[Circulating immune complexes, detection in human glomerulonephritis by the PEG-EDTA technique (author's transl)].

: In a prospective study, we screened sera samples of 128 patients with glomerulonephritis (GN) for the presence of circulating immune-complexes (CIC) fixing C1q by precipitation of native C1q with 2% polyethylene glycol (PEG) in the presence of 10 mM EDTA. The amount of precipitated C1q, as measured by Mancini, is less than 27% (m +/- 2 SD) of the original value in control sera. We found 35/128 (27%) positives samples, distributed as follows: 4/17 (24%) in acute GN, 10/15 (67%) in SLE, 2/16 (13%) in membraneous GN, 13/24 (54%) in membranoproliferative GN, 3/16 (19%) in segmental focal hyalinosis, 2/10 (20%) in minimal lesions nephrotic syndrome, and 1/30 (3%) in mesangial IgA GN. We then correlated these results with clinical, serological and pathological data. Whatever the type of GN, the presence of CIC fixing C1q correlated significantly, well with : the presence of chronic renal failure (serum creatinine greater than or equal to 2 mg/dl) (X2 = 5.48, p less than 0.02), the presence of hypocomplementemia (X2 = 12.30, p less than 0.001), the presence of low serum C3 (X2 = 8.25, p less than 0.01), the activation of C3 through normal pathway (low serum C4 and/or C1q) (X2 - 18.12, p less than 0.001) and the presence of glomerular deposits of C3 (X2 = 8.52, p less than 0.01), of C4 (X2 = 7.10, p less than 0.01), and of C1q (X2 = 4.11, p less than 0.05). The technique is simple, does not require labeled C1q, and allows the further study of antigen or antibody determinants of the complexes. Its sensitivity is near that of the 125 I-C1q binding assay technique. Such routine screening is a major immunopathologic step in the investigation of human GN.