Effect of Propionibacterium acnes on the cellular immune responses to tumor-specific antigens on malignant rat liver cells.

The effect of Propionibacterium acnes on the cellular immune responses to tumor-specific membrane antigens was investigated by microcytotoxicity assays (MA) and 51Cr release assays (CRA) with use of mesenteric lymph node cells (LNC) of syngeneic BD IV and BD VI rats. BD rat liver cell lines transformed in vitro by chemical carcinogens were used as target cells with tumor-specific antigens. By MA, the LNC from rats that were inoculated with malignant liver cells under the adjuvant effect of heat-killed P. acnes showed significant cytotoxic response to the target cells but not to nonmalignant liver cells. By CRA, these LNC did not show specific cytolysis to the malignant liver cells. Assays with various target cells derived from BD rat liver and inhibition tests with syngeneic and xenogeneic antisera against tumor-specific antigens on the malignant liver cells proved that LNC reacted with tumor-specific individual or tumor-specific cross-reacting antigens on the malignant liver cells. Cytotoxic responses against the malignant liver cells were not demonstrated even by MA with use of the LNC from rats inoculated with either the malignant liver cells or P. acnes alone. LNC from the rats inoculated with both nonmalignant liver cells and P. acnes were not cytotoxic to malignant or nonmalignant liver cell lines.