Induction of antibody synthesis. Effect of blocking defined determinants of an antigen.

Rabbit antibody specific for bovine γ-globulin (BGG) and for the dinitrophenyl group (DNP) was used to block defined determinants of BGG—DNP, and the immunogenicity of antibody-complexed BGG—DNP in rabbits was compared with that of BGG—DNP. Antibody-complexed BGG—DNP was less immunogenic, eliciting less antibody reactive with BGG—DNP. However, BGG-specific antibody, in contrast to DNP-specific antibody, suppressed primarily the induction of antibody specific for the BGG determinants of BGG—DNP. This finding suggests: (1) that induction of antibody specific for a given determinant of an antigen requires the active participation of that determinant as an inducer, and (2) that the immunosuppressive action of antibody is determinant-specific and not antigen-specific. The immunogenicity of antibody-complexed sheep erythrocytes was also studied in mice. Rabbit antibody to sheep erythrocytes, in different amounts, was used to block determinants on the surface of sheep erythrocytes. The agglutinin response was inversely proportional to the amount of antibody used to complex the erythrocytes. This finding supports the role of determinants as inducers of antibody formation and indicates that the immunogenicity of an antigen is a function of the number of determinants it carries in an accessible reactive state.