Characterization of an experimentally induced inner ear immune response

immune response on the structure and function of the cochlea, Methods: An i mmune response was created in guinea pigs by systemically sensitizing the a nimals to keyhole limpet hemocyanin and subsequently challenging the inner ear with the protein. Animals were allowed to survive for 1 to 5 weeks, aft er which the cochlea was evaluated histologically. Hearing was measured by auditory brainstem response before the inner ear challenge, during the surv ival period, and prior to sacrifice. Results: Inflammatory cells infiltrate d the cochlea from the circulation. Surface preparations and plastic sectio ns of the organ of Corti 1 and 2 weeks after the initiation of the inflamma tion demonstrated degeneration of the sensory and supporting cells in cochl ear turns containing inflammatory cells. Good preservation of structures wa s seen in the more apical cochlear turns with little or no inflammatory cel ls. In cochleas from animals that survived 5 weeks, most of the infiltrated cells were cleared after undergoing apoptosis and the inflammatory matrix in the scala tympani began to calcify. Hearing loss was moderate to severe depending on the amount of inflammation, Conclusion: Although in general th e immune response serves to protect an organism from infection, these resul ts demonstrate that bystander injury associated with local immune responses in the cochlea, an organ incapable of regeneration, causes permanent cochl ear destruction and hearing loss.