Phenotypic and genetic analysis of HLA class I and HLA-DR antigen expression on human melanomas

Class I and HLA-DR antigen expression were studied with histochemical techniques involving monomorphic monoclonal antibodies in 49 cases of human malignant melanomas, 20 primary and 29 metastatic. A large percentage (90%) of primary melanomas were positive for HLA class I, while those primary lesions showing lowest levels of class I antigen expression were at the upper end of the range of invasiveness and possessed a higher metastatic potential. Expression of HLA-DR molecules on primary melanomas was low (25% of all cases) and HLA-DR-positive melanomas were among the most aggressive. In metastatic melanomas, HLA class I expression was less common than in primary lesions. The lowest percentage of cases positive for HLA class I was found for cutaneous metastases. HLA-DR molecules were more frequently expressed by lymph node metastases than on primary melanomas. The comparison of the expression of HLA class I and HLA-DR molecules by primary melanomas and their autologous metastases revealed a high degree of heterogeneity. Class I genes were further studied by Southern blot assays. No differences were found in restriction fragments for class I genes among 4 melanomas and their autologous lymphocytes, 2 of which were positive and 2 negative for class I expression.