Circulating colon-derived intraepithelial lymphocytes exhibit regulatory function at homeostasis 3675

Abstract Description Colon intraepithelial lymphocytes (cIELs) consist mostly of TCRαβ CD4- CD8α- T cells, followed by TCRαβ CD4+, CD8αβ+, and CD8αα+, and few TCRγδ cells. We previously showed that cIELs constitutively traffic systemically using colonoscopy-guided green-to-red photoconversion of the distal colon of KikGR transgenic mice. In this study, we further examined circulating cIELs and the intestinal signals that influence their function. Single cell ATAC and RNA sequencing of sorted KikGreen+ and KikRed+ splenocytes from colonoscopy-photoconverted KikGR mice identified increased transcription of Cd52 and decreased AP-1 and its family members in gut-derived CD4+ T cells. Flow cytometry of splenocytes confirmed significantly higher gut-derived CD52high and anergic CD73+ FR4+ CD4+ T cells and significantly lower naïve CD62L+ CD44- T cells. These data suggested that gut-derived CD4+ T cells may play a role in peripheral tolerance. We then hypothesized that epithelial antigen presentation to cIELs induced anergy. We generated I-Abfl/fl Villin-Cre mice (MHCIIΔIEC), which lack MHCII expression on intestinal epithelial cells. However, we did not see significant differences in regulatory (Foxp3, CD73 and FR4, CD52) or antigen experience (CD62L, CD44) markers by flow cytometry. Although epithelial MHCII does not influence cIEL function, our data demonstrate a role for cIELs resulting in circulating anergic and CD52high gut-derived CD4+ T cells that enforce tolerance to commensals. Funding Sources Supported by a Pfizer Global Medical Grant, the Shear Family Foundation, and NIH grants F31DK138543, T32AI007405, TL1TR002533 Topic Categories Mucosal and Regional Immunology (MUC)