Distribution of immunoglobulin isotypes and subisotypes in equine guttural pouch (auditory tube diverticulum)

To clarify the functions of the equine guttural pouch, the distribution of various immunoglobulin isotypes and subisotypes in the guttural pouch mucosa were examined in healthy horses. IgGa was present in the mucosa of guttural pouch, mucosal lymph nodules and submucosal lymph nodules. IgM was scattered in the mucosal lymph nodules and in the germinal centers of the submucosal lymph nodules. IgGc was recognized only in the submucosal lymph nodules. These immunoglobulin isotypes and subisotypes were found in lymphocytes and plasma cells. On the other hand, IgA was detected in glandular epithelial cells and the surface layer of the mucosal epithelium, as well as in free cells. This finding suggests that IgA is secreted through the glandular epithelium. Based on the above findings, we conclude that the guttural pouch has phylactic ability.