Defective in vivo Fc- and C3b-receptor function in IgA nephropathy.

Reticuloendothelial function was assessed in 17 patients with IgA nephropathy, using 99Tc-labeled autologous erythrocytes coated with either C3B or IgG. Results were compared with clearances in 14 normal control subjects and with a group of 14 patients with idiopathic mesangial proliferative glomerulonephritis without IgA deposition. The half-life of IgG-coated red cells in the IgA group was 69.8 +/- 32.5 minutes (control 42.2 +/- 9.0 minutes, P = 0.001). The half-life in the non-IgA mesangial proliferative group, 77.9 +/- 31.3 minutes, was not significantly different from that of the IgA patients. Clearance of C3b-coated cells, expressed as the percentage of cells cleared at 30 minutes, was 7.1% +/- 2.6% in the IgA patients, compared with 16.0% +/- 3.2% in control subjects (P less than 0.001) and 13.8% +/- 7.5% in the non-IgA mesangial proliferative group (NS). No statistical correlation was found between clearance results in individual patients and age, sex, weight, serum creatinine, or the severity of disease on clinical and pathological criteria. The severity of the defect in Fc- and C3b-receptor dependent clearances were not statistically correlated in individual patients.