Serum Immunoglobulin Sedimentation Patterns and Circulating Immune Complexes in IgA Glomerulonephritis and Schönlein-Henoch Nephritis

Sera from 8 patients with IgA glomerulonephritis and from 6 patients with Schonlein-Henoch nephritis were investigated by the Clq-binding assay (Clq-BA) test and by sucrose gradient centrifugation followed by sensitive solid phase radioimmunoassay determinations of IgA, IgG and IgM in each fraction obtained. Abnormal sedimentation profiles were found in sera from 3 of 8 patients with IgA nephritis and in 3 of 6 patients with Schonlein-Henoch nephritis. The abnormal fraction consisted of low molecular weight IgA in 2 patients, IgG in 1 patient and IgM in 4 patients. The absolute level of polymeric IgA was increased in 3 of 8 patients with IgA nephritis, but the relative distribution was normal. An abnormal sedimentation pattern of immunoglobulins was correlated to a positive Clq-BA test (p<0.001).