MBL2基因突变调控T细胞分化在IgA肾病进展中的作用及分子机制研究

As the most commonly occurring primary glomerulonephritis worldwide, IgA nephropathy (IgAN) is also one of the major causes of end-stage renal failure in China. Studies have confirmed that abnormities of helper T cell differentiation-especially abnormal proliferation of Th2 cell plays an important role in renal injury of IgAN. Complement mannose-binding lectin (MBL) binds to T cells through its collagen-like region (CLR) and inhibits cell proliferation. Low expression of MBL is associated with disease progression of IgAN, but the specific regulatory mechanisms remain unclear. Our preliminary study has confirmed that serum MBL levels in IgAN patients carrying MBL-G54D mutations are significantly reduced, kidney survival time is significantly shortened, and the percentage of Th2 cells is increased. The further experiments presented that the G54D mutation is located in the CLR region, and the T cells with G54D mutation had a tendency to transform into Th2 cells. Therefore, we speculate that the G54D mutation impaired the binding ability of MBL to Th2 cells, consequently the inhibitory effect is weakened, thereby aggravating renal damage. Based on our previous research, the aim of this study is to prove our hypothesis through the whole-cell-molecule levels by constructed mouse model with G54D mutation and T cell model, applied ChIP, protein mass spectrum and other techniques, thus providing new immunotherapy targets and ideas for clinical prevention and treatment.

作为最常见的原发性肾小球肾炎，IgA肾病(IgAN)也是我国终末期肾衰最常见原因之一。辅助性T2细胞（Th2）异常增殖在IgAN肾损伤中起重要作用。有研究表明，补体甘露糖结合凝集素(MBL)通过其胶原样区(CLR)结合并抑制T细胞增殖，且MBL血清水平低表达与IgAN疾病进展相关，但机制不明。前期研究中，我们在多中心IgAN队列中进行MBL基因检测发现：与非突变者相比，携带G54D突变者的血清MBL表达水平更低，肾脏存活时间更短，Th2细胞百分比更高；进一步研究发现，G54D突变位于CLR区，且点突变后T细胞呈现Th2细胞转化趋势。因此，我们推测G54D突变后，MBL结合并抑制Th2细胞增殖的作用减弱，从而加重肾损。本课题立足于前期研究基础，通过已制备的G54D点突变鼠品系及T细胞，应用免疫共沉淀、蛋白质谱等技术，在整体-细胞-分子层次证明假说，为临床防治提供新靶点及思路。

IgA肾病（IgAN）是全球最常见的肾小球肾炎之一，也是我国青壮年肾衰的主要原因。40%的患者在10-20年内进展至终末期肾脏病（ESKD）。目前，IgAN治疗手段欠缺，急需靶标上游病因的治疗手段。辅助性T2细胞（Th2）异常增殖在IgAN肾损伤中起重要作用。有研究表明，补体甘露糖结合凝集素(MBL)通过其胶原样区(CLR)结合并抑制T细胞增殖，且MBL血清水平异常降低的IgAN患者的疾病进展快，预后差，但机制未明。本课题组长期从事IgAN的机制研究，申请者前期通过多中心IgAN队列证实，MBL基因G54D突变是IgAN患者预后相关的危险因素：携带该突变的IgAN患者血清MBL水平明显降低，疾病进展加快，Th2细胞百分比更高；进一步研究发现，G54D突变位于CLR区，且点突变后T细胞呈现Th2细胞转化趋势；继而构建G54D-/-突变鼠，已证实该突变鼠的血清MBL水平降低，出现免疫细胞Th1/Th2失衡且肾损加重。此外，对小鼠粪便进行16s rRNA检测发现，与野生型相比，G54D-/-突变鼠中大肠杆菌菌群丰度增加，其主要的代谢物LPS血清水平升高。已有研究发现MBL可竞争性结合LPS的核心寡糖区，有效抑制其炎症效应。进一步提示G54D突变后MBL低表达，对LPS的负调控作用减弱导致肠道黏膜免疫异常活化而参与IgAN肾脏损伤。本研究为探讨MBL在IgA肾病中的作用及机制，从而为今后抑制异常免疫反应的治疗方案在IgAN中的应用，提供更多的理论依据。本课题受资助以来，研究工作顺利，完成了初步的预期结果，发表SCI论文2篇，中文2篇。