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Tolerance to Allogeneic Cells Induced in Bursectomized Chickens

The question of whether the presence of antibody is necessary for tolerance induction was investigated in hormonally bursectomized chickens in which no antibody production could be demonstrated. Tolerance to allogeneic cells was induced by i.v. injection of whole blood from one donor into newly hatched, bursectomized chickens and normal chickens. The state of tolerance obtained in the T‐cell population was judged by GVH reactions and by whattle grafts from the blood donor. Prolonged graft survival was found in both bursectomized and conventional, tolerant chickens and compared with normal controls. The diminished GVH reactivity of blood lymphocytes from tolerized animals was specific for embryos of the tolerogenic B‐genotype and was equally marked with cells from bursectomized and non‐bursectomized birds. No antibodies against the tolerogenic cells could be demonstrated either by haemagglutination or by the ability of serum from tolerant animals to inhibit GVH reactivity of lymphocytes of the tolerogenic type. It is concluded that although the mechanisms involved for the induction of T‐cell tolerance is unknown, there is no evidence from bursectomized chickens that humoral antibodies facilitate the process, or that they are even a necessary requirement.