QUANTITATION AND CHARACTERIZATION OF SOLUBLE IMMUNE-COMPLEXES PRECIPITATED FROM SERA BY POLYETHYLENE-GLYCOL (PEG)

Abstract

Polyethylene glycol (PEG) was used to isolate immune complexes from sera. Complexes were then quantified and partially characterized by a variety of immunological techniques. Complexes were detected in rheumatoid arthritis (RA), systemic lupus erythematosus (SLE), Felty''s syndrome and vasculitis but not in polymyositis, scleroderma or Behcets syndrome. The level of immune complexes correlated with disease activity in SLE and RA patients. Rheumatoid factors and anti-DNA antibodies were enriched by PEG precipitation of RA and SLE sera, respectively. These antibodies appeared present in the form of soluble immune complexes. Immune complexes usually contained all 3 immunoglobulin (Ig) classes, IgG, IgM and IgA. Complexes from RA patients were generally larger and often contained Clq [q fragment of complement component 1], while C3 was found almost exclusively in SLE complexes which tended to be smaller. Such compositional differences may explain the differences in clinical manifestations of various immune complex- mediated diseases.