Syngeneic monoclonal antibodies to B16 melanoma viral antigens.

Four stable IgM monoclonal antibody-producing hybridomas were generated by fusing mouse myeloma cells with spleen lymphocytes from C57BL/6 mice hyperimmunized against the syngeneic B16 melanoma. All four monoclonal antibodies (R31/15, R37/4, R37/6, and R37/7), in common with polyclonal antiserum from immunized mice, recognized antigens on the same complex of related cell surface molecules specified by endogenous AKR-type murine leukemia virus, designated the B16-gp/70/80/85 antigen complex. Reactivity with this antigen complex was demonstrated by radioimmunoprecipitation. Specificity for viral Mr 70,000 glycoprotein-related antigens was indicated by absorption of antibody activity by endogenous AKR virus and by inhibition of antibody binding to B16 melanoma cells by monospecific antiserum to murine leukemia virus Mr 70,000 glycoprotein. Neither polyclonal nor monoclonal antibodies recognized antigens on fish, guinea pig, swine, or human melanoma cell lines. Polyclonal antiserum reacted with several other mouse melanomas and with certain mouse lymphoma lines induced by, or harboring, endogenous murine leukemia viruses, but the monoclonal antibodies were unreactive except for recognition of antigens on Harding-Passey mouse melanoma cells by antibody R37/4 and on RL male 1 mouse lymphoma cells by antibody R37/7. Only monoclonal R37/7 was cytotoxic for cultured B16 melanoma cells in an antibody- and complement-dependent assay with guinea pig complement, although all antibodies were cytotoxic with rabbit complement. In reflecting the predominant humoral immune response to the B16 melanoma detected in syngeneic mice during tumor growth, these monoclonal antibodies will permit experimental amplification of that response to help determine how that immunity influences tumor growth and metastatic dissemination.