[Detection of circulating immune complexes by three techniques using polyethylene glycol (author's transl)].

The search for circulating immune complexes (IC) by precipitation tests using polyethylene glycole was performed in a large series of normal (150 subjects) and 1200 pathological sera (over 800 patients). Increased precipitability of IgG and C4 was seen in a great percentage (80%) of pathological sera giving positive PEG precipitation without direct influence of IgG, IgM, C1q, C3 and C4 serum levels. The labeled C1q binding test gave similar results in 90 normal and 640 pathological sera. The C1q binding test could be replaced by the more direct and simple evaluation of the amount of C4 precipitated with IgG by 3.5% PEG. Positive results obtained in the three methods were particularly found in patients with diseases generally presumed to represent immune complexes diseases including acute glomerulonephritis, systemic lupus erythematosus, polyarteritis nodosa, subacute bacterial endocarditis, and acute or chronic hepatitis.