Comprehensive evaluation of the significance of immunofluorescent findings on clinicopathological features in IgA nephropathy

Background The clinicopathological significance of immunofluorescent findings in IgA nephropathy remains controversial. Methods The relations of the deposition of IgA, IgG, IgM, C3, C1q and fibrinogen (Fib) with pathological findings, baseline clinical findings, and renal outcome were evaluated in 688 patients with IgA nephropathy. Pathological features included cellular or fibrocellular crescents, endocapillary or mesangial hypercellularity, segmental or global glomerulosclerosis and the Oxford classification. Results The median age at biopsy was 30 years. There were 289 men. With 74 months median follow-up, 32% of patients received steroids. Twelve percent of patients developed end-stage renal disease (ESRD). The degree of IgA was closely related to the degree of C3, IgG and IgM deposition. The degree of IgA, C3, IgG and Fib deposition was significantly related to the percentage of glomeruli with crescent, endocapillary and mesangial hypercellularity. IgM deposition showed significant association with crescent, mesangial hypercellularity, segmental sclerosis, global glomerulosclerosis and tubular atrophy/interstitial fibrosis. In the patients treated with steroids, the risk for ESRD in patients with 2–3+ IgA deposition was significantly lower with reference of 1+ IgA deposition. Conclusion We found the different roles of glomerular immune reactants’ deposition in the inflammatory process from acute to chronic stage. IgA deposition together with IgG, Fib and C3 may produce acute inflammatory injury. IgM deposition might occur in the early stage of inflammation and remains until late sclerotic stage. The prominent deposition of IgA related to low risk for ESRD in patients who received steroids might suggest effectiveness of steroids in such patients.