Immunohistochemical localization of secretory immunoglobulins in the main excretory duct of the human submandibular gland

The localization of IgA, IgG, and IgM was investigated immunohistochemically in the mucosal surface of the main excretory duct of the human submandibular gland in order to verify the possible antimicrobial properties of this duct. Only secretory IgA-immunoreactivity was recognized in the epithelial cells of the duct. An intense immunoreactivity was observed in the cytoplasm of some cells and at the lumina! surface of most of the cells. Clusters of IgA-positive immunocompetent cells were also recognizable in the subepithelial layers. No reactivity for IgG and IgM was noticed. The results suggest that the ductal epithelium may actively be involved in the release of secretory IgA, which could play a prominent role in the local defense mechanism of the duct