Study on anti-IgA antibody in patients with IgA nephropathy.

Serum IgG antibodies to polyclonal IgA, IgA1 and IgA2 were evaluated by enzyme-linked immunosorbent assay in 50 patients with IgA nephropathy and 30 healthy controls to elucidate the relationship between IgA and IgG in IgA nephropathy. Anti-IgA antibody was considered positive if the titer exceeded the mean value in normal controls by greater than 2 SD. In patients with IgA nephropathy, 18 cases (36%) demonstrated anti-IgA antibody, 19 cases (38%) anti-IgA1 antibody and 7 cases (14%) anti-IgA2 antibody. Western blots confirmed the existence of anti-IgA antibody in these patients. There were no significant differences in serum IgA concentration, serum creatinine concentration, degree of hematuria, amount of urinary protein, and rate of glomerular IgG deposition between the "positive" group and "negative" group. Although the mechanism of production and the role of this antibody remain unknown, it may represent one of the diverse immune abnormalities of IgA nephropathy and may be involved in the pathogenesis of IgA nephropathy.