In Vivo Elimination by Specific Effector Cells of an Established Syngeneic Rat Moloney Virus-Induced Sarcoma

BN rats immunized subcutaneously with a viral induced tumor (MST) or with a chemical-induced fibrosarcoma (BC5) were donors of immune spleen cells. Samples of immune spleen cells were tested in vitro against MST and BC5 in a 51Cr release assay before culturing and after 7 days of culture with mitomycin C-treated MST and/or BC5 tumor cells (MSTMit, BC5Mit). These spleen cells were infused in vivo i.v. into x-rayed (400 R) and nonirradiated BN recipients that bore a vascularized and progressive (1 to 1.5 cm in diameter) subcutaneous MST or BC5. Spleen cells from untreated BN donor rats were also tested in vitro and in vivo as controls. Established MST were specifically eliminated by spleen cells immune to MST after culture with MSTMit, but not by spleen cells immune to MST without further culture nor by cultured or uncultured BC5 immune spleen cells and control spleen cells. Also, the growth of BC5 was not affected by MST immune spleen cells cultured for 7 days with MST and/or BC5. Elimination of Moloney sarcoma (MST) in vivo occurred in less than 35 days and was correlated with the generation of cytotoxicity in vitro since only MST immune spleen cells cultured with MSTMit were able to augment significantly their cytotoxic capability in vitro.