IDENTIFICATION OF COMPONENTS OF IC PURIFIED FROM HUMAN-SERA .1. IMMUNE-COMPLEXES PURIFIED FROM SERA OF PATIENTS WITH SLE

Abstract

Immune complexes (IC) were purified by affinity chromatography on conglutinin columns from human sera (5 SLE [systemic lupus erythematosus], 1 AML [acute myeloid leukemia] and 1 leishmaniasis) and compared with IC formed in vitro in the presence of normal serum (NHS). Analysis by SDS[sodium dodecyl sulfate]-polyacrylamide gel electrophoresis (SDS-PAGE) demonstrated a common qualitative pattern, but with marked quantitative differences, in IC obtained from 5 patients'' sera (4 SLE, 1 leishmaniasis) and for in vitro formed IC. In 2 other patients (1 SLE, 1 AML), the pattern of IC components was very different, with a major band in the 26 kD [kilodalton] region. After electrophoretic transfer of the SDS-PAGE bands to nitrocellulose membranes, the nature of IC components was studied by defining the reactivity of the bands with antisera against human serum antigens. Several serum proteins were identified in the purified IC:IgG, IgA, IgM, C1q [complement component 1q], C1r, C1s, C3bi and Bb. A few bands did not correspond with any normal serum protein. One of them, at 26 kD reacted with anti-C reactive protein (CRP) antiserum. From all the constituents observed in the SDS-PAGE analysis of purified IC, only 2 bands in 1 SLE patient might be corresponding to unidentified antigens.