title: Mannose 6-, fructose 1-, and fructose 6-phosphates inhibit human natural cell-mediated cytotoxicity.
abstract: In vitro human natural cell-mediated cytotoxicity (NCMC) to K-562, Molt-4, and F-265 cells is inhibited in a dose-dependent manner by mannose 6-phosphate, fructose 1-phosphate and fructose 6-phosphate. This inhibition is not observed with mannose, glucose, fucose, glucose 6-phosphate, mannose 1-phosphate, galactose 1-phosphate, or galactose 6-phosphate. Preincubation of the effector cells, obtained from fresh whole blood, with mannose-6-phosphate, fructose-1-phosphate, or fructose-6-phosphate did not inhibit cytotoxicity, which indicated that these hexose phosphates are not nonspecifically toxic towards the effector lymphocytes. Mannose-6-phosphate and the stereochemically similar fructose-1-phosphate are more potent inhibitors than fructose-6-phosphate in terms of concentration required and time of onset of effect. Inhibition of cytotoxicity by mannose-6-phosphate varied with target cell type: F-265 is protected at much lower concentrations of mannose-6-phosphate (less than 1 mM) than is either Molt-4 or K-562. The inhibition of NCMC is also observed with the inhibitors of lysosomal function, NH4Cl, and chloroquine. The presence of a functional mannose-6-phosphate receptor on target cells was demonstrated: (i) Gelonin, a seed protein that inactivates the eukaryotic ribosome but is nontoxic to intact cells, was covalently linked to monophosphopentamannose, and this conjugate ws toxic to both K-562 and F-265 target cells, the latter being by far the more sensitive; and (ii) chloroquine, NH4Cl, and mannose-6-phosphate all inhibited the toxicity of gelonin-monophosphopentamannose. These results suggest either that a cytolytic lymphokine contains a hexose phosphate residue and may be taken up by target cells through the lysosomal/mannose 6-phosphate pathway or that such a residue is involved in target cell-effector cell recognition.
mesh_terms: D003602:Cytotoxicity, Immunologic / Q000187:drug effects*; D005636:Fructosephosphates / Q000494:pharmacology*; D006600:Hexosephosphates / Q000494:pharmacology*; D006601:Hexoses / Q000494:pharmacology; D006801:Humans; D007113:Immunity, Innate / Q000187:drug effects*; D008222:Lymphokines / Q000502:physiology; D008247:Lysosomes / Q000502:physiology; D008360:Mannosephosphates / Q000494:pharmacology*; D011955:Receptors, Drug / Q000502:physiology
chemical_list: D005636:Fructosephosphates; D006600:Hexosephosphates; D006601:Hexoses; D008222:Lymphokines; D008360:Mannosephosphates; D011955:Receptors, Drug