A study of idiotypic suppression in adult rabbits immunized with Salmonella abortus-equi.

It is possible to induce idiotypic suppression in adult rabbits immunized with Salmonella abortus-equi (S.a.e.). Ten months after priming we injected the rabbit with anti-idiotypic serum prepared against its own antibodies to S.a.e. and, 3 weeks later, gave it a booster injection of bacteria. A new anti-idiotypic serum was preparedwith the serum to S.a.e. collected after this boost and was used for the following isiotypic suppression attempt made 10 months after the first one. Using this procedurewe succeeded in two successive idiotypic suppression attempts in the same rabbit. Inthe three attempts we carried out, idiotypic suppression was totally effective, i.e. idiotypes detected by the serum used for the suppression totally disappeared after thesuppression, and the suppression lasted during the life of the rabbits (maximum 10 months). This observation is consistent with a suppression resulti-g from an interaction of anti-idiotypic antibodies with the complementary receptors at the surface of memory cells. This suppression was without effect on antibody to S.a.e. titre and on IgG concentration. Idiotypes detected by the anti-idiotypic serum prepared withthe serum to S.a.e. collected after the suppression. These idiotypes were different from those detected by the anti-idiotypic serum used for the suppression. This observation confirms that idiotypic recognition is confined to a limited number of clonal products, despite the fact that a very heterogeneous antibody population was used forthe anti-idiotypic immunization. Thus we did not observe the appearance of new idiotypes produced previously silent cell clones. All the different idiotypes we detected during the successive idiotypic suppression attempts carried determinants shich remained peculiar to each individual rabbit.