However, with experimentally induced DNA demethylation and in patients with active SLE, CD40L expression is usually elevated in Kir+ T cells32 (physique 5B, E, G) compared with Kir? counterparts (physique 5C, F, G). study was to determine whether these genes are overexpressed on the same or different T cells and whether this subset of CD4+ T cells is also present in patients with lupus and other rheumatic diseases. Methods Multicolour circulation cytometry was used to compare CD11a, CD70, CD40L and KIR expression on CD3+CD4+CD28+ T cells to their expression on experimentally demethylated CD3+CD4+CD28+ T cells and CD3+CD4+CD28+ T cells from patients with active lupus and other autoimmune diseases. Results Experimentally demethylated CD4+ T cells and T cells from patients with active lupus have a CD3+CD4+CD28+CD11ahiCD70+CD40LhiKIR+ subset, and the subset size is usually proportional to lupus flare ML264 severity. A similar subset is found in patients with other rheumatic diseases including rheumatoid arthritis, systemic sclerosis and Sj?gren’s syndrome but not retroperitoneal fibrosis. Conclusions Patients with active autoimmune rheumatic diseases have a previously undescribed CD3+CD4+CD28+CD11ahiCD70+CD40LhiKIR+ T cell subset. This subset may play an important role in flares of lupus and related autoimmune rheumatic diseases, provide a biomarker for disease activity and serve as a novel therapeutic target for the treatment of lupus flares. strong class=”kwd-title” Keywords: Systemic Lupus Erythematosus, T Cells, Kir, Autoimmune Diseases, DNA Methylation Introduction Epigenetically altered CD4+ T cells play a crucial role in human lupus flares. Reports that lupus goes into remission as CD4+ T cell figures decline in patients with AIDS,1 2 and that anti-CD4 antibodies treat lupus in NZB/W and MRL/lpr mice,3 4 show that CD4+ T cells are necessary for lupus disease activity. Our group reported that treating human or mouse CD4+ T cells with the DNA methylation inhibitor 5-azacytidine (5-azaC) alters gene expression and ML264 makes the cells autoreactive,5 and that the epigenetically modified murine T cells are sufficient to cause a lupus-like disease with anti-DNA antibodies and an immune complex glomerulonephritis when injected into syngeneic mice.6 Genes such as the KIR gene family, CD11a, CD70 and CD40L, overexpressed by experimentally demethylated CD4+ T cells are also demethylated and overexpressed by CD4+ T cells from patients with active lupus.7 The number of T cells overexpressing these genes is directly related to lupus disease activity as measured by the systemic lupus erythematosus disease activity index (SLEDAI).7 8 However, whether KIR, CD11a, CD70 and CD40L are aberrantly overexpressed on the same CD4+ T cell, or on different T cells, is unknown. This is important to determine because coexpression on the same cell would lead to the development of new and safer treatments directed at eliminating this pathogenic subset. A growing body of evidence has established that two or more of the related autoimmune rheumatic diseases, including systemic lupus erythematosus (SLE), rheumatoid arthritis (RA), systemic sclerosis (SSc) and Sj?gren’s syndrome can develop both within the same person and within families at higher rates than expected by chance.9C11 Characterisation of commonalities across these autoimmune diseases may yield important insights into their pathogenesis and treatment, and elucidation of the pleiotropic genetic and environmental risk factors for autoimmunity is an active area of investigation.12C14 Thus, to determine whether the epigenetically altered T cell subset is unique to SLE or has broader implications for these related forms of autoimmunity, we extended our studies to include RA, Sj?gren’s syndrome and SSc, as well as retroperitoneal fibrosis (RPF), a fibroinflammatory disease that can exist as an idiopathic process, as part of an IgG4-related (IgG4-RD) inflammatory disease, or in association with underlying disease such as malignancy or connective tissue disease including SLE ML264 and anti-neutrophil cytoplasmic antibody-associated vasculitis.15 16 RPF is not associated with antinuclear antibody production. The present study uses multicolour flow cytometry to determine whether CD11a, CD40L, CD70 and the KIR genes are co-overexpressed on the same or different CD3+CD4+CD28+ T cells using T cells experimentally demethylated with 5-azaC and T cells from patients with active lupus. We also determined whether the size of the epigenetically altered T cell subset is related to lupus disease activity and whether the subset is present in patients with these related autoimmune rheumatic diseases. Methods Subjects Patients with SLE, RA, SSc, Sj?gren’s syndrome and RPF were recruited from the rheumatology and nephrology outpatient clinics at the University of Michigan. Healthy controls, ages 23C64?years, were recruited by advertising. Study subjects’ information is shown in online supplementary table S1. A total of 54 patients, 19 with SLE, 9 with RA, 12 with SSc, 8 with RPF and 6 with Sj?gren’s were recruited. In addition, five healthy control subjects were recruited for the present study. Patients with Sj?gren’s syndrome met criteria for the classification of primary Sj?gren’s syndrome,17 and disease activity was determined using the European League Against Rheumatism (EULAR).The remaining seven patients were still deemed to have idiopathic RPF without IgG4-RD. to their expression on experimentally demethylated CD3+CD4+CD28+ T cells and CD3+CD4+CD28+ T cells from patients with active lupus and other autoimmune diseases. Results Experimentally demethylated CD4+ T cells and T cells from patients with active lupus have a CD3+CD4+CD28+CD11ahiCD70+CD40LhiKIR+ subset, and the subset size is proportional to lupus flare severity. A similar subset is found in patients with other rheumatic diseases including rheumatoid arthritis, systemic sclerosis and Sj?gren’s syndrome but not retroperitoneal fibrosis. Conclusions Patients with active autoimmune rheumatic diseases have a previously undescribed CD3+CD4+CD28+CD11ahiCD70+CD40LhiKIR+ T cell subset. This subset may play an important role in flares of lupus and related autoimmune rheumatic diseases, provide a biomarker for disease activity and serve as a novel therapeutic target for the treatment of lupus flares. strong class=”kwd-title” Keywords: Systemic Lupus Erythematosus, T Cells, Kir, Autoimmune Diseases, DNA Methylation ML264 Introduction Epigenetically altered CD4+ T cells play a crucial role in human lupus flares. Reports that lupus goes into remission as CD4+ T cell numbers decline in patients with AIDS,1 2 and that anti-CD4 antibodies treat lupus in NZB/W and MRL/lpr mice,3 4 indicate that CD4+ T cells are necessary for lupus disease activity. Our group reported that treating human or mouse CD4+ T cells with the DNA methylation inhibitor 5-azacytidine (5-azaC) alters gene expression and makes the cells autoreactive,5 and that the epigenetically modified murine T cells are sufficient to cause a lupus-like disease with anti-DNA antibodies and an immune complex glomerulonephritis when injected into syngeneic mice.6 Genes such as the KIR gene family, CD11a, CD70 and CD40L, overexpressed by experimentally demethylated CD4+ T cells are also demethylated and overexpressed by CD4+ T cells from patients with active lupus.7 The number of T cells overexpressing these genes is directly related to lupus disease activity as measured by the systemic lupus erythematosus disease activity index (SLEDAI).7 8 However, whether KIR, CD11a, CD70 and CD40L are aberrantly overexpressed on the same CD4+ T cell, or on different T cells, is unknown. This is important to determine because coexpression on the same cell would lead to the development of new and safer treatments directed at eliminating this pathogenic subset. A growing body of evidence has established that two or more of the related autoimmune rheumatic diseases, including systemic lupus erythematosus (SLE), rheumatoid arthritis (RA), systemic sclerosis (SSc) and Sj?gren’s syndrome can develop both within the same person and within families at higher rates than expected by chance.9C11 Characterisation of commonalities across these autoimmune diseases may yield important insights into their pathogenesis and treatment, and elucidation of the pleiotropic genetic and environmental risk factors for autoimmunity is an active area of investigation.12C14 Thus, to determine whether the epigenetically altered T cell subset is unique to SLE or has broader implications for these related forms of autoimmunity, we extended our studies to include RA, Sj?gren’s syndrome and SSc, as well as retroperitoneal fibrosis (RPF), a fibroinflammatory disease that can exist as an idiopathic TM4SF20 process, as part of an IgG4-related (IgG4-RD) inflammatory disease, or in association with underlying disease such as malignancy or connective tissue disease including SLE and anti-neutrophil cytoplasmic antibody-associated vasculitis.15 16 RPF is not associated with antinuclear antibody production. The present study uses multicolour flow cytometry to determine whether CD11a, CD40L, CD70 and the KIR genes are co-overexpressed on the same or different CD3+CD4+CD28+ T cells using T cells experimentally demethylated with 5-azaC and T cells from patients with active lupus. We also determined whether the size of the epigenetically altered T cell subset is related to lupus disease activity and whether the subset is present in patients with these related autoimmune rheumatic diseases. Methods Subjects Patients with SLE, RA, SSc, Sj?gren’s syndrome and RPF were recruited from the rheumatology and nephrology outpatient clinics at.