Cell Surface Antigens of H U M a N Malignant Melanoma

Study of malignant melanoma has dominated much of the activity in human cancer immunology (1-9). This reflects the widespread belief that melanoma represents an immunogenic tumor in man. Although many indications exist that melanoma patients respond to their tumor by developing humoral and cellular immunity, critical evidence that these immune reactions are directed to melanoma-specific antigens is lacking. Thus, for instance, interpreting results of tests between serum or lymphoid cells of one patient and melanoma cells of another is frequently difficult, if not at times impossible, because of the unknown participation of alloantigens in the reactions observed. Also, results restricted to melanoma biopsy material or primary cultures (in contrast to sequentially cultured melanoma cells) commonly pose questions related to specificity and reproducibility, since the analysis is necessarily limited by the number and type of tests that can be performed. For this reason, we have directed our serological studies of cell surface antigens of melanoma to analyzing autologous reactions, i.e., serum and melanoma cells from the same patient. The need for repeated tests in substantiating the specificity and reliability of positive or negative reactions requires the ready and continuing availability of target cells, and this has been met by establishing melanoma and accompanying autologous skin fibroblasts in cell culture. We have recently reported that 11 of 35 patients showed reactivity to autologous melanoma by mixed hemadsorpti0n assays (10). Autologous fibroblasts from these same patients were negative. One patient (AU) showed a sufficiently high autologous reactivity to conduct an extensive absorption analysis of his serum. Tests on a range of malignant cell lines, melanoma and nonmelanoma, and normal cells, autelogous and allogeneic, revealed that this melanoma surface antigen was restricted to AU melanoma cells. The present report summarizes our experience with immune adherence (IA) 1 assays for the detection of specific antibody to cell surface antigens of melanoma.