Electron microscopic evidence for an asialoglycoprotein receptor on Kupffer cells: localization of lectin-mediated endocytosis.

Direct evidence is given for the presence of an N-acetyl-D-galactosamine-specific lectin on the Kupffer cell surface by visualization of ligand binding in electron microscopy. When freshly isolated Kupffer cells are incubated with asialofetuin adsorbed onto colloidal gold particles (ASF-gold), binding and endocytosis of ligand are seen. Recognition of ASF-gold by Kupffer cells is completely abolished in the presence of N-acetyl-D-galactosamine (25 mM) or EGTA (3 mM), but is not significantly reduced by N-acetyl-D-glucosamine or D-mannose (25 mM).