B7-H3调控Th细胞分化及其在支气管哮喘免疫病理中的作用研究

Bronchial Asthma (asthma) is the most common respiratory tract disease characterized with chronic inflammation. The unbalance of Th cell plays an important role in immunopathogenesis of asthma and the costimulatory molecule B7-H3 contributes to the Th cell differentiation. However, the results are inconsistent. There are two forms for B7-H3, soluble B7-H3 (sB7-H3) and membrane B7-H3 (mB7-H3). Most former studies neglected the existence of the form sB7-H3, which may be the major factor for the different biological function that B7-H3 exhibited. Our preliminary studies have shown that both sB7-H3 and mB7-H3 exist among children with asthma. Then it is necessary to explore the mechanism of these two forms in regulating Th cell differentiation and immunopathogenesis of asthma. In view of the above, this study will probe into the expression of sB7-H3 and mB7-H3 in children with asthma and its clinical significance and the role of allergen to induce the expression of sB7-H3 and mB7-H3. In addition, this study will explore the different function and the molecular mechanism of both sB7-H3 and mB7-H3 in Th cell differentiation by using anti-B7-H3 mAb, gene transfected cell and B7-H3 knock-out mice in vitro and vivo. In all, this study aims to provide an up-to-date clue for asthma prevention and treatment.

支气管哮喘（哮喘）是儿童最常见的气道慢性炎症性疾病，其发病与Th细胞失衡密切相关。共刺激分子B7-H3被证实在Th细胞分化中发挥重要作用，但结论并不一致。B7-H3存在可溶性（sB7-H3）和膜型（mB7-H3）两种表现形式，但既往研究均忽略了sB7-H3的存在，这可能是导致该分子不同生物学功能的重要因素。本项目前期研究发现，哮喘患儿体内同时存在sB7-H3和mB7-H3两种表现形式，因此比较分析两者在Th细胞分化及哮喘病理进程中的作用机制显得非常必要。本项目拟：1）分析哮喘患儿体内sB7-H3和mB7-H3表达的临床意义；2）致敏原诱导sB7-H3和mB7-H3表达的作用；3）借助表达sB7-H3和mB7-H3的转基因细胞以及B7-H3基因敲除小鼠等工具，通过体内外实验，比较分析sB7-H3和mB7-H3对Th细胞诱导分化的差异及分子机制，从而为支气管哮喘防治提供新线索。

从哮喘发病机制水平寻找干预措施是迫切需要解决的临床实际问题。无论结构学还是功能学都提示B7-H3是调控T细胞生物学活性和分化的关键分子。本项目旨在通过体内外实验，阐明B7-H3在调控Th细胞分化的作用及相关分子机制，为更全面的认识共刺激分子B7-H3在哮喘发病机制中的作用提供新的线索。. 首先，我们发现膜型B7-H3主要表达在单核细胞表面；血浆可溶性B7-H3与IFN-γ的表达水平呈负性相关；既往正规吸入糖皮质激素的患儿其体内表达的sB7-H3明显低于既往未正规吸入糖皮质激素的患儿；哮喘急性发作患儿治疗后血浆可溶性B7-H3明显下降。上述研究提示B7-H3可为哮喘预后评估的靶标之一。. 其次，我们通过体外研究将B7-H3融合蛋白（2IgB7-H3）与原始T细胞共育，结果发现STAT6和RORγt显著升高，且为浓度依赖性；上清液IL-4和IL-17也显著升高，提示B7-H3融合蛋白诱导Th2和Th17细胞分化。. 再次，我们通过体内研究探讨B7-H3干预的临床效果。阻断型抗B7-H3单克隆抗体可以缓解OVA致敏小鼠的喘息症状，减轻粘液分泌和嗜酸性粒细胞的浸润，降低肺泡灌洗液IL-4、 IL-17的水平。 B7-H3融合蛋白可以加剧OVA致敏小鼠气道炎症，增加肺泡灌洗液IL-4、 IL-17的表达水平，促进粘液分泌，但并不依赖于TLR2信号通路。本研究为哮喘的防治提供新线索和潜在干预靶标。