Circulating immune complexes in glomerulonephritis.
The relationship between the presence of circulating immune complexes (CIC), clinical features and renal histology was investigated at the time of renal biopsy in 77 patients with glomerulonephritis. The glomerulonephritides were classified primarily according to light microscopic criteria and later using light microscopy combined with electron microscopy and immunofluorescence. Three methods for detection of CIC were used: C1q-binding-activity, anticomplementary activity and a PEG-precipitation test. When two of the three methods were positive, CIC were regarded as being present. CIC were detected most frequently in patients with "hump-nephritis" (5/6), extracapillary glomerulonephritis (6/7) and lupus-nephritis (7/8), and only rarely in patients with membranous glomerulonephritis (0/7), IgA-nephritis (1/13) and minimal change disease (1/5). A weak correlation was observed between the presence of CIC and the presence of glomerular deposits of IgG +/- IgM detected by immunofluorescence, but no correlation with the presence of electron dense deposits was seen. CIC were detected significantly more often in patients with recent onset of renal disease and in patients with antecedent infections. No correlation could be demonstrated between CIC and renal function, proteinuria, hematuria, blood pressure or progression of renal failure. Serial measurements of CIC in 6 patients with glomerulonephritis showed that CIC may be present transiently and not always be related to the activity of disease.