['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).', '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.', 'TLR9 expression by SNEC in the AR group was significantly reduced compared to normals (35% ± 26% vs 76% ± 10%, p = 0.002).'] Is allergic rhinitis associated with decreased expression of Toll-like receptor 9 by sinonasal epithelial cells?