Using an indirect immunoperoxidase technique, 20 nevocellular
nevi, 5
dysplastic nevi, 14 primary cutaneous
melanomas, and 24 metastatic
melanomas were tested with a panel of
monoclonal antibodies to monomorphic determinants of Class I (
HLA-A,B,C) and Class II (la-like) major histocompatibility complex
antigens. Class I HLA and beta 2-microglobulins were not detected on the majority of
nevus cells but were expressed by 3 of 5
dysplastic nevi, by the majority of
tumor cells in 12 of 14 primary cutaneous
melanomas, and in 13 of 24
metastases. The different expression of Class I HLA and beta 2-microglobulins in primary and metastatic lesions suggests that loss of these
antigens may be associated with progression of
malignancy. Class II HLA were not detected in common
nevi but were locally present in 1 of 5
dysplastic nevi, 7 of 14 cases of primary cutaneous
melanoma, and all 24 cases of metastatic lesions tested. These findings suggest that increase in Class II HLA expression may be associated with progression of
malignancy. The staining patterns obtained with
monoclonal antibodies to distinct determinants of Class I HLA and Class II HLA were superimposable within each type of
antigen. Therefore, the discrepancies in the literature about the expression of
histocompatibility antigens by lesions of melanocytic origin are not likely to reflect the different specificity of the
antibodies used by the various investigators.