Gao Y-H, Xu L-X, Zhang J-J, Zhang Y, Zhao M-H, Wang H-Y
Renal Division, Department of Medicine, Peking University First Hospital, Institute of Nephrology, Peking University, Key Laboratory of Renal Disease, Ministry of Health of China, Beijing, China.
Clin Exp Immunol. 2007 Jun;148(3):507-14. doi: 10.1111/j.1365-2249.2007.03374.x. Epub 2007 Mar 26.
Recent studies had demonstrated that serum and mesangial immunoglobulin A1 (IgA1) in patients with IgA nephropathy (IgAN) were polymeric and deglycosylated. The current study was to investigate the binding characteristics of monomeric and polymeric normal human IgA1 on mesangial cells and the influence of in vitro deglycosylation of IgA1 molecules. The normal human IgA1 was desialylated and degalactosylated with specific enzymes, respectively. The monomeric IgA1 (mIgA1) and polymeric IgA1 (pIgA1) were separated by Sephacryl S-300 chromatography. The binding capacities of the mIgA1 and pIgA1 to primary human mesangial cells (HMC) were evaluated by classical radioligand assay. Both the native mIgA1 and pIgA1 could bind to HMC in a dose-dependent and saturable manner. The maximal binding capacity of the native pIgA1 were significantly higher than that of the native mIgA1 (P < 0.05). However, the affinity of the native mIgA1 was almost 100 times higher than that of the native pIgA1. After deglycosylation, binding of the two deglycosylated mIgA1 to HMC could not be detected. However, the maximal binding capacities of the two deglycosylated pIgA1 to HMC were increased significantly compared with that of native pIgA1. The affinity of the two deglycosylated pIgA1 was similar to that of native pIgA1 (P > 0.05). The current study suggests differential binding characteristics of native monomeric and polymeric IgA1 on mesangial cells. Glycosylation of IgA1 molecules could significantly affect the binding of IgA1 on HMC.
近期研究表明,IgA肾病(IgAN)患者的血清和系膜免疫球蛋白A1(IgA1)呈多聚体且去糖基化。本研究旨在探讨正常人单体和多聚IgA1与系膜细胞的结合特性以及IgA1分子体外去糖基化的影响。分别用特定酶对正常人IgA1进行去唾液酸和去半乳糖处理。通过Sephacryl S - 300层析分离单体IgA1(mIgA1)和多聚IgA1(pIgA1)。采用经典放射性配体分析法评估mIgA1和pIgA1对原代人系膜细胞(HMC)的结合能力。天然mIgA1和pIgA1均能以剂量依赖性和饱和性方式与HMC结合。天然pIgA1的最大结合能力显著高于天然mIgA1(P < 0.05)。然而,天然mIgA1的亲和力几乎比天然pIgA1高100倍。去糖基化后,未检测到两种去糖基化mIgA1与HMC的结合。然而,两种去糖基化pIgA1与HMC的最大结合能力相比天然pIgA1显著增加。两种去糖基化pIgA1的亲和力与天然pIgA1相似(P > 0.05)。本研究提示天然单体和多聚IgA1与系膜细胞的结合特性存在差异。IgA1分子的糖基化可显著影响IgA1与HMC的结合。