Immunohistochemical and Glycohistochemical Localization of the Beta-galactoside-binding S-type Lectin in Human Placenta

The localization of the beta-galactoside binding lectin was studied immunohistochemically on acetone-fixed cryostat sections of full-term placental tissue using a biotinylated monoclonal antibody and glycohistochemically applying biotinylated asialofetuin and lactosylated bovine serum albumin. On blots of placental tissue lysates the lectin is recognized by the biotinylated lactosylated bovine serum albumin. The glycoconjugate recognition of the lectin on blots was inhibited in the presence of 0.1 M lactose showing the specificity of the interactions. The anti-lectin monoclonal antibody stained syncytiotrophoblast and trophoblastic cells. Both reagents applied for glycohistochemistry stained syncytiotrophoblast and trophoblastic cells of placental villi and the trophoblastic layer of extraplacental membranes. A strong uniform cytoplasmic staining was characteristic for syncytiotrophoblast and to a lower extent for cytotrophoblastic cells. The localization of the lectin is discussed with respect to a possible immunosuppressive function.