[Circulating immune complexes in man; precipitation of immune complexes with polyethylene glycol and their characterization by Clq bound to immunoglobulins].

Use of an experimental model consisting of purified tetanal toxoid and sera of patients vaccinated with this antigen reveals that immunodiffusion characterisation of C1q bound to immune complexes (IC) precipitating with 2,5% PEG (6000) represents a very sensitive means of detection of such IC. The majority of sera of patients with disorders in which IC can be suspected gives positive reactions. Precipitates contain IgG and IgM bound to C1q and rheumatoid factor is constantly detected. The reaction is positive among 10% of healthy patients: the possibility of circulating IC free from any pathological cases is under study.