HUMAN EPIDERMAL LANGERHANS CELLS EXPRESS THE MANNOSE-FUCOSE BINDING-RECEPTOR

Sugar receptors are being increasingly implicated in host-pathogen int eractions because of their specific recognition of carbohydrates of mi croorganisms. The aim of this study was to identify sugar receptors ex pressed on the surface of human epidermal Langerhans cells (LC). To th is end, binding of a panel of fluorescent neoglycoproteins to human ep idermal LC was analyzed by quantitative flow cytofluorometry after sta ndardization with calibrated beads. We demonstrate that fresh human LC are the only cells isolated from healthy epidermis which express a me mbrane receptor specific for fucose-bovine serum albumin (BSA) and man nose-BSA. Quantitative analysis of mannose-BSA or fucose-BSA binding s howed non-linear Scatchard plots, denoting the presence of high and mo derate affinity binding on the LC surface. The binding parameters of t hese two ligands were not significantly different. Mannan, the yeast m annose-rich polysaccharide, fucose-BSA mannose-BSA and free fucose are strong competitors of the three known ligands of the mannose receptor , i.e. fucose-BSA, mannose-BSA and fluorescein isothiocyanate dextran. The amount of mannose-BSA and fucose-BSA bound to LC was 1.5-fold hig her at 37 degrees C than at 4 degrees C, suggesting an internalization process. Antibodies raised against the human macrophage mannose recep tor strongly stained CD1a-positive LC but not CD1a-negative population . Taken together, our data demonstrate that fresh human LC are the onl y cells in the epidermis to express a fucose-mannose receptor on their surface.