Specificity of the Immunosuppression Caused by Passive Administration of Antibody

Abstract

Antibody production against Fab and Fc determinants in rabbits immunized with varying doses of human immunoglobulin G (IgG) incorporated in incomplete Freund's adjuvant (ICFA) was determined using an antigen-binding capacity test. The kinetics of antibody formation and the amount of antibody produced against each group of determinants were usually comparable within the range of antigen doses used. Intravenous administration of rabbit hyperimmune anti-Fab or/and anti-Fc antibodies 1 hr before and 7 days after injection of rabbits with IgG in ICFA specifically inhibited antibody production to the corresponding determinants without affecting the immune response to the unrelated determinants inasmuch as kinetics of antibody formation, serum antibody levels and relative avidity of antibodies were concerned. The results suggest that passive antibody may inhibit the antigenic stimulus at the level of antigenic determinants rather than at the level of the whole antigenic molecule.