The effect of Freund's complete adjuvant on the specificity of an immune response, and its relationship to antigenic competition

Abstract

The presence of Freund's complete adjuvant has been found to markedly alter the specificity of the antibody response made to a mixture of antigens. The antigens were rabbit serum proteins, administered either as whole serum or as mixtures of purified gamma globulin and albumin. Antiglobulin and antialbumin levels were measured in Balb/c mice. Following injection of rabbit serum or a globulin-albumin mixture, without the aid of adjuvant, the mouse antibody response was made up of about 95% anti-globulin and only 5% anti-albumin. The presence of Freund's complete adjuvant, while greatly increasing the amounts of antibody produced, significantly altered these proportions to about 40% anti-globulin and 60% anti-albumin. This was to a large extent the result of marked suppression of the antiglobulin response, caused by the combined presence of albumin and Freund's complete adjuvant. Since Freund's complete adjuvant itself has no suppressive effect on the response to globulin injected alone (indeed quite the reverse being the case), it is suggested that the effect of Freund's complete adjuvant is to enable one component of the mixture (albumin) to compete successfully against the other (globulin). The overall specificity of the immune response is thereby altered. An explanation for this in terms of T cell activation is proposed.