INHIBITION OF IMMUNE PRECIPITATION BY COMPLEMENT

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  • 1 January 1980
    • journal article
    • research article
    • Vol. 42  (2) , 387-394
Abstract
Immune precipitation of bovine serum albumin (BSA) by rabbit anti-BSA antibody (Ab) was studied at 37.degree. C in the presence of normal human serum, normal rabbit serum, decomplemented serum and reagents permitting complement (C) activation by the classical pathway or the alternative pathway. Inhibition of precipitation occurred in the presence of C. Antibody-excess complexes were kept soluble more easily than complexes formed at equivalence. Human serum was a better inhibitor than rabbit serum. Analysis of the phenomenon showed that during the first minutes of the reaction immune complexes were maintained in solution by the classical pathway only; at later stages the alternative pathway was essential. Such soluble immune complexes precipitated after further incubation for 24 h. The subsequent addition of EDTA to serum at 37.degree. C holding immune complexes in solution led to a slow aggregation of the complexes. Their size was approximately 25S as assessed by sucrose density-gradient ultracentrifugation, they bore C3 and C4 fragments.