Induction of T and B cell immunity by anti‐idiotypic antibody

A small dose of the IgG1 fraction of anti-idiotypic antibody (aId1) raised in guinea pigs against a strain A/J antibody specific for streptococcal Group A carbohydrate sensitizes A/J mice against Group A streptococci. This is opposed to the previously established suppressive function of anti-idiotypic antibody of the IgG2 class (aId2). Correspondingly, aId1 but not aId2 is eliminated from the circulation in the way typical of an immunogenic molecule. However, the stimulatory component in the IgG1 fraction is not necessarily itself IgG1 antibody. Sensitization occurs in both B and helper T lymphocytes and is specific for Group A streptococci. In the B cell compartment sensitization is restricted to precursor cells expressing the idiotype. The concomitant activation of T helper cells therefore suggests that these cells make use of receptors with a similar or identical idiotype. Efficient sensitization by aId1 of both T and B cells is also demonstrated in strain C57L/J mice which upon immunization with Group A streptococci express a partially cross-reacting idiotype as a minor component. When such animals were primed with aId1, essentially all of the anti-carbohydrate antibody carried the partially cross-reacting idiotype.