B淋巴细胞活化因子(BAFF)参与甲状腺相关眼病发病机制的作用研究

Graves orbitopathy (GO) is most often associated with autoimmune thyroid disease. B lymphocytes play multiple function during the development of GO. BAFF (B cell activation factor) is essential to the activation and maturation of B lymphocytes. Recent studies showed that the overexpression of BAFF was associated with many kinds of autoimmune diseases. Meanwhile, our previous research found that adipocytes from GO patients overexpressed BAFF. Hereby, we postulate that " the overexpression of BAFF is related to the inflammatory stage of GO; proinflammatory cytokines IFN-γ/TNF-α stimulate adipocytes to produce BAFF, and then activate B lymphocytes to mediate autoimmune response in GO; BAFF is not only critical to the development of GO, but could also be the treatment target". In this study, we will investigate the expression of BAFF in the serum, and make a correlation between the expression of BAFF and the disease stage, yielding the identi?cation of predictive biomarkers of progressive disease. Meanwhile, an in vitro study will be conducted to explore the effect of BAFF produced by the adipocytes (having stimulated by IFN-γ/TNF-α) on the activation of B lymphocytes, which will illuminate the role of BAFF in the immune pathogenesis of GO. Finally, a mouse model of GO will be established, and anti-BAFF antibody will be employed to evaluate the therapy effect on GO. All this will contribute to our understanding and treatment of GO.

甲状腺相关眼病(GO)是器官特异性自身免疫病，B淋巴细胞在其发病中具有多重免疫功效。BAFF是B细胞激活和成熟的必须因子。新近研究表明BAFF的高表达与多种自身免疫性疾病密切相关，同时，我们前期研究发现活动期GO眶脂肪细胞高表达BAFF，据此，我们推测 "GO的炎症活动状态与BAFF的高表达密切相关；炎症因子IFN-γ、TNF-α刺激眶脂肪细胞产生BAFF，进而激活B淋巴细胞介导GO自身免疫反应；BAFF的升高不仅为GO发生、发展的关键环节，也是治疗的潜在靶点"。本课题拟从GO患者外周血BAFF表达水平入手，研究BAFF与GO炎症活动度的关系，为预测GO病情进展找到新的生物标记物；体外探讨经IFN-γ、TNF-α刺激后眶脂肪细胞分泌BAFF激活B淋巴细胞分泌抗体的情况，阐明BAFF参与GO发病的免疫机制；建立GO小鼠模型，采用抗BAFF抗体评估其对GO的治疗作用，为GO防治开辟新的途径。

甲状腺相关眼病(GO)是一种器官特异性自身免疫性疾病。既往关于GO发病免疫机制的研究主要集中在T淋巴细胞的作用，关于B淋巴的作用研究相当少。近年多项临床研究显示使用Rituximab靶向CD20+ B淋巴细胞能有效治疗难治性炎症GO，提示B淋巴细胞在其发病机制中具有重要作用。BAFF是B淋巴细胞激活和成熟的必须因子。因此本课题探讨BAFF参与甲状腺相关眼病发病机制的作用研究。. 首先，我们检测常人、静止期GO、炎症期GO、炎症期GO使用全身糖皮质激素治疗患者的外周血清的BAFF表达情况，结果显示炎症期GO的BAFF水平约明显高于与正常人或静止期GO；糖皮质激素能显著降低炎症期GO患者外周血的BAFF表达水平。BAFF的表达水平与GO疾病的炎症状态明显相关。其次，我们收集3例活动期GO行开眶减压手术者以及3例正常对照组行额肌瓣悬吊手术的眶脂肪组织，分别提取其RNA，Real time PCR结果显示GO组的TNF-α、IFN-γ以及BAFF表达明显高于正常对照组。病理切片显示GO眶脂肪组织不同于正常对照组，GO眶脂肪组织见大量炎症细胞浸润，其中存在大量CD20+B细胞，免疫组化结果显示TNF-α、IFN-γ以及BAFF表达强阳性，均表达于脂肪细胞之间以及纤维肌肉组织之间，而正常眶脂肪标本显示为阴性，此外，GO眼眶脂肪组织之间见大量IgG表达。再次，我们培养眼眶前脂肪细胞，并给予不同的炎症因子刺激，结果显示在不经刺激的情况下，GO眶前脂肪细胞比正常人眶前脂肪细胞高表达BAFF，经刺激后不管是GO前脂肪细胞还是正常前脂肪细胞，BAFF表达均增加，且TNF-α+IFN-γ刺激作用最强。最后，我们分选CD19+ B细胞与经炎症因子刺激后的前脂肪细胞共培养，结果显示经刺激后的前脂肪细胞可减少B细胞凋亡，增加存活率。同时，促进B细胞发生免疫球蛋白类别转换重组，促进B细胞分泌IgG。给予BAFF-R阻断后，IgG浓度下降。. 以上结果提示炎症因子IFN-γ、TNF-α刺激眼眶脂肪细胞产生大量BAFF，进而激活B淋巴细胞产生自身抗体，从而介导GO眼眶局部免疫反应。此研究结果阐明了BAFF及脂肪细胞参与GO发病的免疫机制，也揭示了GO的器官特异性机理，具有理论创新性，也为后续局部靶向眼眶BAFF治疗GO奠定了理论基础。目前研究结果已撰写投稿。