NOS2 and otitis media with effusion: Assuming that microbial infection in the middle ear cavity of OME patients induces the expression of toll-like receptors (TLRs), cytokines, and NO, a study without a normal control group divided participants into otitis-prone and non-otitis-prone groups to compare TLR, cytokine, and NOS mRNA levels in middle ear effusion using real-time polymerase chain reaction.