Characterization of an experimentally induced inner ear immune response.
OBJECTIVE
To determine the effects of a sterile immune response on the structure and function of the cochlea.


METHODS
An immune response was created in guinea pigs by systemically sensitizing the animals to keyhole limpet hemocyanin and subsequently challenging the inner ear with the protein. Animals were allowed to survive for 1 to 5 weeks, after which the cochlea was evaluated histologically. Hearing was measured by auditory brainstem response before the inner ear challenge, during the survival period, and prior to sacrifice.


RESULTS
Inflammatory cells infiltrated the cochlea from the circulation. Surface preparations and plastic sections of the organ of Corti 1 and 2 weeks after the initiation of the inflammation demonstrated degeneration of the sensory and supporting cells in cochlear turns containing inflammatory cells. Good preservation of structures was seen in the more apical cochlear turns with little or no inflammatory cells. 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.


CONCLUSIONS
Although in general the immune response serves to protect an organism from infection, these results demonstrate that bystander injury associated with local immune responses in the cochlea, an organ incapable of regeneration, causes permanent cochlear destruction and hearing loss.
Ma
C
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Division of Otolaryngology-Head and Neck Surgery, University of California, San Diego, Department of Veterans Affairs, La Jolla 92093-0666, USA.
Billings
P
P
Harris
J P
JP
Keithley
E M
EM
D000276:Adjuvants, Immunologic / Q000008:administration & dosage; D000818:Animals; D000941:Antigens / Q000276:immunology; D017209:Apoptosis; D002114:Calcinosis / Q000276:immunology / Q000473:pathology; D003051:Cochlea / Q000276:immunology* / Q000473:pathology / Q000503:physiopathology; D004396:Coloring Agents; D016057:Evoked Potentials, Auditory, Brain Stem / Q000502:physiology; D005260:Female; D006168:Guinea Pigs; D006241:Haptens / Q000276:immunology; D006309:Hearing / Q000502:physiology; D006311:Hearing Disorders / Q000209:etiology; D006433:Hemocyanins / Q000276:immunology; D007114:Immunization; D007760:Labyrinth Supporting Cells / Q000276:immunology / Q000473:pathology; D007762:Labyrinthitis / Q000276:immunology / Q000473:pathology; D007962:Leukocytes / Q000276:immunology / Q000473:pathology; D008264:Macrophages / Q000276:immunology / Q000473:pathology; D009475:Neurons, Afferent / Q000276:immunology / Q000473:pathology; D009925:Organ of Corti / Q000276:immunology / Q000473:pathology / Q000503:physiopathology; D012533:Scala Tympani / Q000276:immunology / Q000473:pathology; D014048:Tolonium Chloride
D000276:Adjuvants, Immunologic; D000941:Antigens; D004396:Coloring Agents; D006241:Haptens; D014048:Tolonium Chloride; D006433:Hemocyanins; C032808:keyhole-limpet hemocyanin