Cellular and humoral immunity to rat hepatoma‐specific antigens correlated with tumour status

Abstract

Abstract Lymphocytes from rats bearing primary or transplanted aminoazo‐dye‐induced hepatomas were specifically cytotoxic for cells of the same tumour. Cytotoxic antibody was not present in the serum of these animals, although humoral factors capable of abrogating lymph‐node cell‐mediated cytotoxicity in vitro were detected. Following excision of transplanted hepatomas, cytotoxic lymph‐node cells were still demonstrable, with slightly increased reactivities comparable to those detected in a previous study of repeatedly immunized rats. Cytotoxic antibody was present in serum after tumour excision, and this correlates with the loss of serum blocking activity for lymph‐node cell‐mediated cytotoxic effects. In comparison, serum from rats repeatedly immunized to hepatomas, where high levels of cytotoxic antibody are also present, blocks lymph‐node cell‐mediated reactions in vitro , despite the immune status of the donor. These considerations suggest qualitative differences between the blocking factors in the serum of tumour‐bearer and tumour‐immune hosts, the former being antigen‐antibody complexes, and the latter free antibody.