Tumour-specific complement-dependent serum cytotoxicity against a chemically induced rat hepatoma

A short-term 51Cr release test was used for the detection of complement-dependent cytolytic activity of syngeneic serum for transplanted aminoazo dye-induced rat hepatoma cells in suspension. Serum samples from rats bearing intraperitoneal implants of one hepatoma (hepatoma D23) were specifically cytotoxic for hepatoma D23 target cells, although this activity was not detected in sera from donors bearing subcutaneous tumour grafts. Other sera containing demonstrable IgG antibodies reactive in membrane immunofluorescence tests with individually distinct tumour-specific antigens or tumour-associated embryonic antigens were not cytotoxic for hepatoma D23 cells; and even though serum from donors carrying intraperitoneal tumour grafts contained tumour-specific IgG antibody, the complement-dependent reactivity was confined to the 19s region of fractionated tumour-bearer serum. These findings are discussed in relation to the development of humoral responses in the tumour-bearing host and with regard to the significance of the availability of an objective and reproducible assay for measuring humoral responses directed against the tumour-specific antigens associated with chemically induced rat tumours.