Investigating the functional capacity of autoantibodies in primary membranous nephropathy

项目总结/摘要 膜性肾病（MN）是一种自身免疫性肾病，其中抗内源性抗体 由足细胞表达的肾小球蛋白导致足细胞亚致死性损伤，滤过屏障丧失， 最终导致肾病综合征整个病程可能相当长， 蛋白尿的程度是肾功能进行性下降和终末期肾病的风险。PLA2R 是80%原发性MN病例和循环抗PLA 2 R抗体（PLA 2 R-）监测的主要目标 ab）在跟踪免疫疾病活动和允许更快速的治疗方面起着重要作用 决策然而，尽管存在PLA 2 R-ab血清学的使用指南，肾病学家继续 由于存在显著的差异性， 结果。患者可能发展为严重的肾病综合征，PLA 2 R-ab滴度相对较低， 轻微的疾病，水平很高，这一观察结果仍然无法解释。本提案的目的是 鉴定与PLA 2 R-ab的可变库相关的疾病结果的新预测因子（其在以下方面不同： 亚类和表位特异性），并更好地了解PLA 2 R-ab介导的功能性后果。 损伤目的1描述了两种新的检测方法的发展，这两种方法可以增加总PLA 2 R-ab滴度， 临床缓解的可能性。一种测定将是简单的ELISA，以评估表位的存在或不存在。 扩展到PLA 2 R的N-末端免疫显性表位之外。第二个将是C3 c的衡量标准 通过PLA 2 R-ab产生（补体激活），以总结所有IgG亚类的功能效应 和表位特异性。将使用考克斯比例风险模型（生存分析）检验相关性 PLA 2 R-ab水平、C3 c生成和表位随时间的扩展与主要结局（实现 部分或完全缓解），使用两个良好表征的MN队列。目标2将使用从 MN患者的残余肾活检，以询问是否有PLA 2 R-ab的库， 在免疫沉积物中反映了循环形式。PLA 2 R连接在聚乳酸内的方式可以通过以下方式进行： 还将评估肾小球基底膜（GBM）。了解致病性PLA 2 R-ab， 与肾脏沉积物中的抗原一起积累，以及了解PLA 2 R是如何掺入沉积物中的 可能会提供新的见解，疾病的途径，可以有针对性的治疗。有人建议， 动物研究表明，MN中对免疫损伤反应产生的细胞外基质含有异位 健康GBM中通常不存在的元素;这些在人类疾病中尚未被广泛研究。在Aim中 3、表达PLA 2 R的人足细胞将用作PLA 2 R-ab诱导的细胞损伤的体外模型，以评估 导致抗体介导的PLA 2 R从细胞释放的早期事件，其与常规的和更多的 新的基质元素，并广泛地观察细胞外基质产生的变化。新知识 从这些研究中获得的信息将扩大我们对人类MN中沉积物如何形成和持续存在的知识。

PROJECT SUMMARY / ABSTRACT Membranous nephropathy (MN) is an autoimmune kidney disease in which antibodies against intrinsic glomerular proteins expressed by the podocyte lead to sublethal podocyte cell injury, loss of the filtration barrier, and ultimately the nephrotic syndrome. The overall disease course can be quite protracted and the duration and extent of proteinuria are risks for progressive decline of kidney function and end-stage kidney disease. PLA2R is the major target in 80% of primary MN cases and the monitoring of circulating anti-PLA2R antibodies (PLA2R- ab) has been instrumental in following immunologic disease activity and allowing for more rapid treatment decisions. Yet despite the existence of guidelines for such use of PLA2R-ab serology, nephrologists continue to have substantial ambiguity about whom to treat with immunosuppression, and when, due to significant variability in outcome. Patients may develop severe nephrotic syndrome with relatively low titers of PLA2R-ab or relatively mild disease with very high levels, an observation which remains unexplained. The goal of this proposal is to identify novel predictors of disease outcome associated with the variable repertoire of PLA2R-ab (which differ in subclass and epitope specificity) and to better understand the functional consequences of PLA2R-ab-mediated injury. Aim 1 describes the development of two novel assays that may add to total PLA2R-ab titer in determining likelihood of clinical remission. One assay will be a simple ELISA to assess the absence or presence of epitope spreading beyond the N-terminal immunodominant epitope of PLA2R. The second will be a measure of C3c generation (complement activation) by PLA2R-ab to summate the functional effects of all the IgG subclasses and epitope specificities. Cox proportional hazards models (survival analysis) will be used to test the associations between PLA2R-ab levels, C3c generation and epitope spreading with time to the primary outcome (achievement of partial or complete remission), using two well-characterized MN cohorts. Aim 2 will use IgG eluted from remnant kidney biopsies from patients with MN to ask whether or not the repertoire of PLA2R-ab that is bound within the immune deposits mirrors the circulating forms. The manner by which PLA2R is attached within the glomerular basement membrane (GBM) will also be assessed. Understanding the pathogenic PLA2R-ab that accumulate with antigen in the kidney deposits, as well as knowing how PLA2R is incorporated into deposits may offer new insights into disease pathways that could be targeted therapeutically. It has been suggested from animal studies that the extracellular matrix produced in reaction to the immune injury in MN contains ectopic elements not usually present in healthy GBM; these have not been extensively studied in human disease. In Aim 3, PLA2R-expressing human podocytes will serve as an in vitro model of PLA2R-ab-induced cell injury to assess early events that lead to antibody-mediated release of PLA2R from the cell, its binding to conventional and more novel matrix elements, and to broadly look at changes in extracellular matrix production. The new knowledge gained from these studies will expand our knowledge of how deposits form and persist in human MN.