FC-MEDIATED IMMUNE PRECIPITATION .4. ANTIGEN DEPENDENCY AND SPECIFICITY

  • 1 January 1983
    • journal article
    • research article
    • Vol. 48  (3) , 477-488
Abstract
The antigen dependency of Fc-mediated immune precipitation was investigated by comparing the immune precipitation of 3 different protein antigens (bovine serum albumin, BSA, human plasma transferrin, HPT, and human fibrinogen, HFg) using specific intact rabbit IgG antibodies and isomolar solutions of the corresponding F(ab'')2 fragments. This precipitin mechanism is highly antigen-dependent both quantitatively and qualitatively. Sucrose density gradient ultracentrifugation was used for the identification of Fc-precipitating immune complexes, and it was demonstrated that different types of complexes take part in Fc-mediated immune precipitation in the different antigen-antibody systems. Only small complexes are involved in the HFg system, whereas small and large complexes precipitate by this mechanism in the BSA and the HPT systems. The specificity of Fc-mediated immune precipitation was studied by mixing human serum albumin (HSA)-anti-HSA IgG complexes with either HPT-anti-HPT IgG or HFg-anti-HFg IgG complexes. Fc-mediated immune precipitation is a specific process due to the preferential binding of homologous complexes.