Toll-like receptor 2 (TLR2) plays a key role in the host defense against Gram staining positive (Gram ϩ ) bacteria and their cell wall envelope components. However, little is known about the expression of TLR2 in the middle ear under otitis media (OM) conditions, and its role in the persistent otitis media with effusion (OME). In this study, we demonstrated that the pneumococcal cell wall component, peptidoglycan-polysaccharides (PGPS), activated the expression of TLR2 in the middle ear epithelial cells through the nuclear factor kappa B (NF-B)-cytokine signaling pathway while I kappa B alpha mutant (IB␣M), a dominant negative inhibitor of NF-B, abrogated the expression of TLR2 induced by PGPS. This study suggests that the existence of residual PGPS may maintain a low profile of cytokine production in the middle ear mucosa and thus contribute to the pathogenesis of OME. (Pediatr Res 69: 101-105, 2011)