Complement system is activated in patients with trauma. Although complement activation is presumed to contribute to organ damage and constitutional symptoms, little is known about the involved mechanisms. Because complement components may deposit on red blood cells (RBC), we asked whether complement deposits on the surface of RBC in trauma and whether such deposition alters RBC function.
A prospective experimental study
Blood samples collected from 42 trauma patients and 21 healthy donors
Measurements and Main Results
RBC and sera were collected from trauma patients and control donors. RBC from trauma patients (n=40) were found to display significantly higher amounts of C4d on their surface by flow cytometry compared to normal RBC (n=17) (P<0.01). Increased amounts of iC3b were found in trauma sera (n=27) (vs. 12 controls, P<0.01) by ELISA. Incubation of RBC from universal donors (O,Rh-) with trauma sera (n=10) promoted C4d deposition on their surface (vs. 6 controls, P<0.05). Complement-decorated RBC (n=6) displayed limited their deformability (vs. 6 controls, P<0.05) in 2-dimensional microchannel arrays. Incubation of RBC with trauma sera (n=10) promoted the phosphorylation of band 3, a cytoskeletal protein important for the function of the RBC membrane (vs. 8 controls, P<0.05), and also accelerated calcium influx (n=9) and enhanced nitric oxide production (n=12) (vs. 4 and 8 controls respectively, P<0.05) in flow cytometry.
Our study found the presence of extensive complement activation in trauma patients and presents new evidence in support of the hypothesis that complement activation products deposit on the surface of RBC. Such deposition could limit RBC deformability and promote the production of nitric oxide. Our findings suggest that RBC in trauma patients malfunction, which may explain organ damage and constitutional symptoms that is not accounted for otherwise by previously known pathophysiologic mechanisms.
red blood cell; trauma; C4d; complement; deformability; nitric oxide
Foxp3+ regulatory T cells (Treg) are pivotal for the maintenance of peripheral tolerance and prevent development of autoimmune diseases. We have reported that calcium/calmodulin-dependent protein kinase IV (CaMK4) deficient MRL/lpr mice display less disease activity by promoting IL-2 production and increasing the activity of Treg cells. To further define the mechanism of CaMK4 on Treg cells in systemic lupus erythematosus (SLE), we used the Foxp3-GFP reporter mice and treated them with KN-93, an inhibitor of CaMK4.
We generated MRL/lpr Foxp3-GFP mice to record Treg cells; stimulated naïve CD4+ T cells from MRL/lpr Foxp3-GFP mice under Treg polarizing conditions in the absence or presence of KN-93; evaluated the number of GFP positive cells in lymphoid organs and examined skin and kidney pathology at 16 weeks of age. We also examined the infiltration of cells and recruitment of Treg cells in the kidney.
We show that culture of MRL/lpr Foxp3-GFP T cells in the presence of KN-93 promotes Treg differentiation in a dose-dependent manner. Treatment of MRL/lpr Foxp3-GFP mice with KN-93 results in a significant induction of Treg cells in the spleen, peripheral lymph nodes and peripheral blood and this is accompanied by decreased skin and kidney damage. Notably, KN-93 clearly diminishes the accumulation of inflammatory cells along with reciprocally increased Treg cells in target organ.
Our results indicate that KN-93 treatment enhances the generation of Treg cells in vitro and in vivo highlighting its potential therapeutic use for the treatment of human autoimmune diseases.
Calcium/calmodulin-dependent protein kinase IV; KN-93; organ damage; regulatory T cells; systemic lupus erythematosus
To identify miRNA in human T cells that can explain known anti-inflammatory properties of steroids.
Materials and Methods
Activated human CD4+ T cells from healthy donors were exposed to 1 μM of methylprednisolone in vitro were subjected to miRNA and mRNA microarray analysis and changes in expression profiles were recorded. Using qPCR, flow cytometry, and ELISA we confirmed suppression of predicted targets and through miRNA transfection experiments suggest mechanistic links.
We identified numerous steroid-responsive genes and miRNA — many known and some novel — including multiple previously unknown pro-inflammatory genes suppressed by methylprednisolone. Further studies using qPCR, flow cytometry, and ELISA demonstrated that methylprednisolone increased the expression of miR-98 and suppressed the levels of predicted targets including interleukin-13 and three TNF receptors FAS, FASL, and TNFRSF1B. Forced expression of miR-98 into T cells resulted in suppression of the same targets.
In this communication we demonstrate a link between miR-98 expression and the effects of methylprednisolone and provide evidence, which suggests that methylprednisolone acts through miR-98 to inhibit specific pro-inflammatory targets. Identification of this anti-inflammatory mechanism of glucocorticoids is important as it may pave the way toward the elusive goal of dissociating adverse from therapeutic effects.
T lymphocytes from many patients with systemic lupus erythematosus (SLE) express decreased levels of the T cell receptor (TCR)-associated CD3 zeta (ζ) signaling chain, a feature directly linked to their abnormal phenotype and function. Reduced mRNA expression partly due to defective alternative splicing, contributes to the reduced expression of CD3ζ chain. We previously identified by oligonucleotide pulldown and mass spectrometry approaches, the serine arginine-rich splicing factor 1 (SRSF1) binding to the 3’ untranslated region (UTR) of CD3ζ mRNA. We showed that SRSF1 regulates alternative splicing of the 3’UTR of CD3ζ to promote expression of the normal full length 3`UTR over an unstable splice variant in human T cells. In this study we show that SRSF1 regulates transcriptional activation of CD3ζ. Specifically, overexpression and silencing of SRSF1 respectively increases and decreases CD3ζ total mRNA and protein expression in Jurkat and primary T cells. Using promoter-luciferase assays, we show that SRSF1 enhances transcriptional activity of the CD3ζ promoter in a dose dependent manner. Chromatin immunoprecipitation assays show that SRSF1 is recruited to the CD3ζ promoter. These results indicate that SRSF1 contributes to transcriptional activation of CD3ζ. Thus our study identifies a novel mechanism whereby SRSF1 regulates CD3ζ expression in human T cells and may contribute to the T cell defect in SLE.
The CD28 co-stimulatory pathway is well established for T cell activation. However, there is evidence suggesting the existence of additional co-stimulatory pathways. Here we report that a member of the SLAM superfamily, SLAMF6, or CD352 plays an important role in T cell co-stimulation. Cross-linking of SLAMF6 with anti-CD3 primes human T cell to secrete Th1 cytokines. Among the T cell subsets, CD8+ and CD3+CD4−CD8− cells display the highest Th1 production responses. Engagement of SLAMF6 mobilizes the modulation of the same set of NF-κB-associated genes. Although the expression of SLAMF6 on the surface of T cells from patients with systemic lupus erythematosus (SLE) T cells is comparable to that on the normal T cells, engagement of SLAMF6 results in severely reduced Th1 and IL-2 cytokine production. Our results suggest the existence of an additional co-stimulatory pathway in human T cells, which is defective in SLE T cells.
SLAMF6; co-stimulation; systemic lupus erythematosus; Th1; NF-κB
Tissue inflammation in several autoimmune diseases, including SLE and MS, has been linked to an imbalance of IL-17–producing Th (Th17) cells and Tregs; however, the factors that promote Th17-driven autoimmunity are unclear. Here, we present evidence that the calcium/calmodulin-dependent protein kinase IV (CaMK4) is increased and required during Th17 cell differentiation. Isolation of naive T cells from a murine model of lupus revealed increased levels of CaMK4 following stimulation with Th17-inducing cytokines but not following Treg, Th1, or Th2 induction. Furthermore, naive T cells from mice lacking CaMK4 did not produce IL-17. Genetic or pharmacologic inhibition of CaMK4 decreased the frequency of IL-17–producing T cells and ameliorated EAE and lupus-like disease in murine models. Inhibition of CaMK4 reduced Il17 transcription through decreased activation of the cAMP response element modulator α (CREM-α) and reduced activation of the AKT/mTOR pathway, which is known to enhance Th17 differentiation. Importantly, silencing CaMK4 in T cells from patients with SLE and healthy individuals inhibited Th17 differentiation through reduction of IL17A and IL17F mRNA. Collectively, our results suggest that CaMK4 inhibition has potential as a therapeutic strategy for Th17-driven autoimmune diseases.
CTLA-4 is a negative regulator of the immune response expressed by regulatory T cells and activated T cells. Polymorphisms in the CTLA4 gene have been associated with autoimmune diseases including systemic lupus erythematosus. Disease-associated polymorphisms have been shown to affect the production of the different CTLA-4 variants through an effect on alternative splicing.
We have generated a MRL/lpr mouse strain that transgenically over-expresses a short isoform of CTLA-4 (1/4 CTLA-4) by backcrossing C57BL/6.1/4CTLA4 transgenic mice into the MRL/lpr strain for 9 generations. A new antibody was generated to detect the expression of the 1/4 CTLA-4 isoform. Routine methods were used to evaluate kidney pathology, humoral and cellular immunity.
We show that expression of the 1/4 CTLA-4 isoform accelerates autoimmune disease. Transgenic mice display early onset of mortality, increased renal pathology and higher titers of anti-DNA antibodies, when compared to wild type MRL/lpr mice. Acceleration of autoimmunity and disease pathology by the presence of the short (1/4) isoform of CTLA-4 was linked to increased numbers of activated T cells and B cells and heightened interferon gamma production, but not to altered expression of the full length CTLA-4 molecule or regulatory T cell numbers.
Our results indicate that the presence of the alternatively spliced 1/4 CTLA-4 isoform can further promote autoimmunity and autoimmune pathology in lupus-prone mice and suggest that altered splicing of CTLA4 contributes to the expression of autoimmune disease.
Signaling lymphocyte activation molecule family member 2 (SLAMF2/CD48) is a co-activator and adhesion molecule on cells with hematopoietic origin. It ligates mainly SLAMF4 on effector/memory CD8+ T cells and natural killer cells, suggesting a potential role during viral infection, with SLAMF2 acting as a ligand to activate SLAMF4-bearing cells. The ability of SLAMF2 to signal on its own after it is engaged, and the functional consequences are largely unknown. We found that cytosolic DNA-activated DCs upregulate the expression of SLAMF2 molecules. Using anti-SLAMF2 antibody and SLAMF4 recombinant protein we found that SLAMF2 engagement activates immature DCs, and more interestingly, prolongs the survival of DNA-activated DCs by inhibiting IFNβ production and IFNβ-induced apoptosis, and promotes the production of the granzyme B inhibitor protease inhibitor-9. Thus, SLAMF2 can serve as a survival molecule for DNA-activated DCs during their interaction with SLAMF4-expressing cytotoxic T cells. Based on our results we propose that SLAMF2 engagement regulates adaptive immune responses by providing longer access of putative antigen presenting cells to virus-specific effector T cells by prolonging the time frame of effective stimulation.
dendritic cell; SLAMF2; CD48; SLAMF4; CD244; survival; cytotoxic T lymphocyte
The activity of calcium/calmodulin-dependent protein kinase IV (CaMK4) is increased in T cells from patients with SLE and has been shown to reduce IL-2 production by promoting the effect of the transcriptional repressor cAMP responsive element modulator (CREM)-α on the IL2 promoter. Here we demonstrate that T cells from MRL/lpr mice display increased levels of CaMK4 in the nucleus and that genetic deletion of Camk4 results in improved survival. We demonstrate that absence of CaMK4 restores IL-2 production, curbs increased T cell activation, and augments the number and activity of regulatory T cells. Analogously, silencing of CaMK4 in T cells from patients with SLE increases the expression of FoxP3 upon stimulation in the presence of TGF-β. Our results demonstrate the importance of the serine/threonine kinase CaMK4 in the generation and function of regulatory T cells in patients with SLE and lupus-prone mice and its potential to serve as a therapeutic target.
T cells from patients with systemic lupus erythematosus exhibit a notable array of defects that probably contribute to the origin and development of the disease. Such abnormalities include an abnormal response to stimulation, aberrant expression of molecules that play key roles in intracellular signalling pathways, altered transcription factor activation and binding, and skewed gene expression. The combination of these alterations leads the cell to the expression of a particular phenotype that intense research has gradually uncovered over the last years. The aim of this article is to review the findings that have allowed us to better understand the behaviour of the lupus T cell and highlight the molecules that represent potential therapeutic targets.
Spleen tyrosine kinase (Syk) is involved in membrane-mediated signaling in various cells, including immune cells. It is overexpressed in T cells from patients with systemic lupus erythematosus (SLE), and its inhibition has been shown to improve T cell function as well as to improve disease manifestations in (NZB × NZW)F1 lupus-prone mice and in patients with rheumatoid arthritis. While clinical trials examining Syk inhibition in patients with SLE are being considered, the aim of our experiments was to determine whether the therapeutic effects of Syk inhibition extend to other strains of lupus-prone mice and whether they result in improvement in skin disease and modification of established disease.
Female MRL/lpr or BAK/BAX mice were studied. Starting either at age 4 weeks (before disease) or at age 16 weeks (after established disease) and continuing for up to 16 weeks, mice were fed chow containing the Syk inhibitor R788 or control chow.
We found that inhibition of Syk in MRL/lpr and BAK/BAX mice prevented the development of skin disease and significantly reduced established skin disease. Similarly, Syk inhibition reduced the size of the spleen and lymph nodes, suppressed the development of renal disease, and suppressed established renal disease. Discontinuation of treatment resulted in extended suppression of skin disease for at least 8 weeks and suppression of renal disease for 4 weeks.
Syk inhibition suppresses the development of lupus skin and kidney disease in lupus-prone mice, suppresses established disease in lupus-prone mice, and may represent a valuable treatment for patients with SLE.
Multiple elements are known to participate in ischemia reperfusion (I/R)-mediated tissue injury. Amongst them, B cells have been shown to contribute by the production of antibodies that bind to ischemic cells and fix complement. It is currently unknown whether B cells participate through antibody-independent mechanisms in the pathogenesis of I/R. In a mesenteric I/R model we found that B cells infiltrate the injured intestine of normal and autoimmune mice 2 hours after reperfusion is established. B cell depletion protected mice from the development of I/R-mediated intestinal damage. The protection conferred by B cell depletion was significantly greater in MRL/lpr mice. Finally, we show that ischemic tissue expressed the B cell-attractant CXCL13 and infiltrating B cells expressed the corresponding receptor CXCR5. Our data grants B cells an antibody-independent role in the pathogenesis of intestinal I/R and suggests that B cells accumulate in the injured tissue in response to the chemokine CXCL13.
B cell; CXCL13; inflammation; ischemia/reperfusion
The contribution of individual molecular aberrations to the pathogenesis of systemic lupus erythematosus (SLE), an autoimmune disease that affects multiple organs, is often difficult to evaluate because of the presence of abundant confounding factors. To assess the effect of increased expression of the phosphatase PP2A in T cells, as recorded in SLE patients, we generated a transgenic mouse that overexpresses the PP2Ac subunit in T cells. The transgenic mouse displays a heightened susceptibility to immune-mediated glomerulonephritis in the absence of other immune defects. CD4+ T cells produce increased amounts of IL-17 while the number of neutrophils in the peripheral blood is increased. IL-17 neutralization abrogated the development of glomerulonephritis. We conclude that increased PP2Ac expression participates in SLE pathogenesis by promoting inflammation through unchecked IL-17 production and facilitating the development of end-organ damage.
T cells from patients with systemic lupus erythematosus (SLE) display increased amounts of spleen tyrosine kinase (SYK) which is involved in the aberrant CD3/T cell receptor-mediated signaling process and increased amounts of cAMP response element modulator (CREM) α which suppresses the production of interleukin-2. Because SYK expression can be suppressed by CREM α we asked why CREM α fails to suppress SYK expression in SLE T cells.
Healthy T cells were overexpressed with CREM α expression vector and SYK expression and phosphorylation was measured. A newly identified CRE site on SYK promoter was characterized by ChIP and EMSA. The CREM α-mediated repression of SYK expression was further evaluated by analyzing SYK promoter activity. T cells from SLE patients and healthy individuals were subjected to ChIP to evaluate the CREM α binding and histone-H3 acetylation.
We demonstrate that increased CREM α level can suppress SYK expression by direct binding on a CRE site of the SYK promoter in T cells from healthy individuals but failed to do so in SLE T cells. We demonstrate that failure of CREM α to suppress SYK expression in SLE T cells is due to weaker binding to the CRE site of the SYK promoter compared to healthy T cells because the promoter site is hypoacetylatylated and therefore of limited access to transcription factors.
Epigenetic alteration of the SYK promoter in SLE T cells results in inability of the transcriptional repressor CREM α to bind and suppress the expression of SYK resulting in aberrant T cell signaling.
Altered T cell function in systemic lupus erythematosus (SLE) is determined by various molecular and cellular abnormalities including increased IL-17 production. Recent evidence suggests a crucial role for signaling lymphocyte activation molecules (SLAMs) in the expression of autoimmunity. In this report, we demonstrate that SLAMF3 and SLAMF6 expression is increased on the surface of SLE T cells compared to normal cells. SLAM co-engagement with CD3 under Th17 polarizing conditions results in increased IL-17 production. SLAMF3 and SLAMF6 T cell surface expression and IL-17 levels significantly correlate with disease activity in SLE patients. Both naïve and memory CD4+ T cells produce more IL-17 in response to SLAM co-stimulation as compared to CD28 co-stimulation. In naïve CD4+ cells, IL-17 production after CD28 co-stimulation peaks on day 3, whereas co-stimulation with anti-SLAMF3 and anti-SLAMF6 antibodies results in a prolonged and yet increasing production over 6 days. Unlike co-stimulation with anti-CD28, SLAM co-stimulation requires the presence of the adaptor molecule SLAM-associated protein (SAP). Thus, engagement of SLAMF3 and SLAMF6 along with antigen-mediated CD3/TCR stimulation represents an important source of IL-17 production and disruption of this interaction with decoy receptors or blocking antibodies should mitigate disease expression in SLE and other autoimmune conditions.
Renal involvement in systemic lupus erythematosus (SLE) remains a major cause of morbidity and mortality. Although immune parameters that instigate renal damage have been characterized, their link to local processes, which execute tissue damage, is poorly understood. Using genetic deletion and pharmalogical inhibition approaches we demonstrate that calcium/calmodulin-dependent protein kinase type IV (CaMKIV) which contributes to altered cytokine production in SLE patients controls spontaneous and platelet derived growth factor (PDGF)-stimulated mesangial cell proliferation and promotes IL-6 production through AP-1. Our studies identify CaMKIV as a valuable treatment target for lupus nephritis and point out the importance of local kidney factors in the expression of tissue damage which if properly targeted should enhance clinical benefit and limit toxicity.
autoimmunity; lupus nephritis; systemic lupus erythematosus; mesangial cells; CaMKIV
Systemic lupus erythematosus (SLE) is characterized by multiple cellular abnormalities culminating in the production of autoantibodies and immune complexes, resulting in tissue inflammation and organ damage. Besides active disease, the main cause of morbidity and mortality in SLE patients is infections, including those from opportunistic pathogens. To understand the failure of the immune system to fend off infections in systemic autoimmunity, we infected the lupus-prone murine strains B6.lpr and BXSB with the intracellular parasite Toxoplasma gondii and survival was monitored. Furthermore, mice were sacrificed days post infection and parasite burden and cellular immune responses such as cytokine production and cell activation were assessed. Mice from both strains succumbed to infection acutely and we observed greater susceptibility to infection in older mice. Increased parasite burden and a defective antigen-specific IFN-gamma response were observed in the lupus-prone mice. Furthermore, T cell:dendritic cell co-cultures established the presence of an intrinsic T cell defect responsible for the decreased antigen-specific response. An antigen-specific defect in IFN- gamma production prevents lupus-prone mice from clearing infection effectively. This study reveals the first cellular insight into the origin of increased susceptibility to infections in SLE disease and may guide therapeutic approaches.
Systemic lupus erythematosus (SLE) is an autoimmune disease associated with chronic immune activation and tissue damage. Organ damage in SLE results from the deposition of immune complexes and the infiltration of activated T cells into susceptible organs. Cytokines are intimately involved in every step of the SLE pathogenesis. Defective immune regulation and uncontrolled lymphocyte activation, as well as increased antigen presenting cell maturation are all influenced by cytokines. Moreover, expansion of local immune responses as well as tissue infiltration by pathogenic cells is instigated by cytokines. In this review, we describe the main cytokine abnormalities reported in SLE and discuss the mechanisms that drive their aberrant production as well as the pathogenic pathways that their presence promotes.
Recent studies in cell lines and genetically engineered mice have demonstrated that cytosolic double-stranded (ds) DNA could activate dendritic cells (DCs) to become effector antigen presenting cells. Recognition of DNA might be a major factor in antimicrobial immune responses against cytosolic pathogens and also in human autoimmune diseases such as systemic lupus erythematosus. However, the role of cytosolic dsDNA in human DC activation and its effects on effector T and B cells are still elusive. Here we demonstrate that intracellular dsDNA is a potent activator of human monocyte-derived DCs, as well as primary DCs. Activation by dsDNA depends on NF-κB activation, partially on the adaptor molecule IPS-1 and the novel cytosolic dsDNA receptor IFI16, but not on the previously recognized dsDNA sentinels AIM2, DAI, RNA polymerase III or HMGBs. More importantly, we report for the first time that human dsDNA-activated DCs, rather than LPS- or inflammatory cytokine cocktail-activated DCs, represent the most potent inducers of naïve CD4+ T cells to promote Th1-type cytokine production and to generate CD4+ and CD8+ cytotoxic T cells. dsDNA-, but not LPS- or cocktail-activated DCs induce B cells to produce complement fixing IgG1 and IgG3 antibodies. We propose that cytosolic dsDNA represents a novel, more effective approach to generate DCs to enhance vaccine effectiveness in reprogramming the adaptive immune system to eradicate infectious agents, autoimmunity, allergy and cancer.
The catalytic subunit α isoform of protein phosphatase 2A (PP2Acα) activity, protein, and mRNA have been found increased in systemic lupus erythematosus (SLE) T cells and to contribute to decreased IL-2 production. The PP2Acα promoter activity is controlled epigenetically through the methylation of a CpG within a cAMP response element (CRE) motif defined by its promoter. We considered that hypomethylation may account for the increased expression of PP2Acα in patients with SLE. Using bisulfite sequencing, we found that SLE T cells displayed decreased DNA methylation in the promoter region compared with normal T cells. More importantly, we found that the CRE-defined CpG, which binds p-CREB, is significantly less methylated in SLE compared with normal T cells, and the levels of methylation correlated with decreased amounts of DNA methyltransferase 1 transcripts. Methylation intensity correlated inversely with levels of PP2Acα mRNA and SLE disease activity. Chromatin immunoprecipitation assays revealed more binding of p-CREB to the CRE site in SLE T cells, resulting in increased expression of PP2Acα. We propose that PP2Acα represents a new methylation-sensitive gene that, like the previously reported CD70 and CD11a, contributes to the pathogenesis of SLE.
Systemic lupus erythematousus (SLE) is a chronic inflammatory disease associated with aberrant immune cell function. Treatment involves the use of indiscriminate immunosuppression with significant side effects. SLE T cells express high levels of calcium/calmodulin-dependent protein kinase type IV (CaMKIV) which translocates to the nucleus upon engagement of the T cell receptor (TCR)/CD3 and accounts for abnormal T cell function. We hypothesized that inhibition of CaMKIV should improve disease pathology.
We treated MRL/lpr mice with KN-93, a CaMKIV inhibitor, starting either at week 8 or week 12 of age through week 16 and evaluated skin lesions, proteinuria, kidney histopathology, pro-inflammatory cytokine production and co-stimulatory molecule expression. We also determined the effect of silencing of CaMKIV on IFN-γ expression by human SLE T cells.
We report that CaMKIV inhibition in MRL/lpr mice results in significant suppression of nephritis, skin disease, decreased expression of the co-stimulatory molecules CD86 and CD80 on B cells and suppression of IFN-γ and TNF-α production. In human SLE T cells, silencing of CaMKIV resulted in suppression of IFN-γ production.
We conclude that suppression of CaMKIV mitigates disease development in lupus-prone mice by suppressing cytokine production and co-stimulatory molecule expression. Specific silencing of CaMKIV in human T cells results in similar suppression of IFN-γ production. Our data justify the development of small molecule CaMKIV inhibitors for the treatment of patients with SLE.
Although a population of T cells with CD3ζ chain deficiency has been found in patients with systemic lupus erythematosus, rheumatoid arthritis, cancer, and infectious disease, the role of CD3ζ chain in the disease pathogenesis remains unknown. To understand the contribution of CD3ζ deficiency to the expression of organ injury, we have performed the following studies. We used CD3ζ-deficient mice to investigate the role of CD3ζ in the pathogenesis of organ tissue inflammation. We found that the CD3ζ−/− mice can spontaneously develop significant organ inflammation that can be accelerated following the administration of polyinosinic:polycytidylic acid or allogeneic cells (graft versus host). T cells from CD3ζ−/− mice display increased expression of the adhesion molecules CD44 and CCR2 and produce increased amounts of IFN-γ blockade, which mitigates tissue inflammation. Our results demonstrate that CD3ζ deficiency bestows T cells with the ability to infiltrate various tissues and instigate inflammation. Decreased CD3ζ expression noted in T cells from various diseases contributes independently to tissue inflammation and organ damage. Approaches to restore CD3ζ expression of the surface of T cells should be expected to mitigate tissue inflammation.
Skin disease is the second most common manifestation in patients with systemic lupus erythematosus (SLE). TNF receptor (TNFR) preligand assembly domain (PLAD) has been found to block the effect of TNF-α and TNFR1 PLAD (P60 PLAD) inhibits inflammatory arthritis. We asked whether TNFR PLAD can limit inflammatory skin injury in SLE.
Female MRL/lpr mice received P60 PLAD (100 µg/mouse, i.p.) or P80 PLAD (100 µg/mouse, i.p.) or PBS (100 µl/mouse, i.p.) three times a week starting at age of 6 weeks for 26 weeks.
Immunohistochemistry studies demonstrated that TNFR1 but not TNFR2 is dominantly expressed in skin lesions in MRL/lpr mice. We found that TNFR1 PLAD but not TNFR2 PLAD (P80 PLAD) protein significantly inhibited skin injury in lupus MRL/lpr mice. P60 PLAD significantly inhibited NF-κB, MCP-1 and iNOS expression in skin lesions. P60 PLAD reduced lupus serum-induced monocyte differentiation into dendritic cells. P60 PLAD did not reduce IgG deposition in the skin and improve kidney pathology progression in MRL/lpr mice.
Our results indicate that TNFR1 is involved in the expression of skin injury in lupus MRL/lpr mice and P60 PLAD or similar biologics may be of clinical value if applied locally.