The present study was performed to elucidate the anti-tumor mechanism of
Corynebacterium anaerobium (CA) against Ehrlich ascites tumor by using athymic nude mice (nu/nu) and hetero (nu/+) mice of the BALB/c strain.
1) The anti-tumor effect of CA on both nu/nu and nu/+ groups injected intraperitoneally with a mixture of tumor cells and CA was dose dependent. The most effective dose was 250μg per mouse. The overdose administration was much less effective or ineffective.
2) Treatment with carrageenan, which preferentially suppresses the macrophage function, decreased the anti-tumor effect of CA on both groups.
3) A remarkable enhancement was demonstrated in the anti-tumor effect of CA on the nu/nu group to which had been transferred the thymic cells of the nu/+ group.
4) No significant enhancement was shown in the anti-tumor effect of CA on the nu/nu group with CA-sensitized splenic cells transferred from the nu/+ group exhibiting delayedtype hypersensitivity to CA.
5) The nu/+ group, as well as the nu/nu group, to which had been transferred thymic cells, the tumor of which had been completely suppressed by CA, was highly resistant to rechallenge with the tumor cells, presenting a complete rejection.
6) Non-adherent cells derived from the spleen and lymph node of the nu/+ group being resistant to rechallenge with the tumor cells, as well as peritoneal macrophages derived from the CA-treated nu/nu group, exerted a strong cytotoxicity on the tumor cells
in vitro.
From the findings mentioned above, it was concluded that the anti-tumor activity of CA against Ehrlich ascites tumor was effectuated by CA-activated macrophages and cell-mediated immunity to tumor induced by administration with CA and the tumor cells. Another possible anti-tumor mechanism due to the bystander effect of delayed-type hypersensitivity to CA could not be ascertained.
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