Embryo-derived teratocarcinoma. IV. The role of immune factors in the regulation of teratocarcinogenesis.

Seven-day-old mouse embryos were transplanted under the kidney capsule of adult syngeneic recipients which were either X-irradiated, treated with cyclophosphamide, splenectomized or immunized with teratocarcinoma cell lines prior to embryonic transplantation. The yield of malignant tumors was decreased in preirradiated, as well as in cyclophosphamide-pretreated animals, as compared with untreated hosts. The effect of the pretreatment could be fully abrogated by allowing animals to spontaneously recover for 4 weeks or by adoptive transfer of thymus cells from untreated animals. Partial recovery was obtained by the adoptive transfer of spleen cells. Splenectomy at the time of embryonic transplantation did not affect the embryo-derived teratocarcinogenesis in C3H mice but reduced the yield of malignancy and the weight of tumors produced in C57BL/6 mice. Immunization of hosts with teratocarcinoma cells did not influence the subsequent embryo-derived teratocarcinogenesis. These data indicate that embryo-derived teratocarcinogenesis is regulated by X-ray and cyclophosphamide-sensitive cells residing in the thymus and the spleen. The permissiveness to teratocarcinogenesis seems to be a function of the total number of these regulatory cells in the host.