Group 2 innate lymphoid cells (ILC2s) regulate inflammation, tissue repair and metabolic homeostasis1. ILC2 activation is driven by host-derived cytokines and alarmins1. While discrete immune cell subsets integrate nervous system cues2–4, it remains unclear whether neuronal-derived signals control ILC2s. Here we show that Neuromedin U (NMU) is a uniquely fast and potent regulator of type 2 innate immunity in the context of a novel neuron-ILC2 unit. We found that ILC2s selectively express Neuromedin U receptor 1 (Nmur1), while mucosal neurons express NMU. ILC2-autonomous activation with NMU resulted in immediate and strong production of innate inflammatory and tissue repair cytokines, in a NMUR1-dependent manner. NMU controlled ILC2s downstream of extracellular signal–regulated kinase (ERK) and calcium (Ca2+)-influx-dependent activation of Calcineurin and nuclear factor of activated T cells (NFAT). NMU treatment in vivo resulted in immediate protective type 2 responses. Accordingly, ILC2-autonomous ablation of Nmur1 led to impaired type 2 responses and poor worm infection control. Strikingly, mucosal neurons were found adjacent to ILC2s, directly sensed worm products and alarmins to induce NMU and to control innate type 2 cytokines. Our work reveals that neuron-ILC2 cell units are poised to confer a first-line of immediate tissue protection via coordinated neuro-immune sensory responses.

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.

SummaryGroup 3 innate lymphoid cells (ILC3s) sense environmental signals and are critical for tissue integrity in the intestine. Yet, which signals are sensed and what receptors control ILC3 function remain poorly understood. Here, we show that ILC3s with a lymphoid-tissue-inducer (LTi) phenotype expressed G-protein-coupled receptor 183 (GPR183) and migrated to its oxysterol ligand 7α,25-hydroxycholesterol (7α,25-OHC). In mice lacking Gpr183 or 7α,25-OHC, ILC3s failed to localize to cryptopatches (CPs) and isolated lymphoid follicles (ILFs). Gpr183 deficiency in ILC3s caused a defect in CP and ILF formation in the colon, but not in the small intestine. Localized oxysterol production by fibroblastic stromal cells provided an essential signal for colonic lymphoid tissue development, and inflammation-induced increased oxysterol production caused colitis through GPR183-mediated cell recruitment. Our findings show that GPR183 promotes lymphoid organ development and indicate that oxysterol-GPR183-dependent positioning within tissues controls ILC3 activity and intestinal homeostasis.

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Because Tissue-Resident Memory T (TRM) cells contribute critically to body-surface immunoprotection and/or immunopathology in multiple settings, their regulation is biologically and clinically important. Interestingly, TRM commonly develop in epithelia part-shaped by innate-like lymphocytes that become tissue-intrinsic during development. Here we show that polyclonal TRM cells induced by allergic contact dermatitis (ACD) interact with signature intraepidermal γδT cells, facilitating a feedback-loop wherein TRM-derived IFNγ upregulates PD-L1 on γδ cells that can thereupon regulate PD1+ TRM. Thus, TRM induced by ACD in mice lacking either local γδ cells, or lacking a single gene (IFNγR) expressed by local γδ cells, displayed enhanced proliferative and effector potentials. Those phenotypes were associated with strikingly limited motility, reduced TRM quality. and an impaired capacity to restrain melanoma. Thus, inter-individual and tissue-specific variation in how tissue-intrinsic lymphocytes integrate with TRM may sit upstream of variation in responses to cancer, allergens and other challenges, and may likewise underpin inflammatory pathologies repeatedly observed in γδ-deficient animals.

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