Effect of combination treatment with cyclophosphamide and isogeneic or allogeneic spleen and bone marrow cells in leukemic (l1210) mice

Generalized leukemia was observed on day 3 following intra‐peritoneal inoculation of leukemic (L1210) ascites cells in CDF 1 mice. On day 3 after tumor implantation, residual viable leukemic cells were detected in the peritoneal cavities and spleens of leukemic mice 6 h following treatment with 180 mg/kg of cyclophosphamide. Mice receiving weekly intraperitoneal injections of X‐irradiated leukemic (L1210) cells for 6 weeks were resistant to a challenge of tumor cells. When incubated in vitro , spleen and bone marrow cells of immune mice were able to inactivate viable leukemic cells, as evidenced by failure of tumor growth in mice inoculated with these cells. Leukemic mice injected with immune spleen or bone‐marrow cells from isogeneic mice following treatment with cyclophosphamide survived a 60‐day observation period. In one such experiment 90‐day survivors were able to resist re‐inoculation of tumor cells. Leukemic (DBA/2) mice inoculated with allogeneic spleen cells following cyclophosphamide treatment survived for longer periods than mice injected with isogeneic spleen cells.