Abstract
The plaque technique of Cunningham and Szenberg was used to demonstrate the influences of various kinds of antitumor agents on the hemolytic plaque-forming cells (PFC) of the spleen of C57BL/6 mice after immunization with sheep red blood cells (SRBC) . The agents were intraperitoneally administrated before or after the intraperitoneal injection of SRBC. 1) Influence of alkylating agents: Post-treatment of mice with carboquone or cyclophosphamide proved to decrease markedly the number of PFC. 2) Antimetabolites: Azathioprine, cyclocytidine, cytarabine, 5-fluorouracil, 6-mecaptopurine, methotrexate and tegafur suppressed the production of PFC by the post-treatment. 3) Antitumor antibiotics: Bleomycin, chromomycin A3, doxorubicin, mitomycin C, peplomycin and spadicomycin showed strong suppression of PFC by the pre-treatment. Aclarubicin and actinomycin D inhibited the production of PFC by either pre-or post-treatment. Anthramycin and daunorubicin were found to show suppression by the pre-treatment and enhancement by the post-treatment. 4) Alkaloids: PFC decreased by the post-treatment with vinblastine and vincristine. 5) Steroid hormones: Dexamethasone and prednisolone suppressed the production of PFC by the post-treatment. 6) L-Asparaginase and cisplatin inhibited the PFC by the post-treatment, and cyclosporin A by the pre-treatment. 7) Immunopotentiating agents: Krestin showed suppression by the pretreatment and enhancement by the post-treatment. Schizophyllan increased the number of PFC by either pre- or post-treatment. When the drugs were intravenously administrated, the enhancement of the production of PFC were recognized by the pre-treatment in the cases of anthramycin, chromomycin A3 and spadicomycin.
