Commensal Microbes and Hair Follicle Morphogenesis Coordinately Drive Treg Migration into Neonatal Skin

The study demonstrated that hair follicle (HF) development played a crucial role in the accumulation of regulatory T cells (Tregs) in neonatal skin, where these cells localized to HFs, which are primary reservoirs for skin commensals. Germ-free neonates exhibited reduced skin Tregs, indicating that commensal microbes enhanced Treg accumulation. The researchers identified Ccl20 as a HF-derived, microbiota-dependent chemokine, with its receptor Ccr6 being preferentially expressed by Tregs in neonatal skin. The Ccl20-Ccr6 pathway was shown to mediate Treg migration both in vitro and in vivo. Thus, HF morphogenesis, commensal microbe colonization, and local chemokine production collectively facilitated the recruitment of Tregs into neonatal skin, establishing a tissue Treg niche early in life.