Objective: The epithelial cells of the middle ear and Eustachian tube must maintain an adequate mucosal defense system against various antigenic stimuli. Since toll-like receptors (TLRs) are known to play a critical role in mucosal defense, we investigated their expression in the mucosa of the tubotympanum, nasopharynx, and oral cavity of the rat.
Method: The expression of TLR2 and TLR4 was examined in the mucosa of the tubotympanum, nasopharynx and oral cavity of the rat using real time RT-PCR and Western blot analysis.
Results: Transcripts for TLR2 and TLR4 were detected in the mucosa of the tubotympanum, nasopharynx, and oral cavity of the rat. The expression of TLR2 and TLR4 in the middle ear was increased more than in the other anatomical areas. Differential expression of these molecules at the protein level was confirmed by Western blot analysis.
Conclusions: Diverse expression of TLR2 and TLR4 in different parts of the tubotympanum and upper aerodigestive tract suggests region-specific functional modulation of the innate immune system. Differential expression of subtypes of the TLR in the normal physiology of the tubotympanum and upper aerodigestive tract also suggests that they may play a role in the pathophysiology of otitis media.