IDENTIFICATION OF MELANOMA CELL-SURFACE ANTIGENS IMMUNOGENIC IN MICE

Active immunization to B16 melanoma cells or vaccines induces anti-mel anoma immune responses in syngeneic mice. The immunogenic antigens sti mulating immunity to this tumor have not been identified. In this stud y we detected several B16 melanoma antigens immunogenic in syngeneic m ice using as probes anti-melanoma antibodies induced by immunization t o B16 melanoma vaccines. These antigens were identified by SDS-PAGE an d autoradiographic analysis of specific immunoprecipitates. They were cell-surface components with approximate molecular weights of 41, 46, 50, 75, 80, and 104 KD. All these antigens were expressed by syngeneic and xenogeneic melanomas and by some unrelated syngeneic tumors but n ot by normal syngeneic cells, xenogeneic melanocytes, or by B16 melano ma cells obtained from fresh turmors or grown in defined medium. The a ntigens were distinct from murine viral antigens expressed by B16 mela noma cells and from components of the culture medium used to grow cell s for vaccine production. These results indicate that several B16 mela noma cell-surface antigens are immunogenic in syngeneic mice. Expressi on of these antigens appears to be related to malignant transformation as they were found on all melanomas studied, and some other cancers, but not on normal cells.