Disparities in TLR5 expression and responsiveness to flagellin in equine neutrophils and mononuclear phagocytes.
Abstract: As sentinel cells of the innate immune system, neutrophils and mononuclear phagocytes use specific TLRs to recognize the conserved molecular patterns that characterize microbes. This study was performed to compare the responses of equine neutrophils and mononuclear phagocytes to LPS and flagellin, components of bacteria that are recognized by TLR4 and TLR5, respectively. Neutrophils and mononuclear phagocytes isolated from healthy horses were incubated in vitro with LPS, flagellin, or pronase-inactivated flagellin in the presence or absence of polymyxin B. Production of reactive oxygen species and expression of mRNA for proinflammatory cytokines were used as readouts for activation of neutrophils; production of TNF-α was used for the mononuclear cells. Western blot analysis and flow cytometry were used to detect TLR5 protein in both cell types. Although the neutrophils responded to both LPS and flagellin by producing reactive oxygen species and expressing mRNA for proinflammatory cytokines, flagellin had no stimulatory effect on monocytes or macrophages. Although both neutrophils and monocytes expressed mRNA for TLR5, it appeared to be translated into protein only by the neutrophils. Incubation with neither LPS nor IFN-γ altered TLR5 expression by the monocytes. These findings indicate that flagellin has disparate effects on neutrophils and mononuclear phagocytes isolated from horses, a species that is exquisitely sensitive to the TLR4 ligand, LPS, and that equine mononuclear phagocytes, unlike corresponding cells of other mammalian species, lack surface expression of TLR5 and do not respond to flagellin.
Publication Date: 2011-04-25 PubMed ID: 21518971DOI: 10.4049/jimmunol.1003824Google Scholar: Lookup
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- Journal Article
- Research Support
- Non-U.S. Gov't
Summary
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This research looks at how certain horse immune cells respond to bacterial components such as LPS and flagellin by analysing reactive oxygen species production and proinflammatory cytokine expression. Results showed differences in response from the immune cells, with neutrophils responding to LPS and flagellin, but monocytes and macrophages only responding to LPS.
Objective and Methodology
- The researchers aimed to compare the cellular responses of two types of horse immune cells, neutrophils and mononuclear phagocytes, to bacterial elements LPS and flagellin.
- Cells were taken from healthy horses and activated with LPS, flagellin, or a deactivated form of flagellin, under different conditions.
- Production of pro-inflammatory cytokines and reactive oxygen species, both indications of an immune response, were assessed. TLR5 – a protein that recognises flagellin – was also looked for using Western blot and flow cytometry methods.
Findings
- Upon exposure to LPS and flagellin, neutrophils responded by generating reactive oxygen species and expressing mRNA for pro-inflammatory cytokines.
- Interestingly, monocytes and macrophages showed no stimulatory response to flagellin, despite its recognised role in evoking immune responses in other species.
- Despite mRNA for TLR5 being present in both types of cells, only the neutrophils appeared to translate this into protein form.
- The expression of TLR5 by monocytes was not altered by exposure to either LPS or IFN-γ.
Implications
- These results suggest a differential response to flagellin by horse immune cells, with neutrophils reacting but monocytes and macrophages seeming immune.
- Such disparity could have implications for understanding the horse’s immune response, particularly reactions to bacteria with flagellin.
- Further, the lack of surface TLR5 expression on mononuclear phagocytes, contrasting with most mammalian species, raises interesting questions regarding the unique sensitivities of the horse’s immune system.
- The results could have implications for developing treatments targeting specific immune responses in horses.
Cite This Article
APA
Kwon S, Gewirtz AT, Hurley DJ, Robertson TP, Moore JN, Vandenplas ML.
(2011).
Disparities in TLR5 expression and responsiveness to flagellin in equine neutrophils and mononuclear phagocytes.
J Immunol, 186(11), 6263-6270.
https://doi.org/10.4049/jimmunol.1003824 Publication
Researcher Affiliations
- Department of Large Animal Medicine, College of Veterinary Medicine, University of Georgia, Athens, GA 30602, USA.
MeSH Terms
- Animals
- Blotting, Western
- Cells, Cultured
- Dose-Response Relationship, Drug
- Flagellin / immunology
- Flagellin / metabolism
- Flagellin / pharmacology
- Flow Cytometry
- Gene Expression
- Horses
- Interleukin-10 / genetics
- Interleukin-10 / immunology
- Interleukin-10 / metabolism
- Leukocytes, Mononuclear / drug effects
- Leukocytes, Mononuclear / immunology
- Leukocytes, Mononuclear / metabolism
- Lipopolysaccharides / immunology
- Lipopolysaccharides / pharmacology
- Macrophages, Alveolar / drug effects
- Macrophages, Alveolar / immunology
- Macrophages, Alveolar / metabolism
- Macrophages, Peritoneal / drug effects
- Macrophages, Peritoneal / immunology
- Macrophages, Peritoneal / metabolism
- Neutrophils / drug effects
- Neutrophils / immunology
- Neutrophils / metabolism
- Phagocytes / drug effects
- Phagocytes / immunology
- Phagocytes / metabolism
- Reactive Oxygen Species / immunology
- Reactive Oxygen Species / metabolism
- Reverse Transcriptase Polymerase Chain Reaction
- Salmonella typhimurium / metabolism
- Time Factors
- Toll-Like Receptor 5 / genetics
- Toll-Like Receptor 5 / immunology
- Toll-Like Receptor 5 / metabolism
- Tumor Necrosis Factor-alpha / genetics
- Tumor Necrosis Factor-alpha / immunology
- Tumor Necrosis Factor-alpha / metabolism
Citations
This article has been cited 9 times.- Ma ZG, Kong CY, Wu HM, Song P, Zhang X, Yuan YP, Deng W, Tang QZ. Toll-like receptor 5 deficiency diminishes doxorubicin-induced acute cardiotoxicity in mice.. Theranostics 2020;10(24):11013-11025.
- Hellman S, Hjertner B, Morein B, Fossum C. The adjuvant G3 promotes a Th1 polarizing innate immune response in equine PBMC.. Vet Res 2018 Oct 22;49(1):108.
- Zhang B, Oyewole-Said D, Zou J, Willliams IR, Gewirtz AT. TLR5 signaling in murine bone marrow induces hematopoietic progenitor cell proliferation and aids survival from radiation.. Blood Adv 2017 Sep 26;1(21):1796-1806.
- Tarlinton RE, Alder L, Moreton J, Maboni G, Emes RD, Tötemeyer S. RNA expression of TLR10 in normal equine tissues.. BMC Res Notes 2016 Jul 19;9:353.
- Uddin MJ, Suen WW, Bosco-Lauth A, Hartwig AE, Hall RA, Bowen RA, Bielefeldt-Ohmann H. Kinetics of the West Nile virus induced transcripts of selected cytokines and Toll-like receptors in equine peripheral blood mononuclear cells.. Vet Res 2016 Jun 7;47(1):61.
- Ebid R, Lichtnekert J, Anders HJ. Hyaluronan is not a ligand but a regulator of toll-like receptor signaling in mesangial cells: role of extracellular matrix in innate immunity.. ISRN Nephrol 2014;2014:714081.
- Metcalfe HJ, La Ragione RM, Smith DG, Werling D. Functional characterisation of bovine TLR5 indicates species-specific recognition of flagellin.. Vet Immunol Immunopathol 2014 Feb 15;157(3-4):197-205.
- Werners AH, Bryant CE. Pattern recognition receptors in equine endotoxaemia and sepsis.. Equine Vet J 2012 Jul;44(4):490-8.
- Lewis DH, Chan DL, Pinheiro D, Armitage-Chan E, Garden OA. The immunopathology of sepsis: pathogen recognition, systemic inflammation, the compensatory anti-inflammatory response, and regulatory T cells.. J Vet Intern Med 2012 May-Jun;26(3):457-82.
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