Anti-melanoma monoclonal antibody HMB-45 on enhanced chemiluminescene Western blotting recognizes a 30-35 kDa melanosome-associated sialated glycoprotein

HMB-45 is an anti-melanoma monoclonal antibody widely used in diagnostic pathology owing to its great specificity in identifying poorly differentiated melanomas, In this study, by a series of sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) immunoblots with the enhanced chemiluminescent (ECL) detection method on the HU-214 melanoma cell line, we identified the antigen of HMB-45 in a protein or proteins of 30-35 kDa, Although this result is in discrepancy with the previous literature which identified the antigen as a protein of 7 or 10 kDa, a family of proteins of 25-70 kDa or as a protein of 100 kDa (gp100), the present data indicate that the antigen signal we found might be specific. Furthermore, immunoblots on neuraminidase-treated cell lysates show, in agreement with already published data, that the antigen might be a sialated glycoprotein with the sialic acid involved in the epitope. Immunoblots on partially purified melanosomes confirmed the presence of the antigen in these organelles.