MHC class II antigen presentation by intestinal epithelial cells fine-tunes bacteria-reactive CD4 T cell responses

Abstract

AbstractAlthough intestinal epithelial cells (IECs) can express major histocompatibility complex class II (MHC II), especially during intestinal inflammation, it remains unclear if antigen presentation by IECs favours pro- or anti-inflammatory CD4+T cell responses. Using selective gene ablation of MHC II in IECs and IEC organoid cultures, we assessed the impact of MHC II expression by IECs on CD4+T cell responses and disease outcomes in response to enteric bacterial pathogens. We found that intestinal bacterial infections elicit inflammatory cues that greatly increase expression of MHC II processing and presentation molecules in colonic IECs. Whilst IEC MHC II expression had little impact on disease severity followingCitrobacter rodentiumorHelicobacter hepaticusinfection, using a colonic IEC organoid-CD4+T cell co-culture system, we demonstrate that IECs can activate antigen-specific CD4+T cells in an MHC II-dependent manner, modulating both regulatory and effector Th cell subsets. Furthermore, we assessed adoptively transferredH. hepaticus-specific CD4+T cells during intestinal inflammationin vivoand report that IEC MHC II expression dampens pro-inflammatory effector Th cells. Our findings indicate that IECs can function as non-conventional antigen presenting cells and that IEC MHC II expression fine-tunes local effector CD4+T cell responses during intestinal inflammation.