Dependence of the regression of sarcoma 180 in vitamin B 6-deficient mice upon the immunologic competence of the host.

The incidence of complete regression of Sarcoma 180 (S-180) in vitamin He-deficient Swiss mice was significantly reduced in ani mals thymectomized 1-5 days after birth but not in shamthymectomized mice, neonatally thymectomized mice implanted s.c. with thymus autografi«,mice thymectomized 9 or 30 days after birth, or neonatally splenectomized mice. The initial retardation of the growth of S-180 caused by the dietary deple tion was not different in neonatally thymectomized and shamoperated mice; the delayed retardation of tumor growth was reduced in mice which had been thymectomized neonatally. Thus in nonthymectomized mice the delayed retardation of tumor growth appears to be caused by both the therapeutic treatment and the immunologie response of the host. Comparison of the regression of S-180 and the rejection of allogenic skin grafts indicated that dietary vitamin B6 depletion causes only minor impairment of the immunologie responses of the host at levels sufficient to impair the tumor effectively.