[Free radicals in inner ear immune responses; immunohistochemical study of myeloperoxidase]

Previously, we reported that immune reactions in the endolymphatic sac of guinea pigs caused spontaneous nystagmus, a suppressed caloric response, and fluctuating hearing loss. In order to evaluate immune injury to the sensory organs of the inner ear, we conducted an immunohistochemical investigation of the distribution and time course of myeloperoxidase (MPO) following immune reaction in the endolymphatic sac. MPO staining can be seen in the endolymphatic sac, outer hair cells, stria vascularis and lateral canal (ampulla), from several hours to 3 weeks after a secondary KLH challenge, and its time course parallels the time course of neutrophil infiltration of the endolymphatic sac. This result indicates that free radicals in the MPO-H2O2-Cl system are responsible for the tissue damage and dysfunction resulting from inner ear immune reactions.