ABSTRACT
T-helper 2 (Th2) cell responses defend against parasites. Although dendritic cells (DCs) are vital for the induction of T-cell responses, the DC subpopulations that induce Th2 cells in the intestine are unidentified. Here we show that intestinal Th2 responses against Trichuris muris worms and Schistosoma mansoni eggs do not develop in mice with IRF-4-deficient DCs (IRF-4f/f CD11c-cre). Adoptive transfer of conventional DCs, in particular CD11b-expressing DCs from the intestine, is sufficient to prime S. mansoni-specific Th2 responses. Surprisingly, transferred IRF-4-deficient DCs also effectively prime S. mansoni-specific Th2 responses. Egg antigens do not induce the expression of IRF-4-related genes. Instead, IRF-4f/f CD11c-cre mice have fewer CD11b+ migrating DCs and fewer DCs carrying parasite antigens to the lymph nodes. Furthermore, CD11b+CD103+ DCs induce Th2 responses in the small intestine, whereas CD11b+CD103- DCs perform this role in the colon, revealing a specific functional heterogeneity among intestinal DCs in inducing Th2 responses.
Subject(s)
CD11b Antigen/immunology , Colon/immunology , Dendritic Cells/immunology , Intestine, Small/immunology , Schistosomiasis mansoni/immunology , Th2 Cells/immunology , Trichuriasis/immunology , Animals , CD11b Antigen/genetics , Colon/cytology , Humans , Interferon Regulatory Factors/genetics , Interferon Regulatory Factors/immunology , Intestine, Small/cytology , Male , Mice , Mice, Inbred C57BL , Schistosoma mansoni/physiology , Schistosomiasis mansoni/parasitology , Trichuriasis/parasitology , Trichuris/physiologyABSTRACT
The role of dendritic cells (DCs) in intestinal immune homeostasis remains incompletely defined. Here we show that mice lacking IRF8 transcription-factor-dependent DCs had reduced numbers of T cells in the small intestine (SI), but not large intestine (LI), including an almost complete absence of SI CD8αß(+) and CD4(+)CD8αα(+) T cells; the latter requiring ß8 integrin expression by migratory IRF8 dependent CD103(+)CD11b(-) DCs. SI homing receptor induction was impaired during T cell priming in mesenteric lymph nodes (MLN), which correlated with a reduction in aldehyde dehydrogenase activity by SI-derived MLN DCs, and inefficient T cell localization to the SI. These mice also lacked intestinal T helper 1 (Th1) cells, and failed to support Th1 cell differentiation in MLN and mount Th1 cell responses to Trichuris muris infection. Collectively these results highlight multiple non-redundant roles for IRF8 dependent DCs in the maintenance of intestinal T cell homeostasis.