The Immune Response of BSA Tolerant Rabbits to Injections of BSA Following the Termination of the Tolerant State

Summary The immune response to BSA was examined in rabbits after a tolerant state to BSA was terminated by injections of related antigens. The previously tolerant rabbits usually made an immune response to monthly injections of I*BSA as evidenced by the immune elimination of the I*BSA and an increase in the level of anti-BSA in the sera. However, after the first injection of I*BSA, subsequent injections resulted in synthesis of less antibody and a portion of the rabbits eventually regained the tolerant state. Similar results were obtained when the BSA was incorporated into Freund's adjuvant. Once the tolerant state returned it could again be terminated by reinjection of the related antigen. In rabbits which had their tolerant state terminated by injections of HSA, none of the antibody produced following a subsequent injection of BSA was specific either for BSA or HSA, but all was directed to the shared determinants.