Embryo-derived teratocarcinomas elicit splenomegaly in syngeneic host

Abstract

MOUSE egg-cylinders transplanted to extrauterine sites develop either as teratomas (benign tumours composed of adult tissues) or as teratocarcinomas (retransplantable malignant tumours containing, in addition, undifferentiated embryonic carcinoma cells)^1–4. Rat egg-cylinders similarly transplanted, however, always develop as teratoma⁵. When transplanted to a syngeneic host, C57BL mouse egg-cylinders develop as teratomas but when transplanted to (C3H × C57BL)F₁ hybrids they develop into teratocarcinoma^3,4. This suggests that the host reaction is important in determining the fate of a transplanted embryo. Specific embryonic and foetal antigens which are re-expressed during malignant transformation are now well established^6–8, and we thought that an immunological reaction of the host against embryonic antigens in the egg-cylinder might determine whether the transplant develops as teratoma or teratocarcinoma. Splenomegaly is considered to be a sign that a host has reacted to the antigenic stimulation of a graft or tumour^9,10, and we have found that although it is always present in mice with transplanted egg-cylinders, it is much more pronounced in those with teratocarcinoma. Splenectomy, however, reduced the growth of the transplanted embryos, suggesting that the immunological reaction of the host stimulates the growth of the graft.