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Expression and ultrastructural localization of HMB‐45 antigen
Author(s) -
KIKUCHI A.,
SHIMIZU H.,
NISHIKAWA T.
Publication year - 1996
Publication title -
british journal of dermatology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.304
H-Index - 179
eISSN - 1365-2133
pISSN - 0007-0963
DOI - 10.1046/j.1365-2133.1996.d01-1012.x
Subject(s) - melanosome , tyrosinase , melanin , biology , immunogold labelling , neoplastic transformation , melanoma , antigen , hmb 45 , melanocyte , immunohistochemistry , pathology , microbiology and biotechnology , cancer research , immunology , antibody , biochemistry , medicine , carcinogenesis , gene , enzyme
Summary HMB‐45 is a monoclonal antibody specific for melanoma cells and premature developing melanocytes. We examined the expression and specific subcellular binding sites of HMB‐45 in various types of melanocytes including epidermal melanocytes from fetuses and infants with or without tyrosinase‐negative oculocutaneous albinism (type IA), melanin‐producing and non‐producing melanoma cell lines (G361 and MeWo), and in vivo melanoma cells (melanotic and amelanotic malignant melanoma). Subcellular HMB‐45 binding was examined by using post‐embedding immunogold electron microscopy with rapid freezing and freeze substitution fixation methods without the use of chemical fixatives to preserve the intracytoplasmic delicate antigen property of HMB‐45. HMB‐45 antigen was detected not only in in vivo melanoma cells and normal fetal melanocytes, but also in melanocytes in the other conditions. Post‐embedding immunogold electron microscopy revealed that HMB‐45 antigen was exclusively localized to stages I and III melanosomes in the melanocytes from fetuses and infants. In tyrosinase‐negative oculocutaneous albinism, only stages I and II melanosomes were detected in the cytoplasm, but both stages of melanosomes were HMB‐45 positive. We conclude that HMB‐45 appears mainly on the immature melanosomes during melanogenesisin both neoplastic and non‐neoplastic melanocytes regardless of their tyrosinase activity, but the intracytoplasmic localization of HMB‐45 antigen is different by each condition of melanocytes.