ABSTRACT
Objective To establish the measurement of IgA1 O-glycan-specific antiglycan autoantibodies in patients with IgA nephropathy (IgAN),and evaluate their role in the development and progression of IgAN.Methods In the IgAN regular follow-up cohort of Peking University Institute of Nephrology from January 2006 to December 2015,170 patients drawn by stratified randomization were enrolled in this study.Enzyme-linked immunosorbent assay (ELISA) was used to determine the levels of plasma galactose-deficient IgA1 (Gd-IgA1) and antiglycan autoantibody (IgG and IgA1).The correlation between antiglycan autoantibodies and clinicopathological parameters was analyzed by linear correlation and multiple linear regression analysis.The receiver operating characteristic curve (ROC) was used to evaluate the value of plasma anti glycide antibodies in the diagnosis of IgAN.Results IgG and IgA1 antiglycan antoantibodies that specifically recognized Fab-hinge region (Fab-HR) antigens could be detected in both IgAN and healthy control group.Agglutinin inhibition test showed that the specific antigen epitope was N-acetylgalactosamine (GalNAc) residue exposed to galactose deficiency in IgA1 hinged region.There was no significant difference in the absolute levels of plasma IgG antiglycan autoantibodies between IgAN and healthy controls (P=0.963).After adjustment of the plasma level of IgG,the normalized antiglycan autoantibody (ln[IgG antiglycan antibody/IgG]) in patients with IgANwas significantly higher than that in healthy controls (0.58±0.31 vs 0.37±0.11,P ＜ 0.01).The normalized level of IgG antiglycan autoantibody in IgAN patients was positively correlated with 24 h urine protein level during renal biopsy (Spearman r=0.183,P ＜ 0.05),and was also significantly correlated with 24 h urinary protein level after adjusting for baseline clinical and pathological factors (β=0.713,95％CI 0.323-1.102,P ＜ 0.01).The area under ROC curve (AUC) of normalized IgG antiglycan autoantibody in the diagnosis of IgAN was 0.764 (95％ CI 0.682-0.845,P ＜ 0.05).Using the cut-off value of 0.396,the sensitivity and specificity of normalized IgG antiglycan autoantibody for IgAN were 0.729 and 0.700 respectively.There was no significant difference in the absolute or normalized levels of IgA1 antiglycan autoantibodies between IgAN patients and healthy controls.Conclusions Gd-IgA1-specific antiglycan autoantibodies can be detected both in IgAN patients and healthy controls.They are elevated in some patients with IgAN and possibly involved in the development of IgAN.