The neuropeptide Neuromedin U stimulates innate lymphoid cells and promotes type 2 inflammation [ILC2 and ILC3]

The type 2 cytokines interleukin (IL)-4, IL-5, IL-9 and IL-13 play critical roles in stimulating innate and adaptive immune responses required for resistance to helminth infection and promotion of allergic inflammation, metabolic homeostasis and tissue repair. Group 2 innate lymphoid cells (ILC2s) are a potent source of type 2 cytokines and while significant advances have been made in understanding the cytokine milieu that promotes ILC2 responses, there are fundamental gaps in knowledge regarding how ILC2 responses are regulated by other stimuli. In this report, we demonstrate that ILC2s in the gastrointestinal tract co-localize with cholinergic neurons that express the neuropeptide neuromedin U (NMU). In contrast to other hematopoietic cells, ILC2s selectively express the NMU receptor 1 (NMUR1). In vitro stimulation of ILC2s with NMU induced rapid cell activation, proliferation and secretion of type 2 cytokines IL-5, IL-9 and IL-13 that was dependent on cell-intrinsic expression of NMUR1 and Gaq protein. In vivo administration of NMU triggered potent type 2 cytokine responses characterized by ILC2 activation, proliferation and eosinophil recruitment that was associated with accelerated expulsion of the gastrointestinal nematode Nippostrongylus brasiliensis or induction of lung inflammation. Conversely, worm burden was higher in Nmur1-/- mice compared to control mice. Further, use of gene-deficient mice and adoptive cell transfer experiments revealed that ILC2s were necessary and sufficient to mount NMU-elicited type 2 cytokine responses. Together, these data indicate that the NMU-NMUR1 neuronal signaling circuit provides a selective and previously unrecognized mechanism through which the enteric nervous system and innate immune system integrate to promote rapid type 2 cytokine responses that can induce anti-microbial, inflammatory and tissue-protective type 2 responses at mucosal sites.