Inhibition of cell-mediated cytotoxicity to tumor alloantigens by systemic administration of Corynebacterium parvum

Summary Intravenous administration of C. parvum following SC immunization with a tumor allograft markedly impaired the generation and expression of primary cell-mediated cytotoxicity to the immunizing alloantigens. For the inhibition to become manifest, a minimum of 4 days of in vivo exposure to C. parvum was necessary, and the effect was seen only when C. parvum was injected during the developing immune response; injection prior to or simultaneously with alloimmunization resulted in no impairment. The inhibition of cell-mediated cytotoxicity was selective. While spleen cell populations exhibited decreased cytotoxic activity, lymphoid cell populations from lymph nodes and blood were unaffected. The inhibitory effect was restricted to the cellular component of the immune response. Complement-dependent cytotoxic antibodies developed normally and their titer was comparable to that of control alloimmunized mice.