Preliminary Evidence for Autoimmune Regulator Occupancy at Promoter Regions of Known Autoantigens in Human Peripheral Lymphocytes Obtained by Chromatin Immunoprecipitation Assay

Central tolerance is provided by the autoimmune regulator (AIRE) expressing medullary thymic epithelial cells through high-avidity recognition of self-antigens. Peripheral mechanisms regulate adaptive immunity by deleting autoreactive T-cells that escape thymic selection, or by inducing their functional unresponsiveness through interaction with antigen-presenting cells, exposing cognate antigens. Multiple types of extrathymic AIRE-expressing cells residing in secondary lymphoid organs have been consistently described. We investigated whether AIRE binds to promoters of known autoantigens in human peripheral blood mononuclear cells by chromatin immunoprecipitation from four healthy donors using an anti-AIRE monoclonal antibody. Quantitative real-time PCR was used to detect AIRE occupancy at promoters of selected autoantigens. Accordingly, we revealed promoter amplicons of all tested autoantigen genes, and their corresponding transcripts. Expression of AIRE was further confirmed at both transcriptional and protein levels. Overall, although the role of AIRE in regulating autoantigen expression in thymic epithelial cells has been well reported, our study provides preliminary descriptive evidence of AIRE occupancy at promoters of known autoantigens in human bulk peripheral blood mononuclear cells, suggesting the presence of AIRE-mediated regulatory events in peripheral blood. Our data provide a rationale for future investigations aimed at elucidating the underlying molecular and immunological mechanisms.