Hideaki Morita

IL-33 is a crucial amplifier of innate rather than acquired immunity

IL-33, a member of the IL-1-related cytokines, is considered to be a proallergic cytokine that is especially involved in Th2-type immune responses. Moreover, like IL-1α, IL-33 has been suggested to act as an “alarmin” that amplifies immune responses during tissue injury. In contrast to IL-1, however, the precise roles of IL-33 in those settings are poorly understood. Using IL-1- and IL-33-deficient mice, we found that IL-1, but not IL-33, played a substantial role in induction of T cell-mediated type IV hypersensitivity such as contact and delayed-type hypersensitivity and autoimmune diseases such as experimental autoimmune encephalomyelitis. Most notably, however, IL-33 was important for innate-type mucosal immunity in the lungs and gut. That is, IL-33 was essential for manifestation of T cell-independent protease allergen-induced airway inflammation as well as OVA-induced allergic topical airway inflammation, without affecting acquisition of antigen-specific memory T cells. IL-33 was significantly involved in the development of dextran-induced colitis accompanied by T cell-independent epithelial cell damage, but not in streptozocin-induced diabetes or Con A-induced hepatitis characterized by T cell-mediated apoptotic tissue destruction. In addition, IL-33-deficient mice showed a substantially diminished LPS-induced systemic inflammatory response. These observations indicate that IL-33 is a crucial amplifier of mucosal and systemic innate, rather than acquired, immune responses.

IL-33 Mediates Inflammatory Responses in Human Lung Tissue Cells

IL-33 is a member of the IL-1 family and mediates its biological effects via the ST2 receptor, which is selectively expressed on Th2 cells and mast cells. Although polymorphic variation in ST2 is strongly associated with asthma, it is currently unclear whether IL-33 acts directly on lung tissue cells at sites of airway remodeling. Therefore, we aimed to identify the IL-33–responsive cells among primary human lung tissue cells. ST2 mRNA was expressed in both endothelial and epithelial cells but not in fibroblasts or smooth muscle cells. Correspondingly, IL-33 promoted IL-8 production by both endothelial and epithelial cells but not by fibroblasts or smooth muscle cells. Transfection of ST2 small interference RNA into both endothelial and epithelial cells significantly reduced the IL-33–dependent upregulation of IL-8, suggesting that IL-33–mediated responses in these cells occur via the ST2 receptor. Importantly, Th2 cytokines, such as IL-4, further enhanced ST2 expression and function in both endothelial and epithelial cells. The IL-33–mediated production of IL-8 by epithelial cells was almost completely suppressed by corticosteroid treatment. In contrast, the effect of corticosteroid treatment on the IL-33–mediated responses of endothelial cells was only partial. IL-33 induced activation of both ERK and p38 MAPK in endothelial cells but only ERK in epithelial cells. p38 MAPK was required for the IL-33–mediated responses of endothelial cells, whereas ERK was required for IL-33–mediated IL-8 production by epithelial cells. Taken together, these findings suggest that IL-33–mediated inflammatory responses of lung tissue cells may be involved in the chronic allergic inflammation of the asthmatic airway.

Epithelial cell-derived IL-25, but not Th17 cell-derived IL-17 or IL-17F, is crucial for murine asthma.

IL-17A, IL-17F, and IL-25 are ligands for IL-17RA. In the current study, we demonstrated that IL-25–deficient mice—but not IL-17A–, IL-17F–, IL-17A/F–, IL-23p19–, or retinoic acid-related orphan receptor (ROR)-γt–deficient mice—showed significant suppression of 1) the number of eosinophils and the levels of proinflammatory mediators in bronchoalveolar lavage fluids, 2) airway hyperresponsiveness to methacholine, and 3) OVA-specific IgG1 and IgE levels in the serum during OVA-induced Th2-type/eosinophilic airway inflammation. The IL-25 deficiency did not affect lung dendritic cell migration or Ag-specific memory–Th2 cell expansion during Ag sensitization. Adoptive transfer of T cells, mast cells, or bone marrow cells from IL-25–deficient mice revealed that induction of Th2-type/eosinophilic airway inflammation was dependent on activation of lung epithelial cells and eosinophils by IL-25 produced by airway structural cells such as epithelial cells but not by such hematopoietic stem-cell-origin immune cells as T cells and mast cells. Therefore, airway structural cell-derived IL-25—rather than Th17 cell-derived IL-17A and IL-17F—is responsible for induction of local inflammation by promoting activation of lung epithelial cells and eosinophils in the elicitation phase of Th2-type/eosinophilic airway inflammation. It is not required for Ag-specific Th2 cell differentiation in the sensitization phase.

Interleukin‐33 in allergy

Interleukin‐33 (IL‐33) is a member of the IL‐1 cytokine family, which includes IL‐1 and IL‐18, and is considered to be important for host defense against nematodes by inducing Th2 cytokine production via the IL‐33 receptor. IL‐33 receptor is a heterodimer of IL‐1 receptor‐like 1 (IL‐1RL1; also called ST2, T1, Der4, and fit‐1) and IL‐1 receptor accessory protein (IL‐1RAcP). On the other hand, excessive and/or inappropriate production of IL‐33 is considered to be involved in the development of various disorders, such as allergic and autoimmune diseases. Unlike IL‐1β and IL‐18, IL‐33 does not seem to be secreted through the activation of inflammasomes in events such as apoptosis. However, IL‐33 is localized in the nucleus of cells and is released during tissue injury associated with necrosis. This suggests that it acts as an alarmin, like IL‐1α and high‐mobility group box chromosomal protein‐1 (HMGB‐1). This review summarizes current knowledge regarding the roles of IL‐33 in the functions of various cell types and the pathogenesis of allergy.

IL-10–overexpressing B cells regulate innate and adaptive immune responses

BACKGROUND Distinct human IL-10-producing B-cell subsets with immunoregulatory properties have been described. However, the broader spectrum of their direct cellular targets and suppressive mechanisms has not been extensively studied, particularly in relation to direct and indirect IL-10-mediated functions. OBJECTIVE The aim of the study was to investigate the effects of IL-10 overexpression on the phenotype and immunoregulatory capacity of B cells. METHODS Primary human B cells were transfected with hIL-10, and IL-10-overexpressing B cells were characterized for cytokine and immunoglobulin production by means of specific ELISA and bead-based assays. Antigen presentation, costimulation capacity, and transcription factor signatures were analyzed by means of flow cytometry and quantitative RT-PCR. Effects of IL-10-overexpresing B cells on Toll-like receptor-triggered cytokine release from PBMCs, LPS-triggered maturation of monocyte-derived dendritic cells, and tetanus toxoid-induced PBMC proliferation were assessed in autologous cocultures. RESULTS IL-10-overexpressing B cells acquired a prominent immunoregulatory profile comprising upregulation of suppressor of cytokine signaling 3 (SOCS3), glycoprotein A repetitions predominant (GARP), the IL-2 receptor α chain (CD25), and programmed cell death 1 ligand 1 (PD-L1). Concurrently, their secretion profile was characterized by a significant reduction in levels of proinflammatory cytokines (TNF-α, IL-8, and macrophage inflammatory protein 1α) and augmented production of anti-inflammatory IL-1 receptor antagonist and vascular endothelial growth factor. Furthermore, IL-10 overexpression was associated with a decrease in costimulatory potential. IL-10-overexpressing B cells secreted less IgE and potently suppressed proinflammatory cytokines in PBMCs, maturation of monocyte-derived dendritic cells (rendering their profile to regulatory phenotype), and antigen-specific proliferation in vitro. CONCLUSION Our data demonstrate an essential role for IL-10 in inducing an immunoregulatory phenotype in B cells that exerts substantial anti-inflammatory and immunosuppressive functions.

Antigen-specific T-cell responses in patients with non-IgE-mediated gastrointestinal food allergy are predominantly skewed to TH2

Age (mo) 12 38.0 (26.5-60.0) 65 2.0 (1.0-4.0) Male/female sex 12 7/5 65 40/25 Day of onset 12 — 65 32.5 (7.0-115.5) Symptoms at onset Vomiting 12 0% (0/12) 65 53.8% (35/65) Bloody stool 12 0% (0/12) 65 47.7% (31/65) Diarrhea 12 0% (0/12) 65 47.7% (31/65) Failure to thrive 12 0% (0/12) 65 38.4% (22/65) Lethargy 12 0% (0/12) 65 38.4% (22/65) Fever 12 0% (0/12) 65 18.5% (12/65) Eczema 12 100% (12/12) 65 7.7% (5/65) Wheeze 12 33.3% (3/12) 65 0% (0/65) Laboratory data Milk-specific IgE (IU/mL) 12 56.95 (11.74-90.8) 65 <0.34 (<0.34)

The Complex Type 2 Endotype in Allergy and Asthma: From Laboratory to Bedside

Better management of allergic diseases needs a sharpened understanding of disease heterogeneity and mechanisms in relation to clinically significant outcomes. Phenotypes describing observable clinical and morphologic characteristics and unique responses to treatment have been developed; however, they do not relate to disease mechanisms. Recently, extended heterogeneous and disease-related metabolic, inflammatory, immunological, and remodeling pathways have been described, and reproducible patterns are defined as disease endotypes. An endotype might consist of several intricated mechanisms that cannot be clearly separated into “pure single molecular mechanism” thus being a “complex endotype.” The description of an endotype may rely on biomarkers, which can be the signature of a complex underlying pathway or a key molecule associated with or directly playing a role in a particular disease endotype. The Th2 type inflammation can be defined as a complex endotype in asthma and linked to mechanisms of disease development and response to treatment and to disease outcomes such as exacerbations and remodeling. The type 2 complex endotype in allergies and asthma includes innate lymphoid cells, T helper 2 cells, tissue eosinophilia, and IgE production. Currently, emerging endotype-driven strategies in asthma, particularly the development of biologicals that target a single molecular pathway, are being focused for solving individualized clinical problems on disease outcomes. Progress is also being made for endotyping rhinitis, chronic rhinosinusitis, and atopic dermatitis.

Development of IL-17-mediated Delayed-Type Hypersensitivity Is Not Affected by Down-Regulation of IL-25 Expression

BACKGROUND IL-25, which is a member of the IL-17 family, induces Th2 cell differentiation and Th2 cytokine production, contributing to induction of Th2-type immune responses and diseases, as a result of which it suppresses Th1- and Th17-type immune responses. METHODS To elucidate the role of IL-25 in the pathogenesis of IL-17-mediated delayed-type hypersensitivity (DTH), IL-25-deficient mice were sensitized with methylated BSA (mBSA), and then a DTH reaction was induced by mBSA challenge. mBSA-specific T-cell induction was assessed on the basis of cell proliferation and cytokine production. The DTH reaction was evaluated on the basis of tissue swelling, histology and inflammatory mediator expression. RESULTS IL-25 expression was markedly reduced in local DTH lesions. However, mBSA-specific Th1, Th2 and Th17 cell induction, and the mBSA-induced DTH reaction were comparable in IL-25-deficient and wild-type mice. CONCLUSIONS IL-25 is not essential for differentiation of Th1, Th2 and Th17 cells in the sensitization phase or induction of local inflammation in the elicitation phase of the mBSA-induced DTH reaction.

Type 2 innate lymphoid cells disrupt bronchial epithelial barrier integrity by targeting tight junctions through IL-13 in asthmatic patients

&NA; Figure. No caption available. Background: Bronchial epithelial barrier leakiness and type 2 innate lymphoid cells (ILC2s) have been separately linked to asthma pathogenesis; however, the influence of ILC2s on the bronchial epithelial barrier has not been investigated previously. Objective: We investigated the role of ILC2s in the regulation of bronchial epithelial tight junctions (TJs) and barrier function both in bronchial epithelial cells of asthmatic patients and healthy subjects and general innate lymphoid cell– and ILC2‐deficient mice. Methods: Cocultures of human ILC2s and bronchial epithelial cells were used to determine transepithelial electrical resistance, paracellular flux, and TJ mRNA and protein expressions. The effect of ILC2s on TJs was examined by using a murine model of IL‐33–induced airway inflammation in wild‐type, recombination‐activating gene 2 (Rag2)−/−, Rag2−/−Il2rg−/−, and Rorasg/sg mice undergoing bone marrow transplantation to analyze the in vivo relevance of barrier disruption by ILC2s. Results: ILC2s significantly impaired the epithelial barrier, as demonstrated by reduced transepithelial electrical resistance and increased fluorescein isothiocyanate–dextran permeability in air‐liquid interface cultures of human bronchial epithelial cells. This was in parallel to decreased mRNAs and disrupted protein expression of TJ proteins and was restored by neutralization of IL‐13. Intranasal administration of recombinant IL‐33 to wild‐type and Rag2−/− mice lacking T and B cells triggered TJ disruption, whereas Rag2−/−Il2rg−/− and Rorasg/sg mice undergoing bone marrow transplantation that lack ILC2s did not show any barrier leakiness. Direct nasal administration of IL‐13 was sufficient to induce deficiency in the TJ barrier in the bronchial epithelium of mice in vivo. Conclusion: These data highlight an essential mechanism in asthma pathogenesis by demonstrating that ILC2s are responsible for bronchial epithelial TJ barrier leakiness through IL‐13.

Non–IgE-Mediated Gastrointestinal Food Allergies: Distinct Differences in Clinical Phenotype Between Western Countries and Japan

Non-IgE-mediated gastrointestinal food allergies, including food-protein-induced enterocolitis, enteropathy, proctocolitis and allergic eosinophilic gastroenteritis, seem to be increasing in several regions in the world. However, unlike the case of IgE-mediated food allergy, development of diagnostic laboratory tests and our understanding of the immunological mechanisms involved in non-IgE-mediated gastrointestinal food allergies lag. Although the clinical entities in Western countries have been well established, the clinical phenotypes might differ somewhat among the human races and geographical regions. In Japan, non-IgE-mediated gastrointestinal food allergies have increased sharply since the late 1990s, and clinicians have sometimes experienced confusion because of differences in the clinical phenotypes from those seen in Western countries. Aiming to solve this problem, we performed clinical research and determined a useful method for dividing patients into four clusters with distinctive clinical symptoms. We are confident this method will help in diagnosing and treating these patients. We also tried to clarify the differences between these patients in Japan and Western countries.