Specific cytostatic effect of lymph node cells from normal and T cell-deficient mice on syngeneic tumor target cells in vitro and its specific abrogation by body fluids from syngeneic tumor-bearing mice

Lymphoid cells from tumor-bearing animals were shown to be cytostatic for syngeneic tumor target cells in vitro using a post labeling radioactive assay. The specific decrease or removal of this cytostatic activity was possible using a “blocking” serum or ascitic fluid from syngeneic tumor-bearing animals. Further lymphoid cells from chronically irradiated, thymectomized mice, which were shown to be extensively deprived of T cells by reduced PHA responsiveness and anti-θ cytotoxicity tests, were also found to cause cytostasis of target tumor cells and to a greater extent than with nondeprived lymphoid cells.