[Avidity of anti-glomerular basement membrane autoantibodies was associated with renal pathological damage]

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.

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.

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.

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.