固有淋巴样2型细胞表达Toll样受体2/4直接识别过敏原参与哮喘发病的机制研究

Asthma is a common disease, seriously threatening public health. ILC2 is recently discovered as a subset of cells, termed as type 2 innate lymphoid cells, mainly participating in pathogenesis of allergic diseases and parasite defence in host. Our preliminary data showed that ILC2 cells gathered to lung tissues and expressed Toll-like receptor (TLR) 2 and TLR4 in murine models of asthma. However, the significance and function of expression of TLR2 and TLR4 on ILC2 cells is unclear. Studies have found that allergens can directly activate TLRs of epithelial cells. Therefore, we believe that ILC2 cells may be involved in the pathogenesis of asthma, by expressing TLR2/4 directly to recognize the allergens. In order to verify this hypothesis, the expressions of TLR2/4 on ILC2 cells in peripheral blood in asthmatic patients are examined. The effects of TLR2/4 signal transduction pathways on the proliferation, secretion, chemotaxis and autophagy of ILC2 cells was investigated by in vitro experiments. In vivo animal experiments are used to clarify activation of TLR2/4 on ILC2 cells-mediated allergic inflammatory response mechanism. We hope that the project will provide experimental basis for elucidating the pathogenesis and screen new therapeutic targets for treatment in asthma.

哮喘是严重威胁公众健康的常见疾病。固有淋巴样2型细胞（ILC2）是新近发现的参与过敏性疾病的重要免疫效应细胞。本课题组前期研究发现哮喘模型小鼠ILC2细胞向肺组织定向聚集且表达Toll样受体(TLR)2/4。然，TLR2/4在ILC2细胞上表达的意义及其对ILC2细胞功能的影响尚不清楚。有研究发现，过敏原可作为病原相关模式分子直接活化上皮细胞表面TLRs，在哮喘发生发展中起重要作用。因此，我们认为ILC2细胞可能通过表达TLR2/4直接识别过敏原从而参与哮喘的发病过程。为验证这一假说，本课题拟检测哮喘患者外周血ILC2细胞TLR2/4的表达水平；通过体外实验，探讨TLR2/4信号传导途径对ILC2细胞增殖、分泌、趋化、自噬等功能的调节作用；通过体内动物实验，阐明TLR2/4在接受过敏原刺激后ILC2细胞介导的过敏性炎症反应机制。项目实施将丰富对哮喘发病机制的认识，为寻找新治疗靶点奠定基础。

本课题对2型固有淋巴细胞（ILC2）的激活及其在哮喘发病机制中的作用进行了深入探索。课题组获得的重要结果如下：1、细胞因子IL-33和趋化因子CXCL16是诱导ILC2细胞向肺组织定向聚集的关键靶分子。课题组检测了哮喘模型各组织器官中ILC2的分布、数量及趋化因子受体的表达，发现气道上皮细胞来源的IL-25和IL-33能够诱导ILC2细胞向肺组织、纵隔淋巴结和气道管腔中定向聚集。通过体外实验和动物模型进一步明确IL-33可直接诱导ILC2细胞迁移。尽管ILC2细胞表达趋化因子受体CXCR6和CCR9，但只有CXCR6的配体CXCL16可直接诱导ILC2细胞趋化。该研究在世界上首次确证了ILC2细胞向肺组织定向趋化的分子机制。2、过敏原尘螨（HDM）可直接活化ILC2细胞，参与哮喘发生发展。课题组采用HDM刺激ILC2细胞，发现HDM可直接促使ILC2细胞分泌IL-5和IL-13，并能抑制细胞凋亡。进一步研究发现HDM可通过作用于ILC2细胞上的TLR2和TLR4，进而活化细胞，参与哮喘发生发展。3、IL-37b可通过对ILC2细胞和Th2细胞的负向调控进而发挥对哮喘气道炎症、气道高反应性的抑制作用。慢性哮喘模型中IL-37b可通过下调ILC2细胞和Th2细胞数量，降低Th2型炎症因子表达起到抑制炎症的作用。上述研究表明IL-33和CXCL16可诱导ILC2细胞向肺组织定向聚集，肺组织内的ILC2细胞可直接被过敏原活化参与哮喘发生发展，而IL-37b可通过负向调控ILC2细胞发挥对哮喘炎症的抑制作用。该研究有助于丰富对哮喘发病机制的认识，并为研发针对哮喘的药物治疗新靶点奠定基础。