Induction, Maintenance and Termination of Immunologic Unresponsiveness to Bovine Thyroglobulin in Rabbits

Abstract

Rabbits were rendered unresponsive with periodic injections of very small doses of bovine thyroglobulin starting on the day of birth. All of the animals receiving periodic injections of 0.25 mg (total 6.0 mg), 62% of rabbits given 0.05 mg injections (total 1.2 mg) and 29% of rabbits given 0.025 mg injections of bovine thyroglobulin (total 0.6 mg) were unresponsive. In the latter group, the amount of bovine thyroglobulin in the blood at the time of challenge was below that detectable by a sensitive serologic technique. After no further antigen injection, the induced unresponsive state to bovine thyroglobulin lasted at least 3 months; however, there was a gradual loss of the unresponsive state which began 3 to 4 months after the last injection. Similar mechanisms appear to be involved in the termination of the acquired unresponsive state to bovine thyroglobulin and production of experimental autoimmune thyroiditis. The unresponsive state to bovine thyroglobulin was readily terminated by injections of a serologically related human thyroglobulin, and simultaneous injections of bovine thyroglobulin inhibited this termination.