Anti CD163+, Iba1+, and CD68+ Cells in the Adult Human Inner Ear: Normal Distribution of an Unappreciated Class of Macrophages/Microglia and Implications for Inflammatory Otopathology in Humans.

HYPOTHESIS: Identification, characterization, and location of cells involved in the innate immune defense system of the human inner ear may lead to a better understanding of many otologic diseases and new treatments for hearing and balance-related disorders. BACKGROUND: Many otologic disorders are thought to have, as part of their disease process, an immune component. Although resident macrophages are known to exist in the mouse inner ear, the innate immune cells in the human inner ear are, to date, unknown. METHODS: Primary antibodies against CD163, Iba1, and CD68 (markers known to be specific for macrophages/microglia) were used to immunohistochemically stain celloidin embedded archival temporal bone tissue of normal individuals with no known otologic disorders other than changes associated with age. RESULTS: Cells were positively stained throughout the temporal bone within the connective tissue and supporting cells with all three markers. They were often associated with neurons and on occasion entered the sensory cell areas of the auditory and vestibular epithelium. CONCLUSIONS: We have immunohistochemically identified an unappreciated class of cells in the normal adult inner ear consistent in staining characteristics and morphology with macrophages/microglia. As in other organ systems, it is likely these cells play an essential role in organ homeostasis that has not yet been elucidated within the ear.