title: Cell activation of human macrophages by lipoteichoic acid is strongly attenuated by lipopolysaccharide-binding protein.
abstract: Lipoteichoic acid (LTA) represents immunostimulatory molecules expressed by Gram-positive bacteria. They activate the innate immune system via Toll-like receptors. We have investigated the role of serum proteins in activation of human macrophages by LTA from Staphylococcus aureus and found it to be strongly attenuated by serum. In contrast, the same cells showed a sensitive response to LTA and a significantly enhanced production of tumor necrosis factor alpha under serum-free conditions. We show that LTA interacts with the serum protein lipopolysaccharide-binding protein (LBP) and inhibits the integration of LBP into phospholipid membranes, indicating the formation of complexes of LTA and soluble LBP. The addition of recombinant human LBP to serum-free medium inhibited the production of tumor necrosis factor alpha and interleukins 6 and 8 after stimulation of human macrophages with LTA in a dose-dependent manner. Using anti-LBP antibodies, this inhibitory effect could be attributed to soluble LBP, whereas LBP in its recently described transmembrane configuration did not modulate cell activation. Also, using primary alveolar macrophages from rats, we show a sensitive cytokine response to LTA under serum-free culture conditions that was strongly attenuated in the presence of serum. In summary, our data suggest that innate immune recognition of LTA is organ-specific with negative regulation by LBP in serum-containing compartments and sensitive recognition in serum-free compartments like the lung.
authors.affiliation: Research Center Borstel, Leibniz-Center for Medicine and Biosciences, Division of Biophysics, 23845 Borstel, Germany.
authors.forename: Mareike
authors.initials: M
authors.lastname: Mueller
authors.forename: Cordula
authors.initials: C
authors.lastname: Stamme
authors.forename: Christian
authors.initials: C
authors.lastname: Draing
authors.forename: Thomas
authors.initials: T
authors.lastname: Hartung
authors.forename: Ulrich
authors.initials: U
authors.lastname: Seydel
authors.forename: Andra B
authors.initials: AB
authors.lastname: Schromm
mesh_terms: D000209:Acute-Phase Proteins / Q000378:metabolism / Q000502:physiology*; D002352:Carrier Proteins / Q000378:metabolism / Q000502:physiology*; D016895:Culture Media, Serum-Free / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D006801:Humans; D015850:Interleukin-6 / Q000378:metabolism; D016209:Interleukin-8 / Q000378:metabolism; D008070:Lipopolysaccharides / Q000494:pharmacology*; D008168:Lung / Q000378:metabolism; D008264:Macrophages / Q000187:drug effects / Q000378:metabolism*; D008562:Membrane Glycoproteins / Q000378:metabolism / Q000502:physiology*; D008954:Models, Biological; D009154:Mutation; D013211:Staphylococcus aureus / Q000378:metabolism; D020349:Surface Plasmon Resonance; D013682:Teichoic Acids / Q000494:pharmacology*; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism; D000099231:Lipopolysaccharide-Binding Protein
chemical_list: D000209:Acute-Phase Proteins; D002352:Carrier Proteins; D016895:Culture Media, Serum-Free; D015850:Interleukin-6; D016209:Interleukin-8; D008070:Lipopolysaccharides; D008562:Membrane Glycoproteins; D013682:Teichoic Acids; D014409:Tumor Necrosis Factor-alpha; D000099231:Lipopolysaccharide-Binding Protein; C009900:lipoteichoic acid