Ultrastructural localization of lectin binding sites in human melanocytes

Summary 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 -d-glucose and -d-mannose binding sites; 3. Ulex europaeus agglutinin (UEA I) specific for -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--2,3-Gal and Neu5Ac--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.