Objective: To investigate the avidity of anti-glomerular basement membrane (GBM) antibodies and their association with clinical and pathological parameters of patients with anti-GBM disease.
Methods: Sera from 52 patients and serial samples from 11 patients with anti-GBM disease, diagnosed in our hospital in the last 11 years, were collected. Purified bovine alpha chain non-collagen 1 domains of type IV collagen [alpha(IV)NC1] was employed to exam avidity of anti-GBM antibodies using antigen-inhibition enzyme-linked immunosorbent assay (ELISA). The amount of alpha(IV)NC1 needed for 50% inhibition of antibody binding was compared between patients with different clinical and pathological manifestations.
Results: After the sera were diluted to give the same absorbance, the amount of alpha(IV)NC1 used was different among different patients, with an average at 0.625 microg (0.02-20 microg). A significant correlation was observed between the amount of alpha(IV)NC1 used and the percentage of glomerular crescents (P = 0.001). Higher avidity of anti-GBM antibodies predicted a higher percentage of glomerular crescents (R(2) = 0.58, P = 0.000). No correlation was observed between avidity and age, gender, interval between onset and diagnosis and other clinical data. No changing avidity was observed in serial samples with time.
Conclusion: Affinity maturation might have been completed by the time that patients presented with anti-GBM disease. The different avidity of anti-GBM antibodies was associated with the degree of renal damage and might play a key role in the pathogenesis of anti-GBM disease.