title: Expression profiling and functional analysis of Toll-like receptors in primary healthy human nasal epithelial cells shows no correlation and a refractory LPS response.
abstract: BACKGROUND
  Innate immune recognition via Toll-like receptors (TLRs) on barrier cells like epithelial cells has been shown to influence the regulation of local immune responses. Here we determine expression level variations and functionality of TLRs in nasal epithelial cells from healthy donors.
  
  
  METHODS
  Expression levels of the different TLRs on primary nasal epithelial cells from healthy donors derived from inferior turbinates was determined by RT-PCR. Functionality of the TLRs was determined by stimulation with the respective ligand and evaluation of released mediators by Luminex ELISA.
  
  
  RESULTS
  Primary nasal epithelial cells express different levels of TLR1-6 and TLR9. We were unable to detect mRNA of TLR7, TLR8 and TLR10. Stimulation with Poly(I:C) resulted in a significant increased secretion of IL-4, IL-6, RANTES, IP-10, MIP-1β, VEGF, FGF, IL-1RA, IL-2R and G-CSF. Stimulation with PGN only resulted in significant increased production of IL-6, VEGF and IL-1RA. Although the expression of TLR4 and co-stimulatory molecules could be confirmed, primary nasal epithelial cells appeared to be unresponsive to stimulation with LPS. Furthermore, we observed huge individual differences in TLR agonist-induced mediator release, which did not correlate with the respective expression of TLRs.
  
  
  CONCLUSIONS
  Our data suggest that nasal epithelium seems to have developed a delicate system of discrimination and recognition of microbial patterns. Hypo-responsiveness to LPS could provide a mechanism to dampen the inflammatory response in the nasal mucosa in order to avoid a chronic inflammatory response. Individual, differential expression of TLRs on epithelial cells and functionality in terms of released mediators might be a crucial factor in explaining why some people develop allergies to common inhaled antigens, and others do not.
authors.affiliation: Department of Otorhinolaryngology, Academic Medical Center (AMC), Amsterdam, The Netherlands.
authors.forename: J
authors.initials: J
authors.lastname: van Tongeren
authors.affiliation: Department of Otorhinolaryngology, Academic Medical Center (AMC), Amsterdam, The Netherlands.
authors.forename: K I L
authors.initials: KIL
authors.lastname: Röschmann
authors.affiliation: Department of Otorhinolaryngology, Academic Medical Center (AMC), Amsterdam, The Netherlands.
authors.forename: S M
authors.initials: SM
authors.lastname: Reinartz
authors.affiliation: Department of Otorhinolaryngology, Academic Medical Center (AMC), Amsterdam, The Netherlands.
authors.forename: S
authors.initials: S
authors.lastname: Luiten
authors.affiliation: Department of Otorhinolaryngology, Academic Medical Center (AMC), Amsterdam, The Netherlands.
authors.forename: W J
authors.initials: WJ
authors.lastname: Fokkens
authors.affiliation: Department of Cell Biology & Histology, Academic Medical Center (AMC), Amsterdam, The Netherlands.
authors.forename: E C
authors.initials: EC
authors.lastname: de Jong
authors.affiliation: Department of Otorhinolaryngology, Academic Medical Center (AMC), Amsterdam, The Netherlands.
authors.forename: C M
authors.initials: CM
authors.lastname: van Drunen
keywords: Chemokines; Cytokines; Nasal epithelial cells; Pattern recognition receptors; Toll-like receptor