AUGMENTATION OF SPECIFIC IMMUNE-RESPONSE AGAINST A SYNGENEIC SV40-INDUCED SARCOMA IN MICE BY DEPLETION OF SUPPRESSOR T-CELLS WITH CYCLOPHOSPHAMIDE

When cyclophosphamide was administered to mice before immunization with syngeneic SV40-transformed cells, the specific immune response elicited, as was measured by the tumor cell neutralization assay with a syngeneic SV40-induced sarcoma, was stronger and lasted longer as compared to the response generated in non-cyclophosphamide-treated mice. The augmentation effect of the drug was dependent on cyclophosphamide concentration, being optimal at 100 mg/kg, and on the time of drug administration in relation to antigen immunization, being optimal at 2-4 days before antigen administration. Transfer of T cells from normal syngeneic mice to drug-treated animals abolished the cyclophosphamide-induced augmentation of immune response. These results implied that cyclophosphamide-sensitive T cells suppressed the in vivo generation of specific effector T cells against SV40-induced sarcoma. © 1979.