Interleukin-2 affects cochlear function gradually but reversibly

Interleukin-2 (IL-2), one of the chemical mediators produced by helper T cells, activates its target cells via its receptor and induces inflammatory reactions indirectly. In this study, IL-2 was instilled into the round window niche of rats and the electrophysiological effects of inflammation on the inner ear were evaluated by a frequency-specific auditory brainstem response (ABR) technique. ABR threshold curves and intensity-latency (I-L) curves were investigated. In most cases, moderate sensorineural hearing loss (SNHL) was observed in the high-frequency areas (16-31.5 kHz). In the time course investigation of I-L curves, the responses of SNHL type appeared only 1 day after instillation (day 1) gradually becoming more prominent, to become most pronounced on days 5-7. The electrophysiological impairment was reversible within 2 weeks. Differing degrees of responsiveness of effusion production were observed following the instillation of IL-2, varying from pronounced middle ear effusion causing rather severe mixed hearing loss, to complete lack of effusion. Inflammation induced by IL-2 affects cochlear function gradually but reversibly.