title: Polymyxin B suppresses the endotoxin inhibition of concanavalin a-mediated erythrocyte agglutination.
abstract: The lectin agglutinability of human erythrocytes has been utilized to examine interactions of gram-negative endotoxin with mammalian cell plasma membranes. Erythrocytes treated in buffer with Escherichia coli 0127:B8 lipopolysaccharide (LPS) or Salmonella minnesota Re595 glycolipid for 1 h became resistant to agglutination by the lectin concanavalin A (ConA) in buffer free of LPS or glycolipid. Polymyxin B, a cationic cyclic lipopeptide which specifically binds to the lipid A toxophore, was tested for possible effects on the LPS and glycolipid inhibition of Con A erythrocyte agglutination. The presence of polymyxin B during the initial 1-h treatment with LPS or glycolipid blocked the ability of the endotoxins to render erythrocytes refractory to agglutination by ConA. Inhibition by polymyxin B was stoichiometric, and in repeated experiments, LPS was completely suppressed in the hemagglutination assay at a polymyxin B:LPS weight ratio of 1:4.1 (increasing polymyxin concentration, constant LPS concentration) and 1:5.1 (constant polymyxin concentration, increasing LPS concentration). These stoichiometry values are similar to values obtained for inhibition by polymyxin B of LPS lymphoid cell activation. It was concluded, therefore, that endotoxin inhibition of ConA erythrocyte agglutination reflects interactions of erythrocyte membranes with the lipid A region of endotoxin. In addition, the stoichiometry of polymyxin B inhibition suggests a similar extent of lipid A-dependent LPS interaction with erythrocytes and lymphoid cells.
mesh_terms: D003208:Concanavalin A / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D004731:Endotoxins / Q000378:metabolism / Q000494:pharmacology*; D004910:Erythrocyte Membrane / Q000378:metabolism; D004926:Escherichia coli / Q000032:analysis; D006017:Glycolipids / Q000494:pharmacology; D006384:Hemagglutination / Q000187:drug effects*; D006801:Humans; D008070:Lipopolysaccharides / Q000494:pharmacology; D008213:Lymphocyte Activation; D011112:Polymyxin B / Q000494:pharmacology*; D011113:Polymyxins / Q000494:pharmacology*; D012475:Salmonella / Q000032:analysis
chemical_list: D004731:Endotoxins; D006017:Glycolipids; D008070:Lipopolysaccharides; D011113:Polymyxins; D003208:Concanavalin A; D011112:Polymyxin B