PerspectiveMicrobiome

Microbiota RORgulates intestinal suppressor T cells

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Science  28 Aug 2015:
Vol. 349, Issue 6251, pp. 929-930
DOI: 10.1126/science.aad0865

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Summary

The immune system in the intestine is highly adapted to resist invading pathogens while residing peacefully with the abundant and diverse commensal bacteria that colonize the gastrointestinal tract. In turn, bacterial signals shape immunity in the intestine, promoting intestinal homeostasis in part by inducing and expanding specialized regulatory T (Treg) cells that prevent aberrant inflammatory responses to self and environmental stimuli (1). On pages 989 and 993 of this issue, Ohnmacht et al. (2) and Sefik et al. (3), respectively, report the development and function of a subpopulation of Treg cells found primarily in the large intestine, and characterized by expression of the nuclear hormone receptor retinoic acid receptor-related orphan receptor γt (RORγt). This is surprising because RORγt classically promotes the differentiation of T helper 17 (TH17) cells, a population associated with tissue inflammation in many inflammatory diseases (4). Both studies show that microbiota-derived signals induce the expression of RORγt in Treg cells that control intestinal inflammation (see the figure). These findings highlight the diversity of colonic Treg cells, their complex transcriptional programs, and their important role in the intestine.