Effect of Thymectomy on Induction of Tumors and on the Transplantability of Polyoma-induced Tumors.

reduced immunologic responses that are broadly classified as cellular histocompatibility reactions. Thus, after neo natal thymectomy, allogenic and even xenogenic skin grafts survived in mice over extended periods (15) ; rejec tion of allogenic skin grafts was delayed in hamsters and the second set reaction to skin homografts was abolished (22) ; the incidence of allergic encephalomyelitis was greatly reduced in rats (2, 7) ; lymphocytic choriomeningitis virus infection was not lethal for mice (23). Also, tumors were successfully grafted between unrelated strains of mice in thymectomized recipients (14). Antibody formation was greatly impaired after neonatal thymectomy, although variations have been observed among animals and with different antigens (20, 27). Recently, specific antigen(s) have been associated with either virus or chemical carcinogen-induced tumors (4, 10,