concanavalin-a and Nevus--Pigmented

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-acetylgalactosamine; 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.

Topics: Arachis; Concanavalin A; Humans; Lectins; Melanocytes; Microscopy, Immunoelectron; Nevus, Pigmented; Peanut Agglutinin; Plant Lectins; Receptors, Mitogen; Reference Values; Wheat Germ Agglutinins

Concanavalin A (con A) is a plant-derived lectin that has the capability of agglutinating malignant cells in vitro. We studied the binding of fluorescein isothiocyanate-conjugated con A to formalin-fixed, paraffin-embedded malignant melanomas and nevocellular nevi. Both malignant melanoma cells and nevus cells emitted partial or circumferential, cytoplasmic rim, apple green fluorescence. There was no demonstrable difference between fluorescence distribution or intensity between the two groups. Control, unstained tissue specimens yielded a brilliant nuclear and nucleolar yellow-green autofluorescence, which is peculiar to melanoma cells and rare to absent in nevus cells. Fluorescein isothiocyanate-conjugated con A provided no clear differentiation between malignant melanomas and nevocellular nevi in fixed tissue. However, characteristic melanoma cell autofluorescence may prove to be of benefit for differentiating malignant melanocytic from benign nevocytic lesions.

Topics: Binding Sites; Concanavalin A; Diagnosis, Differential; Fluorescein-5-isothiocyanate; Fluoresceins; Fluorescent Dyes; Histocytochemistry; Humans; Melanoma; Nevus, Pigmented; Skin Neoplasms