Antigen diffusion from the perilymphatic space of the cochlea.

The diffusion pattern of horseradish peroxidase (HRP) injected into the scala tympani of the cochlear basal turn of guinea pigs was studied to test whether antigen presented in this manner can gain access to the endolymphatic sac. By two hours, HRP reaction product was found throughout the cochlea, with the greatest amounts in the spiral ligament, spiral limbus, basilar membrane, and organ of Corti. In several cochleas, very weak labeling was seen in the stria vascularis. HRP reaction product was maximal in the basal turn. By two hours, HRP reaction product was also observed in the endolymphatic sac lumen, epithelial cells, subepithelial tissue, and perisaccular connective tissue. It was more common in the proximal portion. At this time, macrophages within the lumen already appeared to have phagocytosed the HRP. By 72 hours after injection, the inner ear was cleared of HRP. The results of this study support the hypothesis that antigen in the scala tympani gains access to the endolymphatic sac lumen, where it may be presented by macrophages to the systemic immune system. Antigen most likely does not gain access to the endolymphatic space in the cochlea, but it gets to the endolymphatic sac through the perilymph and the perisaccular tissue.