In vitro induction of tumor specific immunity: requirements for T lymphocytes and tumor growth inhibition in vivo

Cortisone‐resistant thymocytes, spleen cells, thoracic duct lymphocytes, peritoneal exudate cells and peripheral blood lymphocytes of BALB/c mice were immunized in vitro against syngeneic HPC‐108 plasma cell tumor cells. Cocultivation of spleen lymphocytes together with HPC‐108 cells generated the highest cytotoxic immune response in comparison to other lymphocyte sources. Cytotoxicity was tested in a 6 hour 51 Cr release assay using HPC‐108 cells as target cells. The use of AKR anti‐θ C3H serum indicated that thymus‐derived (T) lymphocytes are essential to the initiation phase of the immune response to plasma cell tumor cells. Furthermore, evidence is presented that the cytotoxic effector cells in the in vitro tumor immune response are T lymphocytes. Spleen cells activated in vitro against HPC‐108 tumor cells were shown to specifically prevent tumor growth from simultaneously injected HPC‐108 cells in irradiated recipient mice.