Sexual dimorphism in skin immunity is mediated by an androgen-ILC2-dendritic cell axis.

Males and females exhibit profound differences in immune responses and disease susceptibility. However, the factors responsible for sex differences in tissue immunity remain poorly understood. Here, we uncovered a dominant role for type 2 innate lymphoid cells (ILC2s) in shaping sexual immune dimorphism within the skin. Mechanistically, negative regulation of ILC2s by androgens leads to a reduction in dendritic cell accumulation and activation in males, along with reduced tissue immunity. Collectively, our results reveal a role for the androgen-ILC2-dendritic cell axis in controlling sexual immune dimorphism. Moreover, this work proposes that tissue immune set points are defined by the dual action of sex hormones and the microbiota, with sex hormones controlling the strength of local immunity and microbiota calibrating its tone.

Depleting myeloid-biased haematopoietic stem cells rejuvenates aged immunity.

Ageing of the immune system is characterized by decreased lymphopoiesis and adaptive immunity, and increased inflammation and myeloid pathologies1,2. Age-related changes in populations of self-renewing haematopoietic stem cells (HSCs) are thought to underlie these phenomena3. During youth, HSCs with balanced output of lymphoid and myeloid cells (bal-HSCs) predominate over HSCs with myeloid-biased output (my-HSCs), thereby promoting the lymphopoiesis required for initiating adaptive immune responses, while limiting the production of myeloid cells, which can be pro-inflammatory4. Ageing is associated with increased proportions of my-HSCs, resulting in decreased lymphopoiesis and increased myelopoiesis3,5,6. Transfer of bal-HSCs results in abundant lymphoid and myeloid cells, a stable phenotype that is retained after secondary transfer; my-HSCs also retain their patterns of production after secondary transfer5. The origin and potential interconversion of these two subsets is still unclear. If they are separate subsets postnatally, it might be possible to reverse the ageing phenotype by eliminating my-HSCs in aged mice. Here we demonstrate that antibody-mediated depletion of my-HSCs in aged mice restores characteristic features of a more youthful immune system, including increasing common lymphocyte progenitors, naive T cells and B cells, while decreasing age-related markers of immune decline. Depletion of my-HSCs in aged mice improves primary and secondary adaptive immune responses to viral infection. These findings may have relevance to the understanding and intervention of diseases exacerbated or caused by dominance of the haematopoietic system by my-HSCs.

A type 2 immune circuit in the stomach controls mammalian adaptation to dietary chitin.

Dietary fiber improves metabolic health, but host-encoded mechanisms for digesting fibrous polysaccharides are unclear. In this work, we describe a mammalian adaptation to dietary chitin that is coordinated by gastric innate immune activation and acidic mammalian chitinase (AMCase). Chitin consumption causes gastric distension and cytokine production by stomach tuft cells and group 2 innate lymphoid cells (ILC2s) in mice, which drives the expansion of AMCase-expressing zymogenic chief cells that facilitate chitin digestion. Although chitin influences gut microbial composition, ILC2-mediated tissue adaptation and gastrointestinal responses are preserved in germ-free mice. In the absence of AMCase, sustained chitin intake leads to heightened basal type 2 immunity, reduced adiposity, and resistance to obesity. These data define an endogenous metabolic circuit that enables nutrient extraction from an insoluble dietary constituent by enhancing digestive function.

Inhibition of Piezo1 Ameliorates Intestinal Inflammation and Limits the Activation of Group 3 Innate Lymphoid Cells in Experimental Colitis.

Piezo1, the mechanosensory ion channel, has attracted increasing attention for its essential roles in various inflammatory responses and immune-related diseases. Although most of the key immune cells in inflammatory bowel disease (IBD) have been reported to be regulated by Piezo1, the specific role of Piezo1 in colitis has yet to be intensively studied. The present study investigated the impact of pharmacological inhibition of Piezo1 on dextran sulfate sodium (DSS)-induced colitis and explored the role of Piezo1 in intestinal immune cells in the context of colitis. We observed upregulated expression of Piezo1 in the colon tissue of mice with DSS-induced colitis. Pharmacological inhibition of Piezo1 by GsMTx4 diminished the severity of colitis. Piezo1 inhibition downregulated the expression of pro-inflammatory mediators Il1b, Il6, and Ptgs2 in colonic tissue and suppressed the production of IL-6 from macrophages and dendritic cells without altering the balance of T helper (Th) cells. In particular, Piezo1 did not affect cell viability but regulated cell proliferation and production of IL-17A in group 3 innate lymphoid cells (ILC3s), which is dependent on the PI3K-Akt-mTOR signaling pathway. Our findings uncover Piezo1 as an effective regulator of gut inflammation. Targeting Piezo1 could be a promising strategy to modulate intestinal immunity in IBD.

Distinguishing features of long COVID identified through immune profiling.

Post-acute infection syndromes may develop after acute viral disease1. Infection with SARS-CoV-2 can result in the development of a post-acute infection syndrome known as long COVID. Individuals with long COVID frequently report unremitting fatigue, post-exertional malaise, and a variety of cognitive and autonomic dysfunctions2-4. However, the biological processes that are associated with the development and persistence of these symptoms are unclear. Here 275 individuals with or without long COVID were enrolled in a cross-sectional study that included multidimensional immune phenotyping and unbiased machine learning methods to identify biological features associated with long COVID. Marked differences were noted in circulating myeloid and lymphocyte populations relative to the matched controls, as well as evidence of exaggerated humoral responses directed against SARS-CoV-2 among participants with long COVID. Furthermore, higher antibody responses directed against non-SARS-CoV-2 viral pathogens were observed among individuals with long COVID, particularly Epstein-Barr virus. Levels of soluble immune mediators and hormones varied among groups, with cortisol levels being lower among participants with long COVID. Integration of immune phenotyping data into unbiased machine learning models identified the key features that are most strongly associated with long COVID status. Collectively, these findings may help to guide future studies into the pathobiology of long COVID and help with developing relevant biomarkers.

The gut microbiota reprograms intestinal lipid metabolism through long noncoding RNA Snhg9.

The intestinal microbiota regulates mammalian lipid absorption, metabolism, and storage. We report that the microbiota reprograms intestinal lipid metabolism in mice by repressing the expression of long noncoding RNA (lncRNA) Snhg9 (small nucleolar RNA host gene 9) in small intestinal epithelial cells. Snhg9 suppressed the activity of peroxisome proliferator-activated receptor γ (PPARγ)-a central regulator of lipid metabolism-by dissociating the PPARγ inhibitor sirtuin 1 from cell cycle and apoptosis protein 2 (CCAR2). Forced expression of Snhg9 in the intestinal epithelium of conventional mice impaired lipid absorption, reduced body fat, and protected against diet-induced obesity. The microbiota repressed Snhg9 expression through an immune relay encompassing myeloid cells and group 3 innate lymphoid cells. Our findings thus identify an unanticipated role for a lncRNA in microbial control of host metabolism.

m6A RNA modification regulates innate lymphoid cell responses in a lineage-specific manner.

Innate lymphoid cells (ILCs) can quickly switch from a quiescent state to an active state and rapidly produce effector molecules that provide critical early immune protection. How the post-transcriptional machinery processes different stimuli and initiates robust gene expression in ILCs is poorly understood. Here, we show that deletion of the N6-methyladenosine (m6A) writer protein METTL3 has little impact on ILC homeostasis or cytokine-induced ILC1 or ILC3 responses but significantly diminishes ILC2 proliferation, migration and effector cytokine production and results in impaired antihelminth immunity. m6A RNA modification supports an increase in cell size and transcriptional activity in activated ILC2s but not in ILC1s or ILC3s. Among other transcripts, the gene encoding the transcription factor GATA3 is highly m6A methylated in ILC2s. Targeted m6A demethylation destabilizes nascent Gata3 mRNA and abolishes the upregulation of GATA3 and ILC2 activation. Our study suggests a lineage-specific requirement of m6A for ILC2 responses.

Regulation and function of poised mRNAs in lymphocytes.

Pre-existing but untranslated or 'poised' mRNA exists as a means to rapidly induce the production of specific proteins in response to stimuli and as a safeguard to limit the actions of these proteins. The translation of poised mRNA enables immune cells to express quickly genes that enhance immune responses. The molecular mechanisms that repress the translation of poised mRNA and, upon stimulation, enable translation have yet to be elucidated. They likely reflect intrinsic properties of the mRNAs and their interactions with trans-acting factors that direct poised mRNAs away from or into the ribosome. Here, I discuss mechanisms by which this might be regulated.

Papel de la dinámica mitocondrial en los linfocitos Th17 durante la autoinmunidad / Role of mitochondrial dynamics in Th17 lymphocytes during autoimmunity

Las mitocondrias remodelan sus membranas en respuesta a estímulos fisiológicos y estrés para adaptar su actividad y sustentar la viabilidad celular. La proteína mitocondrial OPA1 (optic atrophy 1), fusiona las membranas internas mitocondriales y regula la morfología de sus crestas, por lo que su actividad controla la respiración mitocondrial. Baixauli y colaboradores han estudiado su papel durante la diferenciación y función de células T, hallando que las células Th17 -que regulan la homeostasis del intestino, pero también participan en el desarrollo de enfermedades autoinmunes- requieren OPA1 en mayor medida que otras subpoblaciones de linfocitos, como las células Th1, Th2 o T reguladoras. Su estudio, publicado en Nature, demuestra que la falta de OPA1 en células Th17 desregula el ciclo de Krebs (o ciclo de los ácidos tricarboxílicos), incrementando la producción de metabolitos como el 2-hidroxiglutarato (2-HG). 2-HG modifica las marcas epigenéticas de distintos genes, entre ellos el de la citoquinaIL-17, inhibiendo su producción en ausencia de OPA1. Este defecto metabólico no reduce la viabilidad celular, pero es relevante para la función de las células Th17 tanto en la lámina propria del intestino, como en su papel patogénico. Así, en el modelo de encefalomielitis autoinmune experimental, los animales deficientes en Opa1 en células IL17, están fuertemente protegidos frente a la respuesta autoinmune contra el sistema nervioso central. El estudio desvela que esta protección está mediada por la enzima LKB1, que se hiperactiva al estar las crestas mitocondriales dañadas e incrementa la incorporación de glutamina y la producción de 2-HG. Así, el silenciamiento de LKB-1, no rescata el defecto mitocondrial, pero si reduce la incorporación de glutamina y la generación de 2-HG, evitando los defectos epigenéticos y restituyendo la producción de IL-17. ... (AU)

CD69 regula la expresión de PD-1 en linfocitos T CD4 / CD69 regulates PD-1 expression on CD4 T lymphocytes

D69 es una molécula inmunorreguladora que es expresada rápidamente por los leucocitos tras su activación, cuyo papel como inmunoregulador negativo, y no pro-inflamatorio, es cada vez más patente por las investigaciones in vivo que se están realizando. En el artículo publicado en Cell Mol Life Sci por María Jiménez como primera autora, se pone de manifiesto la capacidad de CD69 para unir y responder a lipoproteínas de baja densidad(LDL) aisladas y oxidadas in vitro (oxLDL). Esta unión incrementa la expresión de los receptores nucleares anti-inflamatorios NR4A, especialmente de NR4A3, y de PD1, molécula que actúa como freno para la activación de linfocitos T. Para ello, los autores han usado una línea estable de Jurkat que sobre-expresaCD69, linfocitos CD4 primarios, secuenciación masiva de ARNm, así como otras técnicas de biología molecular como el silenciamiento mediante ARN pequeño de interferencia para NR4A3,receptor nuclear que está implicado en la expresión de PD1. La unión de las oxLD La CD69 produjo el incremento de PD1 tanto a nivel de transcripción (ARNm) como de proteína (citometría deflujo). En este contexto, CD69 señaliza a través NFAT, un factor de transcripción dependiente de calcio. Por otra parte, los autores estudiaron biopsias de pacientes intervenidos por aneurisma de la aorta abdominal; en aquellos con inflamación crónica la expresión de PD1, NR4A3y CD69 está incrementada. Además, se observó una correlación positiva entre los niveles de ARNm de CD69 y de PD1 en estos pacientes, delos que más de la mitad presentaban hiperlipidemia. Estos datos apoyan el papel inmunoregulador negativo de CD69 en patologías como la aterosclerosis, y lo sitúan en el centro de rutas de señalización que actúan como freno de respuestas inflamatorias de origen inmunitario. (AU)

Altered Fatty Acid Oxidation in Lymphocyte Populations of Myalgic Encephalomyelitis/Chronic Fatigue Syndrome.

Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS) is a disabling multisystem illness in which individuals are plagued with fatigue, inflammatory symptoms, cognitive dysfunction, and the hallmark symptom, post-exertional malaise. While the cause of this disease remains unknown, there is evidence of a potential infectious component that, along with patient symptoms and common onsets of the disease, implicates immune system dysfunction. To further our understanding of the state of ME/CFS lymphocytes, we characterized the role of fatty acids in isolated Natural Killer cells, CD4+ T cells, and CD8+ T cells in circulation and after overnight stimulation, through implicit perturbations to fatty acid oxidation. We examined samples obtained from at least 8 and as many as 20 subjects for immune cell fatty acid characterization in a variety of experiments and found that all three isolated cell types increased their utilization of lipids and levels of pertinent proteins involved in this metabolic pathway in ME/CFS samples, particularly during higher energy demands and activation. In T cells, we characterized the cell populations contributing to these metabolic shifts, which included CD4+ memory cells, CD4+ effector cells, CD8+ naïve cells, and CD8+ memory cells. We also discovered that patients with ME/CFS and healthy control samples had significant correlations between measurements of CD4+ T cell fatty acid metabolism and demographic data. These findings provide support for metabolic dysfunction in ME/CFS immune cells. We further hypothesize about the consequences that these altered fuel dependencies may have on T and NK cell effector function, which may shed light on the illness's mechanism of action.

Group 2 Innate Lymphoid Cells Protect Mice from Abdominal Aortic Aneurysm Formation via IL5 and Eosinophils.

Development of abdominal aortic aneurysms (AAA) enhances lesion group-2 innate lymphoid cell (ILC2) accumulation and blood IL5. ILC2 deficiency in Rorafl/fl Il7rCre/+ mice or induced ILC2 depletion in Icosfl-DTR-fl/+ Cd4Cre/+ mice expedites AAA growth, increases lesion inflammation, but leads to systemic IL5 and eosinophil (EOS) deficiency. Mechanistic studies show that ILC2 protect mice from AAA formation via IL5 and EOS. IL5 or ILC2 from wild-type (WT) mice, but not ILC2 from Il5-/- mice induces EOS differentiation in bone-marrow cells from Rorafl/fl Il7rCre/+ mice. IL5, IL13, and EOS or ILC2 from WT mice, but not ILC2 from Il5-/- and Il13-/- mice block SMC apoptosis and promote SMC proliferation. EOS but not ILC2 from WT or Il5-/- mice block endothelial cell (EC) adhesion molecule expression, angiogenesis, dendritic cell differentiation, and Ly6Chi monocyte polarization. Reconstitution of WT EOS and ILC2 but not Il5-/- ILC2 slows AAA growth in Rorafl/fl Il7rCre/+ mice by increasing systemic EOS. Besides regulating SMC pathobiology, ILC2 play an indirect role in AAA protection via the IL5 and EOS mechanism.

Linfoma em cão da raça cane corso: relato de caso / Lymphoma in a cane corso dog: case report / Linfoma en un perro cane corso: relato de un caso

Os linfócitos são células de defesa do organismo que funcionam como barreira contra infecções e células cancerígenas, elas circulam pelo sistema linfático e estão presentes por todo o organismo do animal, podem se proliferar de forma maligna, caracterizando o linfoma. Acometem em sua maioria, cães de raças de grande porte, animais de meia idade e idosos. Sendo uma doença de etiologia desconhecida, vários fatores podem contribuir para sua evolução, como deficiências autoimunes, bem como hábitos alimentares ao longo da vida do animal, ou até por predisposição genética. O presente relato de caso, tem o objetivo de mostrar a evolução gradual da doença, quais sinais clínicos o animal poderá apresentar, e como os exames laboratoriais podem nos auxiliar em seu diagnóstico.(AU)

The lymphocytes are defense cells of the body that act as a barrier against infection and cancer cells, they circulate through the lymphatic system and are present throughout the animal's body, and can proliferate in a malignant way, characterizing the lymphoma. They mostly affect large breed dogs, middle-aged and elderly animals. Being a disease of unknown etiology, several factors may contribute to its evolution, such as autoimmune deficiencies, as well as food habits throughout the animal's life, or even genetic predisposition. The present case report has the objective of showing the gradual evolution of the disease, which clinical signs the animal may present, and how laboratory tests can help us in its diagnosis.(AU)

Los linfocitos son células de defensa del organismo que actúan como barrera contra infecciones y células cancerígenas, circulan por el sistema linfático y están presentes en todo el organismo del animal, pudiendo proliferar de forma maligna, caracterizando el linfoma. Afectan sobre todo a perros de razas grandes, animales de mediana edad y ancianos. Siendo una enfermedad de etiología desconocida, varios factores pueden contribuir a su evolución, como deficiencias autoinmunes, así como hábitos alimentarios a lo largo de la vida del animal, o incluso predisposición genética. El presente caso clínico tiene como objetivo mostrar la evolución gradual de la enfermedad, qué signos clínicos puede presentar el animal y cómo las pruebas de laboratorio pueden ayudarnos en su diagnóstico.(AU)

m6A regulators are differently expressed and correlated with immune response of pancreatic adenocarcinoma.

BACKGROUND: N6 methyladenosine (m6A) RNA methylation regulators play a key role in the occurrence and development of many tumors. However, the function of N6 methyladenosine (m6A) RNA methylation regulators in pancreatic adenocarcinoma (PAAD) has not been fully clarified. METHODS: We used data set from GEPIA 2, UALCAN, TIMER, TISIDB, CBioPortal database to analyze the gene expression of 20 major m6A RNA methylation regulators. RESULTS: Our study revealed that the irregularity of m6A regulators were associated with poor prognosis in PAAD. Meantime, 13 m6A regulators showed high expression in PAAD samples (ALKBH5, ELAVL1, FTO, HNRNPC, IGF2BP2, METTL14, METTL16 (METT10D), RBM15, VIRMA (KIAA1429), YTHDF1, YTHDF2, YTHDF3 and ZC3H13). In these regulators, we evaluated HNRNPC and IGF2BP2 were significantly correlated with worse outcomes and ALKBH5, IGF2BP2, METTL16 (METT10D), RBM15 were significantly correlated with PAAD in advanced stage. Moreover, we showed m6A regulators is correlated with Immuno-regulators' (Immunoinhibitors, Immunostimulators and MHC molecules) expression and levels of immune infiltration in PAAD. Bioinformatics further demonstrate m6A regulators were participated in revising in RNA processing. CONCLUSIONS: Our study investigated that the m6A regulatory factors may serve as a biomarker and a potential target of immunotherapy for PAAD.

ILC1: Development, maturation, and transcriptional regulation.

Type 1 Innate Lymphoid cells (ILC1s) are tissue-resident cells that partake in the regulation of inflammation and homeostasis. A major feature of ILC1s is their ability to rapidly respond after infections. The effector repertoire of ILC1s includes the pro-inflammatory cytokines IFN-γ and TNF-α and cytotoxic mediators such as granzymes, which enable ILC1s to establish immune responses and to directly kill target cells. Recent advances in the characterization of ILC1s have considerably furthered our understanding of ILC1 development and maintenance in tissues. In particular, it has become clear how ILC1s operate independently from conventional natural killer cells, with which they share many characteristics. In this review, we discuss recent developments with regards to the differentiation, polarization, and effector maturation of ILC1s. These processes may underlie the observed heterogeneity in ILC1 populations within and between different tissues. Next, we highlight transcriptional programs that control each of the separate steps in the differentiation of ILC1s. These transcriptional programs are shared with other tissue-resident type-1 lymphocytes, such as tissue-resident memory T cells (TRM ) and invariant natural killer T cells (iNKT), highlighting that ILC1s utilize networks of transcriptional regulation that are conserved between lymphocyte lineages to respond effectively to tissue-invading pathogens.

The Value of Lymphocyte-CRP Ratio Predicting the Prognosis in COVID-19 Patients / El valor de la relación linfocito-PCR para predecir el pronóstico en pacientes con COVID-19

Introduction: Although prevention of the disease and its spread is the primary goal in the fight against the pandemic, studies on the correct management of those who have the disease and the predictability of the prognosis are also important. This study aimed to determine whether lymphocyte-C-reactive protein ratio, together with other inflammation markers, would be useful in predicting intensive care unit admission and mortality in Coronavirus disease 2019 cases.Material and methods: 883 patients were followed in 758 wards and 125 intensive care units. Data of the patients included in the study were compared with those admitted to the service and intensive care unit, and with those who survived and developed mortality.Results: According to the receiver operating characteristic analysis to distinguish the patients followed in the intensive care unit from the patients hospitalized in the ward that was determined that lymphocyte-C-reactive protein ratio, C-reactive protein ratio, CRP-albumin ratio, and neutrophil-lymphocyte ratio were moderate (70%–80%). D-dimer was good (80%–90%) predicting follow-up in intensive care unit. Increase in age, increase in lactate dehydrogenase and interleukin-6 levels, and uptake in tomography were determined as independent risk factors that increase intensive care unit admission. 243 (27.5%) of the patients were mortal. The mean age of the patients with a mortal course was 70±14 years, and mortality increased with increasing age. In the receiver operating characteristic analysis of patients with a mortal course that was determined that lymphocyte-C-reactive protein ratio, neutrophil-lymphocyte ratio, and D-dimer had a good (80–90%) ability to distinguish patients with a mortal course. Age, fever, and increases in lactate dehydrogenase and interleukin-6 levels were determined to be independent risk factors increasing mortality. Conclusions: ... (AU)

Introducción: Si bien la prevención de la enfermedad y su propagación es el objetivo principal en la lucha contra la pandemia, también son importantes los estudios sobre el correcto manejo de los pacientes con la enfermedad y la previsibilidad del pronóstico. El objetivo de este estudio fue determinar si la proporción de linfocitos y proteína C reactiva, junto con otros marcadores inflamatorios, sería útil para predecir el ingreso a la unidad de cuidados intensivos y la mortalidad en casos de enfermedad por coronavirus en 2019.Material y métodos: Se siguieron 883 pacientes en 758 salas y 125 unidades de cuidados intensivos. Los datos de los pacientes incluidos en el estudio se compararon con los ingresados en el servicio y unidad de cuidados intensivos, y con los que sobrevivieron y desarrollaron mortalidad.Resultados: Según el análisis de las características operativas del receptor para distinguir los pacientes seguidos en la unidad de cuidados intensivos de los pacientes hospitalizados en el servicio, se encontró que la relación linfocitos a proteína C reactiva, proteína C reactiva a albúmina y neutrófilos a la proporción de linfocitos fue moderada y el dímero D fue bueno para predecir el seguimiento en la unidad de cuidados intensivos. Se encontró que el aumento de la edad, el aumento de los niveles de lactato deshidrogenasa e interleucina-6 y la captación en la tomografía eran factores de riesgo independientes para el ingreso a la unidad de cuidados intensivos. 243 (27,5%) de los pacientes fallecieron. En el análisis de las características operativas del receptor de pacientes con un desenlace fatal, se encontró que la proporción de linfocitos a proteína C reactiva, la proporción de neutrófilos a linfocitos y el dímero D tenían una buena capacidad para discriminar a los pacientes con un desenlace fatal. ... (AU)

Inulin fibre promotes microbiota-derived bile acids and type 2 inflammation.

Dietary fibres can exert beneficial anti-inflammatory effects through microbially fermented short-chain fatty acid metabolites^1,2, although the immunoregulatory roles of most fibre diets and their microbiota-derived metabolites remain poorly defined. Here, using microbial sequencing and untargeted metabolomics, we show that a diet of inulin fibre alters the composition of the mouse microbiota and the levels of microbiota-derived metabolites, notably bile acids. This metabolomic shift is associated with type 2 inflammation in the intestine and lungs, characterized by IL-33 production, activation of group 2 innate lymphoid cells and eosinophilia. Delivery of cholic acid mimics inulin-induced type 2 inflammation, whereas deletion of the bile acid receptor farnesoid X receptor diminishes the effects of inulin. The effects of inulin are microbiota dependent and were reproduced in mice colonized with human-derived microbiota. Furthermore, genetic deletion of a bile-acid-metabolizing enzyme in one bacterial species abolishes the ability of inulin to trigger type 2 inflammation. Finally, we demonstrate that inulin enhances allergen- and helminth-induced type 2 inflammation. Taken together, these data reveal that dietary inulin fibre triggers microbiota-derived cholic acid and type 2 inflammation at barrier surfaces with implications for understanding the pathophysiology of allergic inflammation, tissue protection and host defence.

Neuropeptide regulation of non-redundant ILC2 responses at barrier surfaces.

Emerging studies indicate that cooperation between neurons and immune cells regulates antimicrobial immunity, inflammation and tissue homeostasis. For example, a neuronal rheostat provides excitatory or inhibitory signals that control the functions of tissue-resident group 2 innate lymphoid cells (ILC2s) at mucosal barrier surfaces1-4. ILC2s express NMUR1, a receptor for neuromedin U (NMU), which is a prominent cholinergic neuropeptide that promotes ILC2 responses5-7. However, many functions of ILC2s are shared with adaptive lymphocytes, including the production of type 2 cytokines8,9 and the release of tissue-protective amphiregulin (AREG)10-12. Consequently, there is controversy regarding whether innate lymphoid cells and adaptive lymphocytes perform redundant or non-redundant functions13-15. Here we generate a new genetic tool to target ILC2s for depletion or gene deletion in the presence of an intact adaptive immune system. Transgenic expression of iCre recombinase under the control of the mouse Nmur1 promoter enabled ILC2-specific deletion of AREG. This revealed that ILC2-derived AREG promotes non-redundant functions in the context of antiparasite immunity and tissue protection following intestinal damage and inflammation. Notably, NMU expression levels increased in inflamed intestinal tissues from both mice and humans, and NMU induced AREG production in mouse and human ILC2s. These results indicate that neuropeptide-mediated regulation of non-redundant functions of ILC2s is an evolutionarily conserved mechanism that integrates immunity and tissue protection.

Non-redundant functions of group 2 innate lymphoid cells.

Protective immunity relies on the interplay of innate and adaptive immune cells with complementary and redundant functions. Innate lymphoid cells (ILCs) have recently emerged as tissue-resident, innate mirror images of the T cell system, with which they share lineage-specifying transcription factors and effector machinery1. Located at barrier surfaces, ILCs are among the first responders against invading pathogens and thus could potentially determine the outcome of the immune response2. However, so far it has not been possible to dissect the unique contributions of ILCs to protective immunity owing to limitations in specific targeting of ILC subsets. Thus, all of the available data have been generated either in mice lacking the adaptive immune system or with tools that also affect other immune cell subsets. In addition, it has been proposed that ILCs might be dispensable for a proper immune response because other immune cells could compensate for their absence3-7. Here we report the generation of a mouse model based on the neuromedin U receptor 1 (Nmur1) promoter as a driver for simultaneous expression of Cre recombinase and green fluorescent protein, which enables gene targeting in group 2 ILCs (ILC2s) without affecting other innate and adaptive immune cells. Using Cre-mediated gene deletion of Id2 and Gata3 in Nmur1-expressing cells, we generated mice with a selective and specific deficiency in ILC2s. ILC2-deficient mice have decreased eosinophil counts at steady state and are unable to recruit eosinophils to the airways in models of allergic asthma. Further, ILC2-deficient mice do not mount an appropriate immune and epithelial type 2 response, resulting in a profound defect in worm expulsion and a non-protective type 3 immune response. In total, our data establish non-redundant functions for ILC2s in the presence of adaptive immune cells at steady state and during disease and argue for a multilayered organization of the immune system on the basis of a spatiotemporal division of labour.

IL-33-ILC2 axis promotes anti-tumor CD8+ T cell responses via OX40 signaling.

Group 2 innate lymphoid cells (ILC2s) are resident cells and participate in innate and adaptive immunity. In the tumor microenvironment (TME), ILC2s contribute to both tumorigenesis and inhibition of tumor growth, but the true role of ILC2s in TME construction remains unclear. We show that IL-33 treatment induces an anti-tumor effect in vivo in a mouse model of melanoma in which ILC2s and CD8+ T cells infiltrate into tumor tissue. This anti-tumor effect is dependent on CD8+ T cells, however, IL-33 does not act directly on CD8+ T cells because the cells lack ST2, the receptor for IL-33. ILC2s and CD8+ T cells in tumors of IL-33-treated mice express OX40 ligand (OX40L) and OX40, respectively, and in vivo blockade of OX40L-OX40 interaction canceled the anti-tumor effect of IL-33. Co-culture of CD8+ T cells expressing OX40 with IL-33-stimulated ILC2 expressing OX40L promoted cell activation and proliferation of CD8+ T cells, which was significantly suppressed by administration of anti-OX40L blocking antibody. Thus, the IL-33-ILC2 axis promotes CD8+ T cell responses via OX40/OX40L interaction and exerts an anti-tumor effect.