The Prevalence and Characteristics of Circulating IgA Anti-Glomerular Basement Membrane Autoantibodies in Anti-Glomerular Basement Membrane Disease

Introduction: In some cases, immunoglobulin (IgA)-mediated antiglomerular basement membrane (anti-GBM) disease has been reported. Whether circulating IgA anti-GBM antibodies affect the clinico-pathologic characteristics and outcome of typical anti-GBM disease deserves further study. Methods: Circulating IgA anti-a3(IV)NC1 antibodies were examined by enzyme-linked immunosorbent assay (ELISA) using recombinant human a3(IV)NC1 as solid phase antigens in 107 patients with anti-GBM disease and 115 controls. Clinical, pathological, and follow-up data of patients were retrospectively analyzed. Results: Circulating IgA anti-a3(IV)NC1 antibodies were found in 18.7% (20/107) of patients with anti-GBM disease but were not detected in healthy controls or in patients with other glomerular diseases. The positivity of circulating IgA anti-a3(IV)NC1 antibodies was not associated with whether the patient was with combined IgA nephropathy or other glomerulonephritis. Kidney immunofluorescence showed no statistical difference in IgA deposition between patients with circulating IgA anti-a3(IV)NC1 antibodies and patients without (30.0% vs. 40.4%, P = 0.725). The titers of circulating immunoglobulin G (IgG) anti-a3(IV) NC1 antibodies in patients with circulating IgA anti-a3(IV)NC1 antibodies were significantly higher than those without (200 [183.3, 200] vs. 161 [85.5, 200] U/ml, P = 0.005). There were no significant differences in kidney outcome and mortality between the 2 groups. Conclusion: Circulating IgA anti-a3(IV)NC1 antibodies occurred in 18.7% (20/107) of patients with anti-GBM in our center and were specific to anti-GBM disease. Patients with circulating IgA anti-a3(IV)NC1 antibodies showed a higher levels of serum IgG anti-a3(IV)NC1 antibodies than those without.