Retardation and promotion of growth of spontaneously appearing tumors using immune lymphocytes previously exposed to embryonic antigens.

Spleen lymphocytes taken from mice at various stages of pregnancy or growth of s.c. syngeneic tumor implants have been examined for their ability to cause cytolysis of embryo fibroblasts in culture or to affect the growth of the transplanted tumor cells in vivo. Activity of different lymphoid populations in affecting tumor growth in vivo was correlated with activity in vitro, whether cytolysis (growth inhibition) or blocking of cytolysis (growth promotion) was considered. The evidence favors an important role for lymphoid responses to embryo-associated antigens in the control of spontaneous tumor growth, although one cannot yet rule out a crucial role for the host milieu rather than, or in addition to, host cellular elements being the important feature of this control process.