ULTRASTRUCTURAL-LOCALIZATION OF LECTIN BINDING-SITES IN HUMAN MELANOCYTES

The ultrastructural localization of carbohydrate residues in human melanocytes of normal epidermis and of one compound naevus was studied. The following lectins were used in a post-embedding technique: 1. peanut agglutinin (PNA), which reacts specifically with N-acetyl-galactosamine; 2. Concanavalia ensiformis (Con A) indicating alpha-D-glucose and alpha-D-mannose binding sites; 3. Ulex europaeus agglutinin (UEA I) specific for alpha-L-fucose; 4. Wheat germ agglutinin (WGA), reacting specifically with N-acetyl-glucosamine and neuraminic acid (sialic acid); and 5. Limax flavus agglutinin (LFA), also specific for sialic acid (Neu5Ac-alpha-2,3-Gal and Neu5Ac-alpha-2,6-Gal). When incubated with WGA, Con A and LFA strong labelling was seen within the cytoplasm and in the plasma membrane of melanocytes, whereas incubations with PNA and UEA I revealed an occasional gold particle only. The determination of the distribution of carbohydrate residues in normal melanocytes is a prerequisite for future studies of abnormal melanocytes.