成田 知也

Abstract Eosinophils are typical effector cells associated with type 2 immune responses and play key roles in the pathogenesis of allergic diseases. These cells are activated by various stimuli, such as cytokines, chemokines, and growth factors, but the regulatory mechanisms of eosinophil effector functions remain unclear. Glucocorticoid-induced TNF receptor family-related protein (GITR), a transmembrane protein belonging to the TNF receptor superfamily, is a well-known regulatory molecule for T cell activation. Here, we show that GITR is also constitutively expressed on eosinophils and functions as a co-stimulatory molecule for these cells. Although degranulation was unaffected by GITR engagement of murine bone marrow-derived eosinophils (bmEos), secretion of inflammatory cytokines such as interleukin (IL)-4, IL-6, and IL-13 from IL-33-activated bmEos were augmented by anti-mouse GITR agonistic antibody (DTA-1). In conclusion, our results provide a new regulatory pathway of cytokine secretion from eosinophils where GITR functions as a co-stimulatory molecule.

The γδT cells that produce IL-17 (γδT17 cells) play a key role in various pathophysiologic processes in host defense and homeostasis. The development of γδT cells in the thymus requires γδT cell receptor (γδTCR) signaling mediated by the spleen tyrosine kinase (Syk) family proteins, Syk and Zap70. Here, we show a critical role of Syk in the early phase of γδT cell development using mice deficient for Syk specifically in lymphoid lineage cells (Syk-conditional knockout (cKO) mice). The development of γδT cells in the Syk-cKO mice was arrested at the precursor stage where the expression of Rag genes and αβT-lineage-associated genes were retained, indicating that Syk is required for γδT-cell lineage commitment. Loss of Syk in γδT cells weakened TCR signal-induced phosphorylation of Erk and Akt, which is mandatory for the thymic development of γδT17 cells. Syk-cKO mice exhibited a loss of γδT17 cells in the thymus as well as throughout the body, and thereby are protected from γδT17-dependent psoriasis-like skin inflammation. Collectively, our results indicate that Syk is a key player in the lineage commitment of γδT cells and the priming of γδT17 cell differentiation.

BACKGROUND: Myeloid differentiation protein-2 (MD-2) is a lipopolysaccharide-binding protein involved in lipopolysaccharide signalling via Toll-like receptor 4 (TLR4). TLR4 plays an essential role in HDM-mediated allergic airway inflammation. Moreover, MD-2 is structurally similar to Der f 2, a major allergen from house dust mite (HDM). OBJECTIVES: We aimed to clarify the role of MD-2 in the pathogenesis of HDM-mediated allergic airway inflammation. METHODS: Wild-type (WT), TLR4 knockout and MD-2 knockout mice were subjected to intranasal instillation of HDM extract, and asthmatic features were evaluated. We also evaluated gene sets regulated by MD-2 in HDM-treated airway epithelial cells and examined the function of dendritic cells from lymph nodes and from lungs. RESULTS: Aggravated allergic airway inflammation with increased airway hyperresponsiveness was observed in MD-2 knockout mice compared with WT and TLR4 knockout mice. Global gene expression analysis revealed an MD-2 regulated proinflammatory response and reconstituted TLR4 signalling in airway epithelial cells. The ability of dendritic cells to evoke an allergic immune response was enhanced in MD-2 knockout mice. CONCLUSIONS & CLINICAL RELEVANCE: MD-2 plays a protective role in HDM-induced airway allergy with the proinflammatory regulation of airway epithelial cells and dendritic cells. MD-2 may serve as a therapeutic target in the treatment of asthma.

<title>Abstract</title>Stimulator of interferon genes (STING) is a DNA sensor that responds to pathogens and induces type I interferon production. Herein, the role of STING in house dust mite extract (HDM)-induced allergic asthma was investigated. C57BL/6 wild-type (WT) and <italic>Sting</italic>^−/− mice were intratracheally sensitized with HDM, and the bronchoalveolar lavage fluid (BALF), sera, lungs, and mediastinal lymph nodes (MLNs) were analyzed. The total and HDM-specific serum IgE levels were lower in <italic>Sting</italic>^−/− mice than in WT mice. B cell and IgE-positive B cell proportion in BALF and MLNs, respectively, was significantly lower in <italic>Sting</italic>^{<italic>−/−</italic>} mice than in WT mice. Additionally, cyclic GMP-AMP, a STING ligand, augmented total and HDM-specific serum IgE levels and B cell proportion in BALF when applied in combination with HDM. To elucidate the role of STING in IgE production, follicular helper T (Tfh) cells, which are involved in B cell maturation, were investigated. Tfh cell proportion in MLNs decreased in <italic>Sting</italic>^{<italic>−/−</italic>} mice, and IL-4 and IL-13 production by HDM-restimulated MLN cells from HDM-sensitized mice was decreased in <italic>Sting</italic>^{<italic>−/−</italic>} mice compared with WT mice. Thus, STING plays an important role in the maturation and class switching of IgE-producing B cells in allergic inflammation via Tfh cells.

<title>Abstract</title> Allergic asthma is one of most famous allergic diseases, which develops lung and airway inflammation. Recent studies have revealed the relationship between the pathology of allergic asthma and the increase of host-derived DNA in inflamed lung, but the role of the DNA-recognizing innate immune receptor for the inflammation is unknown well. Here we investigated the role of Toll-Like Receptor 9 in the pathogenesis of allergic asthma without synthesized CpG-ODNs. To examine that, we analyzed the pathology and immunology of house-dust-mite (HDM)-induced allergic asthma in <italic>Tlr9</italic>^{<italic>–/–</italic>} mice and TLR9-inhibitory-antibody-treated mice. In <italic>Tlr9</italic>^{<italic>–/–</italic>} mice, airway hyperresponsiveness (AHR) and the number of eosinophils decreased, and production of the Th2 cytokines IL-13, IL-5, and IL-4 was suppressed, compared with in wild-type mice. Interestingly, unlike Th2 cytokine production, IL-17A production was increased in <italic>Tlr9</italic>^{<italic>–/–</italic>} mice. Furthermore, production of IL-2, which decreases IL-17A production, was reduced in <italic>Tlr9</italic>^{<italic>–/–</italic>} mice. Blockade of TLR9 by treatment with TLR9-inhibitory-antibody, NaR9, effectively suppressed the development of allergic asthma pathology. IL-17A production in NaR9-treated mice was enhanced, which is comparable to <italic>Tlr9</italic>^{<italic>-/-</italic>} mice. These results suggest that the TLR9–IL-2 axis plays an important role in Th2 inflammation by modulating IL-17A production in HDM-induced allergic asthma and that targeting of TLR9 might be a novel therapeutic method for allergic asthma.