Regional localization of intestinal dendritic cell subsets control Th‐17 responses

Mucosal immunity is influenced in large part by the dynamic interplay between various intestinal antigen‐presenting cell subsets and T lymphocytes. Using 10‐color flow cytometry, we have defined the major DC and macrophage subsets in the small and large intestine LP as distinguishable by the reciprocal expression of CD103 and F4/80, respectively, and not exclusively by CD11b or CD11c. Intestinal F4/80 + macrophages expressed IL‐10, TGF‐β, retinoic acid‐generating enzymes and promoted the differentiation of inducible FoxP3 + regulatory T cells. Alternatively, CD11b + , but not CD11b − , CD103 + LP DCs expressed IL‐6 and TGF‐β as well as retinoic acid‐generating enzymes and efficiently induced the differentiation of T H ‐17 cells. These CD103 + LP DC subsets displayed striking region‐specific localization along the intestine with CD11b − CD103 + LP DCs appearing most abundantly in the large intestine while CD11b + CD103 + LP DCs were most prevalent in the upper small intestine. The distribution pattern of CD11b + CD103 + LP DCs in particular correlated with the representation of T H ‐17 cells in the intestine and during intestinal inflammation CD11b + CD103 + LP DCs accumulated in the colonic LP as did T H ‐17 cells. Our results suggest that CD11b + CD103 + LP DCs may be targets for modulating IL‐17 producing T cell responses during intestinal inflammation.