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Despite recent advances in asthma treatments, the search for novel therapies remains necessary because there are still patients with recurrent asthma exacerbations and poor responses to the existing treatments. Since group 2 innate lymphoid cells (ILC2) play a pivotal role in asthma by triggering and exacerbating type 2 inflammation, controlling ILC2s function is key to combating severe asthma. Mucosal-associated invariant T (MAIT) cells are innate-like T cells abundant in humans and are activated both in a T cell receptor-dependent and -independent manner. MAIT cells are composed of MAIT1 and MAIT17 based on the expression of transcription factors T-bet and RORγt, respectively. MAIT cells play pivotal roles in host defense against pathogens and in tissue repair and are essential for the maintenance of immunity and hemostasis. Our recent studies revealed that MAIT cells inhibit both ILC2 proliferation and functions in a mouse model of airway inflammation. MAIT cells may alleviate airway inflammation in two ways, by promoting airway epithelial cell barrier repair and by repressing ILC2s. Therefore, reagents that promote MAIT cell-mediated suppression of ILC2 proliferation and function, or designer MAIT cells (genetically engineered to suppress ILC2s or promote repair of airway damage), may be effective therapeutic agents for severe asthma.

Introduction: Bacterial pneumonia is a common lower respiratory tract infectious disease. Gypsum, a type of calcium sulfate mineral, primarily consists of calcium sulfate and contains trace amounts of other metallic elements. In traditional Chinese medicine, gypsum has been widely applied, possessing effects such as heat-clearing, detoxification, cooling blood, arresting bleeding, reducing swelling, and alleviating pain. The purpose of this study was to investigate the mechanism of gypsum inhibition of Streptococcus pneumoniae -induced pneumonia by mediating interregional migration of ILC2 through the gut-lung axis. Methods: Normal pneumonia model was induced by Streptococcus pneumoniae, and pseudo-sterile mouse model was established using broad-spectrum antibiotics. The influence of gypsum on the intestinal flora was analyzed using 16S rDNA. Flow cytometry was used to analyze the typing and content of ILC2 in mouse mesenteric lymph nodes and lung tissues. The expression levels of inflammatory cytokines and specific targets associated with immune migration were assessed using ELISA, RT-qPCR, and western blotting methods. And the effects of gypsum on mucosal barrier using IHC. Results: Gypsum effectively alleviates pulmonary inflammation in mice with pneumonia. Gypsum restores the gut microbiota in mice with Streptococcus pneumoniae and gypsum can regulate the expression of miR-155, miR-146a, IL-25, and S1P, promoting the migration of intestinal ILC2s to the lungs. Finally promotes type 2 immunity, alleviating pneumonia and restore lung mucosal barrier. Discussion: Our study contributes to the understanding of gypsum's function in treating infectious pulmonary conditions. Its mechanism involves remedying gut dysbiosis and initiating ILC2 migration, culminating in decreased lung inflammation and enhanced mucosal immunity in the lungs.

Cryptococcus neoformans and Cryptococcus gattii are pathogenic fungi that infect the human respiratory system and cause life-threatening pulmonary cryptococcosis. The immunopathology of cryptococcosis is completely different from that of other fungal allergies. In murine cryptococcal infection models, cryptococcal cells are usually injected via nasal or intratracheal routes. After the infection, the alveolar epithelial cells are impaired and release IL-33, an IL-1 family cytokine that functions as an alarmin. This cytokine detrimentally amplifies allergic responses, and also induces a protective immune response against parasitic infection. In the pulmonary cryptococcosis model, type-II alveolar epithelial cells are the major source of IL-33, and the alveolar epithelial cells, ILC2, and Th2 cells express the IL-33 receptor (ST2). In IL-33- or ST2-deficient mice, allergy-like immune responses are attenuated after the C. neoformans infection. The numbers of ILC2 and Th2 cells and the levels of type 2 cytokines, including IL-4, IL-5, and IL-13, are decreased in the mouse lungs in both models. In association with these changes, total blood IgE, bronchus mucus production, and the number of eosinophils are decreased. Conversely, lung neutrophils and M1-type macrophages are increased. These are protective immune subsets suppressing cryptococcal growth. As a result, the lung fungal burden of IL-33- and ST2-deficient mice is decreased post-infection, and both deficient mice show significantly improved mortality. This pathogenesis varies depending on the cryptococcal and murine strains used in the animal experiments. Here, we overview and discuss the itmmunopathology of the IL-33/ST2 axis in a murine lethal cryptococcal infection model.

Background & Aims: Type 2 innate lymphoid cells (ILC2s) and interleukin-13 (IL-13) promote the onset of spasmolytic polypeptide-expressing metaplasia (SPEM) cells. However, little is known about molecular effects of IL-13 in SPEM cells. We now sought to establish a reliable organoid model, Meta1 gastroids, to model SPEM cells in vitro. We evaluated cellular and molecular effects of ILC2s and IL-13 on maturation and proliferation of SPEM cells. Methods: We performed single-cell RNA sequencing to characterize Meta1 gastroids, which were derived from stomachs of Mist1-Kras transgenic mice that displayed pyloric metaplasia. Cell sorting was used to isolate activated ILC2s from stomachs of IL-13-tdTomato reporter mice treated with L635. Three-dimensional co-culture was used to determine the effects of ILC2s on Meta1 gastroids. Mouse normal or metaplastic (Meta1) and human metaplastic gastroids were cultured with IL-13 to evaluate cell responses. Air-Liquid Interface culture was performed to test long-term culture effects of IL-13. In silico analysis determined possible STAT6-binding sites in gene promoter regions. STAT6 inhibition was performed to corroborate STAT6 role in SPEM cells maturation. Results: Meta1 gastroids showed the characteristics of SPEM cell lineages in vitro even after several passages. We demonstrated that co-culture with ILC2s or IL-13 treatment can induce phosphorylation of STAT6 in Meta1 and normal gastroids and promote the maturation and proliferation of SPEM cell lineages. IL-13 up-regulated expression of mucin-related proteins in human metaplastic gastroids. Inhibition of STAT6 blocked SPEM-related gene expression in Meta1 gastroids and maturation of SPEM in both normal and Meta1 gastroids. Conclusions: IL-13 promotes the maturation and proliferation of SPEM cells consistent with gastric mucosal regeneration.

Background and aim: Dachengqi Decoction (DCQD) as a classic traditional Chinese medicine has been reported to be effective in treating asthma, but its mechanism remains unknown. This study aimed to reveal the mechanisms of DCQD on the intestinal complications of asthma mediated by group 2 innate lymphoid cells (ILC2) and intestinal microbiota. Experimental procedure: Ovalbumin (OVA) was used to construct asthmatic murine models. IgE, cytokines (e.g., IL-4, IL-5), fecal water content, colonic length, histopathologic appearance, and gut microbiota were evaluated in asthmatic mice treated with DCQD. Finally, we administered DCQD to antibiotic-treated asthmatic mice to measure the ILC2 in the small intestine and colon. Results and conclusion: DCQD decreased pulmonary IgE, IL-4, and IL-5 levels in asthmatic mice. The fecal water content, the colonic length weight loss, and the epithelial damage of jejunum, ileum, and colon of asthmatic mice were ameliorated by DCQD. Meanwhile, DCQD greatly improved intestinal dysbiosis by enriching Allobaculum, Romboutsia and Turicibacter in the whole intestine, and Lactobacillus gasseri only in the colon. However, DCQD caused less abundant Faecalibaculum and Lactobacillus vaginalis in the small intestine of asthmatic mice. A higher ILC2 proportion in different gut segments of asthmatic mice was reversed by DCQD. Finally, significant correlations appeared between DCQD-mediated specific bacteria and cytokines (e.g., IL-4, IL-5) or ILC2. These findings indicate that DCQD alleviated the concurrent intestinal inflammation in OVA-induced asthma by decreasing the excessive accumulation of intestinal ILC2 in a microbiota-dependent manner across different gut locations.

Background & Aims: Deep crypt secretory (DCS) cells are a critical component of the colonic stem cell niche. However, the regulatory mechanisms controlling DCS cell numbers and function are not well understood. Sprouty2 is an inflammation-responsive regulator of intracellular signaling that influences colonic secretory cell numbers in colitis via an epithelial–stromal interleukin (IL)33/IL13 signaling loop. Here, we tested the hypothesis that IL13, induced by epithelial Sprouty2 down-regulation, promotes DCS cell differentiation and function. Methods: Distal colons from mice with an intestinal epithelial-specific Sprouty2 deletion (Spry2ΔIE) and littermate controls were analyzed by in situ hybridization for Reg4+ DCS cells. Single-cell RNA sequencing and immunostaining were used to identify DCS cell–derived host defense peptides (HDPs) and localization of IL13 and IL13 receptor; bulk RNA sequencing and quantitative polymerase chain reaction were used to quantify changes in expression of identified HDPs. Cytokine-treated colonoids were assessed for DCS cells. A requirement for an IL33/IL13 signaling loop in the regulation of DCS cells was assessed in vivo using IL13 null mice. Results: Reg4+ DCS cell numbers were increased 2-fold in distal colons of Spry2ΔIE mice with a concomitant overall increase in DCS cell marker expression (Reg4, Spink4, and Agr2). Single-cell transcriptomics showed the HDP Retnlb/Resistin Like Beta (RELMβ) is highly enriched in DCS cells. Retnlb/RELMβ expression was increased in Spry2ΔIE colons. IL13, but not IL33, induced Reg4 and Retnlb expression in colonic epithelial organoids, and IL33-mediated expansion of the DCS cell population in vivo was dependent on IL13, which was expressed predominantly by type II innate lymphoid cells in the colonic mucosa. Conclusions: Sprouty2 limits colonic DCS cell differentiation through suppression of IL13 signaling. At homeostasis, DCS cells are marked by high levels of the HDP RELMβ. Loss of epithelial Sprouty2 activates type II innate lymphoid cells to release IL13, promoting expansion of the DCS cell population and increased colonic RELMβ levels.

Osthole is widely used in medicine because of its anti-oxidative, anti-allergenic and anti-inflammatory. In this study, we explored the protective effects of osthole on food allergenic mice and investigated its potential mechanism of action. We first established a food allergic mouse model by intraperitoneal sensitization and OVA (ovalbumin) oral challenge. Osthole were orally administered before OVA challenge. Diarrhea and allergy scores were used to assess food allergy symptoms. The pathological changes of the intestine were examined by H&E staining and electron microscopy. OVA-IgE, mucosal mast cell protease-1 (mMCP-1), IL-33, ST2, group 2 innate lymphoid cell (ILC2), and regulatory T (Treg) related-cytokine levels were assessed.We found that the oral administration of osthole after OVA sensitization could improve food allergy symptoms and induce beneficial intestinal pathological changes in mice. Osthole reduce the levels of IgE and mMCP-1 and inhibited the IL33/ST2 signaling pathway, thereby blocking ILC2 response and improving Treg response.

Innate Lymphoid cells (ILCs) are innate counterparts of helper T cells. Although low in number, they have proven to play major roles in many autoimmune diseases. In Pemphigus Vulgaris (PV), the gaps in the knowledge of functional role of ILCs remain. To bridge the gap, our study investigated the phenotype along with the functional determinants of ILCs involved in PV immunopathogenesis. Our data suggested augmentation in overall ILC population in circulation of PV patients. Specifically, ILC1 and ILC3 subtypes were significantly increased in peripheral circulation of PV patients compared to healthy controls. We observed no changes in ILC2 population. mRNAs from ILC enriched population showed significant upregulation in transcription factors- ID2, T bet and RORγt and a downregulation in GATA3 and RORα. The mRNA levels of ILC related cytokines- IFNγ and IL17 were significantly upregulated while no change was observed in the levels of IL13, IL 22, AHR. The levels of autoantibodies against desmoglein (Dsg) 3 which is the characteristic of PV pathogenesis were also checked in the serum which confirmed significant upregulation in PV patients. The levels of proinflammatory- IFNγ, IL 17 and IL 15 were elevated and anti-inflammatory cytokines- IL10 was downregulated in the serum of PV patients. The results of this study offer insights into the functional attributes of ILCs and related cytokines, potentially contributing to the development of future therapeutic interventions., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Inc. All rights reserved.)

Bronchial asthma is the most common multifactorial and heterogeneous disease in childhood. The glucocorticoid dexamethasone is a classic treatment for asthma. Research indicates that group 2 innate lymphoid cells (ILC2s) are crucial to the pathogenesis of asthma. However, few studies have focused on ILC2s metabolism and transcription. This study aims to establish an ovalbumin (OVA)-induced asthma model and a dexamethasone-treated asthma model to explore the regulation of lung ILC2s at the genetic and metabolic levels during the progression and remission of asthma, utilizing single-cell metabolomics and transcriptomics approaches. The results showed that ILC2s regulated the metabolic pathways and transcriptional levels of amino acids (such as arginine, proline, and histidine) and linoleic acid, as well as the metabolic biomarkers of arginine, urocanic acid, and linoleic acid in asthma. Additionally, the cytokine pathways and NF-γB pathways have been altered at the genetic level. At the same time, we revealed that dexamethasone regulates ILC2s amino acid and aminoacyl tRNA metabolism, as well as related genes, thereby alleviating asthma symptoms. Furthermore, we identified the genes Eno3 and Tap1, which are significantly associated with asthma. Quantitative real-time polymerase chain reaction (qRT-PCR) was performed to verify the accuracy of the RNA sequencing results. This study, for the first time, revealed the mechanistic changes of ILC2s in the development and treatment of asthma using multiomics techniques, laying a foundation for targeted therapies in asthma., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Authors. Published by Elsevier B.V. All rights reserved.)

Pulmonary arterial hypertension (PAH) is characterized by the severe obstruction of the small pulmonary arteries and concomitant high pulmonary arterial pressure, resulting in progressive right ventricular failure. Previously, we demonstrated that long-term interleukin (IL)-33 administration in mice induces severe occlusive medial hypertrophy of pulmonary arteries (PA) in the lungs, which is mediated by group 2 innate lymphoid cells (ILC2s). In response to IL-33, ILC2s accumulate around the blood vessels and produce IL-5, leading to perivascular eosinophil recruitment. In this study, we characterized IL-33-induced medial hypertrophy of PA. We demonstrated that long-term IL-33 administration causes an increase in right ventricular pressure. In IL-33-deficient mice, medial hypertrophy of PA mediated by eggs of Schistosoma mansoni was attenuated, accompanied by a partial reduction in ILC2s, eosinophils, and CD4 + T cells. In addition, proteomic analysis revealed dramatic changes in the urine samples from mice treated with IL-33 or S. mansoni eggs. Resistin-like alpha (RELMα), a pulmonary hypertension-related molecule, was commonly detected in the urine in both treatments. Large amounts of RELMα were observed in the lungs of the IL-33-treated mice. These observations suggest that IL-33-induced medial hypertrophy of PA is a useful model for studying the mechanism underlying the development of PAH and finding biomarkers to indicate the onset of PAH., Competing Interests: Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests. Masashi Ikutani reports financial support was provided by Hiroshima University. Shoichi Shimizu reports financial support was provided by University of Occupational and Environmental Health, Japan. Koki Okada reports financial support was provided by Hiroshima University. Koshi Imami reports financial support was provided by RIKEN. Tadakatsu Inagaki reports financial support was provided by National Cerebral and Cardiovascular Center Research Institute. Yoshikazu Nakaoka reports financial support was provided by National Cerebral and Cardiovascular Center Research Institute. Yoshio Osada reports financial support was provided by University of Occupational and Environmental Health, Japan. Susumu Nakae reports financial support was provided by Hiroshima University., (Copyright © 2024 Elsevier Inc. All rights reserved.)

Introduction: The interleukin-33/interleukin-13 pathway is involved in the immunopathology of liver fibrosis and recently characterized group 2 innate lymphoid cells (ILC2) were identified as profibrotic immune cells in the liver of mouse models. Our aim was to elucidate whether ILC2 might be present in human liver tissue and whether ILC2 contribute to liver fibrosis. Materials and methods: To identify ILC2 in liver tissue and blood, we purified mononuclear immune cells from needle biopsies, cirrhotic explant specimen, and paired peripheral blood samples. Cell suspensions were incubated with specific markers for ILC2 and analyzed by flow cytometry. The CD69 marker was included to assess the activation level of ILC2. In addition, we determined the IL-33 plasma level. Results: Results were correlated with the METAVIR fibrotic score of patients enrolled in this study. We detected ILC2 in a higher percentage of CD45+ cells in liver tissue than in paired peripheral blood. The number of ILC2 was significantly increased in fibrotic tissue, but only slightly increased in paired peripheral blood. A higher percentage of CD69+ ILC2 was observed in fibrotic tissue, and this increase correlates positively with aggravation of liver fibrosis measured by fibrotic METAVIR score. A higher level of plasma IL-33 was only detected in samples obtained from cirrhotic patients. Conclusion: Our study indicates that ILC2 are present in the human liver and are activated in tissue contributing to the immunopathology of human liver fibrosis, independently of the etiology; which might be a potential new therapeutic target.

Summary: Despite the well-accepted view that chronic inflammation contributes to the pathogenesis of Duchenne muscular dystrophy (DMD), the function and regulation of eosinophils remain an unclear facet of type II innate immunity in dystrophic muscle. We report the observation that group 2 innate lymphoid cells (ILC2s) are present in skeletal muscle and are the principal regulators of muscle eosinophils during muscular dystrophy. Eosinophils were elevated in DMD patients and dystrophic mice along with interleukin (IL)-5, a major eosinophil survival factor that was predominantly expressed by muscle ILC2s. We also find that IL-33 was upregulated in dystrophic muscle and was predominantly produced by fibrogenic/adipogenic progenitors (FAPs). Exogenous IL-33 and IL-2 complex (IL-2c) expanded muscle ILC2s and eosinophils, decreased the cross-sectional area (CSA) of regenerating myofibers, and increased the expression of genes associated with muscle fibrosis. The deletion of ILC2s in dystrophic mice mitigated muscle eosinophilia and impaired the induction of IL-5 and fibrosis-associated genes. Our findings highlight a FAP/ILC2/eosinophil axis that promotes type II innate immunity, which influences the balance between regenerative and fibrotic responses during muscular dystrophy.

Despite recent advances in asthma treatments, the search for novel therapies remains necessary because there are still patients with recurrent asthma exacerbations and poor responses to the existing treatments. Since group 2 innate lymphoid cells (ILC2) play a pivotal role in asthma by triggering and exacerbating type 2 inflammation, controlling ILC2s function is key to combating severe asthma. Mucosal-associated invariant T (MAIT) cells are innate-like T cells abundant in humans and are activated both in a T cell receptor-dependent and -independent manner. MAIT cells are composed of MAIT1 and MAIT17 based on the expression of transcription factors T-bet and RORγt, respectively. MAIT cells play pivotal roles in host defense against pathogens and in tissue repair and are essential for the maintenance of immunity and hemostasis. Our recent studies revealed that MAIT cells inhibit both ILC2 proliferation and functions in a mouse model of airway inflammation. MAIT cells may alleviate airway inflammation in two ways, by promoting airway epithelial cell barrier repair and by repressing ILC2s. Therefore, reagents that promote MAIT cell-mediated suppression of ILC2 proliferation and function, or designer MAIT cells (genetically engineered to suppress ILC2s or promote repair of airway damage), may be effective therapeutic agents for severe asthma., (Copyright © 2023 Japanese Society of Allergology. Published by Elsevier B.V. All rights reserved.)

Allergic airway diseases are caused by inappropriate immune responses directed against inhaled environmental antigens. We previously reported that the inhibition of diacylglycerol (DAG) kinaseζ (DGKζ),an enzyme that terminates DAG-mediated signaling,protects against T cell-mediated allergic airway inflammation by blocking Th2 cell differentiation.In this study, we tested whether DGKζ deficiency also affects allergic airway disease mediated by type 2 innate lymphoid cells (ILC2)s. DGKζ-deficient mice displayed diminished ILC2 function and reduced papain-induced airway inflammation compared to wildtype mice. Unexpectedly, however, mice with hematopoietic cell-specific deletion ofDGKζ displayed intact airway inflammation upon papain challenge. Rather, bone marrow chimera studies revealed thatDGKζ deficiency in the non-hematopoietic compartment was responsible for the reduction in papain-induced airway inflammation. These data suggest that DGK might represent a novel therapeutic target not only for T cell-dependent but also ILC2-dependent allergic airway inflammation by affecting non-hematopoietic cells., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier Inc. All rights reserved.)

Cryptococcus neoformans and Cryptococcus gattii are pathogenic fungi that infect the human respiratory system and cause life-threatening pulmonary cryptococcosis. The immunopathology of cryptococcosis is completely different from that of other fungal allergies. In murine cryptococcal infection models, cryptococcal cells are usually injected via nasal or intratracheal routes. After the infection, the alveolar epithelial cells are impaired and release IL-33, an IL-1 family cytokine that functions as an alarmin. This cytokine detrimentally amplifies allergic responses, and also induces a protective immune response against parasitic infection. In the pulmonary cryptococcosis model, type-II alveolar epithelial cells are the major source of IL-33, and the alveolar epithelial cells, ILC2, and Th2 cells express the IL-33 receptor (ST2). In IL-33- or ST2-deficient mice, allergy-like immune responses are attenuated after the C. neoformans infection. The numbers of ILC2 and Th2 cells and the levels of type 2 cytokines, including IL-4, IL-5, and IL-13, are decreased in the mouse lungs in both models. In association with these changes, total blood IgE, bronchus mucus production, and the number of eosinophils are decreased. Conversely, lung neutrophils and M1-type macrophages are increased. These are protective immune subsets suppressing cryptococcal growth. As a result, the lung fungal burden of IL-33- and ST2-deficient mice is decreased post-infection, and both deficient mice show significantly improved mortality. This pathogenesis varies depending on the cryptococcal and murine strains used in the animal experiments. Here, we overview and discuss the itmmunopathology of the IL-33/ST2 axis in a murine lethal cryptococcal infection model., (Copyright © 2023 Japanese Society of Allergology. Published by Elsevier B.V. All rights reserved.)

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., Competing Interests: Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Naoto Ishii reports financial support was provided by Tohoku University Graduate School of Medicine. Naoto Ishii reports financial support was provided by Japan Society for the Promotion of Science., (Copyright © 2022 Elsevier Inc. All rights reserved.)

Dedicator of cytokinesis 8 (DOCK8) is a guanine nucleotide exchange factor (GEF) for Cdc42. In humans, homozygous or compound heterozygous deletions in DOCK8 cause a combined immunodeficiency characterized by various allergic diseases including food allergies. Although group 2 innate lymphoid cells (ILC2s) contribute to the development of allergic inflammation by producing interleukin (IL)-5 and IL-13, the role of ILC2s in DOCK8 deficiency has not been fully explored. With the use of cytometry by time-of-flight (CyTOF), we performed high-dimensional phenotyping of intestinal immune cells and found that DOCK8-deficient (Dock8 -/- ) mice exhibited expansion of ILC2s and other leukocytes associated with type 2 immunity in the small intestine. Moreover, IL-5- and IL-13-producing cells markedly increased in Dock8 -/- mice, and the majority of them were lineage-negative cells, most likely ILC2s. Intestinal ILC2s expanded when DOCK8 expression was selectively deleted in hematopoietic cells. Importantly, intestinal ILC2 expansion was also observed in Dock8 VAGR mice having mutations in the catalytic center of DOCK8, thereby failing to activate Cdc42. Our findings indicate that DOCK8 is a negative regulator of intestinal ILC2s to inhibit their expansion via Cdc42 activation, and that deletion of DOCK8 causes a skewing to type 2 immunity in the gut., (Copyright © 2021 The Authors. Published by Elsevier Inc. All rights reserved.)

Group 2 innate lymphoid cells (ILC2s) are increasingly recognized as a key controller of type 2 inflammation, and are well known to be highly elevated in human airway type 2 inflammatory diseases including allergic rhinitis, chronic rhinosinusitis with nasal polyps, and asthma. ILC2-mediated production of type 2 cytokines initiates and amplifies airway inflammation via activation of eosinophils, B cells, mast cells, macrophages, fibroblasts, and epithelial cells in these diseases. ILC2s require at least three major signals to fully activate and robustly produce type 2 cytokines. IL-1 family cytokines (IL-1β, IL-18, IL-33), IL-25, and TNF superfamilies (TNF, TL1A, GITR-L, RANK-L) activate the NF-κB and AP-1 pathways that initiate production of IL-5 and IL-13. Lipid mediators (LTC 4 , LTD 4 , PGD 2 ) and neuropeptide NMU promote production of IL-4 through the NFAT pathway. IL-2 and IL-7 family cytokines (IL-2, IL-7, IL-9, TSLP) activate the STAT5 pathway that induces survival of ILC2s and enhances cytokine production. The activation of STAT5 is necessary to potently induce cytokine- and lipid mediator-mediated production of type 2 cytokines. Inhibitory pathways for ILC2s have also become clearer. Type I and II interferons and IL-27 inhibit ILC2 functions through the activation of STAT1. Suppression mediated via β 2 -adrenergic receptor agonists, PGE 2 , and PGI 2 occurs through cAMP and PKA. Glucocorticoid, testosterone, IL-10, and TGF-β are also able to inhibit ILC2-mediated production of type 2 cytokines. Blockage of ILC2 activators, activation of inhibitory pathways of ILC2s, and suppression of ILC2-mediated pathways including type 2 cytokines (IL-5, IL-13, IL-4Ra) may become therapeutic strategies for airway type 2 inflammatory diseases., (Copyright © 2019 American College of Chest Physicians. Published by Elsevier Inc. All rights reserved.)

Group 2 innate lymphoid cells (ILC2s) play an important role in the initiation of type-2 immune responses. Numerous targets have been identified that may activate or repress ILC2 function, though few negative regulatory feedback pathways induced upon activation have been shown to be operative in ILC2s. Here we demonstrate that loss of ADAM17 from ILC2s results in a selective defect in IL-33 responsiveness, but not IL-25 responsiveness. We find that IL1R2 is significantly upregulated at both the transcript and protein level in IL-33 activated ILC2s. We are also able to demonstrate that ADAM17 regulates IL1R2 levels on ILC2s in both a constitutive and activation induced manner. Additionally, IL1R2 + ILC2s, a unique subset of ILC2s, have decreased Il5 and Il13 transcripts following IL-33 stimulation. Overall, these data suggest that the expression of IL1R2 may act as an activation-induced negative regulatory feedback mechanism to decrease ILC2 responsiveness to IL-33., (Copyright © 2019 Elsevier Inc. All rights reserved.)

The recent discovery of innate lymphoid cells has revolutionized our understanding of the pathogenesis of immune diseases including allergy and asthma. Innate lymphoid cells (ILCs) are a heterogeneous collection of lymphocytes that lack antigen-specificity (non-T, non-B cells) and potently produce characteristic cytokines of T cell subsets (Th1, Th2, Th17). ILCs are divided into group 1 (ILC1s), group 2 (ILC2s), or group 3 (ILC3s). Similar to Th2 cells, ILC2s produce IL-4, IL-5, and IL-13, among others, and are present in increased numbers in samples from patients with many allergic disorders including asthma and chronic rhinosinusitis (CRS). Animal models have identified that ILC2s contribute to eosinophilic tissue infiltration, airway hyperresponsiveness, mucus production, as well as coordinate adaptive immune responses. Finally, recent studies support regulation of ILC2s by neuro-immune mechanisms as well as demonstrate a significant degree of plasticity between ILC subsets that may impact the immune responses in asthma and allergic airway diseases. Here, we review the current literature on ILC2s in human asthma and allergic airway diseases, as well as highlight some recent mechanistic insights into ILC2 function from in vitro studies and in vivo animal models., (Copyright © 2018 Japanese Society of Allergology. Production and hosting by Elsevier B.V. All rights reserved.)

Cyclosporin A (CsA) is a well-known immunosuppressant that is used against steroid-resistant asthma. Group 2 innate lymphoid cells (ILC2s) and type 2 helper T (Th2) cells produce Th2 cytokines including IL-5 and play important roles in asthma pathogenesis. Here, we studied the effects of CsA in allergen-induced lung inflammation in mice and found that CsA decreased the number of lung ILC2s and attenuated papain-induced activation of ILC2s accompanied with IL-5 expression. The ILC2 suppression mediated by CsA was not observed in culture or in lymphocyte-deficient Rag2 -/- mice. Thus, we propose a new suppressive effect of CsA, i.e., administration of CsA indirectly suppresses maintenance and activation of lung ILC2s in addition to direct suppression of T-cell activation and cytokine production., (Copyright © 2017 Elsevier Inc. All rights reserved.)

Background: Pathogenesis of atopic dermatitis (AD) involves interaction between type 2 cells that include basophils, mast cells, innate lymphoid type 2 cells (ILC2), and Th2 cells. Levels of IL-4 and IL-13 are elevated in AD patients., Objective: Here, we investigated the distribution of type 2 cells and the source of IL-4 and IL-13 in skin and blood of AD relative to psoriasis., Methods: Lesional skin biopsies and blood were collected from patients. Skin cell suspensions were prepared by mild enzymatic digestion and mechanical dissociation. IL-4 and IL-13 expression was analyzed at single-cell level before or after stimulation using flow cytometry., Results: Frequencies of basophils, ILC2 and Th2 but not mast cells were significantly elevated in skin, and not blood, of AD relative to psoriasis. IL-4 production by circulating basophils and Th2 cells, and IL-13 by ILCs and Th2 cells was similar in both diseases. In contrast, skin T cells expressed IL-4 and IL-13 prior to stimulation in AD when compared to psoriasis. Moreover, skin basophils, which were detected in AD only, expressed IL-4 following stimulation. Interestingly, basophils and ILC2 were positively correlated in skin, whereas skin basophils were inversely correlated with blood ILC2., Conclusions: Lesional AD skin harbors a distinctive innate and adaptive type 2 profile, which is characterized by basophils producing IL-4, Th2 cells expressing IL-4 or IL-13, and ILC2. This underlies the therapeutic efficacy of targeting IL-4 and IL-13 signaling pathways in AD., (Copyright © 2017 Japanese Society for Investigative Dermatology. Published by Elsevier B.V. All rights reserved.)

Inflammation is a hallmark of many airway diseases. Improved understanding of the cellular and molecular mechanisms of airway disease will facilitate the transition in our understanding from phenotypes to endotypes, thereby improving our ability to target treatments based on pathophysiologic characteristics. For example, allergic asthma has long been considered to be driven by an allergen-specific T helper 2 response. However, clinical and mechanistic studies have begun to shed light on the role of other cell subsets in the pathogenesis and regulation of lung inflammation. In this review, we discuss the importance of different lymphocyte subsets to asthma and other airway diseases, while highlighting the growing evidence that asthma is a syndrome that incorporates many immune phenotypes., (Copyright © 2016 American College of Chest Physicians. Published by Elsevier Inc. All rights reserved.)

Background: Eosinophilic airway inflammation can predict the exacerbation of asthma, and we can improve the management of asthma by monitoring the eosinophilic airway inflammation. Although induced sputum and sputum eosinophil count is the gold standard test for diagnosing eosinophilic asthma, a more accessible and receptive method is needed for clinical practice. Type 2 innate lymphoid cells (ILC2) have recently been proposed to play a crucial role in eosinophilic inflammation and have been identified in peripheral blood from patients with asthma., Objectives: We sought to identify simple and feasible biomarkers which can predict eosinophilic airway inflammation in asthmatic patients., Methods: Sputum was induced for the assessment of eosinophils in 150 asthmatic patients. In parallel, the proportion of ILC2s of peripheral blood lymphocytes (%ILC2), blood eosinophil counts, total immunoglobulin E (IgE), fractional exhaled nitric oxide (FeNO) and lung function tests were measured. 42 healthy donors served as controls., Results: 126 patients finished sputum induction and produced adequate sputum. The ILC2 level was significantly increased in eosinophilic asthmatic patients compared with non-eosinophilic asthmatic patients (0.117 ± 0.090versus0.035 ± 0.021, p < 0.001). A multiple regression model, including age, sex, BMI, blood eosinophil counts, FeNO, IgE and %ILC2, showed that %ILC2, blood eosinophil counts and FeNO were correlative factors of sputum eosinophil counts (p < 0.001, p = 0.037, p < 0.001, respectively) and %ILC2 was the most significant subset of airway eosinophilic inflammation (Estimate = 11.385). A receiver operating characteristic (ROC) analysis showed a sensitivity of 67.7% and a specificity of 95.3% for %ILC2 of 0.076 to distinguish eosinophilic asthmatic patients from non-eosinophilic asthmatic patients., Conclusion: ILC2 is a surrogate marker of airway eosinophilic inflammation in patients with mild to moderate asthma and has great potential advantages for selecting the asthmatic patients most likely to benefit from therapeutics targeting Th2 inflammation., (Copyright © 2015 Elsevier Ltd. All rights reserved.)