Background/Purpose: Systemic sclerosis (SSc) is an autoimmune connective tissue disease epitomized numerous cellular and humoral immunological abnormalities.   The immune system undoubtedly plays a pivotal role in SSc pathogenesis.  And a growing body of evidence indicates that alterations to epigenetic DNA methylation patterns contribute to many autoimmune diseases including SSc.  CD11a, a subunit of the lymphocyte function-associated antigen 1alpha LFA-1 (CD11a/CD18)with costimulatory functions by adhesive interactions between T cells and other immune system cells including macrophages, dendritic cells and B cells plays a central role in inflammatory and immune responses.  CD11a is overexpressed due to hypomethylation of its regulatory elements in CD4+ T cells from patients with several autoimmune diseases.   However, it is unknown whether aberrant expression and methylation of CD11a occur in T cells from patients with SSc.  We aimed to compare the CD11a expression level and the methylation status of the CD11a promoter and enhancer regions in CD4+ T cells from SSc patients, healthy controls (HC) and CD4+ T cells with DNA methylation inhibitors. 

Methods: CD11a expression in CD4+T cells from patients with SSc and healthy control subjects was measured by flow cytometry and real-time reverse transcription polymerase chain reaction. Related DNA methylation modifier enzymes such as DNA methyltransferases (DNMTs), Methyl DNA binding domain proteins (MBDs) and Ten-eleven translocation proteins(TETs) were measured by RT-PCR.   Bisulfite sequencing was used to determine the methylation status of the CD11a promoter and flanking regions in CD4+ T cells from SSc and HC and in CD4+ T cells with DNA methylation inhibitors.  Detection of CD4+T cell proliferation and autologous B cell IgG antibodies was performed using commercially available kits. Modified Rodnan total skin score(MRTSS) and Valentini Scleroderma Disease Activity Index (SDAI) for Systemic Scleroderma patients were performed

Results: Elevated CD11a expression were observed in CD4+T cells from patients with SSc.  Expression of TET1 was significantly increased but DNMT1, MBD3, and MBD4 were significantly down-regulated in SSc CD4+T cells relative to controls. Expression of DNMT1 mRNA was negatively correlated with transcript level of CD11a.  The methylation levels of the DNA regulatory sequences of CD11a were reduced in patients with SSc compared with HC, and there was a significant inverse correlation between the average methylation level and CD11a mRNA expression in patients with SSc. Treatment with a DNA methylation inhibitor decreased CD11a regulatory sequences methylation contribution to CD11a overexpression and increased B cell costimulation and subsequent immunoglobulin over-production. Further more, transcript level of CD11a was positively correlated with disease activity.

Conclusion: Demethylation of CD11a regulatory elements contributes to CD11a overexpression and results in T cell autoreactivity and B cell immunoglobulin overproduction in CD4+T cells from patients with SSc correlating with disease activity.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/demethylation-of-itgal-cd11a-regulatory-sequences-in-cd4t-lymphocytes-of-systemic-sclerosis/