Rous sarcoma virus-transformed avian cells express four different cell surface antigens that are distinguishable by a cell-mediated cytotoxicity-blocking test.

Japanese quails bearing avian sarcoma virus-induced tumors develop immune spleen cells that are cytotoxic in vitro against virally and chemically transformed cells, as well as against embryonic cells. The cell-mediated cytotoxicity can be blocked by soluble antigens extracted from in vitro cultured cells. The existence of partial as well as total blocking effects in tests with extracts from various transformed and untransformed virus-producing cells makes it possible to distinguish up to four different kinds of antigens expressed on sarcoma virus transformed cells: a) a subgroup-specific determinant of the virus-envelope glycoprotein gp85 (s-gp85) is expressed at the surface of productively infected, tranformed as well as untransformed cells; b) a group-specific determinant of gp85 (g-gp85) that is only expressed on the surface of virus-transformed cells; c) embryonic antigens, also detectable on chemically transformed as well as on primary normal embryonic cells, and finally; d) a sarcoma virus transformation-specific antigen (TSSA) that is not a structural constituent of the virus.