title: Endoplasmic reticulum chaperone gp96 in macrophages is essential for protective immunity during Gram-negative pneumonia.
abstract: Klebsiella pneumoniae is among the most common Gram-negative bacteria that cause pneumonia. Gp96 is an endoplasmic reticulum chaperone that is essential for the trafficking and function of Toll-like receptors (TLRs) and integrins. To determine the role of gp96 in myeloid cells in host defence during Klebsiella pneumonia, mice homozygous for the conditional Hsp90b1 allele encoding gp96 were crossed with mice expressing Cre-recombinase under control of the LysM promoter to generate LysMcre-Hsp90b1-flox mice. LysMcre-Hsp90b1-flox mice showed absence of gp96 protein in macrophages and partial depletion in monocytes and granulocytes. This was accompanied by almost complete absence of TLR2 and TLR4 on macrophages. Likewise, integrin subunits CD11b and CD18 were not detectable on macrophages, while being only slightly reduced on monocytes and granulocytes. Gp96-deficient macrophages did not release pro-inflammatory cytokines in response to Klebsiella and displayed reduced phagocytic capacity independent of CD18. LysMcre-Hsp90b1-flox mice were highly vulnerable to lower airway infection induced by K. pneumoniae, as reflected by enhanced bacterial growth and a higher mortality rate. The early inflammatory response in Hsp90b1-flox mice was characterized by strongly impaired recruitment of granulocytes into the lungs, accompanied by attenuated production of pro-inflammatory cytokines, while the inflammatory response during late-stage pneumonia was not dependent on the presence of gp96. Blocking CD18 did not reproduce the impaired host defence of LysMcre-Hsp90b1-flox mice during Klebsiella pneumonia. These data indicate that macrophage gp96 is essential for protective immunity during Gram-negative pneumonia by regulating TLR expression.
authors.affiliation: Center of Experimental and Molecular Medicine, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands.
authors.forename: Adam A
authors.initials: AA
authors.lastname: Anas
authors.affiliation: Center of Experimental and Molecular Medicine, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands.
authors.forename: Alex F
authors.initials: AF
authors.lastname: de Vos
authors.affiliation: Center of Experimental and Molecular Medicine, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands.
authors.forename: Arie J
authors.initials: AJ
authors.lastname: Hoogendijk
authors.affiliation: Center of Experimental and Molecular Medicine, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands.
authors.forename: Miriam H P
authors.initials: MH
authors.lastname: van Lieshout
authors.affiliation: Center of Experimental and Molecular Medicine, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands.
authors.forename: Jeroen W J
authors.initials: JW
authors.lastname: van Heijst
authors.affiliation: Center of Experimental and Molecular Medicine, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands.|Department of Pathology, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands.
authors.forename: Sandrine
authors.initials: S
authors.lastname: Florquin
authors.affiliation: Hollings Cancer Center, Department of Microbiology and Immunology, Medical University of South Carolina, Charleston, SC, USA.
authors.forename: Zihai
authors.initials: Z
authors.lastname: Li
authors.affiliation: Center of Experimental and Molecular Medicine, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands.
authors.forename: Cornelis
authors.initials: C
authors.lastname: van 't Veer
authors.affiliation: Center of Experimental and Molecular Medicine, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands.|Division of Infectious Diseases, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands.
authors.forename: Tom
authors.initials: T
authors.lastname: van der Poll
mesh_terms: D000818:Animals; D015153:Blotting, Western; D004195:Disease Models, Animal; D004721:Endoplasmic Reticulum / Q000276:immunology / Q000378:metabolism; D005434:Flow Cytometry; D007710:Klebsiella Infections / Q000276:immunology*; D007711:Klebsiella pneumoniae; D008264:Macrophages / Q000276:immunology; D008562:Membrane Glycoproteins / Q000276:immunology*; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D018832:Molecular Chaperones / Q000276:immunology; D018410:Pneumonia, Bacterial / Q000276:immunology*; D016133:Polymerase Chain Reaction
chemical_list: D008562:Membrane Glycoproteins; D018832:Molecular Chaperones; C053387:endoplasmin
keywords: Klebsiella; Toll-like receptors; gp96; integrins; pneumonia