MrgprA3 neurons selectively control myeloid-derived IL-33 for IL-17 dependent cutaneous immunity [ATAC-Seq]

Skin contains poorly understood interdependent cellular networks that facilitate barrier integrity and host immunity, including neurons, and myeloid cells; the latter of which intrinsically express the pleiotropic cytokine IL-33. This work shows selective suppression of IL-33 expression in myeloid cells by activation of itch-sensing neurons bearing the Mas-related G protein receptor A3 (A3). Optogenetic activation of A3 neurons also increased IL-17-expressing γδ T cells, epidermal thickening, and resistance to the human pathogen Schistosoma mansoni, partially through the neuropeptide CGRP. Cell-intrinsic loss of IL-33 in myeloid cells alters chromatin conformation, basally elevates expression and release of IL-17-inducing cytokines (e.g., IL-1β, IL-6), and expands macrophage and cDC2 differentiation, driving both tissue pathology (e.g., epidermal thickening, keratinocyte hyperplasia) and resistance to helminth infection. Our findings suggest a mechanism of cellular cross-talk allowing “itch” neuron activation to alter myeloid composition and cytokine expression patterns for reshaping skin architecture and driving immunity