哮喘是严重威胁公众健康的常见疾病，慢性炎症和气道重塑为其病理特征。近年发现IL-25诱导产生的固有淋巴样2型细胞（ILC2）是参与过敏性疾病和宿主寄生虫防御的免疫效应细胞。本课题组前期研究发现鼻腔吸入IL-25可诱导小鼠气道高反应性，哮喘样气道炎症反应和气道重塑等病理学改变，并伴随Lin-ICOS+T1/ST2variable ILC2细胞在肺内聚集，该细胞通过合成分泌IL-13等生物活性介质导致上述反应的发生。这些结果提示ILC2细胞及其介导的生物学效应是继IL-25作用之后参与哮喘发生发展，引发哮喘慢性炎症和气道重塑的重要原因，在Th2细胞介导的适应性免疫应答过程中起到重要的桥梁作用。本课题利用哮喘模型小鼠，通过流式细胞术、小动物活体成像等技术研究ILC2细胞参与Th2型免疫应答的机制及其与哮喘慢性炎症和气道重塑的关系，以期为阐明哮喘发生机制和新型靶向药物的筛选提供实验依据。

Asthma is a common disease, seriously threatening public health, characterized with chronic airways inflammation and remodeling. ILC2 is recently discovered as a subset of cells, termed as Type 2 innate lymphoid cells, mainly participating in pathogenesis of allergic atopic diseases and parasite defence in host. Our preliminary data showed that nasal inhalation of IL-25 induces airway hyperresponsiveness, airways inflammation and remodeling, companying with accumulation of Lin-ICOS+ T1/ST2variable ILC2 in murine lungs，suggesting that these cells are possibly associated with pathological changes as above, through producing IL-13 and other mediators. These data indicate that the effects of ILC2 and the ILC2-relevant mediators are the consequences of acting of IL-25, which contribute to pathogenesis of asthma, such as chronic airways inflammation and remodeling. These cells may serve as a bridge between innate and adaptive immunities in asthma. Using murine asthma models and a number of techniques such as flow cytometry and in vivo imaging of small animals, we attempt to investigate the mechanisms of ILC2 participating in Th2-mediated responses and to evaluate the relationships between ILC2 and airways chronic inflammation and remodeling in asthma. We hope that the project will provide experimental basis for elucidating the pathogenesis and screen new therapeutic targets for treatment in asthma.

本课题对固有淋巴样2型细胞（Type 2 innate lymphoid cell，ILC2）的基本特性及其在哮喘发病机制中的作用进行了探索。课题组获得的重要结果如下：一，细胞因子IL-25和IL-33是诱导慢性哮喘发生发展的重要靶分子。课题组采用滴鼻法成功制备了过敏原OVA、IL-25和IL-33诱导的过敏原依赖/非依赖性慢性哮喘小鼠模型。发现OVA诱导的哮喘模型小鼠其气道高反应性、肺内炎症细胞浸润、粘液分泌、气道平滑肌增生、支气管壁周围胶原纤维沉积和新生血管形成等病理学改变的出现时相都较IL-25和IL-33组为早，而IL-33的效应更强且持久。二，IL-25和IL-33诱导ILC2细胞在哮喘模型小鼠肺部聚集。在哮喘发展进程中，OVA、IL-25和IL-33组的ILC2细胞在肺泡灌洗液、肺组织、纵膈淋巴结、脾脏中的数量均有所增加，且IL-25和IL-33诱导ILC2细胞在引流淋巴结和肺内聚集的能力比OVA更强。三，IL-33和CXCL16是趋化ILC2细胞向肺部聚集的主要因素。通过基因芯片、流式细胞术、Transwell实验和小动物活体成像技术等在世界上首次证实IL-33和CXCL16对ILC2细胞具有直接趋化作用。且CXCL16对ILC2细胞具有特异性肺内趋化募集作用但不能引起其他炎症效应。四，ILC2细胞是哮喘慢性炎症和气道重塑发生发展的核心环节之一。利用上述模型，进一步发现肺内ILC2细胞的时间动力学变化趋势与哮喘气道高反应性、Th2型细胞因子表达水平、嗜酸性粒细胞浸润、粘液分泌程度、胶原沉积和新生血管形成的多寡具有相关性。五，ILC2细胞可能是潜在的抗原提呈细胞。ILC2细胞表达模式识别受体和MHCII类分子，且可被抗原活化并产生相应细胞因子的特点是ILC2细胞参与适应性免疫应答的主要途径。上述研究表明，上皮源性细胞因子IL-25、IL-33可诱导ILC2细胞向肺内定向趋化，后者在接受抗原刺激后活化产生Th2型细胞因子，在慢性炎症和气道重塑发生发展过程中发挥重要作用。因此，阻断ILC2细胞及其上游IL-25和IL-33的作用，可能是哮喘免疫治疗的潜在靶点。此课题为阐明临床难治性哮喘的发生机制和干预治疗奠定了良好基础。