Changes of lymphoid cell cytotoxicity, shown in vitro, of mice bearing a syngeneic tumor after injection of killed tumor cells]

Lymphoid cells from mice bearing a syngeneic tumour show a cytotoxic activity in vitro, occuring in two succesive waves. Normally inactive during the second week after grafting, lymphoid cells have a marked killing ability during this period when heavily irradiated tumour cells have been injected on the 6th day. On the contrary, the cytotoxicity due to the graft, which is important from the 20th to the 30th day, is inhibited by injection of killed tumour cells 15 days before the test. Quantitative variations of the tumour antigen liberated in the animal may be responsible for those effects.