Heterogeneous expression of melanoma-associated antigens and HLA antigens by primary and multiple metastatic lesions removed from patients with melanoma.

Indirect immunofluorescence staining with a large battery of monoclonal antibodies of primary and autologous metastatic lesions removed from seven patients with melanoma has detected heterogeneity in the expression of various types of melanoma-associated antigens (MAAs), of distinct determinants of the high molecular weight melanoma-associated antigen (HMW-MAA), of the two subunits of Class I HLA antigens, and of the gene products of the HLA-D region. Among the 10 MAAs tested, the HMW-MAA had the highest frequency and the Mr 87,000 MAA the lowest. Furthermore, the HMW-MAA displayed the lowest heterogeneity. These findings, in conjunction with the restricted tissue distribution of the HMW-MAA, its lack of susceptibility to antibody-mediated modulation, and the high affinity of the available anti-HMW-MAA monoclonal antibodies, indicate that this antigen may be a useful marker for radioimaging and immunotherapy in patients with melanoma. The common acute lymphoblastic leukemia antigen was detected only in five lesions. Class I HLA antigens were detected in a larger number of lesions than HLA-DR antigens, which had a significantly higher frequency than HLA-DQ antigens. The degree of antigenic heterogeneity did not appear to correlate with the histopathological features of the lesions and/or with the clinical course of the disease. The results of the present study indicate that immunodiagnostic and immunotherapeutic approaches to melanoma should rely on the use of combinations of monoclonal antibodies to distinct MAAs.