Functional analysis of BAFF, APRIL and their receptors, and the study of their role in the pathogenesis of autoimmune disease

目标。目的探讨BAFF、APRIL及其受体在系统性红斑狼疮（SLE）、类风湿性关节炎（RA）等自身免疫性疾病发病机制中的作用。通过外显子特异性PCR/SSCP，我们在BR3基因中发现了一个新的多态性P21R。P21R位于BAFF特异性受体BR3的富含半胱氨酸的区域，可能具有重要的功能。为了研究BAFF膜的反向信号，我们利用定点诱变技术构建了未被furin转化酶裂解的BAFF膜的cDNA。流式细胞术观察转染Jurkat细胞膜BAFF的表达。流式细胞术分析BR3、TACI和BCMA在外周血B细胞亚群上的表达情况，发现BR3在幼稚B细胞上高表达，BCMA在质母细胞上高表达。SLE患者浆母细胞数量增加。滑膜成纤维细胞样细胞在TNF-a和IFN-y的作用下合成。BAFF和APRIL的共同受体BCMA-Ig，而BAFF的受体BR3-Ig，在TNF-α和IFN-γ存在下，能抑制滑膜成纤维细胞样细胞的增殖。这些数据表明BCMA在SLE患者浆母细胞的生存中具有重要作用。APRIL与滑膜成纤维细胞样细胞以自分泌方式增殖有关。APRIL和BAFF可作为自身免疫性疾病的治疗靶点。

Objective. To investigate the role of BAFF, APRIL and their receptors in the pathogenesis of autoimmune diseases such as systemic lupus erythematosus (SLE) and rheumatoid arthritis (RA).Results. By exon-specific PCR/SSCP, we identified a novel polymorphism, P21R, in BR3 gene. P21R is located in the cystein-rich domain of BR3, a specific receptor for BAFF, and could be functionally important. To investigate the reverse-signal through membrane BAFF, we constructed cDNA for membrane BAFF, which was not cleaved by furin convertase, by site-directed mutagenesis. Expression of membrane BAFF was observed on transfected Jurkat cells by flow cytometry. When we analyzed the expression of BR3, TACI and BCMA on each peripheral B cell subset by flow cytometry, BR3 was highly expressed on naive B cells while BCMA was highly expressed on plasmablasts. The number of plasmablasts was increased in patients with SLE. Synovial fibroblast-like cells synthesized APRIL when they were cultured in the presence of TNF-a and IFN-y. BCMA-Ig, which was common receptor for BAFF and APRIL, but not BR3-Ig, receptor for BAFF, inhibited the proliferation of synovial fibroblast-like cells in the presence of TNF-α and IFN-γ.Conclusions. These data suggest that BCMA has important role in the survival of plasmablasts in SLE patients. APRIL is associated with the proliferation of synovial fibroblast-like cells in autocrine fashon. APRIL and BAFF could be a therapeutic target in the treatment of autoimmune disease.