TCR-αβ+ double negative (DN; CD4-CD8-) T cells represent a poorly understood cellular subset suggested to contribute to the pathogenesis of the autoimmune disease systemic lupus erythematosus. DN T cells have been proposed to derive from CD8+ cells. However, the conditions that govern the loss of CD8 expression after antigen encounter are unknown. Here we tracked the fate of CD8 T cells from transgenic TCR mice exposed to their cognate antigens as self or in the context of infection. We demonstrate that CD8 T cells lose CD8 expression and become DN only when cognate antigen is sensed as self. This process is restricted to tissues where the antigen is present. We also show that DN T cells derived from self-reactive CD8 cells express the inhibitory molecules PD-1 and Helios. These molecules identify a subset of DN T cells in normal mice. A similar population expands when CD8 T cells from repertoires enriched in self-reactive cells (Aire-deficient) are transferred into cognate hosts. Collectively, our data suggest that a subset of DN T cells, identified by the expression of PD-1 and Helios, represent self-reactive cells. Our results provide an explanation for the origin of DN T cells and introduce CD8 loss as a process associated to self-antigen encounter.
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
Systemic lupus erythematosus (SLE) is a multisystem autoimmune disease characterized by a loss of tolerance to multiple endogenous antigens. SLE etiology remains largely unknown, despite recent insight into the immunopathogenesis of the disease. T cells are important in the development of the disease by amplifying the immune response and contributing to organ damage. Aberrant signaling, cytokine secretion and tissue homing displayed by SLE T cells have been extensively studied and the underlying pathogenic molecular mechanisms are starting to be elucidated. T-cell targeted treatments are being explored in SLE patients. This review is an update on the T-cell abnormalities and related therapeutic options in SLE.
Systemic lupus erythematosus; T cells; Interleukin-2 (IL-2); epigenetics; treatment
Interleukin-2 (IL-2), a cytokine with pleiotropic effects, is critical for immune cell activation and peripheral tolerance. Although the therapeutic potential of IL-2 has been previously suggested in autoimmune diseases, the mechanisms whereby IL-2 mitigates autoimmunity and prevents organ damage remains unclear. Using an inducible recombinant adeno-associated virus (rAAV) vector we investigated the effect of low systemic levels of IL-2 in lupus-prone MRL/Faslpr/lpr (MRL/lpr) mice. Treatment of mice after the onset of disease with IL-2-rAAV resulted in reduced mononuclear cell infiltration and pathology of various tissues including skin, lungs and kidneys. In parallel, we noted a significant decrease of IL-17-producing CD3+CD4−CD8− double-negative T cells and an increase in CD4+CD25+Foxp3+ immunoregulatory T cells (Treg) in the periphery. We also show that IL-2 can drive DN T cell death through an indirect mechanism. Notably, targeted delivery of IL-2 to CD122+ cytotoxic lymphocytes effectively reduced the number of DN T cells and lymphadenopathy whereas selective expansion of Treg by IL-2 had no effect on DN T cells. Collectively, our data suggest that administration of IL-2 to lupus-prone mice protects against end-organ damage and suppresses inflammation by dually limiting IL-17-producing DN T cells and expanding Treg.
Hypomorphic mutation; Recombination activating gene 2 (RAG2); lupus; receptor editing; autoimmunity; central tolerance
Spleen tyrosine kinase (Syk) is a member of the Src family of non-receptor tyrosine kinases, which associates directly with surface receptors, including B-cell receptor and Fcγ receptor, and is involved in a variety of signal transduction pathways. Rheumatoid arthritis (RA) and systemic lupus erythematosus are autoimmune diseases in which autoantibodies, immune complexes, and autoreactive T cells account for the expression of tissue inflammation and damage. Syk inhibitors efficiently suppress RA in patients albeit in the expression of unwanted side effects, including gastrointestinal effects, hypertension, and neutropenia. Syk inhibitors also inhibit clinical manifestations in lupus-prone mice. Here, we review the evidence that supports the use of Syk inhibitors to treat rheumatic and other autoimmune diseases.
Syk; autoimmune disease; Syk inhibitor; IgG; Fcgamma receptors
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.
T cells regulate the adaptive immune response and have altered function in autoimmunity. Systemic Lupus Erythematosus (SLE) has great diversity of presentation and treatment response. Peripheral blood component gene expression affords an efficient platform to investigate SLE immune dysfunction and help guide diagnostic biomarker development for patient stratification.
Gene expression in peripheral blood T cell samples for 14 SLE patients and 4 controls was analyzed by high depth sequencing. Unbiased clustering of genes and samples revealed novel patterns related to disease etiology. Functional annotation of these genes highlights pathways and protein domains involved in SLE manifestation.
We found transcripts for hundreds of genes consistently altered in SLE T cell samples, for which DAVID analysis highlights induction of pathways related to mitochondria, nucleotide metabolism and DNA replication. Fewer genes had reduced mRNA expression, and these were linked to signaling, splicing and transcriptional activity. Gene signatures associated with the presence of dsDNA antibodies, low complement levels and nephritis were detected. T cell gene expression also indicates the presence of several patient subtypes, such as having only a minimal expression phenotype, male type, or severe with or without induction of genes related to membrane protein production.
Unbiased transcriptome analysis of a peripheral blood component provides insight on autoimmune pathophysiology and patient variability. We present an open source workflow and richly annotated dataset to support investigation of T cell biology, develop biomarkers for patient stratification and perhaps help indicate a source of SLE immune dysfunction.
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
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
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.
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
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.
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.
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
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.
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.
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.
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