Iijima, Koji

Abstract Group 2 innate lymphoid cells (ILC2s) reside in multiple organs in the body, where they play roles in immunity, tissue homeostasis, and metabolic regulation. However, little is known about the regulatory mechanisms of ILC2s in different organs. Here, we identified ILC2s in the mouse uterus and found that they express cell surface molecules, including the IL-33 receptor, ST2, that are roughly comparable to those expressed by lung ILC2s. Both in vivo and in vitro treatment with IL-33 induced type 2 cytokine production in uterine ILC2s, suggesting that they respond to IL-33 in a manner similar to ILC2s in other organs. Importantly, uterine ILC2s were nearly absent in ovariectomized mice and were increased in wild-type mice by estrogen administration, whereas lung ILC2s were unaffected by both ovariectomy and estrogen administration. Likewise, a marked reduction in uterine ILC2s was observed in mice deficient in estrogen receptor α or estrogen receptor β. Furthermore, uterine ILC2s highly expressed estrogen receptor α, and in vitro culture of isolated uterine ILC2s with 17β-estradiol modified expression of a number of genes. Finally, an increased prevalence in neonatal mortality was observed in litters from dams lacking the IL-33 receptor, ST2. Taken together, our findings indicate that unlike lung IL2Cs, uterine ILC2s are regulated by female sex hormones, which may specialize them for specific physiological functions.

AbstractBackgroundInterleukin (IL)‐33 is implicated in the pathophysiology of asthma and allergic diseases. However, our knowledge is limited regarding how IL‐33 release is controlled. The transcription factor nuclear factor‐erythroid‐2‐related factor 2 (Nrf2) plays a key role in antioxidant response regulation.ObjectiveThe goal of this project was to investigate the role of cellular oxidative stress in controlling IL‐33 release in airway epithelium.MethodsComplementary approaches were used that included human bronchial epithelial cells and mouse models of airway type‐2 immunity that were exposed to fungus Alternaria extract. The clinically available Nrf2 activator 2‐cyano‐3,12‐dioxooleana‐1,9‐dien‐28‐oic acid methyl ester (CDDO‐Me) was used to evaluate the role of Nrf2‐induced antioxidant molecules.ResultsHuman bronchial epithelial cells produced reactive oxygen species (ROS) when they were exposed to Alternaria extract. ROS scavengers, such as glutathione (GSH) and N‐acetyl cysteine, prevented extracellular secretion of ATP and increases in intracellular calcium concentrations that precede IL‐33 release. Administration of CDDO‐Me to mice enhanced expression of a number of antioxidant molecules in the lungs and elevated lung levels of endogenous GSH. Importantly, CDDO‐Me treatment reduced allergen‐induced ATP secretion and IL‐33 release by airway epithelial cells in vitro and protected mice from IL‐33 release and asthma‐like pathological changes in the lungs.ConclusionsThe balance between oxidative stress and antioxidant responses plays a key role in controlling IL‐33 release in airway epithelium. The therapeutic potential of Nrf2 activators needs to be considered for asthma and allergic airway diseases.

Abstract Innate lymphoid cells (ILCs) are a new family of immune cells that play important roles in innate immunity in mucosal tissues, and in the maintenance of tissue and metabolic homeostasis. Recently, group 2 ILCs (ILC2s) were found to promote the development and effector functions of Th2-type CD4+ T cells by interacting directly with T cells or by activating dendritic cells, suggesting a role for ILC2s in regulating adaptive immunity. However, our current knowledge on the role of ILCs in humoral immunity is limited. In this study, we found that ILC2s isolated from the lungs of naive BALB/c mice enhanced the proliferation of B1- as well as B2-type B cells and promoted the production of IgM, IgG1, IgA, and IgE by these cells in vitro. Soluble factors secreted by ILC2s were sufficient to enhance B cell Ig production. By using blocking Abs and ILC2s isolated from IL-5–deficient mice, we found that ILC2-derived IL-5 is critically involved in the enhanced production of IgM. Furthermore, when adoptively transferred to Il7r−/− mice, which lack ILC2s and mature T cells, lung ILC2s promoted the production of IgM Abs to a polysaccharide Ag, 4-hydroxy-3-nitrophenylacetyl Ficoll, within 7 d of airway exposure in vivo. These findings add to the growing body of literature regarding the regulatory functions of ILCs in adaptive immunity, and suggest that lung ILC2s promote B cell production of early Abs to a respiratory Ag even in the absence of T cells.

AbstractBackgroundExposure to aeroallergens induces eosinophilic airway inflammation in patients with asthma and allergic airway diseases. The circulating number of eosinophils in peripheral blood is relatively small, leading us to hypothesize that bone marrow needs to be engaged quickly to meet the demands of the tissues.MethodsTo investigate the communication between the lungs and bone marrow, we used acute allergen exposure and airway inflammation models in mice. Gene‐deficient mice and cytokine reporter mice as well as in vitro cell culture models were used to dissect the mechanisms.ResultsNaïve BALB/c mice produced increased numbers of eosinophil precursors and mature eosinophils in the bone marrow when their airways were exposed to a common fungal allergen, Alternaria alternata. Expression of IL‐5 and IL‐33 increased rapidly in the lungs, but not in the bone marrow. Sera from allergen‐exposed mice promoted eosinophilopoiesis in bone marrow cells from naïve mice, which was blocked by anti‐IL‐5 antibody. Mice deficient in the IL‐33 receptor ST2 (i.e., Il1rl1−/− mice) were unable to increase their serum levels of IL‐5 and allergen‐induced eosinophilopoiesis in the bone marrow after allergen exposure. Finally, group 2 innate lymphoid cells (ILC2s) in the lungs showed robust expression of IL‐5 after Alternaria exposure.ConclusionsThese finding suggests that lung IL‐33, through innate activation of ILC2s and their production of IL‐5, plays a key role in promoting acute reactive eosinophilopoiesis in the bone marrow when naïve animals are exposed to airborne allergens. Therefore, bone marrow eosinophilopoiesis may be affected by atmospheric environmental conditions.

Abstract Humans are frequently exposed to various airborne allergens in the atmospheric environment. These allergens may trigger a complex network of immune responses in the airways, resulting in asthma and other chronic airway diseases. In this study, we investigated the immunological mechanisms involved in the pathological changes induced by chronic exposure to multiple airborne allergens. Naive mice were exposed intranasally to a combination of common airborne allergens, including the house dust mite, Alternaria, and Aspergillus, for up to 8 wk. These allergens acted synergistically and induced robust eosinophilic airway inflammation, specific IgE Ab production, type 2 cytokine response, and airway hyperresponsiveness in 4 wk, followed by airway remodeling in 8 wk. Increased lung infiltration of T cells, B cells, and type 2 innate lymphoid cells was observed. CD4+ T cells and type 2 innate lymphoid cells contributed to the sources of IL-5 and IL-13, suggesting involvement of both innate and adaptive immunity in this model. The lung levels of IL-33 increased quickly within several hours after allergen exposure and continued to rise throughout the chronic phase of inflammation. Mice deficient in IL-33R (Il1rl1−/−) and thymic stromal lymphopoietin receptor (Tslpr−/−) showed significant reduction in airway inflammation, IgE Ab levels, and airway hyperresponsiveness. In contrast, mice deficient in IL-25R or IL-1R showed minimal differences as compared with wild-type animals. Thus, chronic exposure to natural airborne allergens triggers a network of innate and adaptive type 2 immune responses and airway pathology, and IL-33 and thymic stromal lymphopoietin most likely play key roles in this process.

Abstract Background Innate lymphoid cells ( ILC s) play important roles in innate immunity and tissue remodeling via production of various cytokines and growth factors. Group 2 ILC s ( ILC 2s) were recently shown to mediate the immune pathology of asthma even without adaptive immunity. However, little is known about possible interactions between ILC 2s and other immune cells. We sought to investigate the capacity of ILC 2s to regulate effector functions of T cells. Methods We isolated ILC 2s from the lungs of naïve mice. We cultured CD 4 + T cells with ILC 2s in vitro and examined the functions of these cell types. The mechanisms were investigated using blocking antibodies and cells isolated from cytokine‐deficient mice. For the in vivo study, we adoptively transferred ILC 2s and CD 4 + T cells into Il7ra −/− mice and subsequently exposed the mice to ovalbumin and a cysteine protease. Results Lung ILC 2s enhanced CD 4 + T‐cell proliferation and promoted production of type 2 cytokines in vitro . The interaction between ILC 2s and CD 4 + T cells involved costimulatory molecule OX 40L and cytokine IL ‐4, which was mainly derived from ILC 2s. Adoptive transfer of both ILC 2 and CD 4 + T‐cell populations, but not each population alone, into Il7ra −/− mice resulted in induction of a robust antigen‐specific type 2 cytokine response and airway inflammation. Conclusion Lung ILC 2s function to promote adaptive immunity in addition to their established roles in innate immunity. This novel function of ILC 2s needs to be taken into account when considering the pathophysiology of asthma and other allergic airway diseases.

Abstract Tissue eosinophilia probably plays important roles in the pathophysiology of bronchial asthma and allergic disorders; however, this concept was challenged recently by controversial results in mouse models of bronchial asthma treated with anti-IL-5 Ab and the failure of anti-IL-5 therapy in humans. We have now used a unique model, IL-5 transgenic (TG) mice, to address a fundamental question: is airway eosinophilia beneficial or detrimental in the allergic response? After sensitization and challenge with OVA, IL-5 TG mice showed a marked airway eosinophilia. Surprisingly, these IL-5 TG mice showed lower airway reactivity to methacholine. Immunohistochemical analysis of the lungs revealed a marked peribronchial infiltration of eosinophils, but no eosinophil degranulation. In vitro, mouse eosinophils from peritoneal lavage fluids did not produce superoxide anion, but did produce an anti-inflammatory and fibrotic cytokine, TGF-β1. Indeed, the TGF-β1 levels in bronchoalveolar lavage fluid specimens from IL-5 TG mice directly correlated with airway eosinophilia (r = 0.755). Furthermore, anti-IL-5 treatment of IL-5 TG mice decreased both airway eosinophilia and TGF-β1 levels in bronchoalveolar lavage fluids and increased airway reactivity. Thus, in mice, marked eosinophilia prevents the development of airway hyper-reactivity during an allergic response. Overall, the roles of eosinophils in asthma and in animal models need to be addressed carefully for their potentially detrimental and beneficial effects.

Abstract We present a novel immunotherapeutic strategy using a human B7-DC cross-linking Ab that prevents lung inflammation, airway obstruction, and hyperreactivity to allergen in a mouse model of allergic inflammatory airway disease. Dendritic cells (DC) have the ability to skew the immune response toward a Th1 or Th2 polarity. The sHIgM12 Ab functions in vitro by cross-linking the costimulatory family molecule B7-DC (PD-L2) on DC up-regulating IL-12 production, homing to lymph nodes, and T cell-activating potential of these APCs. Using chicken OVA as a model Ag, the administration of sHIgM12 Ab to BALB/c mice blocked lung inflammation, airway pathology, and responsiveness to methacholine, even after animals were presensitized and a Th2-polarized immune response was established. This therapeutic strategy was ineffective in STAT4-deficient animals, indicating that IL-12 production is critical in this system. Moreover, the polarity of the immune response upon in vitro restimulation with Ag is changed in wild-type mice, with a resulting decrease in Th2 cytokines IL-4 and IL-5 and an increase in the immunoregulatory cytokine IL-10. These studies demonstrate that the immune response of hypersensitized responders can be modulated using B7-DC cross-linking Abs, preventing allergic airway disease upon re-exposure to allergen.

Abstract To investigate the role of HLA-DQ molecules and/or CD4+ T cells in the pathogenesis of allergic asthma, we generated HLA-DQ6 and HLA-DQ8 transgenic mice lacking endogenous class II (Aβnull) and CD4 genes and challenged them intranasally with short ragweed allergenic extract (SRW). We found that DQ6/CD4null mice developed a strong eosinophilic infiltration into the bronchoalveolar lavage and lung tissue, while DQ8/CD4null mice were normal. However, neither cytokines nor eosinophil peroxidase in the bronchoalveolar lavage of DQ6/CD4null mice was found. In addition, the airway reactivity to methacholine was elevated moderately in DQ6/CD4null mice compared with the high response in DQ/CD4+ counterparts and was only partially augmented by CD4+ T cell transfer. The DQ6/CD4null mice showed Th1/Th2-type cytokines and SRW-specific Abs in the immune sera in contrast to a direct Th2 response observed in DQ6/CD4+ mice. The proliferative response of spleen mononuclear cells and peribronchial lymph node cells demonstrated that the response to SRW in DQ6/CD4null mice was mediated by HLA-DQ-restricted CD4−CD8−NK1.1− T cells. FACS analysis of PBMC and spleen mononuclear cells demonstrated an expansion of double-negative (DN) CD4−CD8−TCRαβ+ T cells in SRW-treated DQ6/CD4null mice. These cells produced IL-4, IL-5, IL-13, and IFN-γ when stimulated with immobilized anti-CD3. IL-5 ELISPOT assay revealed that DN T cells were the cellular origin of IL-5 in allergen-challenged DQ6/CD4null mice. Our study shows a role for HLA-DQ-restricted CD4+ and DN T cells in the allergic response.