TRANSITION FROM T CELL PROTECTION TO T CELL ENHANCEMENT DURING TUMOR GROWTH IN AN ALLOGENEIC HOST

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Abstract
The cell-mediated immune response of mice toward a lethal allogeneic tumor was investigated during tumor development. The activity of spleen cells from the tumor-bearing mice was studied by transferring them together with 3LL tumor cells into normal C3H/eb recipient mice. The activity depended upon the time interval between inoculation of the tumor and transfer. Spleen cells taken relatively early, 1 week after tumor inoculation, mediated protection against tumor growth. In contrast, spleen cells taken 4 weeks after tumor inoculation markedly enhanced tumor growth. The tumor-enhancing cells, like the tumor-protecting cells, appeared to be T lymphocytes. The enhancing activity could be transferred by extracellular medium prepared by incubating the enhancing T cells. Protecting activity could not be transferred by cell-free medium prepared from the protecting T cells. Both activities were found to exist to a relatively slight degree in populations of spleen cells from normal mice. The transition from T cell protection to T cell enhancement might be a determining factor in the outcome of the host-tumor relationship.