T cells support gut Ag-reactive colitogenic effector T-cell generation by enhancing Ag presentation by CD11b(+) DCs in the mesenteric LN

International audienceT cells expressing the TCR are dominant T-cell subsets in the intestinal immune system. We previously demonstrated that T cells play important roles in augmenting Th17-type colitogenic immune responses in a T-cell-induced colitic inflammation model. However, its underlying mechanism remains poorly understood. In this study, an in vitro coculture system using effector T cells enriched in gut Ag-reactive cells was employed as a readout tool to search for gut Ag presenting APCs. We found that the presence of T cells dramatically enhances gut Ag presentation within the mLN in mice. Gut Ag presentation by CD11b(+) DC subsets was particularly controlled by T cells. Interestingly, T-cell entry to the lymph nodes was essential to improve the Ag presentation. Therefore, our results highlight that T cells play a previously unrecognized role to support colitogenic immunity by regulating gut Ag presentation in the draining LN