Numbers Of Innate Lymphoid Cells Research Articles

Oral exposure to high concentrations of polystyrene microplastics alters the intestinal environment and metabolic outcomes in mice.

Oral exposure to microplastics (MPs) is a global health concern. In our previous study, MPs induced glucose intolerance and non-alcoholic fatty liver disease (NAFLD) under a high-fat diet-induced leaky gut syndrome (LGS). This study aims to evaluate the effects of high concentrations of MP on lipid metabolism under normal dietary conditions and to assess the changes in the intestinal tract resulting from MP exposure. C57BL6/J mice were fed a normal diet (ND) without polystyrene MPs (PS-MPs) or with PS-MPs (1000 µg/L or 5000 µg/L) for six weeks. Subsequently, intestinal permeability, gut microbiota, and metabolite levels in the serum, feces, and liver were determined. Mice fed the ND showed no increase in intestinal permeability in either group. However, high MPs concentrations led to increased serum lipid levels and exacerbated fatty liver function. Oral exposure to MPs did not affect the number of innate lymphoid cells or short-chain fatty acids in the intestine. However, it increased the number of natural killer cells, altered the gut microbiota, induced inflammation, and modulated the expression of genes related to nutrient transport in the intestine. The severity of intestinal disturbance tended to worsen with dose. Despite the absence of LGS, high concentrations of MPs induced dyslipidemia and NAFLD. Oral exposure to MPs triggered intestinal inflammation via natural killer cells, altered the gut microbiota, and modulated nutrient metabolism. Our study highlights the need for environmental measures to reduce oral MPs exposure in the future.

Transcriptional and chromatin profiling of human blood innate lymphoid cell subsets sheds light on HIV‐1 pathogenesis

Innate lymphoid cells (ILCs) are a diverse population of cells that include NK cells and contribute to tissue homeostasis and repair, inflammation, and provide protection from infection. The interplay between human blood ILCs, as well as their responses to HIV‐1 infection, remains poorly understood. This study used transcriptional and chromatin profiling to explore these questions. Transcriptional profiling and flow cytometry analysis support that there are four main ILC subsets found in human blood. Unlike in mice, human NK cells expressed the tissue repair protein amphiregulin (AREG). AREG production was induced by TCF7/WNT, IL‐2, and IL‐15, and inhibited by TGFB1, a cytokine increased in people living with HIV‐1. In HIV‐1 infection, the percentage of AREG+ NK cells correlated positively with the numbers of ILCs and CD4+ T cells but negatively with the concentration of inflammatory cytokine IL‐6. NK‐cell knockout of the TGFB1‐stimulated WNT antagonist RUNX3 increased AREG production. Antiviral gene expression was increased in all ILC subsets from HIV‐1 viremic people, and anti‐inflammatory gene MYDGF was increased in an NK‐cell subset from HIV‐1‐infected people whose viral load was undetectable in the absence of antiretroviral therapy. The percentage of defective NK cells in people living with HIV‐1 correlated inversely with ILC percentage and CD4+ T‐cell counts. CD4+ T cells and their production of IL‐2 prevented the loss of NK‐cell function by activating mTOR. These studies clarify how ILC subsets are interrelated and provide insight into how HIV‐1 infection disrupts NK cells, including an uncharacterized homeostatic function in NK cells.

A Salivary Gland Resident Macrophage Subset Regulating Radiation Responses

Radiotherapy of head and neck cancers frequently leads to irreversible hypofunction of salivary glands, which severely compromises the quality of life and is extremely difficult to treat. We found recently that salivary gland resident macrophages are sensitive to radiation and interact with epithelial progenitors and endothelial cells through homeostatic paracrine factors. Heterogeneous subpopulations of resident macrophages are present in other organs with distinct functions, whereas subpopulations of salivary gland resident macrophages with distinct functions or transcriptional profiles have not been reported yet. Using single-cell RNA sequencing, we found that mouse submandibular glands (SMGs) contain 2 distinct self-renewing resident macrophage subsets, an MHC-IIhi subset present in many other organs and an uncommon Csf2r+ subset. The main source of Csf2 in SMGs are innate lymphoid cells (ILCs) that rely on IL15 for maintenance, while the main source of IL15 protein is Csf2r+ resident macrophages, indicating a homeostatic paracrine interaction between these cells. Csf2r+ resident macrophages are the major source of hepatocyte growth factor (Hgf) that regulates homeostasis of SMG epithelial progenitors. Meanwhile, Csf2r+ resident macrophages are responsive to Hedgehog signaling that can rescue salivary function impaired by radiation. Consistently, irradiation persistently decreased numbers of ILCs and levels of IL15 and Csf2 in SMGs, which were all recovered by transient activation of Hedgehog signaling after radiation. Csf2r+ resident macrophages and MHC-IIhi resident macrophages share transcriptome profiles of perivascular macrophages and macrophages associated with nerves and/or epithelial cells in other organs, respectively, and such niche preferences were supported by lineage tracing and immunofluorescent staining. These findings reveal an uncommon resident macrophage subset that regulates the homeostasis of the salivary gland and is promising as the target to restore salivary gland function impaired by radiation.

MSCs-ILC2s-Tecs Axis Promotes the Recovery of Thymic Function in aGVHD

Background: Previous studies found that mesenchymal stem cells (MSCs) administrated at the acute graft versus host disease (aGVHD) phase effectively decreased the incidence and severity of chronic GVHD (cGVHD) by boosting thymic regeneration. However, the mechanism for MSCs repairing the damaged thymus caused by aGVHD is unclear. It has been reported that innate lymphoid cells (ILCs) are also important for the structural remodeling of the thymus in recipients after allogeneic bone marrow transplantation (allo-BMT). Here, we explored the mechanisms on how MSCs promote thymus recovery post allo-BMT through ILCs. Methods: We carried out studies in a aGVHD mice model of fully MHC-mismatched myeloablative bone marrow transplantation (C57BL/6 to BALB/c). MSCs or ILC2s were generated and administrated intravenously at day 7 post-BMT to the treated groups to compare therapeutic effects of GVHD with the untreated group. Clinical scores and survival were recorded once every days. Flow cytometery was employed for analyzing the number and proportion of ILCs and their subtypes (ILCs Lin-CD45+iCD3-CD127+, type 1 ILCs (ILC1s) Tbet+, type 2 ILCs (ILC2s) GATA3+, type 3 ILCs (ILC3s) RORγt+) in the thymus to assess the effect of MSCs on ILCs in the thymus at day 14 post-BMT. We analyzed the thymic T cells subsets and thymic epithelial cells (TECs) substes among these two groups to evaluate the repair effect of ILC2s for thymus. Thymic ILC2s were cultured alone or co-cultured with murine MSCs in vitro to investigate the effect and underlying mechanism of MSCs on ILC2s. Results: We found that ILC2s in the thymus are sensitive to conditioning therapy and and further impaired by aGVHD. But infusion of MSCs was effective in reducing the lethality of aGVHD and promote expansion of thymic ILC2s in aGVHD mice compared with the control group. The absolute number of ILC2s in the thymus had a significant negative correlation with GVHD scores in aGVHD mice. Then we found that ILC2s infusion significant increases in thymus size and weight, as well as the number of total thymocytes and the more organized cortical medullary structure compared to the untreated groups. The number of TECs and its proportion of thymus stroma were significantly improved, including cortical TEC and medullary TECs. As for thymocyte, ILC2s infusion significantly increased the number and proportion of CD4+CD8+T cells. In vitro study showed co-cultured ILC2s had a increased proliferation compared to ILC2s cultured alone, and anti-IL33 antibody inhibited the pro-proliferative effect of MSCs on ILC2. Then we perform in vivo validation by injecting IL33 knocked down MSCs and found that the effect of MSC in repairing the damaged thymus was reduced. And the number and proportion of thymic ILC2s were also significantly decreased in the thymus. Furthermore, treatment with rIL33 on day 7-11 also ameliorated aGVHD and promoted the proliferation of thymic ILC2s in aGVHD mice as well as MSCs infusion. Conclusion: These findings suggest that MSCs participate in thymus regeneration from aGVHD damage through ILC2s-mediated tissue recovery. The study outlined here provide a new insight into the mechanism of MSC therapy for aGVHD.

Contribution of Innate Lymphoid Cells in Supplementing Cytokines Produced by CD4+ T Cells During Acute and Chronic SIV Infection of the Colon.

HIV/SIV (simian immunodeficiency virus) infection leads to a loss of CD4+ T helper (Th) cells in number and function that begins during the acute phase and persists through the chronic phase of infection. In particular, there is a drastic decrease of Th17 and Th22 cells in the HIV/SIV-infected gastrointestinal (GI) tract as a source of interleukin (IL)-17 and IL-22. These cytokines are vital in the immune response to extracellular pathogens and maintenance of the GI tract. However, innate lymphoid cells (ILCs) are a source of IL-17 and IL-22 during the early stages of an immune response in mucosal tissue and remain vital cytokine producers when the immune response is persistent. Here, we wanted to determine whether ILCs are a source of IL-17 and IL-22 in the SIV-infected colon and could compensate for the loss of Th17 and Th22 cells. As a control, we evaluated the frequency and number of ILCs expressing interferon-gamma (IFNγ) and tumor necrosis factor-alpha (TNFα). We determined the frequency and number of cytokine expressing ILC subsets and T cell subsets within leukocytes from the colons of uninfected as well as acute and chronic SIV-infected colons without in vitro mitogenic stimulation. In the present study, we find that: (1) the frequency of IL-22, IFNγ, and TNFα but not IL-17 producing ILCs is increased in the acutely infected colon and remains high during the chronically infected colon relative to cytokine expressing ILCs in the uninfected colon, (2) ILCs are a significant source of IL-22, IFNγ, and TNFα but not IL-17 when CD4+ T lymphocytes in the gut lose their capacity to secrete these cytokines during SIV infection, and (3) the changes in the cytokines expressed by ILCs relative to CD4+ T cells in the infected colon were not due to increases in the frequency or number of ILCs in relation to T lymphocytes found in the tissue.

Activation of CD81+ skin ILC2s by cold-sensing TRPM8+ neuron-derived signals maintains cutaneous thermal homeostasis.

As the outermost barrier tissue of the body, the skin harbors a large number of innate lymphoid cells (ILCs) that help maintain local homeostasis in the face of changing environments. How skin-resident ILCs are regulated and function in local homeostatic maintenance is poorly understood. We here report the discovery of a cold-sensing neuron-initiated pathway that activates skin group 2 ILCs (ILC2s) to help maintain thermal homeostasis. In stearoyl-CoA desaturase 1 (SCD1) knockout mice whose skin is defective in heat maintenance, chronic cold stress induced excessive activation of CCR10-CD81+ST2+ skin ILC2s and associated inflammation. Mechanistically, stimulation of the cold-sensing receptor TRPM8 expressed in sensory neurons of the skin led to increased production of IL-18, which, in turn, activated skin ILC2s to promote thermogenesis. Our findings reveal a neuroimmune link that regulates activation of skin ILC2s to support thermal homeostasis and promotes skin inflammation after hyperactivation.

Metabolic Syndrome in Psoriasis Is Associated With Upregulation of CXCL16 on Monocytes and a Dysbalance in Innate Lymphoid Cells.

Psoriasis is frequently associated with the metabolic syndrome and occurs more often in obese individuals. In order to understand innate immune mechanisms mediating this inflammatory pattern we investigated expression of the chemokine and lipid scavenger receptor CXCL16 in patients with psoriasis and associated comorbidities. CXCL16 expression was enhanced on all monocyte subsets in psoriatic patients compared with healthy controls and positively correlated with psoriasis activity and severity index, body mass index and the risk for cardiovascular disease indicated by PROCAM score. The intensity of CXCL16 expression on monocytes further correlated with their capability to phagocytose oxidized LDL indicating the possibility to transform into foam cells in atherosclerotic plaques. Patients with psoriasis and atherosclerosis or obesity displayed elevated numbers of innate lymphoid cells in blood with specific increase of the IFN-γ or IL-17 producing ILC1 and ILC3 subpopulations. The expression of the CXCL16 receptor, CXCR6, was increased in ILCs and co-expressed with CCR6 but not CCR7 indicating their migratory potential to psoriatic skin or adipose tissue that is characterized by strong CXCL16 and CCL20 expression. This hypothesis was supported by the finding that the percentage of CXCR6 expressing ILCs was alleviated in blood of psoriatic patients. Together these data link a strong expression of CXCL16 to metabolic syndrome in psoriasis and indicate a possible link to ILC activation and tissue distribution in obese psoriatic patients. These data contribute to the understanding of the complex interaction of innate immunity and metabolic state in psoriasis.

Characterization of cord blood CD3+ TCRVα7.2+ CD161high T and innate lymphoid cells in the pregnancies with gestational diabetes, morbidly adherent placenta, and pregnancy hypertension diseases.

Although pregnant women with gestational diabetes (GD), morbidly adherent placenta (MAP), and pregnancy hypertension (pHT) diseases lead to intrauterine growth restriction (IUGR), little is known about their effect on mucosal-associated invariant T (MAIT) and innate lymphoid cells (ILC) in the umbilical cord. This study aimed to quantify and characterize MAIT cells and ILCs in the cord blood of pregnant women with GD, MAP, and pHT diseases. Cord blood mononuclear cells (CBMCs) were isolated by Ficoll-Paque gradient. CD3+ TCRVα7.2+ CD161high cells and ILC subsets were quantified by flow cytometry. CBMCs were stimulated with PMA/Ionomycin and Golgi Plug for 4h and stained for IFN-γ, TNF-α, and granzyme B. The stained cells were analyzed on FACS ARIA III. Compared with healthy pregnancies, in the cord blood of the pHT group, elevated number of lymphocytes was observed. Moreover, the absolute number of IFN-γ producing CD4+ or CD4- subsets of CD3+ TCRVα7.2+ CD161high cells as well as those producing granzyme B were significantly elevated in the pHT group compared to healthy controls suggesting increased MAIT cell activity in the pHT cord blood. Similarly, in the MAP group, the absolute number of total CD3+ TCRVα7.2+ CD161high cells, but not individual CD4+ or negative subsets, were significantly increased compared with healthy controls' cord blood. Absolute numbers of total CD3+ TCRVα7.2+ CD161high cells and their subsets were comparable in the cord blood of the GD group compared with healthy controls. Finally, the absolute number of total ILCs and ILC3 subset were significantly elevated in only pHT cord blood compared with healthy controls. Our data also reveal that IFN-γ+ or granzyme B+ cell numbers negatively correlated with fetal birth weight. CD3+ TCRVα7.2+ CD161high cells and ILCs show unique expansion and activity in the cord blood of pregnant women with distinct diseases causing IUGR and may play roles in fetal growth restriction.

HOIL1 regulates group 2 innate lymphoid cell numbers and type 2 inflammation in the small intestine

Patients with mutations in HOIL1 experience a complex immune disorder including intestinal inflammation. To investigate the role of HOIL1 in regulating intestinal inflammation, we employed a mouse model of partial HOIL1 deficiency. The ileum of HOIL1-deficient mice displayed features of type 2 inflammation including tuft cell and goblet cell hyperplasia, and elevated expression of Il13, Il5 and Il25 mRNA. Inflammation persisted in the absence of T and B cells, and bone marrow chimeric mice revealed a requirement for HOIL1 expression in radiation-resistant cells to regulate inflammation. Although disruption of IL-4 receptor alpha (IL4Rα) signaling on intestinal epithelial cells ameliorated tuft and goblet cell hyperplasia, expression of Il5 and Il13 mRNA remained elevated. KLRG1hi CD90lo group 2 innate lymphoid cells were increased independent of IL4Rα signaling, tuft cell hyperplasia and IL-25 induction. Antibiotic treatment dampened intestinal inflammation indicating commensal microbes as a contributing factor. We have identified a key role for HOIL1, a component of the Linear Ubiquitin Chain Assembly Complex, in regulating type 2 inflammation in the small intestine. Understanding the mechanism by which HOIL1 regulates type 2 inflammation will advance our understanding of intestinal homeostasis and inflammatory disorders and may lead to the identification of new targets for treatment.

ILC Differentiation in the Thymus.

The thymus provides a microenvironment conducive to the differentiation of innate lymphoid cells (ILCs), supplying IL-7 as well as Notch ligands. Early T cell precursors also express a number of obligatory transcription factors essential for ILC differentiation. Therefore, the thymus could be a powerhouse for ILC production. However, coordinated regulation by transcription factors and T cell receptor signaling events ensure that T cell production is the dominating output of the thymus. One group of the key regulators are the basic helix-loop-helix E protein transcription factors and their inhibitors, Id proteins. When E protein activities are downregulated, T cell development is blocked and massive ILC2 production occurs in the thymus. Normally, the thymus indeed generates a small number of ILCs, mostly group 2 ILCs (ILC2s). It has been shown in vitro that ILC2s can be differentiated from multipotent early T cell progenitors (ETPs) as well as committed T cell precursors. Moreover, thymus-derived ILC precursors have been found in the blood of adult mice. They then home to peripheral tissues and undergo differentiation into distinct ILC subsets. These ILC precursors may replenish tissue ILC pools in steady state or on demand in pathophysiological conditions. Collectively, emerging evidence suggests that the thymus plays an underappreciated role in ILC homeostasis.

The Reaction of Innate Lymphoid Cells in the Mouse Female Genital Tract to Chlamydial Infection.

Innate lymphoid cells (ILCs) comprise five distinct subsets. ILCs are found at mucosal barriers and may fight invading pathogens. Chlamydia is an intracellular bacterium that infects the mucosa of the genital tract and can cause severe tissue damage. Here, we used a mouse infection model with Chlamydia muridarum to measure the reaction of genital tract ILCs to the infection. Tissue-resident natural killer (NK) cells were the largest group in the uninfected female genital tract, and their number did not substantially change. Conventional NK cells were present in the greatest numbers during acute infection, while ILC1s continuously increased to high numbers. ILC2 and ILC3s were found at lower numbers that oscillated by a factor of 2 to 4. The majority of ILC3s transdifferentiated into ILC1s. NK cells and ILC1s produced gamma interferon (IFN-γ) and, rarely, tumor necrosis factor (TNF), but only early in the infection. Lack of B and T cells increased ILC numbers, while the loss of myeloid cells decreased them. ILCs accumulated to a high density in the oviduct, a main site of tissue destruction. ILC subsets are part of the inflammatory and immune reaction during infection with C. muridarum and may contribute to tissue damage during chlamydial infection.

Differences in pulmonary group 2 innate lymphoid cells are dependent on mouse age, sex and strain.

Innate lymphoid cells (ILCs) are resident in the lung and are involved in both the maintenance of homeostasis and the pathogenesis of respiratory diseases. In this study, murine lung ILCs were characterized using flow cytometry and the impact of mouse age, sex and strain were assessed. Lung ILCs were found as early as postnatal day 4 and numbers peaked at 2weeks, and then decreased as the lung matured. During postnatal lung development, ILC expressed differential amounts of group 2 ILC (ILC2)-associated cell surface antigens including ST2, CD90.2 and ICOS. Using Il5venus Il13td-tomato dual reporter mice, neonates were found to have increased constitutive interleukin (IL)-13 expression compared with adult mice. Neonates and adults had similar ratios of IL-5+ CD45+ leukocytes; however, these cells were mostly composed of ILCs in neonates and T cells in adults. Sex-specific differences in ILC numbers were also observed, with females having greater numbers of lung ILCs than males in both neonatal and adult mice. Female lung ILCs also expressed higher levels of ICOS and decreased KLRG1. Mouse strain also impacted on lung ILCs with BALB/c mice having more ILCs in the lung and increased expression of ST2 and ICOS compared with C57BL/6J mice. Collectively, these data show that lung ILC numbers, cell surface antigen expression, IL-5 and IL-13 levels differed between neonatal and adult lung ILCs. In addition, cell surface antigens commonly used for ILC2 quantification, such as ST2, CD90.2 and ICOS, differ depending on age, sex and strain and these are important considerations for consistent universal identification of lung ILC2s.

Quantification and role of innate lymphoid cell subsets in Chronic Obstructive Pulmonary Disease.

ObjectivesInnate lymphoid cells (ILCs) secrete cytokines, such as IFN‐γ, IL‐13 and IL‐17, which are linked to chronic obstructive pulmonary disease (COPD). Here, we investigated the role of pulmonary ILCs in COPD pathogenesis.MethodsLung ILC subsets in COPD and control subjects were quantified using flow cytometry and associated with clinical parameters. Tissue localisation of ILC and T‐cell subsets was determined by immunohistochemistry. Mice were exposed to air or cigarette smoke (CS) for 1, 4 or 24 weeks to investigate whether pulmonary ILC numbers and activation are altered and whether they contribute to CS‐induced innate inflammatory responses.ResultsQuantification of lung ILC subsets demonstrated that ILC1 frequency in the total ILC population was elevated in COPD and was associated with smoking and severity of respiratory symptoms (COPD Assessment Test [CAT] score). All three ILC subsets localised near lymphoid aggregates in COPD. In the COPD mouse model, CS exposure in C57BL/6J mice increased ILC numbers at all time points, with relative increases in ILC1 in bronchoalveolar lavage (BAL) fluid. Importantly, CS exposure induced increases in neutrophils, monocytes and dendritic cells that remained elevated in Rag2/Il2rg‐deficient mice that lack adaptive immune cells and ILCs. However, CS‐induced CXCL1, IL‐6, TNF‐α and IFN‐γ levels were reduced by ILC deficiency.ConclusionThe ILC1 subset is increased in COPD patients and correlates with smoking and severity of respiratory symptoms. ILCs also increase upon CS exposure in C57BL/6J mice. In the absence of adaptive immunity, ILCs contribute to CS‐induced pro‐inflammatory mediator release, but are redundant in CS‐induced innate inflammation.

Allium tuberosum alleviates pulmonary inflammation by inhibiting activation of innate lymphoid cells and modulating intestinal microbiota in asthmatic mice

ObjectiveThis study tests whether long-term intake of Allium tuberosum (AT) can alleviate pulmonary inflammation in ovalbumin (OVA)-induced asthmatic mice and evaluates its effect on the intestinal microbiota and innate lymphoid cells (ILCs). MethodsBALB/c mice were divided into three groups: phosphate buffer saline, OVA and OVA + AT. The asthmatic murine model was established by sensitization and challenge of OVA in the OVA and OVA + AT groups. AT was given to the OVA + AT group by oral gavage from day 0 to day 27. On day 28, mice were sacrificed. Histopathological evaluation of lung tissue was performed using hematoxylin and eosin, and periodic acid-Schiff staining. The levels of IgE in serum, interleukin-5 (IL-5) and IL-13 from bronchoalveolar lavage fluid (BALF) were measured by enzyme-linked immunosorbent assay. The ILCs from the lung and gut were detected by flow cytometry. 16S ribosomal DNA sequencing was used to analyze the differences in colon microbiota among treatment groups. ResultsWe found that long-term intake of AT decreased the number of inflammatory cells from BALF, reduced the levels of IL-5 and IL-13 in BALF, and IgE level in serum, and rescued pulmonary histopathology with less mucus secretion in asthmatic mice. 16S ribosomal DNA sequencing results showed that AT strongly affected the colonic bacteria community structure in asthmatic mice, although it had no significant effect on the abundance and diversity of the microbiota. Ruminococcaceae and Desulfovibrionaceae were identified as two biomarkers of the treatment effect of AT. Moreover, AT decreased the numbers of ILCs in both the lung and gut of asthmatic mice. ConclusionThe results indicate that AT inhibits pulmonary inflammation, possibly by impeding the activation of ILCs and adjusting the homeostasis of gut microbiota in asthmatic mice.

Pulmonary paracoccidioidomycosis in AhR deficient hosts is severe and associated with defective Treg and Th22 responses

AhR is a ligand-activated transcription factor that plays an important role in the innate and adaptive immune responses. In infection models, it has been associated with host responses that promote or inhibit disease progression. In pulmonary paracoccidioidomycosis, a primary fungal infection endemic in Latin America, immune protection is mediated by Th1/Th17 cells and disease severity with predominant Th2/Th9/Treg responses. Because of its important role at epithelial barriers, we evaluate the role of AhR in the outcome of a pulmonary model of paracoccidioidomycosis. AhR−/− mice show increased fungal burdens, enhanced tissue pathology and mortality. During the infection, AhR−/− mice have more pulmonary myeloid cells with activated phenotype and reduced numbers expressing indoleamine 2,3 dioxygenase 1. AhR-deficient lungs have altered production of cytokines and reduced numbers of innate lymphoid cells (NK, ILC3 and NCR IL-22). The lungs of AhR−/− mice showed increased presence Th17 cells concomitant with reduced numbers of Th1, Th22 and Foxp3+ Treg cells. Furthermore, treatment of infected WT mice with an AhR-specific antagonist (CH223191) reproduced the main findings obtained in AhR−/− mice. Collectively our data demonstrate that in pulmonary paracoccidioidomycosis AhR controls fungal burden and excessive tissue inflammation and is a possible target for antifungal therapy.

Regulation of Human Innate Lymphoid Cells in the Context of Mucosal Inflammation.

Since their identification as a unique cell population, innate lymphoid cells (ILCs) have revolutionized our understanding of immune responses, leaving their impact on multiple inflammatory and fibrotic pathologies without doubt. Thus, a tightly controlled regulation of local ILC numbers and their activity is of crucial importance. Even though this has been extensively studied in murine ILCs in the last few years, our knowledge of human ILCs is still lagging behind. Our review article will therefore summarize recent insights into the function of human ILCs and will particularly focus on their regulation under inflammatory conditions. The quality and intensity of ILC involvement into local immune responses at mucosal sites of the human body can potentially be modulated via three different axes: (1) activation of tissue-resident mature ILCs, (2) plasticity and local transdifferentiation of specific ILC subsets, and (3) tissue migration and accumulation of peripheral ILCs. Despite a still ongoing scientific effort in this field, already existing data on the fate of human ILCs under different pathologic conditions clearly indicate that all three of these mechanisms are of relevance for the clinical course of chronic inflammatory and autoimmune diseases and might likewise provide new target structures for future therapeutic strategies.

Innate lymphoid cells in isocyanate-induced asthma: role of microRNA-155.

Occupational asthma, induced by workplace exposures to low molecular weight agents such as toluene 2,4-diisocyanate (TDI), causes a significant burden to patients and society. Little is known about innate lymphoid cells (ILCs) in TDI-induced asthma. A critical regulator of ILC function is microRNA-155, a microRNA associated with asthma. To determine whether TDI exposure modifies the number of ILCs in the lung and whether microRNA-155 contributes to TDI-induced airway inflammation and hyperresponsiveness. C57BL/6 wild-type and microRNA-155 knockout mice were sensitised and challenged with TDI or vehicle. Intracellular cytokine expression in ILCs and T-cells was evaluated in bronchoalveolar lavage (BAL) fluid using flow cytometry. Peribronchial eosinophilia and goblet cells were evaluated on lung tissue, and airway hyperresponsiveness was measured using the forced oscillation technique. Putative type 2 ILCs (ILC2) were identified in bronchial biopsies of subjects with TDI-induced occupational asthma using immunohistochemistry. Human bronchial epithelial cells were exposed to TDI or vehicle. TDI-exposed mice had higher numbers of airway goblet cells, BAL eosinophils, CD4+ T-cells and ILCs, with a predominant type 2 response, and tended to have airway hyperresponsiveness. In TDI-exposed microRNA-155 knockout mice, inflammation and airway hyperresponsiveness were attenuated. TDI exposure induced IL-33 expression in human bronchial epithelial cells and in murine lungs, which was microRNA-155 dependent in mice. GATA3+CD3- cells, presumably ILC2, were present in bronchial biopsies. TDI exposure is associated with increased numbers of ILCs. The proinflammatory microRNA-155 is crucial in a murine model of TDI asthma, suggesting its involvement in the pathogenesis of occupational asthma due to low molecular weight agents.

STING Gain-of-Function Disrupts Lymph Node Organogenesis and Innate Lymphoid Cell Development in Mice

STING gain-of-function causes autoimmunity and immunodeficiency in mice and STING-associated vasculopathy with onset in infancy (SAVI) in humans. Here, we report that STING gain-of-function in mice prevents development of lymph nodes and Peyer's patches. We show that the absence of secondary lymphoid organs is associated with diminished numbers of innate lymphoid cells (ILCs), including lymphoid tissue inducer (LTi) cells. Although wild-type (WT) α4β7+ progenitors differentiate efficiently into LTi cells, STING gain-of-function progenitors do not. Furthermore, STING gain-of-function impairs development of all types of ILCs. Patients with STING gain-of-function mutations have fewer ILCs, although they still have lymph nodes. In mice, expression of the STING mutant in RORγT-positive lineages prevents development of lymph nodes and reduces numbers of LTi cells. RORγT lineage-specific expression of STING gain-of-function also causes lung disease. Since RORγT is expressed exclusively in LTi cells during fetal development, our findings suggest that STING gain-of-function prevents lymph node organogenesis by reducing LTi cell numbers in mice.

Lead Impairs the Development of Innate Lymphoid Cells by Impeding the Differentiation of Their Progenitors.

Lead (Pb) is a heavy metal toxic to the immune system, yet the influence of Pb on innate lymphoid cells (ILC) remains to be defined. In this study, we found that occupationally relevant level of Pb exposure impaired ILC development at the progenitor level by activating Janus Kinase1. C57BL/6 mice treated with 1250 ppm, but not 125 ppm Pb acetic via drinking water for 8 weeks had reduced number of mature ILC, which was not caused by increased apoptosis or suppressed proliferation. Conversely, Pb increased the number of innate lymphoid cell progenitors (ILCP) in the bone marrow. The discordant observation indicated that an obstruction of ILCP differentiation into mature ILC during Pb exposure existed. Pb directly acted on ILCP to suppress their proliferation, indicating that ILCP were less activated during Pb exposure. Reciprocal ILCP transplantation assay confirmed that Pb impeded the differentiation of ILCP into mature ILC, as ILCP gave rise to fewer mature ILC in Pb-treated recipients compared with control recipients. In vitro assays suggested that the obstruction of ILCP differentiation by Pb exposure was due to increased activation of Janus Kinase1. Thus, Pb impeded ILCP differentiation into mature ILC to result in an accumulation of ILCP in the bone marrow and the resultant decreased number of mature ILC in lymphoid and nonlymphoid tissues in mice. Moreover, by analyses of ILC and ILCP in peripheral blood mononuclear cells of human subjects occupationally exposed to Pb, we revealed that Pb might also impede the development of ILC in human.

Recovery of innate lymphoid cells after allogeneic stem cell transplant: A single institution pilot study

Abstract The response of Innate Lymphoid Cells (ILCs) to conditioning regimens and subsequent recovery in the setting of allogeneic hematopoietic stem cell transplant (aHSCT) in pediatric patients is not known. The impact of this recovery pattern on graft versus host disease (GVHD) has not been prospectively studied. We aim to study the recovery of ILCs after aHSCT in children and discover its role in GVHD. Pediatric patients undergoing aHSCT were enrolled in a prospective translational study since May 2019. Patients blood were analysed by flow cytometry at following time points: prior to the conditioning regimen, weekly starting on day 0 until +30 (+/− 3 days), then +60, +90 and +180 days. Ten patients have been enrolled to date - demographics: median age 9.5 years; 4 malignant, 6 non-malignant; haploidentical donor (n=1), matched sibling (n=3), unrelated (n= 6). Graft source was bone marrow for all patients. Most common conditioning regimen was fludarabine, busulfan and rabbit antithymocyte globulin (40%). GVHD prophylaxis for most patients was tacrolimus with mini-methotrexate (90%). We saw substantial drop in number of ILCs in response to conditioning regimen in all patients, with nadir on +14 that plateaued through +30, followed by a spike on +60 and return to normal levels by +90. Similar trend was seen in type 1 ILCs (Lin− CD127+ CRTH2− CD117−) but showed a slower drop, reaching nadir on +21 with slow recovery by +60. Type 2 ILCs (Lin− CD127+ CRTH2+) and Type 3 ILCs (Lin− CD127+ CRTH2-ve CD117+) however showed a small increase on +7 compared to day 0 with both cell types recovering by +60. We showed that it is feasible to prospectively study the recovery of ILCs after aHSCT. Continued enrollment will allow us to evaluate the correlation between ILCs and GVHD.