Glial cell-derived neuroregulators control type 3 innate lymphoid cells and gut defence

Group 3 innate lymphoid cells (ILC3) are major regulators of inflammation and infection at mucosal barriers1. ILC3 development has been considered to be programmed1. Nevertheless, how ILC3 perceive, integrate and respond to local environmental signals remains unclear. Here we show that ILC3 sense their environment and control gut defence as part of a novel glial-ILC3-epithelial cell unit orchestrated by neurotrophic factors. We found that enteric ILC3 express the neuroregulatory receptor RET. ILC3-autonomous Ret ablation led to decreased innate interleukin-22 (IL-22), impaired epithelial reactivity, dysbiosis and increased susceptibility to bowel inflammation and infection. Neurotrophic factors directly controlled innate II22, downstream of p38 MAPK/ERK-AKT cascade and STAT3 activation. Strikingly, ILC3 were adjacent to neurotrophic factor expressing glial cells that exhibited stellate-shaped projections into ILC3 aggregates. Glial cells sensed microenvironmental cues in a MYD88 dependent manner to control neurotrophic factors and innate IL-22. Accordingly, glial-intrinsic Myd88 deletion led to impaired ILC3-derived IL-22 and pronounced propensity to gut inflammation and infection. Our work sheds light into a novel multi-tissue defence unit, revealing glial cells as central hubs of neuron and innate immune regulation via neurotrophic factor signals.