by macrophages were twice as high in the DBA/1 mice as in the C57BL/6 mice (mean fluorescence, respectively, 440 ± 50 and 240 ± 30 intensity per cell). When peritoneal macrophages of both strains were stimulated with immune complexes (HAGGs), we found that the difference in basal FcγR expression was functional. The stimulated macrophages from DBA/1 mice had significantly higher IL-1α levels (120 and 135 pg/ml at 24 and 48 h, respectively) than cells from C57BL/6 mice (45 and 50 pg/ml, respectively).
When arthritis was induced using other arthritogenic triggers than immune complexes (zymosan, SCW), all the mouse strains tested (DBA/1, FcR γ-chain-/-, and C57BL/6) showed similar inflammation, indicating that the differences described above are found only when immune complexes are used to elicit arthritis.
We next compared articular cartilage damage in arthritic joints of the three mouse strains FcR γ-chain-/-, C57BL/6 (intermediate basal expression of FcγRs), and DBA/1 (high basal expression of FcγRs). Three indicators of cartilage damage were investigated: depletion of PGs, chondrocyte death, and erosion of the cartilage matrix. At day 3 after induction of ICA, there was no PG depletion in FcR γ-chain-/- mice, whereas PG depletion in the matrix of the C57BL/6 mice was marked and that in the arthritic DBA/1 mice was even greater. PG depletion was still massive at days 7 and 14 in the DBA/1 mice, whereas by day 14 the PG content was almost completely restored in knee joints of the C57BL/6 mice. Chondrocyte death and erosion of cartilage matrix, two indicators of more severe cartilage destruction, were significantly higher in the DBA/1 than in the C57BL/6 mice, while both indicators were completely absent in the FcR γ-chain-/- mice. Again, when arthritis was induced using other triggers (SCW, zymosan), all strains showed similar PG depletion and no chondrocyte death or matrix erosion. These findings underline the important role of immune complexes and FcγRs in irreversible cartilage damage.
Our findings indicate that inflammation and subsequent cartilage damage caused by immune complexes may be related to the occurrence of FcγRs on macrophages. The absence of functional FcγRI and RIII prevented inflammation and cartilage destruction after induction of ICA, whereas high basal expression of FcγRs on resident joint macrophages of similarly treated mice susceptible to autoimmune arthritis was correlated with markedly more synovial inflammation and cartilage destruction. The difference in joint inflammation between the three strains was not due to different susceptibilities to inflammation per se, since intra-articular injection of zymosan or SCW caused comparable inflammation. Although extensive inflammatory cell mass was found in the synovium of all strains after intra-articular injection of zymosan, no irreversible cartilage damage (chondrocyte death or matrix erosion) was found. ICA induced in C57BL/6 and DBA/1 mice did cause irreversible cartilage damage at later time points, indicating that immune complexes and FcγRs play an important role in inducing irreversible cartilage damage. Macrophages communicate with immune complexes via Fcγ receptors. Absence of functional activating receptors completely abrogates the synovial inflammation, as was shown after ICA induction in FcR γ-chain-/- mice. However, the γ-chain is essential not only in FcγRI and RIII but also for FcεRI (found on mast cells) and the T cell receptor (TcR)-CD3 (Tcells) complex of γδT cells. However, T, B, or mast cells do not play a role in this arthritis that is induced by passive immunisation. Furthermore, this effect was not caused by a difference in clearance of IgG or complement deposition in the tissue. In this study, DBA/1 mice, which are susceptible to collagen-induced autoimmune arthritis and in a recent study have been shown to react hypersensitively to immune complexes, are shown to express higher levels of FcγRs on both synovial and peritoneal macrophages. Because antibodies directed against the different subclasses of FcγR are not available, no distinction could be made between FcγRII and RIII. Genetic differences in DBA/1 mice in genes coding for or regulating FcγRs may be responsible for altered FcγR expression. If so, these mouse strains would have a heightened risk for immune-complex-mediated diseases.
To provide conclusive evidence for the roles of the various classes of FcγR during ICA, experiments are needed in which FcγRs are blocked with specific antibodies, or in which knockout mice lacking one specific class of FcγR are used. The only available specific antibody to FcγR (2.4G2) has a stimulatory effect on cells once bound to the receptor, and therefore cannot be used in blocking experiments. Experiments using specific knockout mice are now being done in our laboratory.
Macrophages are the dominant type of cell present in chronic inflammation during RA and their number has been shown to correlate well with severe cartilage destruction. Apart from that, in humans, these synovial tissue macrophages express activating FcRs, mainly FcγIIIa, which may lead to activation of these macrophages by IgG-containing immune complexes. The expression of FcRs on the surface of these cells may have important implications for joint inflammation and severe cartilage destruction and therefore FCRs may constitute a new target for therapeutic intervention.
PMCID: PMC17821  PMID: 11056679
autoimmunity; cytokines; Fc receptors; inflammation; macrophages
8.  c-kit+ stem cells and thymocyte precursors in the livers of adult mice 
Livers of the adult mice contain c-kit+ stem cells that can reconstitute thymocytes, multiple lineage cells, and bone marrow (BM) stem cells. Transfer of 1 x 10(7) hepatic mononuclear cells (MNC) and 5 x 10(4) hepatic c-kit+ cells of BALB/c mice induced DP thymocytes within a week in four Gy-irradiated CB17/-SCID mice, but 2 wk were required for BM cells or BM c-kit+ cells to produce DP thymocytes. Moreover, B cell-depleted BM cells or liver MNC of SCID mice that had been rescued by hepatic MNC of BALB/c mice again reconstituted thymus and B cells of other irradiated SCID mice. CD3- IL-2R beta- populations of both BM cells and hepatic MNC of C57BL/6 (B6) mice could generate T cells with intermediate TCR (mostly NK1.1-) in the liver of irradiated B6 SCID mice before thymic reconstitution (extrathymic T cells). Furthermore, transfer of liver c-kit+ cells of B6-Ly 5.1 mice into irradiated B6 SCID (Ly5.2) mice revealed that liver c-kit+ cells can reconstitute myeloid and erythroid lineage cells. These results strongly suggest that the liver contains pluripotent stem cells and serves an important hematopoietic organ even into adulthood.
PMCID: PMC2192738  PMID: 8760822
9.  The role of X-chromosome inactivation in female predisposition to autoimmunity 
Arthritis Research  2000;2(5):399-406.
We propose that the phenomenon of X-chromosome inactivation in females may constitute a risk factor for loss of T-cell tolerance; specifically that skewed X-chromosome inactivation in the thymus may lead to inadequate thymic deletion. Using a DNA methylation assay, we have examined the X-chromosome inactivation patterns in peripheral blood from normal females (n = 30), female patients with a variety of autoimmune diseases (n = 167). No differences between patients and controls were observed. However, locally skewed X-chromsome inactivation may exist in the thymus, and therefore the underlying hypothesis remains to be disproved.
A reduction in the sex ratio (male : female) is characteristic of most autoimmune disorders. The increased prevalence in females ranges from a modest 2:1 for multiple sclerosis [1], to approximately 10:1 for systemic lupus erythematosus [2]. This tendency toward autoimmunity in females is often ascribed to hormonal differences, because in a number of experimental disease models estrogens exacerbated disease, and androgens can inhibit disease activity [3,4]. However, human studies have failed to demonstrate a clear-cut influence of hormonal environment on disease susceptibility to lupus or other autoimmune disorders. In addition, many childhood forms of autoimmunity, such as juvenile rheumatoid arthritis, exhibit female predominance [5]. Interestingly, juvenile (type 1) diabetes is an exception to this general trend, with a sex ratio close to 1 in most studies [6]. Therefore, it is reasonable to consider alternative explanations for the increased prevalence of autoimmune diseases in human females.
A unifying feature of autoimmune disorders appears to be the loss of immunologic tolerance to self-antigens, and in many of these diseases there is evidence that T-cell tolerance has been broken. The most profound form of T-cell tolerance involves deletion of potentially self-reactive T cells during thymic selection. Thus, lack of exposure to a self-antigen in the thymus may lead to the presence of autoreactive T cells and may increase the risk of autoimmunity. An elegant example of this has recently been reported [7].
The existence of X-chromosome inactivation in females offers a potential mechanism whereby X-linked self-antigens may escape presentation in the thymus or in other peripheral sites that are involved in tolerance induction. Early in female development, one of the two X chromosomes in each cell undergoes an ordered process of inactivation, with subsequent silencing of most genes on the inactive X chromosome [8]. This phenomenon occurs at a very early embryonic stage [9], and thus all females are mosaic and may occasionally exhibit extreme skewing towards one or the other parental X chromosome. In theory, this may result in a situation in which polymorphic self-antigens on one X chromosome may fail to be expressed at sufficiently high levels in a tolerizing compartment, such as the thymus, and yet may be expressed at a considerable frequency in the peripheral soma. Thus, females may be predisposed to a situation in which they can occasionally express X-linked autoantigens in the periphery to which they have been inefficiently tolerized. Stewart [10] has recently speculated that such a mechanism may play a role in the predisposition to systemic lupus.
This hypothesis predicts that females with autoimmunity may be particularly prone to this mechanism of `inadequate tolerization' by virtue of extremely skewed X-chromosome inactivation. We therefore performed a comprehensive analysis of X-chromosome inactivation patterns in populations of females with multiple sclerosis, systemic lupus erythematosus, juvenile rheumatoid arthritis, and type 1 (insulin-dependent) diabetes mellitus, and in female control individuals. The results do not provide support for a major role for skewed X-chromosome inactivation in female predisposition to autoimmunity; however, neither is the underlying hypothesis disproved by the present data.
Materials and method:
DNA was obtained from female patients from the following sources: 45 persons with juvenile diabetes seen at the Virginia Mason Research Center in Seattle, Washington; 58 multiple sclerosis patients seen at the New York Hospital Multiple Sclerosis Center; 46 patients with systemic lupus erythematosus seen at the Hospital for Special Surgery (New York); 18 patients with juvenile rheumatoid arthritis seen at the Children's Hospital Medical Center in Cleveland. In addition, 30 healthy age-matched females were studied as normal controls.
Employing a modification of previously described methods [11], we utilized a fluorescent Hpa II/PCR assay of the androgen receptor (AR) locus to assess X-chromosome inactivation patterns. The AR gene contains a polymorphic CAG repeat, which is flanked by Hpa II sites. These Hpa II sites are methylated on the inactive X chromosome, and are unmethylated on the active X chromosome. By performing PCR amplification across this region after cutting with the methylation-sensitive enzyme Hpa II, the relative amounts of the methylated AR alleles can be quantitatively determined with a high degree of accuracy; variance on repeated assays is approximately 4% [12].
Skewing of X-chromosome inactivation is expressed as percentage deviation from equal (50:50) inactivation of the upper and lower AR alleles. Therefore, the maximal possible deviation is 50%, in which case all of the X chromosomes bearing one of the AR alleles are inactivated.
We examined X-chromosome inactivation patterns in several different populations. The results are summarized in Fig. 1. A wide range of X-inactivation skewing was observed in all five groups. Approximately 5% (nine out of 197) of individuals exhibited extreme skewing (greater than 40% deviation from a 50:50 distribution). However, there was no difference between the groups, either in the overall mean skewing, or in the fraction of individuals with extreme skewing (>40%).
Although the present study was not initiated in order to examine allelic variation in the AR gene per se, the data provide an opportunity to address this question. Excessively long CAG repeats in the AR are a rare cause of spinal-bulbar muscular atrophy [13], and AR repeat length appears to have an influence on the biology of certain tumors [14,15]. In this context, it has been shown that transcription of AR correlates inversely with repeat length [16]. We therefore compared AR repeat length in control individuals and patients with autoimmunity. No differences were observed for mean repeat length, or for maximum and minimum repeat length, among the five groups.
The reason for the female predominance in most autoimmune diseases remains obscure. The present study was initiated in order to address the hypothesis that a nonhormonal mechanism related to X inactivation might be involved. The hypothesis rests on the idea that skewing of X inactivation might lead to a deficiency of tolerance induction in the thymus, particularly with respect to polymorphic X-linked autoantigens. The hypothesis predicts that skewed X inactivation would be more prevalent in females with autoimmune diseases than in female control individuals. This was not observed.
Nevertheless, these negative data do not rule out a role for X inactivation in female predisposition to loss of tolerance. A general model for how this mechanism might operate is shown in Fig. 2. Thymocytes undergo selection in the thymic parenchyma and, in the case of negative selection, the selecting elements appear to be derived from the bone marrow and consist mainly of thymic dendritic cells. If the thymic dendritic cell population exhibits random X inactivation, it is highly likely that differentiating thymocytes will contact dendritic cells that express self-antigens on both X chromosomes. This situation is outlined schematically on the left side of Fig. 2. However, if there is extremely skewed X inactivation in the thymic dendritic cell population, a particular thymocyte might not come into contact with dendritic cells that express one of the two X chormosomes. This would lead to a situation where T cells may undergo thymic maturation without having been negatively selected for antigens that are expressed on the predominantly inactive X chromosome. This situation is shown on the right side of Fig. 2.
In order for this mechanism to be physiologically relevant, some assumptions must be made. First, defective tolerance from skewed X inactivation should only be directed at X-linked antigens that are polymorphic, and for which the individual is heterozygous. Thus, this mechanism would not be expected to lead to lack of tolerance commonly, unless there are at least several highly polymorphic X-linked autoantigens in the population that are involved in thymic deletion events. Second, if this actually leads to autoimmunity, it also predicts that the initial break in tolerance that leads to disease should involve an X-linked autoantigen that is expressed in a peripheral nontolerizing site or circumstance.
A recent report [7] has elegantly demonstrated the importance of thymic deletion events in predisposition to autoimmune disease. The proteolipid protein (PLP) autoantigen is expressed in alternatively spliced forms, which exhibit tissue specific expression. A nonspliced variant is expressed in peripheral neural tissue. However, in the thymus a splice variant results in the lack of thymic expression of an immunodominant peptide. This results in loss of tolerace of T cells to this peptide, presumably on the basis of lack of thymic deletion of thymocytes that are reactive with this antigen. Interestingly, PLP is encoded on the X chromsome. However, there is no evidence that genetic polymorphisms control the level splicing of PLP within the thymus. Nevertheless, these data illustrate the potential importance of deficiencies in thymic deletion for autoimmune T-cell reactivity.
The present results suggest that if skewed X inactivation is relevant to thymic tolerance induction, then the effect does not depend on global skewing of X-chromosome inactivation, at least in the hematopoietic compartment. In this study we examined X-inactivation patterns in peripheral blood mononuclear cells, and the results should reflect the state of X inactivation in all mesenchymal tissues, including dendritic cells. X inactivation occurs at a very early time point in development, and thus the results in one tissue should reflect the general situation in the rest of the body. However, there may be exceptions to this. We have occasionally observed differences in X-inactivation patterns between buccal mucosa (an ectodermally derived tissue) and peripheral blood in the same individiual (unpublished observations). This could be a chance event, or it may result from selection for certain X-linked alleles during embryonic development, as has been described in carriers of X-linked immunodeficiencies [17].
Another consideration is that certain tissue microenvironments may be derived from very small numbers of founder cells, and thus may exhibit skewed utilization of one or the other X chromosome, even if the tissue as a whole is not skewed. This situation could vary over time. Thus, there may be time points at which certain thymic microenvironments are populated by dendritic cells that, for stochastic reasons, all utilize the same X chromosome. This would create a `window of opportunity' in which a given thymocyte, in a given selecting location, could escape negative selection by antigens on the inactive X chromosome. The likelihood of this happening would obviously depend on the number of dendritic cells that are usually contacted by a thymocyte during thymic selection. There is limited information on this point, although Stewart [10] has theorized that this number may be as low as 15. If this is the case, then escape from thymic deletion may still occur in females who are heterozygous for a relevant X-linked antigen, even if the hematopoietic cells in general do not exhibit extreme skewing.
In conclusion, we suggest that X-chromosome inactivation needs to be considered as a potential factor in the predominance of females in most autoimmune diseases. Our inability to show an increase in X-chromosome skewing in females with autoimmunity does not eliminate this as an etiologic contributor to loss of immunologic tolerance. Future experiments must be directed at a detailed analysis of tissue patterns of X inactivation, as well as at a search for potential X-linked autoantigens.
PMCID: PMC17816  PMID: 11056674
autoimmunity; gender; immune tolerance; X chromosome
10.  Immunization with T cell receptor V beta chain peptides deletes pathogenic T cells and prevents the induction of collagen-induced arthritis in mice. 
Journal of Clinical Investigation  1996;97(12):2849-2858.
Collagen-induced arthritis (CIA) in susceptible strains of mice is an animal model of T cell-mediated inflammatory polyarthritis. Analysis of T cell receptor (TCR) V beta gene usage in cells isolated from arthritic joints of BUB/BnJ (BUB) mice (H-2q, TCR V beta a) showed that TCR V beta chain gene usage was limited to TCR V beta 3 and V beta 10 gene families. All of the BUB mice immunized with a mixture of TCR V beta 3 and TCR V beta 10 peptides, but not with control TCR V beta 14 peptide, were refractory to the induction of CIA. Immunization with TCR V beta 3 and V beta 10 peptides completely blocked the development of clinical and subclinical inflammation, formation of pannus and synovial hyperplasia, and the erosion of cartilage and bone. Further studies revealed that preimmunization of BUB mice with V beta 10 peptide alone was sufficient to render the mice resistant to CIA. Analysis of TCR V beta chain gene expression in lymph node cells from arthritic and arthritis-protected mice showed the expression of TCR V beta 10 subfamily in all of the arthritic mice, but not in arthritis-protected mice. Immunization with TCR V beta peptides did not diminish the humoral responses to chicken type-II collagen and also elicited significant levels of anti-V beta 3 and anti-V beta 10 peptide antibodies. Antibodies cross-reactive with mouse chicken type-II collagen were detected in both the arthritic and arthritis-protected mice. Adoptive transfer of serum from arthritis-protected BUB mice significantly delayed the onset (P < 0.005) of arthritis in recipient BUB mice. In contrast, mice injected with serum from arthritic mice had early onset of arthritis. These results demonstrate that immunization of BUB mice with TCR V beta chain peptides elicited antibodies reactive with the self-TCR and prevented the induction of collagen-induced arthritis by eliminating or downregulating pathogenic T cells and consequently blocking the development of humoral immune response. These findings may have clinical applications in treating human autoimmune diseases characterized by common TCR gene usage.
PMCID: PMC507379  PMID: 8675697
11.  The repertoire of CD4+ CD28- T cells in rheumatoid arthritis. 
Molecular Medicine  1996;2(5):608-618.
BACKGROUND: While oligoclonality of circulating CD4- CD8 and of CD8+ T cells is not uncommon, clonal dominance within the CD4 compartment is not frequently found in healthy individuals. In contrast, the majority of patients with rheumatoid arthritis (RA) have clonally expanded CD4+ T cell populations. Previous studies have demonstrated that these clonogenic CD4+ T cells do not express the CD28 molecule. To examine the correlation between CD28 expression and clonal proliferation, we have analyzed the T cell receptor (TCR) diversity of CD4+ CD28- T cells in normal individuals and in RA patients. MATERIAL AND METHODS: The size of the peripheral blood CD4+ CD28- compartment was determined in 30 healthy individuals and 30 RA patients by two-color FACS analysis. In 10 RA patients and five controls with more than 2.5% CD4+ CD28- T cells, TCR BV gene segment usage was analyzed with 19 BV-specific antibodies. Oligoclonality was assessed in sorted CD4+ CD28+ and CD28- T cells using TCR BV-BC-specific polymerase chain reaction and size fractionation. Clonal dominance was confirmed by direct sequencing. RESULTS: The CD4+ CD28- T cell compartment was expanded to more than 2.5% in 70% of the RA patients and 30% of the normal individuals. Compared with the CD4+ CD28+ T cells, the TCR BV gene segment usage among CD4+ CD28- cells was grossly skewed with the dominance of single BV elements. Molecular TCR analysis provided evidence for oligoclonality in 17 of 21 expanded BV elements. In two unrelated RA patients who shared both HLA-DRB1 alleles, the TCR beta-chain sequences of dominant clonotypes were highly conserved. CONCLUSIONS: Oligoclonality is a characteristic feature of CD4+ CD28- T cells which are expanded in some healthy individuals and in the majority of RA patients. The lack of CD28 expression is a common denominator of CD4+, CD8+, and CD4- CD8- T cells prone to develop clonal dominance. The limited TCR diversity of clonal CD4+ CD28- populations in RA patients suggests that these T cells recognize a limited spectrum of antigens. The fact that the majority of individuals with marked expansions and oligoclonality of CD4+ CD28- T cells are RA patients suggests a role for these unusual lymphocytes in the pathogenetic events leading to RA.
PMCID: PMC2230198  PMID: 8898376
12.  Activation of synovial fibroblasts in rheumatoid arthritis: lack of expression of the tumour suppressor PTEN at sites of invasive growth and destruction 
Arthritis Research  1999;2(1):59-64.
In the present study, we searched for mutant PTEN transcripts in aggressive rheumatoid arthritis synovial fibroblasts (RA-SF) and studied the expression of PTEN in RA. By automated sequencing, no evidence for the presence of mutant PTEN transcripts was found. However, in situ hybridization on RA synovium revealed a distinct expression pattern of PTEN, with negligible staining in the lining layer but abundant expression in the sublining. Normal synovial tissue exhibited homogeneous staining for PTEN. In cultured RA-SF, only 40% expressed PTEN. Co-implantation of RA-SF and normal human cartilage into severe combined immunodeficiency (SCID) mice showed only limited expression of PTEN, with no staining in those cells aggressively invading the cartilage. Although PTEN is not genetically altered in RA, these findings suggest that a lack of PTEN expression may constitute a characteristic feature of activated RA-SF in the lining, and may thereby contribute to the invasive behaviour of RA-SF by maintaining their aggressive phenotype at sites of cartilage destruction.
PTEN is a novel tumour suppressor which exhibits tyrosine phosphatase activity as well as homology to the cytoskeletal proteins tensin and auxilin. Mutations of PTEN have been described in several human cancers and associated with their invasiveness and metastatic properties. Although not malignant, rheumatoid arthritis synovial fibroblasts (RA-SF) exhibit certain tumour-like features such as attachment to cartilage and invasive growth. In the present study, we analyzed whether mutant transcripts of PTEN were present in RA-SF. In addition, we used in situ hybridization to study the expression of PTEN messenger (m)RNA in tissue samples of RA and normal individuals as well as in cultured RA-SF and in the severe combined immunodeficiency (SCID) mouse model of RA.
Synovial tissue specimens were obtained from seven patients with RA and from two nonarthritic individuals. Total RNA was isolated from synovial fibroblasts and after first strand complementary (c)DNA synthesis, polymerase chain reaction (PCR) was performed to amplify a 1063 base pair PTEN fragment that encompassed the coding sequence of PTEN including the phosphatase domain and all mutation sites described so far. The PCR products were subcloned in Escherichia coli, and up to four clones were picked from each plate for automated sequencing. For in situ hybridization, digoxigenin-labelled PTEN-specific RNA probes were generated by in vitro transcription. For control in situ hybridization, a matrix metalloproteinase (MMP)-2-specific probe was prepared. To investigate the expression of PTEN in the absence of human macrophage or lymphocyte derived factors, we implanted RA-SF from three patients together with normal human cartilage under the renal capsule of SCID mice. After 60 days, mice were sacrificed, the implants removed and embedded into paraffin.
PCR revealed the presence of the expected 1063 base pair PTEN fragment in all (9/9) cell cultures (Fig. 1). No additional bands that could account for mutant PTEN variants were detected. Sequence analysis revealed 100% homology of all RA-derived PTEN fragments to those from normal SF as well as to the published GenBank sequence (accession number U93051). However, in situ hybridization demonstrated considerable differences in the expression of PTEN mRNA within the lining and the sublining layers of RA synovial membranes. As shown in Figure 2a, no staining was observed within the lining layer which has been demonstrated to mediate degradation of cartilage and bone in RA. In contrast, abundant expression of PTEN mRNA was found in the sublining of all RA synovial tissues (Figs 2a and b). Normal synovial specimens showed homogeneous staining for PTEN within the thin synovial membrane (Fig. 2c). In situ hybridization using the sense probe gave no specific staining (Fig. 2d). We also performed in situ hybridization on four of the seven cultured RA-SF and followed one cell line from the first to the sixth passage. Interestingly, only 40% of cultured RA-SF expressed PTEN mRNA (Fig. 3a), and the proportion of PTEN expressing cells did not change throughout the passages. In contrast, control experiments using a specific RNA probe for MMP-2 revealed mRNA expression by nearly all cultured cells (Fig. 3b). As seen before, implantation of RA-SF into the SCID mice showed considerable cartilage degradation. Interestingly, only negligible PTEN expression was found in those RA-SF aggressively invading the cartilage (Fig. 3c). In situ hybridization for MMP-2 showed abundant staining in these cells (Fig. 3d).
Although this study found no evidence for mutations of PTEN in RA synovium, the observation that PTEN expression is lacking in the lining layer of RA synovium as well as in more than half of cultured RA-SF is of interest. It suggests that loss of PTEN function may not exclusively be caused by genetic alterations, yet at the same time links the low expression of PTEN to a phenotype of cells that have been shown to invade cartilage aggressively.
It has been proposed that the tyrosine phosphatase activity of PTEN is responsible for its tumour suppressor activity by counteracting the actions of protein tyrosine kinases. As some studies have demonstrated an upregulation of tyrosine kinase activity in RA synovial cells, it might be speculated that the lack of PTEN expression in aggressive RA-SF contributes to the imbalance of tyrosine kinases and phosphatases in this disease. However, the extensive amino-terminal homology of the predicted protein to the cytoskeletal proteins tensin and auxilin suggests a complex regulatory function involving cellular adhesion molecules and phosphatase-mediated signalling. The tyrosine phosphatase TEP1 has been shown to be identical to the protein encoded by PTEN, and gene transcription of TEP1 has been demonstrated to be downregulated by transforming growth factor (TGF)-β. Therefore, it could be hypothesized that TGF-β might be responsible for the downregulation of PTEN. However, the expression of TGF-β is not restricted to the lining but found throughout the synovial tissue in RA. Moreover, in our study the percentage of PTEN expressing RA-SF remained stable for six passages in culture, whereas molecules that are cytokine-regulated in vivo frequently change their expression levels when cultured over several passages. Also, cultured RA-SF that were implanted into SCID mice and deeply invaded the cartilage did not show significant expression of PTEN after 60 days. The drop in the percentage of PTEN expressing cells from the original cell cultures to the SCID mouse implants is of interest as this observation goes along with data from previous studies that have shown the prominent expression of activation-related molecules in the SCID mice implants that in vivo are found predominantly in the lining layer. Therefore, our data point to endogenous mechanisms rather than to the influence of exogenous human cytokines or factors in the downregulation of PTEN. Low expression of PTEN may belong to the features that distinguish between the activated phenotype of RA-SF and the sublining, proliferating but nondestructive cells.
PMCID: PMC17804  PMID: 11219390
rheumatoid arthritis; synovial membrane; fibroblasts; PTEN tumour suppressor; severe combined immunodeficiency (SCID) mouse model; cartilage destruction; in situ hybridization
13.  Apoptosis and p53 expression in rat adjuvant arthritis 
Arthritis Research  2000;2(3):229-235.
The kinetics of apoptosis and the apoptosis-regulating gene p53 in adjuvant arthritis (AA) were investigated to assess the value of the AA rat model for testing apoptosis-inducing therapies. Very few terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate (dUTP) nick end-labeling (TUNEL)-positive cells were detected during the early phases of AA, but on day 23 (chronic arthritis) the percentage of TUNEL-positive cells was significantly increased. Expression of p53 in synovial tissue gradually increased from days 5-23, which was markedly higher than p53 levels in rheumatoid arthritis (RA) synovium. Significant apoptosis only occurs late in rat AA and is concordant with marked p53 overexpression, making it useful model for testing proapoptotic therapies, but rat AA is not the best model for p53 gene therapy because dramatic p53 overexpression occurs in the latter stages of the disease.
RA is a chronic inflammatory disorder that is characterized by inflammation and proliferation of synovial tissue. The amount of DNA fragmentation is significantly increased in rheumatoid synovium. Only low numbers of apoptotic cells are present in rheumatoid synovial tissue, however. The proportion of cells with DNA strand breaks is so great that this disparity suggests impaired apoptosis. Therefore, the development of novel therapeutic strategies that are aimed at inducing apoptosis in rheumatoid synovial tissue is an attractive goal.
Although animal models for arthritis only approximate RA, they provide a useful test system for the evaluation of apoptosis-inducing therapies. AA in rats is among the most commonly used animal models for RA. For the interpretation of such studies, it is essential to characterize the extent to which apoptosis occurs during the natural course of the disease. Therefore, we evaluated the number of apoptotic cells and the expression of p53 in various phases of AA.
Materials and methods:
In order to generate the AA rat model, Lewis rats were immunized with Mycobacterium tuberculosis in mineral oil on day 0. Paw swelling usually started around day 10. For the temporal analysis rats were sacrificed on days 0, 5 (prearthritis), 11 (onset of arthritis), 17 (accelerating arthritis), or 23 (chronic arthritis).
For the detection of apoptotic cells, the hind paws were harvested on days 0(n=6),5 (n=6), 11 (n=6), 17 (n=6), or 23 (n=4). The right ankle joints were fixed in formalin, decalcified in ethylenediaminetetra-acetic acid, embedded in paraffin, and sectioned. The TUNEL method was applied. The percentage of TUNEL-positive cells of the total inflammatory cell infiltrate was noted.
For Western blot analysis, hind paws were harvested on days 0 (n=2), 5 (n=3), 11 (n=4), 17 (n=4), or 23 (n=4). In addition, hind paws of normal rats (n=2) were studied. The right ankle joints were snap frozen and pulverized. Synovial tissue was also obtained by arthroscopy of three patients with longstanding (>5 years) RA. After protein extraction in lysis buffer, equal amounts of protein samples from lysates were pooled and examined by Western bolt analysis using anti-p53 monoclonal antibody D07, which recognizes wild-type and mutant p53 from rodents and humans.
For immunohistochemical analysis, six rats were sacrificed on day 23 after immunization and synovial tissue of the right ankle joints was snap frozen and evaluated by immunohistochemistry using anti-p53-pan. The sections were evaluated semi-quantitatively using a 0-4 scale.
The kruskal-Wallis test for several group means was used to compare the percentage of TUNEL-positive cells at different time points.
The percentages of TUNEL-positive cells were strongly dependent on the stage of the disease. Very few TUNEL-positive cells were detected in normal rats or in the early phases of AA; the number of TUNEL-positive cells was 1% or less of the total cell infiltrate, including neutrophils, from days 0-17 (Table 1). On day 23, however, the percentage of TUNEL-positive cells was significantly increased [15.8±5.1% (mean ± standard error of the mean); P=0.01]. TUNEL-positive cells were observed in the intimal lining layer and synovial sublining of the invasive front, as well as in the articular cartilage (Fig. 1).
Subsequently, we examined expression of the tumor suppressor gene p53, because this is a key regulator of apoptosis. Expression of p53 in pooled rat AA joint extracts gradually increased from day 0 (6 arbitrary units) to day 23 (173 arbitrary units), which was markedly higher than p53 levels in RA synovium (32 arbitrary units; Table 1). Overexpression of p53 protein on day 23 was confirmed by immunohistochemistry in a separate experiment in six rats with AA. Overexpression of p53 was observed in the intimal lining layer and synovial sublining in all rats on day 23. In all cases a semiquantitative score of 4 was assigned, indicating that 51% or more of the cells were positive, whereas control sections were negative.
The results presented here reveal that the number of TUNEL-positive cells remained very low until chronic arthritis developed. This indicates that, although there was sufficient DNA damage to cause an increment in p53 expression in the early phases, DNA strand breaks that can be detected by TUNEL assays only occurred in chronic AA. The observation that TUNEL-positive cells were nearly absent in early AA clearly indicates that only very few cells were undergoing programmed cell death. This is an important observation, which makes it possible to study the effects of apoptosis-inducing therapies in situ in early and accelerating AA. An effective therapy would obviously increase the number of TUNEL-positive cells.
There is already some overexpression of p53 in the preclinical phase and during the onset of the arthritis, with an additional increment in p53 expression during accelerating and chronic arthritis. Presumably, this is wild-type p53, because the disease duration is likely too short to allow for the development of p53 mutations. Transcription of p53 is probably increased in response to the toxic environment of the inflamed joint. The increased expression of p53 in the joints of rats with chronic AA was even greater than that observed in synovial tissue of RA patients with long-standing disease.
Overexpression of p53 and increased numbers of apoptotic cells did not occur simultaneously in this model; rather p53 overexpression preceded increased apoptosis. Activation of p53 leads to induction of cell growth arrest, allowing time for DNA repair. It appears that DNA damage is only extensive enough to induce apoptosis in the latter stages of AA. Factors other than p53 may also play an important role in the actual induction of apoptosis
Taken together, significant apoptosis only occurs late in AA and it follows marked p53 overexpression, making it a useful model for testing proapoptotic therapies. AA is not the best model for p53 gene therapy, however, because dramatic p53 overexpression occurs in the latter stages of the disease.
PMCID: PMC17810  PMID: 11056668
adjuvant arthritis; apoptosis; p53; rheumatoid arthritis
14.  Acute-phase serum amyloid A production by rheumatoid arthritis synovial tissue 
Arthritis Research  2000;2(2):142-144.
Acute-phase serum amyloid A (A-SAA) is a major component of the acute-phase response. A sustained acute-phase response in rheumatoid arthritis (RA) is associated with increased joint damage. A-SAA mRNA expression was confirmed in all samples obtained from patients with RA, but not in normal synovium. A-SAA mRNA expression was also demonstrated in cultured RA synoviocytes. A-SAA protein was identified in the supernatants of primary synoviocyte cultures, and its expression colocalized with sites of macrophage accumulation and with some vascular endothelial cells. It is concluded that A-SAA is produced by inflamed RA synovial tissue. The known association between the acute-phase response and progressive joint damage may be the direct result of synovial A-SAA-induced effects on cartilage degradation.
Serum amyloid A (SAA) is the circulating precursor of amyloid A protein, the fibrillar component of amyloid deposits. In humans, four SAA genes have been described. Two genes (SAA1 and SAA2) encode A-SAA and are coordinately induced in response to inflammation. SAA1 and SAA2 are 95% homologous in both coding and noncoding regions. SAA3 is a pseudogene. SAA4 encodes constitutive SAA and is minimally inducible. A-SAA increases dramatically during acute inflammation and may reach levels that are 1000-fold greater than normal. A-SAA is mainly synthesized in the liver, but extrahepatic production has been demonstrated in many species, including humans. A-SAA mRNA is expressed in RA synoviocytes and in monocyte/macrophage cell lines such as THP-1 cells, in endothelial cells and in smooth muscle cells of atherosclerotic lesions. A-SAA has also been localized to a wide range of histologically normal tissues, including breast, stomach, intestine, pancreas, kidney, lung, tonsil, thyroid, pituitary, placenta, skin and brain.
To identify the cell types that produce A-SAA mRNA and protein, and their location in RA synovium.
Materials and methods:
Rheumatoid synovial tissue was obtained from eight patients undergoing arthroscopic biopsy and at joint replacement surgery. Total RNA was analyzed by reverse transcription (RT) polymerase chain reaction (PCR) for A-SAA mRNA. PCR products generated were confirmed by Southern blot analysis using human A-SAA cDNA. Localization of A-SAA production was examined by immunohistochemistry using a rabbit antihuman A-SAA polyclonal antibody. PrimaryRA synoviocytes were cultured to examine endogenous A-SAA mRNA expression and protein production.
A-SAA mRNA expression was detected using RT-PCR in all eight synovial tissue samples studied. Figure 1 demonstrates RT-PCR products generated using synovial tissue from three representative RA patients. Analysis of RA synovial tissue revealed differences in A-SAA mRNA levels between individual RA patients.
In order to identify the cells that expressed A-SAA mRNA in RA synovial tissue, we analyzed primary human synoviocytes (n = 2). RT-PCR analysis revealed A-SAA mRNA expression in primary RA synoviocytes (n = 2; Fig. 2). The endogenous A-SAA mRNA levels detected in individual primary RA synoviocytes varied between patients. These findings are consistent with A-SAA expression in RA synovial tissue (Fig. 1). Glyceraldehyde-3-phosphate dehydrogenase (GAPDH) levels were relatively similar in the RA synoviocytes examined (Fig. 2). A-SAA protein in the supernatants of primary synoviocyte cultures from four RA patients was measured using ELISA. Mean values of a control and four RA samples were 77.85, 162.5, 249.8, 321.5 and 339.04 μg/l A-SAA, respectively, confirming the production of A-SAA protein by the primary RA synoviocytes. Immunohistochemical analysis was performed to localize sites of A-SAA production in RA synovial tissue. Positive staining was present in both the lining and sublining layers of all eight RA tissues examined (Fig. 3a). Staining was intense and most prominent in the cells closest to the surface of the synovial lining layer. Positively stained cells were evident in the perivascular areas of the sublining layer. In serial sections stained with anti-CD68 monoclonal antibody, positive staining of macrophages appeared to colocalize with A-SAA-positive cells (Fig. 3b). Immunohistochemical studies of cultured primary RA synoviocytes confirmed specific cytoplasmic A-SAA expression in these cells. The specificity of the staining was confirmed by the absence of staining found on serial sections and synoviocyte cells treated with IgG (Fig. 3c).
This study demonstrates that A-SAA mRNA is expressed in several cell populations infiltrating RA synovial tissue. A-SAA mRNA expression was observed in all eight unseparated RA tissue samples studied. A-SAA mRNA expression and protein production was demonstrated in primary cultures of purified RA synoviocytes. Using immunohistochemical techniques, A-SAA protein appeared to colocalize with both lining layer and sublining layer synoviocytes, macrophages and some endothelial cells. The detection of A-SAA protein in culture media supernatants harvested from unstimulated synoviocytes confirms endogenous A-SAA production, and is consistent with A-SAA mRNA expression and translation by the same cells. Moreover, the demonstration of A-SAA protein in RA synovial tissue, RA cultured synoviocytes, macrophages and endothelial cells is consistent with previous studies that demonstrated A-SAA production by a variety of human cell populations.
The RA synovial lining layer is composed of activated macrophages and fibroblast-like synoviocytes. The macrophage is the predominant cell type and it has been shown to accumulate preferentially in the surface of the lining layer and in the perivascular areas of the sublining layer. Nevertheless, our observations strongly suggest that A-SAA is produced not only by synoviocytes, but also by synovial tissue macrophage populations. Local A-SAA protein production by vascular endothelial cells was detected in some, but not all, of the tissues examined. The reason for the variability in vascular A-SAA staining is unknown, but may be due to differences in endothelial cell activation, events related to angiogenesis or the intensity of local inflammation.
The value of measuring serum A-SAA levels as a reliable surrogate marker of inflammation has been demonstrated for several diseases including RA, juvenile chronic arthritis, psoriatic arthropathy, ankylosing spondylitis, Behçet's disease, reactive arthritis and Crohn's disease. It has been suggested that serum A-SAA levels may represent the most sensitive measurement of the acute-phase reaction. In RA, A-SAA levels provide the strongest correlations with clinical measurements of disease activity, and changes in serum levels best reflect the clinical course.
A number of biologic activities have been described for A-SAA, including several that are relevant to the understanding of inflammatory and tissue-degrading mechanisms in human arthritis. A-SAA induces migration, adhesion and tissue infiltration of circulating monocytes and polymorphonuclear leukocytes. In addition, human A-SAA can induce interleukin-1β, interleukin-1 receptor antagonist and soluble type II tumour necrosis factor receptor production by a monocyte cell line. Moreover, A-SAA can stimulate the production of cartilage-degrading proteases by both human and rabbit synoviocytes. The effects of A-SAA on protease production are interesting, because in RA a sustained acute-phase reaction has been strongly associated with progressive joint damage. The known association between the acute-phase response and progressive joint damage may be the direct result of synovial A-SAA-induced effects on cartilage degradation.
In contrast to noninflamed synovium, A-SAA mRNA expression was identified in all RA tissues examined. A-SAA appeared to be produced by synovial tissue synoviocytes, macrophages and endothelial cells. The observation of A-SAA mRNA expression in cultured RA synoviocytes and human RA synovial tissue confirms and extends recently published findings that demonstrated A-SAA mRNA expression in stimulated RA synoviocytes, but not in unstimulated RA synoviocytes.
PMCID: PMC17807  PMID: 11062604
acute-phase response; rheumatoid arthritis; serum amyloid A; synovial tissue
15.  CD4 T cells in the rheumatoid joint are oligoclonally activated and change during the course of disease. 
Annals of the Rheumatic Diseases  1995;54(4):314-317.
OBJECTIVE--To assess the nature of T cell receptor (TCR) utilisation by CD4 T cells in the rheumatoid joint. METHODS--Sequencing of the joining (NDJ) region of TCR beta chain mRNA isolated from synovial fluid CD4 T cells was performed in three patients in order to determine if oligoclonal expansion of particular sequences was present. Two patients were studied longitudinally to determine if these sequences changed over time. RESULTS--A number of dominant clonotypes were found within the TCR transcripts sequenced in each patient. In the two patients who were studied longitudinally, different dominant clonotypes were detected over time. No single clonotype was persistently dominant during the period of study. CONCLUSIONS--The pattern of TCR usage showed multiple oligoclonally expanded CD4 T cells within the rheumatoid joint. The change in clonotypes within the joint over time suggests that different antigens may be able to elicit synovial inflammation during the course of rheumatoid disease.
PMCID: PMC1005581  PMID: 7763112
16.  Immune function in severe, active rheumatoid arthritis. A relationship between peripheral blood mononuclear cell proliferation to soluble antigens and synovial tissue immunohistologic characteristics. 
Journal of Clinical Investigation  1984;74(4):1173-1185.
The immunohistology of synovium from a tender, swollen knee and peripheral blood cellular immune function were correlated in 24 clinically similar patients with active, seropositive rheumatoid arthritis who were not taking cytotoxic or long-acting antirheumatic drugs. The patients were classified as anergic (n = 6) or nonanergic (n = 18) on the basis of peripheral blood mononuclear cell proliferative responses to a battery of soluble recall antigens. The peripheral blood mononuclear cells of anergic patients failed to respond significantly to any soluble recall antigen, whereas cells from nonanergic patients responded to at least one such antigen. Multiple pieces of synovial tissue were obtained from each patient at arthroscopy. To minimize intrajoint variability, all pieces were analyzed and averaged to determine a composite profile of abnormalities. Synovial specimens from all six anergic patients had "high intensity" lymphocytic infiltration (group A). In sharp contrast, synovial specimens from 15 of 18 nonanergic patients had "low intensity" lymphocytic infiltration (group B) (P = 0.002). Group A tissues typically showed higher intensity T cell and plasma cell infiltration, more synovial lining layer hyperplasia, more HLA-DR bearing cells, and a higher ratio of Leu 3A/Leu 2A T cells than did group B. Group B tissues had fewer infiltrating cells (most of which were OKM1 and HLA-DR bearing), more extensive fibrin deposition, and far fewer T and plasma cells. Although these data do not imply that synovium from different joints in an individual patient are immunohistologically identical, they do provide evidence that peripheral blood mononuclear cell immune function reflects immunopathologic events in the biopsied joint. Moreover, the data further support the view that clinically active rheumatoid arthritis is, like certain other chronic inflammatory conditions, a heterogeneous disorder with polar subgroups.
PMCID: PMC425283  PMID: 6384266
17.  Dominant clonotypes in the repertoire of peripheral CD4+ T cells in rheumatoid arthritis. 
Journal of Clinical Investigation  1994;94(5):2068-2076.
Clonal expansion of T cell specificities in the synovial fluid of patients has been taken as evidence for a local stimulation of T cells. By studying the T cell receptor (TCR) repertoire of CD4+ T cells in the synovial and peripheral blood compartments of patients with early rheumatoid arthritis (RA), we have identified clonally expanded CD4+ populations. Expanded clonotypes were present in the peripheral blood and the synovial fluid but were not preferentially accumulated in the joint. Dominant single clonotypes could not be isolated from CD4+ cells of HLA-DRB1*04+ normal individuals. Clonal expansion involved several distinct clonotypes with a preference for V beta 3+, V beta 14+, and V beta 17+CD4+ T cells. A fraction of clonally related T cells expressed IL-2 receptors, indicating recent activation. The frequencies of clonally expanded V beta 17+CD4+ T cells fluctuated widely over a period of one year. Independent variations in the frequencies of two distinct clonotypes in the same patient indicated that different mechanisms, and not stimulation by a single arthritogenic antigen, were involved in clonal proliferation. These data support the concept that RA patients have a grossly imbalanced TCR repertoire. Clonal expansion may result from intrinsic defects in T cell generation and regulation. The dominance of expanded clonotypes in the periphery emphasizes the systemic nature of RA and suggests that T cell proliferation occurs outside of the joint.
PMCID: PMC294644  PMID: 7962553
18.  Cytokine expression in synovial membranes of patients with rheumatoid arthritis and osteoarthritis. 
Annals of the Rheumatic Diseases  1993;52(12):870-875.
OBJECTIVES--To compare, by immunohistochemistry, the cellular and cytokine profile in rheumatoid arthritis (RA) and osteoarthritis (OA) synovial membranes (SMs). Synovium was obtained at knee arthroplasty from 10 patients with RA and 10 with OA. METHODS--Synovial membranes were stained with a panel of monoclonal antibodies (MAb) to assess cytokine expression (IL-1 alpha, IL-1 beta, IL-6, GM-CSF, TNF-alpha and EGF) and the intensity of the mononuclear cellular infiltrate (MNC). RESULTS--Significantly greater percentages of IL-1 alpha, IL-1 beta, IL-6, TNF-alpha, GM-CSF and EGF cells were detected in all areas of the rheumatoid SMs when compared with osteoarthritic SMs. Five RA but only one OA SM demonstrated focal lymphoid aggregates. Lining layer thickening was noted in RA SMs only. The intensity of the MNC and number of blood vessels were greater in the RA group. CONCLUSION--The results suggest that the differences in cytokine production by RA and OA SMs are quantitative but that the greater thickness of the synovial lining layer and higher vascularity may be specific to RA.
PMCID: PMC1005218  PMID: 8311538
19.  Intramuscular gold decreases cytokine expression and macrophage numbers in the rheumatoid synovial membrane. 
Annals of the Rheumatic Diseases  1994;53(5):315-322.
OBJECTIVES--Cytokines, released from mononuclear cells (MNC) are mediators of joint destruction in rheumatoid arthritis (RA). The mechanisms of action of gold salts used in the treatment of RA are unknown. The aim of this study was to investigate cytokine expression and intensity of MNC infiltrate in the RA synovial membrane (SM) following treatment with sodium aurothiomalate (SAT). METHODS--Sequential blind needle biopsies were obtained at entry into the study and at two and 12 weeks after the start of SAT therapy in 10 patients with active RA. SMs were stained with a panel of monoclonal antibodies to assess cytokine expression (IL-1 alpha, IL-1 beta, TNF-alpha, IL-6, and GM-CSF). RESULTS--There was a significant decrease in IL-1 alpha, IL-1 beta, IL-6 and TNF-alpha expression 12 weeks after treatment (p < 0.004, p < 0.002, p < 0.009 and p < 0.004 respectively). This was noted in the lining layer, the perivascular aggregates and the connective tissue areas. Detailed examination of the MNC infiltrate showed a significant reduction in inflammatory monocytes (MONO) in the lining layer at two weeks (p < 0.03). A decrease in the number of CD68+ macrophages (MAC) was noted in the perivascular and connective tissue areas at 12 weeks. No significant changes were observed in the number of T and B cells and blood vessels. CONCLUSION--The results suggest that gold may suppress RA disease activity by diminishing MONO and MAC numbers and consequently monokine production in the SM.
PMCID: PMC1005330  PMID: 8017985
20.  CXCL16-Mediated Cell Recruitment to Rheumatoid Arthritis Synovial Tissue and Murine Lymph Nodes Is Dependent Upon the MAPK Pathway 
Arthritis and rheumatism  2006;54(3):765-778.
Rheumatoid arthritis (RA) is characterized by profound mononuclear cell (MNC) recruitment into synovial tissue (ST), thought to be due in part to tumor necrosis factor α (TNFα), a therapeutic target for RA. Although chemokines may also be involved, the mechanisms remain unclear. We undertook this study to examine the participation of CXCL16, a novel chemokine, in recruitment of MNCs to RA ST in vivo and to determine the signal transduction pathways mediating this process.
Using a human RA ST–SCID mouse chimera, immunohistochemistry, enzyme-linked immunosorbent assay, real-time reverse transcription–polymerase chain reaction, flow cytometry, and in vitro chemotaxis assays, we defined the expression and function of CXCL16 and its receptor, CXCR6, as well as the signal transduction pathways utilized by them for MNC homing in vitro and in vivo.
CXCL16 was markedly elevated in RA synovial fluid (SF) samples, being as high as 145 ng/ml. Intense macrophage and lining cell staining for CXCL16 in RA ST correlated with increased CXCL16 messenger RNA levels in RA ST compared with those in osteoarthritis and normal ST. By fluorescence-activated cell sorting analysis, one-half of RA SF monocytes and one-third of memory lymphocytes expressed CXCR6. In vivo recruitment of human MNCs to RA ST implanted in SCID mice occurred in response to intragraft injection of human CXCL16, a response similar to that induced by TNFα. Lipofection of MNCs with antisense oligodeoxynucleotides for ERK-1/2 resulted in a 50% decline in recruitment to engrafted RA ST and a 5-fold decline in recruitment to regional lymph nodes. Interestingly, RA ST fibroblasts did not produce CXCL16 in response to TNFα in vitro, suggesting that CXCL16 protein may function in large part independently of TNFα.
Taken together, these results point to a unique role for CXCL16 as a premier MNC recruiter in RA and suggest additional therapeutic possibilities, targeting CXCL16, its receptor, or its signaling pathways.
PMCID: PMC1472704  PMID: 16508941
21.  The effects of 1α,25-dihydroxyvitamin D3 on matrix metalloproteinase and prostaglandin E2 production by cells of the rheumatoid lesion 
Arthritis Research  1999;1(1):63-70.
The biologically active metabolite of vitamin D3, 1α,25-dihydroxyvitamin D3 [1α,25(OH)2D3], acts through vitamin D receptors, which were found in rheumatoid tissues in the present study. IL-1β-activated rheumatoid synovial fibroblasts and human articular chondrocytes were shown to respond differently to exposure to 1α,25(OH)2D3, which has different effects on the regulatory pathways of specific matrix metalloproteinases and prostaglandin E2.
1α,25-dihydroxyvitamin D3 [1α,25(OH)2D3], the biologically active metabolite of vitamin D3, acts through an intracellular vitamin D receptor (VDR) and has several immunostimulatory effects. Animal studies have shown that production of some matrix metalloproteinases (MMPs) may be upregulated in rat chondrocytes by administration of 1α,25(OH)2D3; and cell cultures have suggested that 1α,25(OH)2D3 may affect chondrocytic function. Discoordinate regulation by vitamin D of MMP-1 and MMP-9 in human mononuclear phagocytes has also been reported. These data suggest that vitamin D may regulate MMP expression in tissues where VDRs are expressed. Production of 1α,25(OH)2D3 within synovial fluids of arthritic joints has been shown and VDRs have been found in rheumatoid synovial tissues and at sites of cartilage erosion. The physiological function of 1α,25(OH)2D3 at these sites remains obscure. MMPs play a major role in cartilage breakdown in the rheumatoid joint and are produced locally by several cell types under strict control by regulatory factors. As 1α,25(OH)2D3 modulates the production of specific MMPs and is produced within the rheumatoid joint, the present study investigates its effects on MMP and prostaglandin E2 (PGE2) production in two cell types known to express chondrolytic enzymes.
To investigate VDR expression in rheumatoid tissues and to examine the effects of 1α,25-dihydroxyvitamin D3 on cultured rheumatoid synovial fibroblasts (RSFs) and human articular chondrocytes (HACs) with respect to MMP and PGE2 production.
Rheumatoid synovial tissues were obtained from arthroplasty procedures on patients with late-stage rheumatoid arthritis; normal articular cartilage was obtained from lower limb amputations. Samples were embedded in paraffin, and examined for presence of VDRs by immunolocalisation using a biotinylated antibody and alkaline-phosphatase-conjugated avidin-biotin complex system. Cultured synovial fibroblasts and chondrocytes were treated with either 1α,25(OH)2D3, or interleukin (IL)-1β or both. Conditioned medium was assayed for MMP and PGE2 by enzyme-linked immunosorbent assay (ELISA), and the results were normalised relative to control values.
The rheumatoid synovial tissue specimens (n = 18) immunostained for VDRs showed positive staining but at variable distributions and in no observable pattern. VDR-positive cells were also observed in association with some cartilage-pannus junctions (the rheumatoid lesion). MMP production by RSFs in monolayer culture was not affected by treatment with 1α,25(OH)2D3 alone, but when added simultaneously with IL-1β the stimulation by IL-1β was reduced from expected levels by up to 50%. In contrast, 1α,25(OH)2D3 had a slight stimulatory effect on basal production of MMPs 1 and 3 by monolayer cultures of HACs, but stimulation of MMP-1 by IL-1β was not affected by the simultaneous addition of 1α,25(OH)2D3 whilst MMP-3 production was enhanced (Table 1). The production of PGE2 by RSFs was unaffected by 1α,25(OH)2D3 addition, but when added concomitantly with IL-1β the expected IL-1 β-stimulated increase was reduced to almost basal levels. In contrast, IL-1β stimulation of PGE2 in HACs was not affected by the simultaneous addition of 1α,25(OH)2D3 (Table 2). Pretreatment of RSFs with 1α,25(OH)2D3 for 1 h made no significant difference to IL-1β-induced stimulation of PGE2, but incubation for 16 h suppressed the expected increase in PGE2 to control values. This effect was also noted when 1α,25(OH)2D3 was removed after the 16h and the IL-1 added alone. Thus it appears that 1α,25(OH)2D3 does not interfere with the IL-1β receptor, but reduces the capacity of RSFs to elaborate PGE2 after IL-1β induction.
Cells within the rheumatoid lesion which expressed VDR were fibroblasts, macrophages, lymphocytes and endothelial cells. These cells are thought to be involved in the degradative processes associated with rheumatoid arthritis (RA), thus providing evidence of a functional role of 1α,25(OH)2D3 in RA. MMPs may play important roles in the chondrolytic processes of the rheumatoid lesion and are known to be produced by both fibroblasts and chondrocytes. The 1α,25(OH)2D3 had little effect on basal MMP production by RSFs, although more pronounced differences were noted when IL-1β-stimulated cells were treated with 1α,25(OH)2D3, with the RSF and HAC showing quite disparate responses. These opposite effects may be relevant to the processes of joint destruction, especially cartilage loss, as the ability of 1α,25(OH)2D3 to potentiate MMP-1 and MMP-3 expression by 'activated' chondrocytes might facilitate intrinsic cartilage chondrolysis in vivo. By contrast, the MMP-suppressive effects observed for 1α,25(OH)2D3 treatment of 'activated' synovial fibroblasts might reduce extrinsic chondrolysis and also matrix degradation within the synovial tissue. Prostaglandins have a role in the immune response and inflammatory processes associated with RA. The 1α,25(OH)2D3 had little effect on basal PGE2 production by RSF, but the enhanced PGE2 production observed following IL-1β stimulation of these cells was markedly suppressed by the concomitant addition of 1α,25(OH)2D3. As with MMP production, there are disparate effects of 1α,25(OH)2D3 on IL-1β stimulated PGE2 production by the two cell types; 1α,25(OH)2D3 added concomitantly with IL-1β had no effect on PGE2 production by HACs. In summary, the presence of VDRs in the rheumatoid lesion demonstrates that 1α,25(OH)2D3 may have a functional role in the joint disease process. 1α,25(OH)2D3 does not appear to directly affect MMP or PGE2 production but does modulate cytokine-induced production.
Comparative effects of 1 α,25-dihydroxyvitamin D3 (1 α,25D3) on interleukin (IL)-1-stimulated matrix metalloproteinase (MMP)-1 and MMP-3 production by rheumatoid synovial fibroblasts and human articular chondrocytes in vivo
Data given are normalized relative to control values and are expressed ± SEM for three cultures of each cell type.
Comparative effects of 1α,25-dihydroxyvitamin D3 (1α,25D3) on Interleukin (IL)-1-stimulated prostaglandin E2 production by rheumatoid synovial fibroblasts and human articular chondrocyte in vivo
Data given are normalized relative to control values and are expressed ± SEM for three cultures of each cell type.
PMCID: PMC17774  PMID: 11056661
1α,25-dihydroxyvitamin D3; matrix metalloproteinase; prostaglandin E2; rheumatoid arthritis
22.  ARG098, a novel anti-human Fas antibody, suppresses synovial hyperplasia and prevents cartilage destruction in a severe combined immunodeficient-HuRAg mouse model 
The anti-human Fas/APO-1/CD95 (Fas) mouse/human chimeric monoclonal IgM antibody ARG098 (ARG098) targets the human Fas molecule. The cytotoxic effects of ARG098 on cells isolated from RA patients, on normal cells in vitro, and on RA synovial tissue and cartilage in vivo using implanted rheumatoid tissues in an SCID mouse model (SCID-HuRAg) were investigated to examine the potential of ARG098 as a therapy for RA.
ARG098 binding to each cell was analyzed by cytometry. The effects of ARG098 on several cells were assessed by a cell viability assay in vitro. Effects on the RA synovium, lymphocytes, and cartilage were assessed in vivo using the SCID-HuRAg mouse model.
ARG098 bound to cell surface Fas molecules, and induced apoptosis in Fas-expressing RA synoviocytes and infiltrating lymphocytes in the RA synovium in a dose-dependent manner. However, ARG098 did not affect the cell viability of peripheral blood mononuclear cells of RA patients or normal chondrocytes. ARG098 also induced apoptosis in RA synoviocytes and infiltrating lymphocytes in the RA synovium in vivo. The destruction of cartilage due to synovial invasion was inhibited by ARG098 injection in the modified SCID-HuRAg mouse model.
ARG098 treatment suppressed RA synovial hyperplasia through the induction of apoptosis and prevented cartilage destruction in vivo. These results suggest that ARG098 might become a new therapy for RA.
PMCID: PMC3161399  PMID: 20875116
23.  Skewed distribution of proinflammatory CD4+CD28null T cells in rheumatoid arthritis 
Expanded populations of CD4+ T cells lacking the co-stimulatory molecule CD28 (CD4+CD28null T cells) have been reported in several inflammatory disorders. In rheumatoid arthritis, increased frequencies of CD4+CD28null T cells in peripheral blood have previously been associated with extra-articular manifestations and human cytomegalovirus (HCMV) infection, but their presence in and contribution to joint manifestations is not clear. In the present article we investigated the distribution of CD4+CD28null T cells in the synovial membrane, synovial fluid and peripheral blood of RA patients, and analysed the association with erosive disease and anti-citrullinated protein antibodies. CD4+CD28null T cells were infrequent in the synovial membrane and synovial fluid, despite significant frequencies in the circulation. Strikingly, the dominant TCR-Vβ subsets of CD4+CD28null T cells in peripheral blood were often absent in synovial fluid. CD4+CD28null T cells in blood and synovial fluid showed specificity for HCMV antigens, and their presence was clearly associated with HCMV seropositivity but not with anti-citrullinated protein antibodies in the serum or synovial fluid, nor with erosive disease. Together these data imply a primary role for CD4+CD28null T cells in manifestations elsewhere than in the joints of patients with HCMV-seropositive rheumatoid arthritis.
PMCID: PMC2212553  PMID: 17825098
24.  Kinesin-like protein CENP-E is upregulated in rheumatoid synovial fibroblasts 
Arthritis Research  1999;1(1):71-80.
Our aim was to identify specifically expressed genes using RNA arbitrarily primed (RAP)-polymerase chain reaction (PCR) for differential display in patients with rheumatoid arthritis (RA). In RA, amplification of a distinct PCR product suitable for sequencing could be observed. Sequence analysis identified the PCR product as highly homologous to a 434 base pair segment of the human centromere kinesin-like protein CENP-E. Differential expression of CENP-E was confirmed by quantitative reverse transcription PCR, immunohistochemistry and in situ hybridization. CENP-E expression was independent from prednisolone and could not be completely inhibited by serum starvation. RAP-PCR is a suitable method to identify differentially expressed genes in rheumatoid synovial fibroblasts. Also, because motifs of CENP-E show homologies to jun and fos oncogene products and are involved in virus assembly, CENP-E may be involved in the pathophysiology of RA.
Articular destruction by invading synovial fibroblasts is a typical feature in rheumatoid arthritis (RA). Recent data support the hypothesis that key players in this scenario are transformed-appearing synovial fibroblasts at the site of invasion into articular cartilage and bone. They maintain their aggressive phenotype toward cartilage, even when first cultured and thereafter coimplanted together with normal human cartilage into severe combined immunodeficient mice for an extended period of time. However, little is known about the upregulation of genes that leads to this aggressive fibroblast phenotype. To inhibit this progressive growth without interfering with pathways of physiological matrix remodelling, identification of pathways that operate specifically in RA synovial fibroblasts is required. In order to achieve this goal, identification of genes showing upregulation restricted to RA synovial fibroblasts is essential.
To identify specifically expressed genes using RNA arbitrarily primed (RAP)-polymerase chain reaction (PCR) for differential display in patients with RA.
RNA was extracted from cultured synovial fibroblasts from 10 patients with RA, four patients with osteoarthritis (OA), and one patient with psoriatic arthritis. RAP-PCR was performed using different arbitrary primers for first-strand and second-strand synthesis. First-strand and second-strand synthesis were performed using arbitrary primers: US6 (5' -GTGGTGACAG-3') for first strand, and Nuclear 1+ (5' -ACGAAGAAGAG-3'), OPN28 (5' -GCACCAGGGG-3'), Kinase A2+ (5' -GGTGCCTTTGG-3')and OPN24 (5' -AGGGGCACCA-3') for second-strand synthesis. PCR reactions were loaded onto 8 mol/l urea/6% polyacrylamide-sequencing gels and electrophoresed.Gel slices carrying the target fragment were then excised with a razor blade, eluated and reamplified. After verifying their correct size and purity on 4% agarose gels, the reamplified products derived from the single-strand confirmation polymorphism gel were cloned, and five clones per transcript were sequenced. Thereafter, a GenBank® analysis was performed. Quantitative reverse transcription PCR of the segments was performed using the PCR MIMIC® technique.In-situ expression of centromere kinesin-like protein-E (CENP-E) messenger (m)RNA in RA synovium was assessed using digoxigenin-labelled riboprobes, and CENP-E protein expression in fibroblasts and synovium was performed by immunogold-silver immunohistochemistry and cytochemistry. Functional analysis of CENP-E was done using different approaches (eg glucocorticoid stimulation, serum starvation and growth rate analysis of synovial fibroblasts that expressed CENP-E).
In RA, amplification of a distinct PCR product suitable for sequencing could be observed. The indicated complementary DNA fragment of 434 base pairs from RA mRNA corresponded to nucleotides 6615-7048 in the human centromere kinesin-like protein CENP-E mRNA (GenBank® accession No. emb/Z15005).The isolated sequence shared greater than 99% nucleic acid (P = 2.9e-169) identity with the human centromere kinesin-like protein CENP-E. Two base changes at positions 6624 (A to C) and 6739 (A to G) did not result in alteration in the amino acid sequence, and therefore 100% amino acid identity could be confirmed. The amplification of 10 clones of the cloned RAP product revealed the presence of CENP-E mRNA in every fibroblast culture examined, showing from 50% (271.000 ± 54.000 phosphor imager arbitrary units) up to fivefold (961.000 ± 145.000 phosphor imager arbitrary units) upregulation when compared with OA fibroblasts. Neither therapy with disease-modifying antirheumatic drugs such as methotrexate, gold, resochine or cyclosporine A, nor therapy with oral steroids influenced CENP-E expression in the RA fibroblasts. Of the eight RA fibroblast populations from RA patients who were receiving disease-modifying antirheumatic drugs, five showed CENP-E upregulation; and of the eight fibroblast populations from RA patients receiving steroids, four showed CENP-E upregulation.
Numerous synovial cells of the patients with RA showed a positive in situ signal for the isolated CENP-E gene segment, confirming CENP-E mRNA production in rheumatoid synovium, whereas in OA synovial tissue CENP-E mRNA could not be detected. In addition, CENP-E expression was independent from medication. This was further confirmed by analysis of the effect of prednisolone on CENP-E expression, which revealed no alteration in CENP-E mRNA after exposure to different (physiological) concentrations of prednisolone. Serum starvation also could not suppress CENP-E mRNA completely.
Since its introduction in 1992, numerous variants of the differential display method and continuous improvements including RAP-PCR have proved to have both efficiency and reliability in examination of differentially regulated genes. The results of the present study reveal that RAP-PCR is a suitable method to identify differentially expressed genes in rheumatoid synovial fibroblasts.
The mRNA, which has been found to be upregulated in rheumatoid synovial fibroblasts, codes for a kinesin-like motor protein named CENP-E, which was first characterized in 1991. It is a member of a family of centromere-associated proteins, of which six (CENP-A to CENP-F) are currently known. CENP-E itself is a kinetochore motor, which accumulates transiently at kinetochores in the G2 phase of the cell cycle before mitosis takes place, appears to modulate chromosome movement and spindle elongation,and is degraded at the end of mitosis. The presence or upregulation of CENP-E has never been associated with RA.
The three-dimensional structure of CENP-E includes a coiled-coil domain. This has important functions and shows links to known pathways in RA pathophysiology. Coiled-coil domains can also be found in jun and fos oncogene products, which are frequently upregulated in RA synovial fibroblasts. They are also involved in DNA binding and transactivation processes resembling the situation in AP-1 (Jun/Fos)-dependent DNA-binding in rheumatoid synovium. Most interestingly, these coiled-coil motifs are crucial for the assembly of viral proteins, and the upregulation of CENP-E might reflect the influence of infectious agents in RA synovium. We also performed experiments showing that serum starvation decreased, but did not completely inhibit CENP-E mRNA expression. This shows that CENP-E is related to, but does not completely depend on proliferation of these cells. In addition, we determined the growth rate of CENP-E high and low expressors, showing that it was independent from the amount of CENP-E expression. supporting the statement that upregulation of CENP-E reflects an activated RA fibroblast phenotype. In summary, the results of the present study support the hypothesis that CENP-E, presumably independently from medication, may not only be upregulated, but may also be involved in RA pathophysiology.
PMCID: PMC17776  PMID: 11056662
arthritis; centromere; differential display; immunohistochemistry; in situ hybridization; RNA fingerprinting
25.  Elimination of rheumatoid synovium in situ using a Fas ligand 'gene scalpel' 
Arthritis Research & Therapy  2005;7(6):R1235-R1243.
Surgical synovectomy to remove the inflammatory synovium can temporarily ameliorate rheumatoid inflammation and delay the progress of joint destruction. An efficient medically induced programmed cell death (apoptosis) in the rheumatoid synovium might play a role similar to synovectomy but without surgical tissue damage. Gene transfer of Fas ligand (FasL) has increased the frequency of apoptotic cells in mouse and rabbit arthritic synovium. In this study, we investigated whether repeated FasL gene transfer could remove human inflammatory synovial tissue in situ and function as a molecular synovectomy. Briefly, specimens of human synovium from joint replacement surgeries and synovectomies of rheumatoid arthritis (RA) patients were grafted subcutaneously into male C.B-17 severe combined immunodeficiency (SCID) mice. Injections of a recombinant FasL adenovirus (Ad-FasL) into the grafted synovial tissue at the dosage of 1011 particles per mouse were performed every two weeks. Three days after the fifth virus injection, the mice were euthanized by CO2 inhalation and the human synovial tissues were collected, weighed and further examined. Compared to the control adenovirus-LacZ (Ad-LacZ) and phosphate buffered saline (PBS) injected RA synovium, the Ad-FasL injected RA synovium was dramatically reduced in size and weight (P < 0.005). The number of both synoviocytes & mononuclear cells was significantly reduced. Interestingly, an approximate 15-fold increased frequency of apoptotic cells was observed in RA synovium three days after Ad-FasL injection, compared with control tissues. In summary, our in vivo investigation of gene transfer to human synovium in SCID mice suggests that repeated intra-articular gene transfer of an apoptosis inducer, such as FasL, may function as a 'gene scalpel' for molecular synovectomy to arrest inflammatory synovium at an early stage of RA.
PMCID: PMC1297566  PMID: 16277676

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