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.

SummaryTrypanosoma brucei is an extracellular parasite that causes sleeping sickness. In mammalian hosts, trypanosomes are thought to exist in two major niches: early in infection, they populate the blood; later, they breach the blood-brain barrier. Working with a well-established mouse model, we discovered that adipose tissue constitutes a third major reservoir for T. brucei. Parasites from adipose tissue, here termed adipose tissue forms (ATFs), can replicate and were capable of infecting a naive animal. ATFs were transcriptionally distinct from bloodstream forms, and the genes upregulated included putative fatty acid β-oxidation enzymes. Consistent with this, ATFs were able to utilize exogenous myristate and form β-oxidation intermediates, suggesting that ATF parasites can use fatty acids as an external carbon source. These findings identify the adipose tissue as a niche for T. brucei during its mammalian life cycle and could potentially explain the weight loss associated with sleeping sickness.

Cancer is as unique as the person fighting it. With the exception of a few biomarker-driven therapies, patients go through rounds of trial-and-error approaches to find the best treatment. Using patient-derived cell lines, we show that zebrafish larvae xenotransplants constitute a fast and highly sensitive in vivo model for differential therapy response, with resolution to reveal intratumor functional cancer heterogeneity. We screened international colorectal cancer therapeutic guidelines and determined distinct functional tumor behaviors (proliferation, metastasis, and angiogenesis) and differential sensitivities to standard therapy. We observed a general higher sensitivity to FOLFIRI [5-fluorouracil(FU)+irinotecan+folinic acid] than to FOLFOX (5-FU+oxaliplatin+folinic acid), not only between isogenic tumors but also within the same tumor. We directly compared zebrafish xenografts with mouse xenografts and show that relative sensitivities obtained in zebrafish are maintained in the rodent model. Our data also illustrate how mutations can provide proliferation advantages in relation to KRASWT and how chemotherapy can unbalance this advantage, selecting for a minor clone resistant to chemotherapy. Zebrafish xenografts provide remarkable resolution to measure Cetuximab sensitivity. Finally, we demonstrate the feasibility of using primary patient samples to generate zebrafish patient-derived xenografts (zPDX) and provide proof-of-concept experiments that compare response to chemotherapy and biological therapies between patients and zPDX. Altogether, our results suggest that zebrafish larvae xenografts constitute a promising fast assay for precision medicine, bridging the gap between genotype and phenotype in an in vivo setting.

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.

Hepatocyte cell death, inflammation and oxidative stress constitute key pathogenic mechanisms underlying non-alcoholic fatty liver disease (NAFLD). We aimed to investigate the role of necroptosis in human and experimental NAFLD and its association with tumour necrosis factor α (TNF-α) and oxidative stress. Serum markers of necrosis, liver receptor-interacting protein 3 (RIP3) and phosphorylated mixed lineage kinase domain-like (MLKL) were evaluated in control individuals and patients with NAFLD. C57BL/6 wild-type (WT) or RIP3-deficient (RIP3(-/-)) mice were fed a high-fat choline-deficient (HFCD) or methionine and choline-deficient (MCD) diet, with subsequent histological and biochemical analysis of hepatic damage. In primary murine hepatocytes, necroptosis and oxidative stress were also assessed after necrostatin-1 (Nec-1) treatment or RIP3 silencing. We show that circulating markers of necrosis and TNF-α, as well as liver RIP3 and MLKL phosphorylation were increased in NAFLD. Likewise, RIP3 and MLKL protein levels and TNF-α expression were increased in the liver of HFCD and MCD diet-fed mice. Moreover, RIP3 and MLKL sequestration in the insoluble protein fraction of NASH (non-alcoholic steatohepatitis) mice liver lysates represented an early event during stetatohepatitis progression. Functional studies in primary murine hepatocytes established the association between TNF-α-induced RIP3 expression, activation of necroptosis and oxidative stress. Strikingly, RIP3 deficiency attenuated MCD diet-induced liver injury, steatosis, inflammation, fibrosis and oxidative stress. In conclusion, necroptosis is increased in the liver of NAFLD patients and in experimental models of NASH. Further, TNF-α triggers RIP3-dependent oxidative stress during hepatocyte necroptosis. As such, targeting necroptosis appears to arrest or at least impair NAFLD progression.