Molecular weights of IgA-circulating immune complexes (CIC) in patients with IgA nephropathy: application of HPLC and solid-phase anti-C3 Facb EIA.

The detection of molecular weights of IgA-circulating immune complexes (CIC) in sera is described. Measurement of IgA-, IgG- and IgM-CIC in sera was also performed. Serum samples were obtained from nine patients with IgA nephropathy, nine patients with chronic proliferative glomerulonephritis without IgA deposits (PGN) and 19 healthy adults. Serum samples of these patients were subjected to high performance liquid chromatography (HPLC) and then divided into 50 fractions. Measurement of IgA-, IgG- and IgM-CIC in such fractions was performed using solid-phase anti-C3 Facb EIA. The levels of IgA-CIC in sera from patients with IgA nephropathy were significantly higher than those from patients with PGN or healthy adults. The peak values of molecular weights of IgA-CIC in sera from patients with IgA nephropathy ranged from 2.6 X 10(5) to 3.0 X 10(5) daltons (mean +/- SD; 2.9 +/- 2.0). It was suggested that the increase of IgA-CIC in sera from patients with IgA nephropathy may be mainly due to dimers and/or polymers.