An analysis of conditions allowing Corynebacterium parvum to cause either augmentation or inhibition of natural killer cell activity against tumor cells in mice.

We have analyzed the impact of in vivo administration of Corynebacterium parvum on the mouse immune system against murine tumors, using the natural cytotoxic ability against tumors of normal mouse lymphoid cells as a baseline. A striking difference was found depending on the route of administration. Intravenous inoculation of bacteria would result in a significant decrease or sometimes complete abolition of natural cytotoxicity toward tumor cells of the spleen cells of treated mice. On the other hand, the intraperitoneal route of administration resulted in a dramatic increase in cytolytic ability of the peritoneal exudate cells. Both routes of treatment had the most significant impacts on the local cell population (IV = spleen, IP = peritoneal exudate cells) with only minor effects on other cell populations. Analysis of the spleen cell population from IV-treated mice did also demonstrate a significant reduction in the T lymphocyte function, but in contrast to the natural cytotoxicity this could be corrected for by the removal of suppressor cells of an adherent nature. The lytic cells induced in the peritoneal exudate by the Corynebacterium parvum bacteria were all found to be natural killer, NK, cells with no significant activity found amongst macrophages using short-term cytolytic assays.