Toll-like Receptors 2 and 4 and Their Mutations in Patients with Otitis Media and Middle Ear Effusion

ABSTRACT

OBJECTIVES: Toll-like receptors (TLRs) detect microbial infections and they can directly induce innate host defense responses. TLR 2 has been shown to be primarily involved in the recognition of peptidoglycans and lipoteichoic acid of gram positive bacteria. TLR 4 recognizes lipopolysaccharides and lipoteichoic acids from both gram-negative and gram-positive bacteria. Both mutations lead a reduced capacity to elicit inflammation and they increase the risk for gram-positive and negative infections. This study was performed to investigate the expressions of TLR 2 and 4 and their mutations in patients suffering with otitis media and middle ear effusion. METHODS: Middle ear fluid samples were collected from 40 otitis media effusion (OME) patients who had ventilating tubesinserted. Bacteria in the effusion fluid were detected by standard bacterial culture. The secreted IgG, IgA and IgM were measured by Enzyme-linked immunosorbent assay. TLR 2 and 4 were assessed by performing RT-PCR. The genomic DNA from each patient was isolated from the middle ear fluid samples that were collected from 60 OME patients, and the presence of mutations was determined by performing restriction digestion and DNA sequencing analysis. RESULTS: Among the 40 middle ear fluid samples, bacteria were detected in 13 middle ear fluid samples. The amounts of IgM, IgA, and IgG were 151.20+/-60.94 ng/mL, 21.59+/-7.96 ng/mL and 11.55+/-16.98 ng/mL, respectively. TLR 2 and 4 were expressed in the middle ear fluid and the expression of TLR 2 was higher than that of TLR 4. However, there was no correlation between the expressions of TLR 2 and 4, and the concentration of immunoglobulin or the presence of bacteria (P>0.05). There ware no mutations of TLR 2 (Arg753Gln, Arg677Trp) and TLR 4 (Asp299Gly, Thr399Ile). CONCLUSION: TLR 2 and 4 were expressed in all the middle ear fluid samples of OME, but the mutations of TLR 2 and 4 were not detected. TLR 2 and 4 may play a vital role in the immunological responses of patients with OME.