Intestinal damage is required for the pro-inflammatory differentiation of commensal CBir1-specific T cells

Abstract

Commensal-specific CD4+ T cells are expanded in inflammatory bowel disease (IBD) patients compared to healthy individuals. How and where commensal-specific CD4+ T cells get activated is yet to be fully understood. We used CBir1 TCR-transgenic CD4+ T cells, specific to a commensal bacterial antigen, and different mouse models of IBD to characterize the dynamics of commensal-specific CD4+ T cells activation. We found that CBir1 T cells proliferate following intestinal damage and cognate antigen presentation is mediated by CD11c+ cells in the colon-draining mesenteric lymph nodes (cMLNs). Using assay for transposase-accessible chromatin sequencing (ATAC-seq) and flow cytometry, we showed that activated CBir1 T cells preferentially acquire an effector rather than regulatory phenotype, which is plastic over time. Moreover, CBir1 T cells, while insufficient to initiate intestinal inflammation, contributed to worse disease outcome in the presence of other CD4+ T cells. Our results suggest that the commensal-specific T cell responses observed in IBD exacerbate rather than initiate disease.