Mechanisms of the potentiation of specific antitumor immunity by intratumor injection of Corynebacterium parvum.

Meth A fibrosarcoma-bearing BALB/c mice given intratumoral injections of 0.5 mg of Corynebacterium parvum showed a highly and tumor-specific transplantation antigen specifically potentiated concomitant immunity to a subsequent tumor challenge. This potentiated antitumor immunity could be locally transferred in the Winn assay to normal recipients with whole draining lymph node cells from the tumor-bearing mice, but the potentiated effect disappeared when adherent cells were removed from these cells. Moreover, the potentiated cytostatic effect on tumor cells was detected in the peritoneal macrophages but not in the nonadherent draining lymph node cells in in vitro tests. On the other hand, nonadherent draining lymph node cells from the tumor-bearing mice, when mixed with C. parvum-induced macrophages, exhibited a specifically potentiated antitumor effect. In addition, this effect was completely abolished by treatment of the draining lymph node cells with anti-Thy-1 and complement. Thus, the potentiated antitumor effect following intratumor injection of C. parvum may be ascribed to the collaboration of specifically sensitized T-lymphocytes with C. parvum-activated macrophages.