Phenotypic heterogeneity of HLA products on human melanoma cells.

The expression of class I and class II HLA antigens has been studied on primary and metastatic human melanomas, and on cell clones derived from the latter. A panel of monoclonal antibodies and flow cytofluorometric analysis were used to evaluate the presence of HLA-A, B, C and -DR, DQ antigens on freshly isolated tumour cells. HLA class I antigens were present on 91% and 93% of primary and metastatic tumours, respectively. Sixty per cent of primary and 50% of metastatic melanomas expressed HLA-DR antigens, whereas 38% and 21% of cases were positive for HLA-DQ. A marked heterogeneity was evident among primary and metastatic lesions for expression of class I and II antigens. Similar findings were obtained by analysing the phenotype of melanoma clones which indicates that a marked antigenic heterogeneity for class I and II HLA antigens occurs even among clones isolated from short-term cultures of metastatic melanomas.