Studies on antigenic competition. II. Abolition of antigenic competition by antibody against or tolerance to the dominant antigen: a model for antigenic competition.

Antigenic competition between the Fc and Fab fragments of rabbit IgG in mice could be abolished by passive immunization with antiserum against the dominant antigen (Fc). The induction of tolerance to Fc also eliminated antigenic competition. Anti-Fd production, generally very poor in response to rabbit IgG, was considerably enhanced by these procedures, indicating that it is also subject to antigenic competition with Fc. A model is proposed to explain antigenic competition which proposes that it is the `co-operative antibody' produced to the dominant antigen which acts as an inhibitor to antibody production to the suppressed antigen by competing for sites —presumably on macrophage membranes—where co-operation occurs. The merits and difficulties of such an explanation are discussed.