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

The localization of IgA, IgG, and IgM was investigated immunohistochemicall y in the mucosal surface of the main excretory duct of the human submandibu lar 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 cytoplas m of some cells and at the luminal surface of most of the cells. Clusters o f IgA-positive immunocompetent cells were also recognizable in the subepith elial layers. No reactivity for IgG and IgM was noticed. The results sugges t that the ductal epithelium may actively be involved in the release of sec retory IgA, which could play a prominent role in the local defense mechanis m of the duct.