The gut microbiota promotes distal tissue regeneration via RORy plus regulatory T cell emissaries

Specific microbial signals induce the differentiation of a distinct pool of RORy+ regulatory T (Treg) cells crucial for intestinal homeostasis. We discovered highly analogous populations of microbiota-dependent Treg cells that promoted tissue regeneration at extra-gut sites, notably acutely injured skeletal muscle and fatty liver. Inflammatory meditators elicited by tissue damage combined with MHC-class-II-dependent T cell activation to drive the accumulation of gut-derived RORy+ Treg cells in injured muscle, wherein they regulated the dynamics and tenor of early inflammation and helped balance the proliferation vs. differentia-tion of local stem cells. Reining in IL-17A-producing T cells was a major mechanism underlying the rheostatic functions of RORy+ Treg cells in compromised tissues. Our findings highlight the importance of gut-trained Treg cell emissaries in controlling the response to sterile injury of non-mucosal tissues.