Abstract
Antibody‐dependent cell‐mediated cytotoxic assays have been used to examine antigens on human melanoma cells obtained either directly from patients or from long‐term melanoma cell lines. A panel of melanoma antisera was selected from human subjects which could be shown not to have significant reactivity to histocompatibility antigens. With these antisera extensive cross‐reactions between melanoma cells were found. However, the cross‐reactivity was incomplete and the pattern of reactivity was different for each antiserum tested. These results were not consistent with a common melanoma antigen on human melanoma cells but rather indicated heterogeneity of melanoma antigens and multiple antibody specificities in the sera tested. This appeared to be confirmed by extensive cross‐absorption studies which indicated limited cross‐reactivity of antigens on melanoma cells from either long‐term or short‐term cultures. Several changes in the antigenic profile of melanoma cells in vitro from both long‐term and short‐term cultures were documented which resulted from contamination of the melanoma cell lines with non‐melanoma cells and fibroblasts. Melanoma antisera may therefore be useful to monitor changes in long‐term cultures which would otherwise give spurious results in in vitro tests. These results appear to have considerable significance for understanding tumour/host relationships and for the establishment of rational immunotherapeutic procedures and diagnostic tests in melanoma.