TLR-9, NOD-1, NOD-2, RIG-I and immunoglobulins in recurrent otitis media with effusion

Pattern recognition receptors (PRRs) induce appropriate immune responses after recognizing certain molecular characteristics of pathogens. It is not known, however, whether PRRs are expressed in middle ear infections and whether the expression of PRRs and immunoglobulins is correlated in recurrent otitis media with effusion (OME). We therefore investigated the expression of PRRs and immunoglobulins in children with OME.

The study population consisted of 66 children with OME, of whom 27 had more than 4 episodes in 12 months or more than 3 episodes in 6 months (otitis-prone group), and 39 had fewer than 4 episodes in 12 months or 3 episodes in 6 months (non-otitis-prone group). The expression in middle ear effusion of Toll-like receptor (TLR)-9, nucleotide-binding oligomerization domain (NOD)-1, NOD-2, and retinoic acid-inducible gene (RIG)-I mRNA, as determined by real-time PCR, and the concentrations of IgG, IgA, and IgM, as determined by ELISA, were compared between the two groups.

The levels of TLR-9, NOD-1 and RIG I mRNAs were significantly lower in the otitis-prone than in the non-otitis-prone group (p<0.05 each). The concentrations of IgG, IgA and IgM in effusion fluid did not differ significantly between the two groups (p>0.05), and there were no correlations between immunoglobulin concentration and the expression of PRPs (p>0.05).

Decreased expression of PRRs may be associated with increased susceptibility to OME.