Circulating immune complexes in patients with uncomplicated group A streptococcal pharyngitis and patients with acute poststreptococcal glomerulonephritis.

To investigate the role of circulating immune complexes (CIC) in the pathogenesis of acute poststreptococcal glomerulonephritis (AGN), sera were obtained serially from 13 patients with biopsy-proven AGN, 16 patients with group A streptococcal infection, and 20 age- and sex-matched controls. Samples were analysed for Clq-binding activity (Clq-BA), levels of IgG, IgA, IgM, C3 and C4, and antibody titres to streptococcal enzymes. Significant elevation of Clq-BA was observed in 11 patients (84.5%) with AGN and 7 patients (44%) with streptococcal infection alone. The data suggest that CIC do not necessarily cause glomerular damage, but rather represent a systemic inflammatory response in patients with group A streptococcal infection.