Summary
Adult New Zealand rabbits given 500 or 550 r of x-radiation, followed 2 and 7 days later by intravenous injections totaling 300 mg of bovine serum albumin (BSA), were unable to make antibodies against this antigen when appropriately challenged 2 months later. The degree of immunologic unresponsiveness observed was related to the amount of BSA injected during the first week after irradiation: 1 mg reduced the subsequent antibody response after challenge by 70%, 12 mg reduced it by 95%, and 300 mg reduced it by more than 99%. The resulting unresponsive state was specific, in that tolerance to BSA did not occur following irradiation and injection of 300 mg of human γ-globulin. The unresponsive state was much less complete 4 months after irradiation and treatment with BSA than it was at 2 months. The amount of BSA per kg of body weight required to induce tolerance appears to be approximately the same for irradiated adult rabbits and for neonates.
