Immunohistochemical localization of six galectin subtypes in the mouse digestive tract.

Galectin, an animal lectin that recognizes beta-galactoside of glycoconjugates, is abundant in the gut. This IHC study showed the subtype-specific localization of galectin in the mouse digestive tract. Mucosal epithelium showed region/cell-specific localization of each galectin subtype. Gastric mucous cells exhibited intense immunoreactions for galectin-2 and galectin-4/6 with a limited localization of galectin-3 at the surface of the gastric mucosa. Electron microscopically, galectin-3 immunoreactivity coated indigenous bacteria on the gastric surface mucous cells. Epithelial cells in the small intestine showed characteristic localizations of galectin-2 and galectin-4/6 in the cytoplasm of goblet cells and the baso-lateral membrane of enterocytes in association with maturation, respectively. Galectin-3 expressed only at the villus tips was concentrated at the myosin-rich terminal web of fully matured enterocytes. Epithelial cells of the large intestine contained intense immunoreactions for galectin-3 and galectin-4/6 but not for galectin-2. The stratified squamous epithelium of the forestomach was immunoreactive for galectin-3 and galectin-7, but the basal layer lacked galectin-3 immunoreactivity. Outside the epithelium, only galectin-1 was localized in the connective tissue, smooth muscles, and neuronal cell bodies. The subtype-specific localization of galectin suggests its important roles in host-pathogen interaction and epithelial homeostasis such as membrane polarization and trafficking in the gut.