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The effect of bursectomy on the recovery from immunologic tolerance.


 The role of the bursa of Fabricius of the chicken in the recovery from immunologic tolerance was studied. Newly hatched, sublethally x-irradiated chickens were injected twice weekly intra-abdominally with physiologic saline or large doses of bovine serum albumin (BSA) until they were 5 weeks old. At this time the BSA-injected animals were specifically tolerant. After intravenous challenge with BSA very few spleen cells forming antibody to BSA could be detected with a modified Jerne hemolytic plaque assay. Good responses to sheep erythrocytes were obtained. Surgical bursectomies were performed on half the animals after the injections were stopped. Bursectomy had no effect on the subsequent responsiveness to BSA in the saline-injected chickens. The tolerant chickens had recovered their responsiveness to BSA after 10 weeks. Bursectomy impaired this recovery. These results suggest that the antibody-forming bursa-dependent line of lymphoid cells may be made specifically tolerant. The bursa of Fabricius may serve as an important, if not exclusive, source of new immunocompetent cells in the process of recovery from immunologic tolerance.