Department of Nephrology and Blood Purification, Kidney Disease Center, Tokyo Medical University Hachioji Medical Center, Hachioji, Japan.
Department of Microbiology, Faculty of Pharmacy, Meijo University, Nagoya, Japan.
Ren Fail. 2022 Dec;44(1):714-723. doi: 10.1080/0886022X.2022.2068445.
Anti-neutrophil cytoplasmic antibody (ANCA)-associated glomerulonephritis (AAGN) is the fulminant glomerular diseases with poor renal prognosis. Activation of the complement system has recently been reported in the pathogenesis of AAGN, but it remains to be clarified as to which complement pathway is mainly involved.
20 patients with myeloperoxidase (MPO)-AAGN were retrospectively evaluated. Using serum samples, circulating immune-complexes (CICs) were assessed by the monoclonal rheumatoid factor assay, and C5a and C5b-9 were assessed by ELISA. Complement activation through the classical pathway was further evaluated by the WIESLAB® Complement System Classical Pathway kit. The affinities of ANCAs were evaluated by a competitive inhibition method using ELISA, and were classified into the high, and low-affinity group. Deposition of complement components, such as C3, C5, C4d, C5b-9, factor Bb, mannan-binding lectin serine peptidase (MASP)-1, MASP-2, and mannose/mannan-binding lectin (MBL), in frozen renal sections were analyzed by immunofluorescence staining.
CICs were found to be positive in 65% of the patients. All CIC-positive patients belonged to the high-affinity group. Furthermore, serum C5a and C5b-9 were significantly increased in MPO-AAGN patients, and these levels positively correlated with CIC levels. A significant negative correlation was also found between levels of WIESLAB® classical pathway kit and CICs. By immunofluorescence staining, glomerular deposition of C4d, C5, and C5b-9 were observed in similar distributions in MPO-AAGN patients, whereas the deposition of MASP-1, MASP-2, MBL, and factor Bb were minimal.
These results suggest the involvement of immune-complex induced complement activation through the classical pathway in the pathogenesis of MPO-AAGN.
抗中性粒细胞胞质抗体（ANCA）相关性血管炎相关肾小球肾炎（AAGN）是一种预后不良的暴发性肾小球疾病。补体系统的激活最近被报道参与了 AAGN 的发病机制，但哪种补体途径主要参与仍不清楚。
回顾性评估了 20 例髓过氧化物酶（MPO）-AAGN 患者。使用血清样本，通过单克隆类风湿因子测定法评估循环免疫复合物（CIC），并通过 ELISA 评估 C5a 和 C5b-9。通过 WIESLAB®补体系统经典途径试剂盒进一步评估经典途径的补体激活。通过 ELISA 竞争抑制法评估 ANCAs 的亲和力，并分为高亲和力和低亲和力组。通过免疫荧光染色分析冷冻肾切片中补体成分（如 C3、C5、C4d、C5b-9、因子 Bb、甘露聚糖结合凝集素丝氨酸肽酶（MASP）-1、MASP-2 和甘露糖/甘露聚糖结合凝集素（MBL）的沉积。
发现 65%的患者存在 CIC 阳性。所有 CIC 阳性患者均属于高亲和力组。此外，MPO-AAGN 患者的血清 C5a 和 C5b-9 显著升高，且这些水平与 CIC 水平呈正相关。还发现 WIESLAB®经典途径试剂盒水平与 CIC 水平之间存在显著负相关。通过免疫荧光染色，在 MPO-AAGN 患者中观察到 C4d、C5 和 C5b-9 在肾小球中的沉积呈相似分布，而 MASP-1、MASP-2、MBL 和因子 Bb 的沉积则很少。
这些结果表明，免疫复合物诱导的经典途径补体激活参与了 MPO-AAGN 的发病机制。
