In vitro studies of cellular-mediated immunostimulation of tumor growth.

Abstract

The interaction of normal, sensitized, and concanavalin-A (Con-A)-stimulated isogeneic, allogeneic, and/or xenogeneic lymphocytes with the 816 melcnemc, C578L/6J andlor A/J mouse-embryo cells was examined by an in vitro colony inhibition-stimulation test. Various numbers of lymphocytes were mixed with target cells, incubated for 2 hours in a rotating test tube, and then plated in culture dishes. Three and seven days later, dishes were fixed and stained, and target cells were counted. Specifically and nonspecifically sensitized lymphocytes, at ratios up to 1000: 1, repeatedly and significantly enhanced target cell growth. At higher lymphocyte doses, colony inhibition was evident. The importance of the relative plating efficiency of target systems in the interpretation of results of in vitro cytotoxicity tests is discussed. Rat Con-A-stimulated lymphocytes also enhanced tumor growth, whereas dead lymphocytes or supernatants derived from cultures containing Con-A-stimulated lymphocytes did not. Sensitized lymphocytes appeared to enhance tumor growth by direct interaction. These results support the hypothesis and experimental data by Prehn that the immune response may have a dual role in its relationship to the development of neoplasms.