title: Allergic rhinitis is associated with decreased expression of Toll-like receptor 9 by sinonasal epithelial cells.
abstract: BACKGROUND
  Toll-like receptors (TLRs) are important in sinonasal mucosal innate immunity. Previous studies demonstrate that sinonasal epithelial cell (SNEC) TLR9 expression is reduced in T-helper 2 (Th2) cytokine-predominant chronic rhinosinusitis with polyps, and with the in vitro application of Th2 cytokines. To further investigate in vivo modulation of TLR9 by the local cytokine environment, this study examines TLR9 expression in freshly isolated SNECs from subjects with and without active allergic rhinitis (AR).
  
  
  METHODS
  SNECs were gathered via endoscopic-guided middle meatal brushings from 9 AR subjects who were skin-prick test (SPT)-positive to environmental allergens in season at the time of study, and 8 controls. Flow cytometry was utilized to compare SNEC TLR9 expression in the 2 groups.
  
  
  RESULTS
  TLR9 expression by SNEC in the AR group was significantly reduced compared to normals (35% ± 26% vs 76% ± 10%, p = 0.002).
  
  
  CONCLUSIONS
  Similar to observations in eosinophilic chronic rhinosinusitis, this study shows that active AR is associated with decreased SNEC TLR9 expression. These findings are consistent with the concept that Th2 cytokines suppress expression of TLR9 and other innate immune genes. Multiple endogenous and microbial factors likely modulate sinonasal innate immunity to maintain homeostasis and prevent infection in AR.
authors.affiliation: Department of Otolaryngology-Head and Neck Surgery, Johns Hopkins School of Medicine, Baltimore, MD 21287-0910, USA.
authors.forename: Thuy-Anh N
authors.initials: TA
authors.lastname: Melvin
authors.forename: Mai-Tien
authors.initials: MT
authors.lastname: Nguyen
authors.forename: Andrew P
authors.initials: AP
authors.lastname: Lane
authors.forename: Sandra Y
authors.initials: SY
authors.lastname: Lin
mesh_terms: D000328:Adult; D000485:Allergens / Q000276:immunology; D016022:Case-Control Studies; D002908:Chronic Disease; D004847:Epithelial Cells / Q000378:metabolism; D005260:Female; D005434:Flow Cytometry; D006801:Humans; D007113:Immunity, Innate / Q000502:physiology*; D008297:Male; D009297:Nasal Mucosa / Q000378:metabolism; D012221:Rhinitis, Allergic, Perennial / Q000276:immunology*; D012882:Skin Tests; D051217:Toll-Like Receptor 9 / Q000378:metabolism*
chemical_list: D000485:Allergens; D051217:Toll-Like Receptor 9