Effects of interleukin-6 signal inhibition on Treg subpopulations and association of Tregs with clinical outcomes in rheumatoid arthritis.

OBJECTIVES: Anti-IL-6 receptor antibodies are clinically efficacious in the management of rheumatoid arthritis (RA) with an associated increase in regulatory T cells (Tregs); however, the role of functional Treg subsets has yet to be clarified. This study aimed to evaluate how functional Treg subsets are altered by IL-6 receptor blockade and to analyze the relationship between these Treg subsets and the clinical outcome of RA. METHODS: We collected frozen peripheral blood mononuclear cells (PBMCs) from 40 patients with RA who started tocilizumab (TCZ) with or without MTX and 11 healthy controls (HCs). We fractionated Tregs with flow cytometry based on markers of phenotype and function and measured the proportions of detailed Treg subsets sequentially from baseline to week 52. RESULTS: The proportions of resting Tregs (rTregs) and rTregs+activated Tregs (aTregs) were significantly lower in RA patients at baseline than in HCs. The proportions of all those CD127low Tregs, rTregs, aTregs, and rTregs+aTregs were significantly increased with TCZ treatment. In patients treated with TCZ without MTX, rTreg were increased. Patients with an increase in the proportion of rTregs at week 12 had significantly less arthritis flares during the observation period. CONCLUSIONS: Blocking IL-6 receptor with TCZ increased the proportion of rTregs, a functional Treg subpopulation. Patients with an early increase in rTregs showed a favorable treatment course, and this increase in rTregs may reflect molecular remission induced by IL-6 signal inhibition.

Clinical and immunological effects of hydroxychloroquine in patients with active rheumatoid arthritis despite antirheumatic treatment.

OBJECTIVE: To investigate the efficacy and safety of hydroxychloroquine (HCQ) in patients with rheumatoid arthritis (RA). METHODS: Patients with active RA, despite conventional synthetic disease-modifying antirheumatic drugs (csDMARDs), were recruited. HCQ was administered for 24 weeks, in addition to prior treatment. The primary endpoint was the proportion of American College of Rheumatology (ACR) 20 achievement at week 24, compared to that of a propensity score matched historical control group. RESULTS: Sixty patients were enrolled and administered HCQ. We also identified 276 patients as candidates for the historical control group. Propensity score matching yielded 46 patients in each group. The proportion of ACR20 achievements at week 24 was significantly higher in the HCQ group than that in the control group (54.4% vs. 28.3%, P = 0.007). The proportion of ACR50 and ACR70 achievement at week 24 were also higher in the HCQ group than those in the control group (ACR50, 30.4% vs. 4.3%, P = 0.006; ACR70, 17.4% vs. 0%, P = 0.005). Neither hydroxychloroquine retinopathy nor any new safety signal was observed during the study. CONCLUSION: The addition of HCQ to csDMARDs was effective, with no new safety signal in patients with RA.

A nationwide questionnaire survey on the prevalence of ankylosing spondylitis and non-radiographic axial spondyloarthritis in Japan.

OBJECTIVE: This nationwide study aimed to reveal the prevalence of ankylosing spondylitis (AS), non-radiographic axial spondyloarthritis (nr-ax SpA), and the positivity rate of human leukocyte antigen (HLA) among such patients in Japan. METHODS: The first survey was conducted in 2221 randomly selected facilities (26.3%) in September 2018, where the patients with AS/nr-ax SpA were taken care of from January to December 2017. We estimated the total number of these patients using response and extraction rates. A second survey was conducted in 117 facilities (49.8%) to assess for HLA-B27 positivity rate and clinical features. RESULTS: The estimated total numbers of the patients with AS and nr-ax SpA were 3200 (95% confidence interval [CI]: 2400-3900) and 800 (530-1100), suggesting that the prevalence values of AS and nr-ax SpA in general population were 2.6/100,000 (0.0026%) and 0.6/100,000 (0.0006%), respectively. Although 55.5% (76/137) of patients with AS were HLA-B27-positive, those whose age of onset was estimated to be over 50 years tended to undergo less HLA-B27 testing. CONCLUSION: This study revealed the lower prevalence of AS/nr-ax SpA in Japan, compared to those in other countries. Further studies are required to reveal the association of HLA-B27 with the clinical features.

Cutting Edge: Nanogel-Based Delivery of an Inhibitor of CaMK4 to CD4+ T Cells Suppresses Experimental Autoimmune Encephalomyelitis and Lupus-like Disease in Mice.

Treatment of autoimmune diseases is still largely based on the use of systemically acting immunosuppressive drugs, which invariably cause severe side effects. Calcium/calmodulin-dependent protein kinase IV is involved in the suppression of IL-2 and the production of IL-17. Its pharmacologic or genetic inhibition limits autoimmune disease in mice. In this study, we demonstrate that KN93, a small-molecule inhibitor of calcium/calmodulin-dependent protein kinase IV, targeted to CD4(+) T cells via a nanolipogel delivery system, markedly reduced experimental autoimmune encephalomyelitis and was 10-fold more potent than the free systemically delivered drug in the lupus mouse models. The targeted delivery of KN93 did not deplete T cells but effectively blocked Th17 cell differentiation and expansion as measured in the spinal cords and kidneys of mice developing experimental autoimmune encephalomyelitis or lupus, respectively. These results highlight the promise of cell-targeted inhibition of molecules involved in the pathogenesis of autoimmunity as a means of advancing the treatment of autoimmune diseases.

Ribophorin II is involved in the tissue factor expression mediated by phosphatidylserine-dependent antiprothrombin antibody on monocytes.

OBJECTIVE: Phosphatidylserine-dependent, also called aPS-PT, recognizes the phosphatidylserine-prothrombin complex, which is associated with APS. We have previously reported that aPS-PT induces tissue factor (TF) expression on monocytes through the p38 mitogen-activated protein kinase pathway. However, the cell surface interaction between prothrombin and aPS-PT, which is involved in the activation of cell-signalling pathways, has remained unknown. The objective of this study was to identify membrane proteins involved in the binding of prothrombin and aPS-PT to monocyte surfaces as well as the induction of TF expression. METHODS: RAW264.7 cells with FLAG-tagged prothrombin were incubated and separated using affinity chromatography with anti-FLAG antibody-conjugated Sepharose beads. Immunopurified proteins were then analysed by an online nano-liquid chromatography-tandem mass spectrometry. The binding between prothrombin and the identified protein, ribophorin II (RPN2), was analysed by ELISA and surface plasmon resonance. To elucidate the role of RPN2 in TF expression, the TF mRNA level in RAW264.7 cells treated with RPN2 small interfering RNA was determined by quantitative real-time PCR (qPCR). RESULTS: RPN2 was identified as a candidate molecule involved in the binding of prothrombin to the cell surface. The binding between prothrombin and RPN2 was confirmed by ELISA and surface plasmon resonance. RAW264.7 cells treated with RPN2 small interfering RNA showed significant reduction of the TF expression mediated by prothrombin and a mouse monoclonal aPS-PT. CONCLUSION: We identified that RPN2 is one of the prothrombin-binding proteins on monocyte surfaces, suggesting that RPN2 is involved in the pathophysiology of thrombosis in patients with APS.

The efficacy of tacrolimus in patients with interstitial lung diseases complicated with polymyositis or dermatomyositis.

OBJECTIVE: Interstitial lung diseases (ILDs) complicated with PM or DM are frequently aggressive and refractory to treatment. Recently some reports have suggested the potential benefit of tacrolimus for severe ILD complicated with PM/DM. However, little evidence has yet shown the efficacy of tacrolimus in these settings. The aim of this study was to evaluate the efficacy of tacrolimus as a treatment for PM-/DM-related ILD. METHODS: This retrospective study comprised 49 previously untreated patients diagnosed as PM-/DM-related ILD admitted to Hokkaido University Hospital from January 2000 to July 2013. These patients were treated with tacrolimus plus conventional therapy or only with conventional therapy (prednisolone, i.v. CYC and/or ciclosporin). The primary endpoint was defined as the time to relapse or death of respiratory cause or a serious adverse event. The secondary endpoint was defined as the time from the initiation of immunosuppressive treatment to relapse or death of respiratory cause. Endpoints were compared by adjusted Cox regression model by using inverse probability of treatment weighting in order to reduce the impact of these selection biases and potential confounding factors. RESULTS: After adjustment, the tacrolimus group (n = 25) had significantly longer event-free survival as compared with the conventional therapy group (n = 24). The weighted hazard ratio (HR) was 0.32 (95% CI 0.14, 0.75, P = 0.008). In addition, the tacrolimus group had significantly longer disease-free survival as compared with the conventional therapy group. The weighted HR was 0.25 (95% CI 0.10, 0.66, P = 0.005). CONCLUSION: The addition of tacrolimus to conventional therapy significantly improved the prognosis of patients with PM-/DM-related ILD.

Comparative analysis of different enzyme immunoassays for assessment of phosphatidylserine-dependent antiprothrombin antibodies.

Phosphatidylserine-dependent antiprothrombin antibodies (aPS/PT) were strongly correlated with the presence of lupus anticoagulant showing a high specificity for the diagnosis of antiphospholipid syndrome. However, the main criticism for the clinical applicability of aPS/PT testing is the lack of reproducibility of the results among laboratories. In this study, we measured IgG and IgM aPS/PT using our original in-house enzyme-linked immunosorbent assays (ELISA) and commercial ELISA kits to assess the assay performance and to evaluate the accuracy of aPS/PT results. The study included 111 plasma samples collected from patients and stored at our laboratory for aPS/PT assessment. Sixty-one samples were tested for IgG aPS/PT using two assays: (1) aPS/PT in-house ELISA and (2) QUANTA Lite™ aPS/PT IgG ELISA kit (INOVA Diagnostics, Inc., USA). Fifty samples were evaluated for IgM aPS/PT using two assays: (1) aPS/PT in-house ELISA and (2) QUANTA Lite™ aPS/PT IgM ELISA kit (INOVA Diagnostics). Ninety-eight percent of samples yielded concordant results for IgG aPS/PT and 82 % for IgM aPS/PT. There was an excellent agreement between the IgG aPS/PT assays (Cohen κ = 0.962) and moderate agreement between the IgM aPS/PT assays (κ = 0.597). Statistically significant correlations in the aPS/PT results were obtained from both IgG and IgM aPS/PT assays (r = 0.749, r = 0.622, p < 0.001, respectively). In conclusion, IgG and IgM detection by ELISA is accurate. The performance of aPS/PT is reliable, and concordant results can be obtained using different ELISA methods.

Efficacy of the antiphospholipid score for the diagnosis of antiphospholipid syndrome and its predictive value for thrombotic events.

OBJECTIVE: To define the antiphospholipid score (aPL-S) by testing multiple antiphospholipid antibodies (aPL) and to evaluate its efficacy for the diagnosis of antiphospholipid syndrome (APS) and predictive value for thrombosis. METHODS: This study comprised 2 independent sets of patients with autoimmune diseases. In the first set of patients (n = 233), the aPL profiles were analyzed. Five clotting assays for testing lupus anticoagulant and 6 enzyme-linked immunosorbent assays (IgG/IgM anticardiolipin antibodies, IgG/IgM anti-ß(2)-glycoprotein I, and IgG/IgM phosphatidylserine-dependent antiprothrombin antibodies) were included. The association of the aPL-S with a history of thrombosis/pregnancy morbidity was assessed. In the second set of patients (n = 411), the predictive value of the aPL-S for thrombosis was evaluated retrospectively. Two hundred ninety-six of these patients were followed up for >2 years. The relationship between the aPL-S and the risk of developing thrombosis was analyzed. RESULTS: In the first set of patients, the aPL-S was higher in those with thrombosis/pregnancy morbidity than in those without manifestations of APS (P < 0.00001). For the aPL-S, the area under the receiver operating characteristic curve value was 0.752. In the second set of patients, new thromboses developed in 32 patients. The odds ratio (OR) for thrombosis in patients with an aPL-S of ≥30 was 5.27 (95% confidence interval [95% CI] 2.32-11.95, P < 0.0001). By multivariate analysis, an aPL-S of ≥30 appeared to be an independent risk factor for thrombosis (hazard ratio 3.144 [95% CI 1.383-7.150], P = 0.006). CONCLUSION: The aPL-S is a useful quantitative index for diagnosing APS and may be a predictive marker for thrombosis in autoimmune diseases.

Serum cytokines and bone metabolic markers in patients with rheumatoid arthritis treated with biological disease modifying anti-rheumatic drugs.

INTRODUCTION: /objectives Several biological disease-modifying anti-rheumatic drugs (bDMARDs) have been widely used for the management of rheumatoid arthritis (RA). These drugs target different molecules important for the pathophysiology of RA; however, only a few studies have compared the effects of these biological drugs on cytokines and bone metabolic markers. The main aim of this study is to clarify the effects of bDMARDs with different modes of action on the cytokine and bone metabolic marker levels in patients with RA. METHODS: Patients with RA who were initiated on infliximab, tocilizumab, or abatacept as the first bDMARD were prospectively enrolled in this study. Serum cytokine and bone metabolic marker levels were measured longitudinally, and changes in their levels were compared. RESULTS: A total of 174 patients were enrolled in this study, with 55, 70, and 49 patients in the infliximab, tocilizumab, and abatacept groups, respectively. At six months, despite the similar clinical effectiveness of the three drugs, changes in the cytokine and bone metabolic marker levels were distinct; interferon-γ and tumor necrosis factor-α levels were significantly increased with infliximab, interleukin-6 levels were increased with tocilizumab, and interleukin-1ß and interleukin-8 levels were increased with abatacept treatment. Bone-specific alkaline phosphatase and osteocalcin levels increased more significantly with tocilizumab than with infliximab, while osteopontin and osteonectin levels decreased with infliximab treatment. CONCLUSIONS: bDMARDs with different modes of action exert different effects on the cytokine and bone metabolic marker levels in patients with RA.

Clinical features of reversible posterior leukoencephalopathy syndrome in patients with systemic lupus erythematosus.

To characterize reversible posterior leukoencephalopathy syndrome (RPLS) in systemic lupus erythematosus (SLE) in terms of treatments for resolution and its clinical course, we reviewed 28 cases of RPLS in SLE including our cases in view of the treatment. Of these, 15 cases improved with blood pressure control and 13 required immunosuppressive therapy for activity of SLE presenting neurological manifestations. Patients without immunosuppressants at onset of RPLS more frequently required immunosuppressive therapy to recover it than those precedingly using these agents [31% (4/13) versus 87% (13/15), p = 0.008, chi-square test]. Brain magnetic resonance imaging (MRI) is important for diagnosis of RPLS-SLE in the patient with SLE who develops neurological disturbance and rapidly increasing blood pressure. When 7-day therapy for hypertension and convulsion does not reverse the manifestations, immunosuppressive treatments would be recommended to reverse RPLS.

Osteitis condensans ilii in a patient with ulcerative colitis: a mimic of ankylosing spondylitis or non-radiographic axial spondyloarthritis.

Osteitis condensans ilii (OCI) is known as one of the sacroiliitis diseases and the symptoms or radiographic findings of OCI sometimes resembled those of ankylosing spondylitis (AS) of non-radiographic axial spondyloarthritis (nr-axSpA). Bone marrow edoema (BME) around sacroiliac (SI) joints on magnetic resonance imaging (MRI) is one of the key findings in the classification criteria of axial SpA, but BME on MRI was also found in patients with OCI. The usage of SI joint MRI is increasing due to the need of accurate or early diagnosis of axial SpA in accordance with development of new biological treatments. Here was the case of a 38-year-old female patient with ulcerative colitis (UC) complicated with OCI, which was a mimic of AS or nr-axSpA. She had a persistent low back pain with BME around SI joints on MRI. She could meet the ASAS criteria of axial SpA and might be diagnosed with inflammatory bowel disease (IBD) related axial SpA. OCI is not a rare disease as a differential diagnosis for axial SpA especially in young women. We report this case with a literature review of OCI and would like the clinicians to be aware of the disease when diagnosing AS or nr-axSpA with chronic low back pain.

A case of dropped head syndrome due to focal myositis that worsened with cellulitis and improved only by treatment of cellulitis.

Dropped head syndrome due to focal myositis is extremely rare. Due to the rarity of the disease, its clinical characteristics and prognosis remain unknown. We present a unique case of dropped head syndrome due to focal myositis that exacerbated following cellulitis and was dramatically improved along with the improvement of her cellulitis only treated with antibiotics. We should consider the possibility of preceding trigger event such as infection when we face with the exacerbation of focal myositis before making a decision of strengthening immunosuppressive therapy to avoid unnecessary increase of glucocorticoid.

Refractory IgG4-related Pleural Disease with Chylothorax: A Case Report and Literature Review.

We herein report a rare case of a 66-year-old man with refractory chylothorax. Although he had been treated with moderate doses of prednisolone (PSL) on suspicion of pleuritis with Sjögren syndrome, the pleural effusion expanded after the reduction of PSL. Further workup including histopathological examinations of pleura led to the diagnosis of IgG4-RD with bilateral chylothorax without any leakage from the thoracic duct. Combination therapy with high-dose PSL plus rituximab successfully decreased the pleural effusion. This is a very rare case of IgG4-related pleuritis with chylothorax and the first report of its successful treatment with rituximab.

Uveitis developing in tuberculous lymphadenitis-associated Behçet's disease during anti-tuberculosis therapy.

Behçet's disease (BD) is thought to be elicited by triggers such as tuberculosis (TB) infection in individuals with genetically aberrant immune activity, although the exact pathogenesis remains unknown. Seven cases of BD thought to be triggered by TB have been reported to date. In all cases, Behçet's symptoms improved smoothly after starting TB treatment. We present the first report of uveitis developing two months after starting TB treatment in a 46-year-old woman with tuberculous lymphadenitis presenting with oral and genital ulcers and erythema nodosum-like lesions on diagnosis of TB. The appearance of uveitis was attributed to a paradoxical reaction in TB because of simultaneous relapse of lymphadenopathy and retinal findings on fluorescein angiography. Although rare, physicians should be aware that ocular involvement can occur during anti-TB therapy, most likely with extrapulmonary TB, because ocular involvement may decrease patient quality of life if visual symptoms become irreversible with delayed diagnosis and treatment.

IgG4-related fibrosing mediastinitis diagnosed with computed tomography-guided percutaneous needle biopsy: Two case reports and a review of the literature.

RATIONALE: Immunoglobulin G4-related disease (IgG4-RD) is a fibroinflammatory disease characterized by elevated serum IgG4 levels with infiltration of IgG4+ plasma cells and severe fibrosis in affected tissues. Recently, idiopathic fibrosing mediastinitis (FM), an extremely rare fibroinflammatory disorder, has been recognized as a form of IgG4-RD. As IgG4-RD can be treated by glucocorticoids, identification of the etiology of FM by surgical biopsy is essential; however, mediastinal biopsy is often difficult. We report 2 cases of IgG4-related FM successfully diagnosed with computed tomography (CT)-guided percutaneous needle biopsy. PATIENT CONCERNS: Case 1 was a 66-year-old woman with elevated serum C-reactive protein without any symptoms and case 2 was 78-year-old woman with abnormal mediastinal contour on chest x-ray. By further work-up, both cases were found to have mediastinitis accompanied by elevated serum IgG4. CT-guided percutaneous needle biopsy revealed massive infiltration of IgG4+plasma cells along with storiform fibrosis. DIAGNOSIS: IgG4-related FM. INTERVENTIONS: Glucocorticoid therapy. OUTCOME: The treatment resulted in significant improvement of the lesions after 3 months. LESSONS: Early recognition and diagnosis of IgG4-related FM is essential because a delay in appropriate treatment initiation leads to progressive fibrosis with irreversible organ damage and poor prognosis. Our cases highlight CT-guided percutaneous needle biopsy as a promising option for histological examination in patients with IgG4-related FM.

Adolescent PR3-ANCA-positive hypertrophic pachymeningitis: A case report and review of the literature.

RATIONALE: Hypertrophic pachymeningitis (HP) is an uncommon, life-threatening disease that is seen in elderly patients with antineutrophil cytoplasmic antibody (ANCA) positivity. Proteinase-3 (PR3)-ANCA-positive HP has not been reported in adolescents. Here, we report the first case of adolescent PR3-ANCA-positive HP successfully treated with immunosuppressive therapy. PATIENT CONCERNS: A 14-year-old female presented with fullness and pain in her right ear unresponsive to antibiotics. Laboratory tests showed an elevated C-reactive protein and PR3-ANCA positivity. Computed tomography and magnetic resonance imaging revealed mastoiditis in the right temporal bone. Surgical biopsy revealed severe fibrosis and prominent inflammatory-cell infiltration. She received prednisolone and methotrexate therapy, and then underwent a right mastoidectomy. Five months later, she developed headache, dysarthria, and multiple cranial nerve palsies. Further imaging revealed enhancement and thickening of the right hemispheric dura. DIAGNOSIS: PR3-ANCA-positive HP. INTERVENTIONS: She was successfully treated with steroid pulse therapy for 3 days, followed by high doses of prednisolone and intravenous cyclophosphamide. OUTCOME: The treatment resulted in significant improvement of her symptoms, laboratory data, and radiologic findings. LESSONS: PR3-ANCA-positive HP can present not only in the elderly, but also in adolescence, and prompt diagnosis and treatment with immunosuppressive therapy is vital.

CaMK4 compromises podocyte function in autoimmune and nonautoimmune kidney disease.

Podocyte malfunction occurs in autoimmune and nonautoimmune kidney disease. Calcium signaling is essential for podocyte injury, but the role of Ca2+/calmodulin-dependent kinase (CaMK) signaling in podocytes has not been fully explored. We report that podocytes from patients with lupus nephritis and focal segmental glomerulosclerosis and lupus-prone and lipopolysaccharide- or adriamycin-treated mice display increased expression of CaMK IV (CaMK4), but not CaMK2. Mechanistically, CaMK4 modulated podocyte motility by altering the expression of the GTPases Rac1 and RhoA and suppressed the expression of nephrin, synaptopodin, and actin fibers in podocytes. In addition, it phosphorylated the scaffold protein 14-3-3ß, which resulted in the release and degradation of synaptopodin. Targeted delivery of a CaMK4 inhibitor to podocytes preserved their ultrastructure, averted immune complex deposition and crescent formation, and suppressed proteinuria in lupus-prone mice and proteinuria in mice exposed to lipopolysaccharide-induced podocyte injury by preserving nephrin/synaptopodin expression. In animals exposed to adriamycin, podocyte-specific delivery of a CaMK4 inhibitor prevented and reversed podocyte injury and renal disease. We conclude that CaMK4 is pivotal in immune and nonimmune podocyte injury and that its targeted cell-specific inhibition preserves podocyte structure and function and should have therapeutic value in lupus nephritis and podocytopathies, including focal segmental glomerulosclerosis.

Calcium/Calmodulin-Dependent Kinase IV Facilitates the Recruitment of Interleukin-17-Producing Cells to Target Organs Through the CCR6/CCL20 Axis in Th17 Cell-Driven Inflammatory Diseases.

OBJECTIVE: The recruitment of interleukin-17 (IL-17)-producing T helper (Th17) cells to inflammatory sites has been implicated in the development of organ damage in inflammatory and autoimmune diseases including systemic lupus erythematosus (SLE). To define the mechanism of calcium/calmodulin-dependent kinase IV (CaMKIV) activation of Th17 cell recruitment to target tissues, we performed anti-glomerular basement membrane antibody-induced glomerulonephritis (AIGN) experiments in mice and studied samples from patients with SLE. METHODS: We induced experimental AIGN in CaMKIV-sufficient or CaMKIV-deficient mice and compared histology, Th17 cell-related chemokine expression, and numbers of IL-17-producing cells in kidneys. We also evaluated the efficacy of the CaMKIV inhibitor KN-93 in AIGN-induced kidney disease. The expression of CCR6 in memory CD4+ T cells before AIGN induction was analyzed by flow cytometry. We investigated the correlation between CCR6 expression in peripheral blood and the severity of glomerulonephritis in patients with SLE. RESULTS: CaMKIV-deficient mice displayed less glomerular injury after induction of AIGN. Kidney infiltration by IL-17-producing CD4+ T cells along with CCR6 and CCL20 expression were significantly decreased in CaMKIV-deficient mice. Similarly, treatment of mice with KN-93 improved clinical and pathologic outcomes. Expression and function of CCR6 in peripheral blood memory CD4+ T cells was decreased in CaMKIV-deficient mice. Expression of CCR6 correlated positively with severity of organ damage in SLE patients. CONCLUSION: CaMKIV inhibition represents a novel therapeutic strategy for treatment of Th17 cell-mediated tissue damage in inflammatory diseases.

ICER is requisite for Th17 differentiation.

Inducible cAMP early repressor (ICER) has been described as a transcriptional repressor isoform of the cAMP response element modulator (CREM). Here we report that ICER is predominantly expressed in Th17 cells through the IL-6-STAT3 pathway and binds to the Il17a promoter, where it facilitates the accumulation of the canonical enhancer RORγt. In vitro differentiation from naive ICER/CREM-deficient CD4+ T cells to Th17 cells is impaired but can be rescued by forced overexpression of ICER. Consistent with a role of Th17 cells in autoimmune and inflammatory diseases, ICER/CREM-deficient B6.lpr mice are protected from developing autoimmunity. Similarly, both anti-glomerular basement membrane-induced glomerulonephritis and experimental encephalomyelitis are attenuated in ICER/CREM-deficient mice compared with their ICER/CREM-sufficient littermates. Importantly, we find ICER overexpressed in CD4+ T cells from patients with systemic lupus erythematosus. Collectively, our findings identify a unique role for ICER, which affects both organ-specific and systemic autoimmunity in a Th17-dependent manner.