抗补体C1q关键抗原表位A08自身抗体在狼疮性肾炎发病中的作用机制研究

Lupus nephritis is one of the most serious complications of SLE, and the most prevalent secondary glomerulonephritis in our country. The pathogenesis is still unclear. Previous studies suggested that anti-C1q antibodies were associated with the occurrence, relapse and disease activity of lupus nephritis, but the role in the pathogenesis is not fully understood. The target antigen was supposed to be in the C1q collagen region (CLR). However, the exact epitope was not clear. Recent study found linear peptide epitope A08 in the CLR. More importantly, our study found that serum anti-A08 C1q antibodies could be a specific biomarker to distinguish patients with active lupus nephritis from patients with SLE without renal involvement. The serum level of anti-A08 C1q antibodies was closely associated with disease activity and prognosis in lupus nephritis, which suggested that anti-A08 C1q antibodies might play a role in the pathogenesis in lupus nephritis. Thus, we plan to purify the anti-A08 C1q antibodies, and try to find out the way how the A08 epitope exposed and the role of anti-A08 C1q antibodies in lupus nephritis through both the in vivo functional assay and animal models.

狼疮性肾炎为SLE常见且严重的并发症，是我国最常见的继发性肾小球肾炎，其发病机制尚未完全阐明。既往研究表明循环抗C1q抗体与狼疮性肾炎的发生、复发、疾病活动度相关，其是否参与疾病的发病过程是研究的热点问题。狼疮性肾炎患者的抗C1q抗体主要识别C1q胶原区（CLR），但是其确切的抗原表位一直没有确定。近期研究发现了位于CLR区的线性抗原表位A08。我们的前期研究表明循环抗C1qA08抗体水平与狼疮性肾炎患者的临床和病理指标均较抗C1q抗体具有更好的相关性，更为重要的是抗C1qA08抗体可测狼疮性肾炎预后，提示抗C1qA08抗体在狼疮性肾炎发病机制中很可能发挥了重要作用。本课题拟纯化患者的循环抗C1qA08抗体，探讨A08隐匿性抗原表位暴露的机制，并通过体外功能试验及动物试验探讨抗C1qA08抗体在狼疮性肾炎发病机制中的作用。

狼疮性肾炎为SLE常见且严重的并发症，是我国最常见的继发性肾小球肾炎，其发病机制尚未完全阐明。既往研究表明循环抗C1q抗体与狼疮性肾炎的发生、复发、疾病活动度相关，其是否参与疾病的发病过程是研究的热点问题。狼疮性肾炎患者的抗C1q抗体主要识别C1q胶原区（CLR），但是其确切的抗原表位一直没有确定。近期研究发现了位于CLR区的线性抗原表位A08。我们的前期研究表明循环抗C1qA08抗体水平与狼疮性肾炎患者的临床和病理指标均较抗C1q抗体具有更好的相关性，更为重要的是抗C1qA08抗体可测狼疮性肾炎预后，提示抗C1qA08抗体在狼疮性肾炎发病机制中很可能发挥了重要作用。本课题应用ELISA和SPR发现C1qA08是C1q与mCRP结合的重要表位，且C1qA08可调理巨噬细胞对凋亡细胞的吞噬。通过HuProt 20K蛋白芯片筛选C1q的配体蛋白，并应用SPR验证，发现了A08的新配体蛋白α3（IV）NC1。通过杂交瘤技术筛选出4个C1q A08单抗：32-4、17-9、1A12和4B11。利用突变A08不同部位氨基酸及生物膜干涉技术，研究发现A08为半隐匿抗原表位。利用单克隆抗C1qA08抗体进行了C3沉积实验发现1A12和4B11抗体可直接抑制补体经典途径激活。应用C1qA08免疫BALB/c野生型小鼠，小鼠体内发生了C1q抗原表位扩展，产生了针对C1q其他暴露表位的抗体。进一步进行了MRL/lpr狼疮鼠A08免疫实验，发现给药组小鼠蛋白尿显著增高，提示C1qA08抗体在狼疮性肾炎发病机制中具有一定作用。