Serologically detectable specific and cross‐reactive antigens on the membrane of a polyoma virus‐induced murine tumor

With the aid of an assay measuring complement dependent cytotoxicity mediated by syngeneic antibodies, we performed a serological analysis of surface antigens of a polyoma‐virus‐induced murine tumor (SEYF‐a). In vivo propagated SEYF‐a ascites tumor cells expressed a specific membrane antigen in addition to various other cross‐reacting antigens. Among these we could identify at least four separate specificities. Two of these were present on Mu LV‐induced lymphoma cells, the first on Moloney‐virus‐induced YAC cells and the second on Gross‐virus‐induced GHA cells. The third cross‐reacting antigen was detected on EL‐4 cells. At least one additional specificity was present on two methylcholanthreneinduced murine sarcomas. Normal syngeneic lymphoid cells were insensitive to cytotoxicity mediated by the anti‐tumor antisera. Quantitative and perhaps also qualitative differences between the antigenic expression of in vivo propagated and cultured SEYF‐a cells were indicated. These studies show that hyperimmune sera produced in syngeneic mice against transplanted tumors may contain a considerable number of antibody specificities, only some of which are specific for the tumor. Furthermore the results also suggest that polyoma‐virus‐induced tumors may possess individually distinct antigenic specificities, over and above the known cross‐reacting TSTA or TSSA type antigen.