A monoclonal antibody specific for cells of the melanocyte lineage.

A monoclonal antibody, NKI/beteb, was prepared against membranes from a human melanoma metastasis, and in immunoprecipitates of melanoma cell lysates specific 100- and 7-kd glycoproteins were found. The large glycoproteins were also present in conditioned medium of melanoma cell lines. The antigen is located on the inner side of membranes of (pre)melanosomes and premelanosomelike vesicles. The antibody reacted in the immunoperoxidase test on frozen tissue sections with 27 of 28 nevocellular nevi (15/16 common, 12/12 dysplastic), 39/39 primary melanomas (3 intraepidermal, 24 cutaneous, 12 choroidal), 56/63 melanoma metastases, and 4/4 clear-cell sarcomas (melanoma of soft tissue). With sections of formalin-fixed paraffin-embedded tissues, the reaction was less sensitive. No reactivity was detected with frozen sections of 185 other tumors, except for 1 case of non-Hodgkin's lymphoma in which macrophages were positive. With the exception of melanocytes, all frozen sections of adult tissues that were tested were negative with NKI/beteb. On the basis of its tissue distribution so far, the antigen recognized by NKI/beteb seems to be a specific and sensitive diagnostic marker for cells of the melanocyte lineage.