Abstract
Outer membrane protein A (OmpA) is a conserved major component of the outer membrane of Enterobacteriaceae. Here, we report that OmpA from Klebsiella pneumoniae (KpOmpA) activates macrophages and dendritic cells (DCs) in a TLR2-dependent way. However, TLR2 does not account for binding of KpOmpA to innate immune cells. KpOmpA binds the scavenger receptors (SRs) LOX-1 and SREC-I, but not other members of the same family. LOX-1 colocalizes and cooperates with TLR2 in triggering cellular responses. The TLR2-activated functional program includes production of the long pentraxin PTX3, a soluble pattern recognition receptor involved in resistance against diverse pathogens. PTX3, in turn, binds KpOmpA but does not affect recognition of this microbial moiety by cellular receptors. KpOmpA-elicited in vivo inflammation is abrogated in TLR2(-/-) mice and significantly reduced in PTX3(-/-) mice. Thus, SR-mediated KpOmpA recognition and TLR2-dependent cellular activation set in motion a nonredundant PTX3-mediated humoral amplification loop of innate immunity.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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Animals
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Bacterial Outer Membrane Proteins / immunology*
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C-Reactive Protein / deficiency
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C-Reactive Protein / genetics
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C-Reactive Protein / immunology
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C-Reactive Protein / metabolism
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CHO Cells
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Cricetinae
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Dendritic Cells / immunology
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Humans
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Immunity, Cellular
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Immunity, Innate
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In Vitro Techniques
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Klebsiella pneumoniae / immunology
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Macrophage Activation
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Mice
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Mice, Inbred C57BL
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Mice, Knockout
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Models, Immunological
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Nerve Tissue Proteins / deficiency
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Nerve Tissue Proteins / genetics
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Nerve Tissue Proteins / immunology
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Nerve Tissue Proteins / metabolism
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Receptors, Immunologic / deficiency
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Receptors, Immunologic / genetics
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Receptors, Immunologic / immunology
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Receptors, Immunologic / metabolism*
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Receptors, LDL / genetics
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Receptors, LDL / immunology
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Receptors, LDL / metabolism
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Receptors, Oxidized LDL
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Receptors, Scavenger
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Recombinant Proteins / genetics
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Recombinant Proteins / immunology
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Recombinant Proteins / metabolism
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Scavenger Receptors, Class E
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Scavenger Receptors, Class F
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Signal Transduction
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Toll-Like Receptor 2
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Transfection
Substances
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Bacterial Outer Membrane Proteins
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Nerve Tissue Proteins
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OLR1 protein, human
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Olr1 protein, mouse
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Receptors, Immunologic
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Receptors, LDL
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Receptors, Oxidized LDL
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Receptors, Scavenger
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Recombinant Proteins
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SCARF1 protein, human
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Scavenger Receptors, Class E
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Scavenger Receptors, Class F
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Tlr2 protein, mouse
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Toll-Like Receptor 2
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neuronal pentraxin
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OMPA outer membrane proteins
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C-Reactive Protein