Distribution of KHRI 3 epitopes in the inner ear.

Murine monoclonal antibodies against cochlear structures were previously generated to obtain probes for elucidating the function of cochlear cell subsets. Preliminary immunocytochemical characterization showed that the monoclonal antibody KHRI 3 binds to supporting cells but not sensory cells in the guinea pig cochlea. We have now investigated KHRI 3 epitopes in other species and other parts of the inner ear. The KHRI 3 epitope appears to be species-specific since no immunolabeling was seen in rat inner ear nor in chick inner ear. In immunocytochemical assays in the guinea pig vestibular tissues KHRI 3 stained saccular wall cells and transitional epithelial cells in the utricle and ampules as well as clusters of cells in the endolymphatic sac. In Western blots KHRI 3 stained a broad 70-75 kDa band in lanes loaded with guinea pig cochlea homogenates--as seen previously--as well as in lanes loaded with vestibular tissue homogenates. The immunolabeling patterns suggest that KHRI 3 epitopes are cell membrane components or related to membrane structures. Thus the monoclonal antibody KHRI 3 appears to define a nonsensory cell subset in the guinea pig inner ear that can be identified by expression of KHRI 3 epitopes.