Host and viral genes ionteracting at the tumor cell surface

2 Hamster fibroblasts lines transformed in vitro by Rous Sarcoma Virus (RSV) carry on their surface tumor associated antigenic determinants detectable by a rabbit antiserum after adsorption with the corresponding untransformed line. Some of these determinants are shared with polioma transformed hamster fibroblasts and some with RSV transformed rat fibroblasts. After adsorption with both lines the rabbit antiserum recognized only antigenic determinants, undetectable on purified RSV particles, that were species specific and virus specific. These were operationally called hamster virus cell surface antigen (H-VCSA). H-VCSA seems not to be directly coded either by the hamster genome or by the RSV genome itself. It is suggested that its appearance on the cell surface is the expression of interaction of some kind between cellular and viral gene products.