Functional characterisation of bovine TLR5 indicates species-specific recognition of flagellin.
Mammalian toll-like receptor 5 (TLR5) senses flagellin of several bacterial species and has been described to activate the innate immune system. To assess the role of bovine TLR5 (boTLR5) in the cattle system, we cloned and successfully expressed boTLR5 in human embryonic kidney (HEK) 293 cells, as indicated by quantitative PCR and confocal microscopy. However, in contrast to huTLR5-transfected cells, exposure of boTLR5-transfected cells to flagellin neither activated nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) nor CXCL8 production. Subsequent comparison of the flagellin response induced in human and bovine primary macrophages revealed that flagellin did not lead to phosphorylation of major signalling molecules. Furthermore, the CXCL8 and TNFα response of primary bovine macrophages stimulated with flagellin was very low compared to that observed in human primary macrophages. Our results indicate that cattle express a functional TLR5 albeit with different flagellin sensing qualities compared to human TLR5. However, boTLR5 seemed to play a different role in the bovine system compared to the human system in recognizing flagellin, and other potentially intracellular expressed receptors may play a more important role in the bovine system to detect flagellin.
Molecular Immunology Group, Department of Pathology and Pathogen Biology, Royal Veterinary College, Hawkshead Lane, Hatfield AL9 7TA, UK.
Hannah J
HJ
Metcalfe
School of Veterinary Medicine, University of Surrey, Guildford GU2 7TE, UK; Animal Health and Veterinary Laboratories Agency, Weybridge, Surrey KT15 3NB, UK.
Roberto M
RM
La Ragione
Institute of Infection, Immunity & Inflammation, University of Glasgow, Glasgow G12 8TA, UK; Bacterial Functional Genomics, Moredun Research Institute, Pentlands Science Park, Penicuik, Midlothian EH26 0PZ, UK.
David G E
DG
Smith
Molecular Immunology Group, Department of Pathology and Pathogen Biology, Royal Veterinary College, Hawkshead Lane, Hatfield AL9 7TA, UK. Electronic address: dwerling@rvc.ac.uk.
Dirk
D
Werling
D000818:Animals; D002417:Cattle; D005408:Flagellin / Q000276:immunology*; D057809:HEK293 Cells; D006801:Humans; D016328:NF-kappa B / Q000502:physiology; D010766:Phosphorylation; D013045:Species Specificity; D051198:Toll-Like Receptor 5 / Q000502:physiology*; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism
D016328:NF-kappa B; D051198:Toll-Like Receptor 5; D005408:Flagellin; D048051:p38 Mitogen-Activated Protein Kinases
Cattle; Flagellin; Human; TLR5