title: Specific inhibition of human natural killer cell-mediated cytotoxicity by sialic acid and sialo-oligosaccharides.
abstract: We have tried to identify carbohydrate structures involved in recognition and/or lysis of K562 target cells by human natural killer (NK) cells. Inhibition studies were performed with mono-, di- and trisaccharides, and with glycopeptides and glycoproteins of known carbohydrate composition. When tested with various monosaccharides, lysis of K562 cells was inhibited only by N-acetylneuraminic acid (NeuAc). Di- and trisaccharides and glycopeptides containing NeuAc or N-glycolylneuraminic acid (NeuGc) all inhibited NK cell-mediated lysis. Among the non-sialylated carbohydrates tested, only Gal beta(1----3)GalNAcol was effective. The inhibitory capacity of sialylated compounds appeared to be dependent on the linkage type of the sialic acid residue; carbohydrates containing alpha(2----6)-linked sialic acids were more potent inhibitors than their alpha(2----3) isomers. Also the sugar to which the sialic acid residue was attached was of importance, NeuAc alpha(2----6)GalNAcol being more effective than NeuAc alpha(2----6)Gal beta 1----R (where R = glucose or oligosaccharide-peptide). Sialylated compounds and free sialic acid had minor or no effects on cell-mediated cytotoxicity by allo-sensitized cytotoxic T lymphocytes. The conjugation of target cells and NK effector cells was not inhibited by carbohydrates that effectively blocked the cytolytic response. These results may indicate that cell-surface carbohydrates containing alpha(2----6)-linked sialic acid are crucial structures in a post-binding event in NK-cell-mediated lysis.
mesh_terms: D003602:Cytotoxicity, Immunologic / Q000187:drug effects*; D005677:G(M1) Ganglioside; D006028:Glycosphingolipids / Q000032:analysis; D006801:Humans; D007694:Killer Cells, Natural / Q000187:drug effects* / Q000276:immunology; D007785:Lactose / Q000031:analogs & derivatives / Q000494:pharmacology; D019158:N-Acetylneuraminic Acid; D009844:Oligosaccharides / Q000494:pharmacology*; D012794:Sialic Acids / Q000494:pharmacology*; D012795:Sialoglycoproteins / Q000494:pharmacology
chemical_list: D006028:Glycosphingolipids; D009844:Oligosaccharides; D012794:Sialic Acids; D012795:Sialoglycoproteins; C016735:sialooligosaccharides; D005677:G(M1) Ganglioside; C018835:asialo GM1 ganglioside; D019158:N-Acetylneuraminic Acid; D007785:Lactose