Propionibacterium acnes-mediated humoral immune responses to tumor-specific antigens on rat liver cells transformed in vitro by chemical carcinogens.

Effects of Propionibacterium acnes on production of antibodies against tumor-specific membrane antigens were investigated in syngeneic inbred BD IV and BD VI rats. BD rat liver cell lines transformed in vitro by chemical carcinogens were used as target cells for tumor-specific antigens. By membrane immunofluorescence, antibodies against these rat liver cell lines were detected in syngeneic BD rat sera. Antibodies were produced in syngeneic rats under the adjuvant effect of heat-killed P. acnes only. In assays with various target cells and absorption experiments, the antibodies reacted with a tumor-specific individual antigen or tumor-specific cross-reacting antigen on the surfaces of transformed BD rat liver cells. No antibodies against these antigens were found in the sera obtained from syngeneic rats immunized with either the transformed cell lines or P. acnes but not with both. Freund's complete adjuvant did not induce antibodies against these tumor-specific antigens.