B7-H4共刺激分子对干燥综合征患者T细胞负向调控机制的研究

Sjogren’s syndrome (SS) is a chronic autoimmune disorder characterized by dysfunction and destruction of the salivary,lacrimal, and other exocrine glands. The majority of infiltrating lymphocytes are CD4+ T cells. B7-H4 (also known as B7x and B7S1) was initially reported to be a negative regulator of T cell responses in vitro by inhibiting proliferation, cell-cycle progression, and cytokine production. The elucidation of the precise role of B7-H4 expression by vascular and parenchymal epithelial cells is particularly important for the understanding of the pathophysiology of SS. We present a cohesive analysis of B7-H4 expression in Salivary gland and peripheral blood derived from patients with SS. First, we investigate B7-H4 expression on Labial salivary gland from patients with SS and healthy controls by immunohistochemistry and flow cytometric analysis and define its clinical significance. Second, we performed mixed lymphocyte reactions to detect the potential role of Salivary gland epithelial cells (SGEC) -associated B7-H4 in the regulation of T-cell activation in vitro. Finally, In a mouse model of SS, transgenic expression of sH4 or genetic deletion of B7-H4 accelerated the progression of NOD, accompanied by enhanced T cell. Expression in vivo of an agonist, a B7-H4-immunoglobulin Fc fusion protein, profoundly suppressed disease progression in the mouse model.

B7-H4是共刺激分子B7家族的最新成员，在T细胞的分化发育、细胞周期的进程及细胞因子的产生发挥广泛的负性调控效应。原发性干燥综合征(Primary Sjogren's syndrome，pSS)为累及外分泌腺的自身免疫病，腺体中有大量效应T细胞，导致腺体结构破坏。申请者新近发现SS患者腺上皮细胞B7-H4的表达明显减少，提示患者B7-H4的负性调控减弱致T细胞功能紊乱。本课题以T细胞为切入点，拟通过组织病理、免疫荧光、流式细胞技术等方法检测B7-H4在pSS及对照中的表达；磁珠分选Na?ve T细胞与表达B7-H4的上皮细胞混合培养、结合抗体阻断技术来探讨B7-H4分子是否通过抗体交联作用影响T细胞分化、增殖及细胞因子分泌功能的影响，最后通过动物实验抑制或促进干燥综合征模型鼠B7-H4表达，观察小鼠组织病理及免疫学检测指标的变化，验证B7-H4对SS发病的作用，为治疗SS提供新策略。

B7-H4共刺激分子B7家族的最新成员，在T细胞的分化发育、细胞周期的进程及细胞因子的产生发挥广泛的负性调控效应。原发性干燥综合征为累及外分泌腺的自身免疫病，腺体中有大量效应T细胞，导致腺体结构破坏。本课题以T细胞为切入点，通过组织病理、免疫荧光、流式细胞技术等方法检测B7-H4在pSS及对照中的表达,通过细胞培养探讨B7-H4分子对T细胞分化、增殖及细胞因子分泌功能的影响，并通过动物实验抑制或促进干燥综合征模型鼠B7-H4表达，观察小鼠组织病理及免疫学检测指标的变化。研究表明,B7-H4共刺激分子在pSS患者的唇腺组织及血清表达减少，提示其可能参与了pSS的疾病进展，进一步研究其具体机制发现B7-H4和可溶性B7-H4的表达可抑制T细胞活化和增殖，抑制CD4+T细胞分泌IL-13，IL-5，IL-17A，IL-6等细胞因子，揭示了干燥综合征患者B7-H4表达降低与疾病活动的关系。此外，本研究首次在活体组织研究中证实了在NOD鼠颌下腺中存在B7-H4蛋白的表达，当给予B7-H4蛋白时，可延缓NOD小鼠颌下腺的免疫病理学进展、抑制Th1和Th17的分化、上调Treg细胞。同时我们应用B7-H4蛋白阻断试剂进一步验证了B7-H4共刺激分子在NOD小鼠疾病进展过程中的作用。由此得出B7-H4分子可抑制CD4+T细胞活化和增值，降低疾病活动度， 减少唇腺组织炎性细胞浸润，这将为临床应用B7-H4融合蛋白治疗SS提供理论依据。

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