Gut commensal microbes shape the mucosal immune system by regulating the differentiation and expansion of several types of T cell. Clostridia, a dominant class of commensal microbe, can induce colonic regulatory T (T reg) cells, which have a central role in the suppression of inflammatory and allergic responses. However, the molecular mechanisms by which commensal microbes induce colonic T reg cells have been unclear. Here we show that a large bowel microbial fermentation product, butyrate, induces the differentiation of colonic T reg cells in mice. A comparative NMR-based metabolome analysis suggests that the luminal concentrations of short-chain fatty acids positively correlates with the number of T reg cells in the colon. Among short-chain fatty acids, butyrate induced the differentiation of T reg cells in vitro and in vivo, and ameliorated the development of colitis induced by adoptive transfer of CD4 + CD45RB hi T cells in Rag1 -/- mice. Treatment of naive T cells under the T reg -cell-polarizing conditions with butyrate enhanced histone H3 acetylation in the promoter and conserved non-coding sequence regions of the Foxp3 locus, suggesting a possible mechanism for how microbial-derived butyrate regulates the differentiation of T reg cells. Our findings provide new insight into the mechanisms by which host-microbe interactions establish immunological homeostasis in the gut.
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