The occurrence of IgG in the endolymphatic sac of the guinea pig.

We investigated the occurrence of immunoglobulin G (IgG) in the endolymphatic sac (ES) of the guinea pig in order to show that the ES is an organ involved in the immunoreactivity of the inner ear. By using an immunohistological technique, we were able to show that IgG is located mainly in the subepithelial layer of the ES. We also found that IgG is present in some epithelial cells of the ES as well as in free floating cells in the ES lumen. Although plasma cells have been described previously in the subepithelial layer, none could be recognized in this layer of the ES in our specimens. Our results suggest that the ES is an immunoreactive organ of the inner ear in some pathological states, while IgG in the normal ES is primarily of systemic origin.