We report the production of a new
monoclonal antibody, PNL2, directed against a
fixative resistant melanocyte
antigen. The analysis of PNL2 immunostaining on a broad range of normal or malignant human tissues and on various melanocytic lesions revealed its high specificity. PNL2 gave a strong cytoplasmic staining of skin and oral mucosae melanocytes, and staining of granulocytes when used at high concentration. PNL2 stained all intra-epidermal
nevi irrespective of their histologic type, but common
intradermal nevi and the dermal component of compound
nevi were largely non-reactive as only scattered
nevus cells in the papillary dermis were labeled. PNL2 labeled more than 70% of the neoplastic cells in all primary
melanomas irrespective of their histologic type. However, PNL2 did not label desmoplastic
melanomas. All metastatic
melanomas were also stained but the percentage of labeled cells was occasionally lower than the primary
tumor. PNL2, as anti-
Melan A and HMB-45
antibodies, stained most of the
clear cell sarcoma cells, and a few cells in
angiomyolipomas and
lymphangioleiomyomatosis. None of the other non-melanocytic lesions tested were labeled. Proteomic approaches showed that the immunoaffinity purified PNL2-binding complexes isolated from
melanoma cell lines comprise at least TAP1,
Clathrin 17 and
prealbumin proteins, but not the gp100 recognized by HMB-45. In conclusion, this new
monoclonal antibody, PNL2, is directed against a new
fixative resistant melanocyte associated
antigen. This
antigen is chemically resistant and thus allows immunostaining after
melanin bleaching or decalcification. We also demonstrate that it is different from
Melan A and from gp100, even if PNL2 and HMB-45 staining patterns are sometimes similar.