Commensal skin Staphylococci reshape systemic immune environments 4615

Description The mammalian skin, a formidable protective barrier, also supports a diverse microbiota known to promote local antimicrobial responses, wound healing and neuronal regeneration. Seminal studies of gut microbiota-host interactions show how gut commensals can drive functional interorgan crosstalk. But whether skin commensals promote distal immune effects remains unknown. Here, we report that topical colonization with asymptomatic Staphylococci not only promotes dermal Vg6+ gdT17 accumulation, but also a homeostatic systemic response. Skin colonization-induced dermal Vg6+ gdT17 cells form strikingly large motile clusters, suggesting a role in immunosurveillance. This accumulation is IL1R and microbiome-dependent but, contrary to previous reports, IL23R-independent. Despite being the predominant IL17-producers, dermal Vg6+ gdT17 cells do not regulate anti-Staplylococcal skin immunity. Intriguingly, skin colonization promotes homeostatic Vg6+ gdT17 cell accumulation systemically across mucosal and lymphoid organs. Published reports indicate that prenatally seeded Vg6+ gdT cells take on distinct tissue adaptations. We find that, upon skin colonization, these CCR6+ cells can traffic across tissues, suggesting that their functions may not be tissue-restricted. Overall, we report a hitherto unknown role for asymptomatic skin commensals in reshaping systemic immune environments as a potential adaptation to promote metaorganism fitness.