TY - JOUR T1 - Type 2 innate immunity regulates hair follicle homeostasis to control <em>Demodex</em> pathosymbionts JF - bioRxiv DO - 10.1101/2021.03.29.437438 SP - 2021.03.29.437438 AU - Roberto R. Ricardo-Gonzalez AU - Maya E. Kotas AU - Iliana Tenvooren AU - Diana M. Marquez AU - Marlys S. Fassett AU - Jinwoo Lee AU - Scott G. Daniel AU - Kyle Bittinger AU - Roberto Efraín Díaz AU - James S. Fraser AU - K. Mark Ansel AU - Matthew H. Spitzer AU - Hong-Erh Liang AU - Richard M. Locksley Y1 - 2021/01/01 UR - http://biorxiv.org/content/early/2021/03/30/2021.03.29.437438.abstract N2 - Allergic skin diseases are common, but basal roles for type 2 immunity in cutaneous homeostasis are incompletely understood. Here, we show that skin group 2 innate lymphoid cells (ILC2s) are the predominant resident cells that secretes IL-13, which attenuates epithelial cell proliferation during anagen throughout the hair follicle (HF), including in HF stem cells. Although HF are normal in the absence of type 2 immunity, colonization with the commensal mite, Demodex musculi, results in epithelial proliferation and aberrant hair follicle morphology accompanied by loss of stable commensalism with massive infestation and expansion of inflammatory ILC2s and other immune cells. Topical anti-parasitic agents, but not broad-spectrum antibiotics, reversed the phenotype. Commensal Demodex colonization of mammalian hair follicles is ubiquitous, including in humans, revealing an unanticipated role for ILC2s and type 2 immunity for skin homeostasis in the normal environment.One Sentence Summary Dynamic regulation of skin physiology by Type 2 innate immunity regulates healthy commensalism by parasitic Demodex mites.Competing Interest StatementThe authors have declared no competing interest. ER -