To elucidate the role of cytokines in the pathogenesis of otitis media with effusion (OME), levels of IL-1β, TNF-α, IL-6, and IL-8 in the middle ear effusions (MEEs) collected from 62 ears of patients with OME were determined by enzyme-linked immunosorbent assay (ELISA). MEEs were estimated by the naked eye to be either a mucoid or a serous variety and were classified into neutrophil-rich, lymphocyte-rich, and few cell types by cytological analysis. Following the centrifugation of the diluted samples of MEEs, the supernatants were stored for cytokine-specific ELISA and ribonucleic acids were extracted from the pellets for RT-PCR assay. Endotoxin levels and the activities of lysozyme and collagenase were also measured in the supernatants of MEEs and compared with the concentrations of cytokines. Levels of IL-1β, IL-8, endotoxin, and the activities of lysozyme and collagenase were higher in mucoid type MEEs than in serous type MEEs, and were significantly increased in neutrophil-rich group. Significant correlation was observed between the levels of endotoxin and that of IL-1β and IL-8. The incidence of IL-6 and IL-8 detected by ELISA was higher than that detected by RT-PCR, suggesting that these cytokines might be produced by middle ear mucosa as well as inflammatory cells contained in MEEs. Erythromycin therapy is known to be effective for OME and decreased the levels of IL-1β, IL-6, IL-8, endotoxin, and the activities of lysozyme and collagenase in MEEs. The findings suggest that the production of cytokines in MEEs might be influenced by the presence of endotoxin and that these factors are associated with the persistence of MEEs.
