Expression of Galβ1,4GlcNAc α2,6-sialyltransferase and α2,6-linked sialoglycoconjugates in normal human and rat tissues

We performed histochemical studies on normal human and rat tissues using anti-Galβ1,4GlcNAc α2,6-sialyltransferase (α2,6-ST) antibody and Sambucus nigra agglutinin (SNA). α2,6-ST and its products were detected in almost all tissues examined. However, the staining intensities varied significantly with different cell types. Some secretory epithelial cells, such as hepatocytes and choroid plexus cells, were vividly stained with either anti-α2,6-ST or SNA. In several cell types the intensity of α2,6-ST staining did not always correlate with SNA stainability. Neurons and gastrointestinal epithelia were rarely stained with SNA, even though they were positive for α2,6-ST. In contrast, the endothelial cells of blood vessels strongly reacted with SNA despite their weak α2,6-ST expression. The precise physiological roles played by α2,6-linked sialylated glycoconjugates have been unclear. However, the findings described here lend further support to their important role in cell growth and differentiation, since immature blood cells, including megakaryocytes in bone marrow, were intensely stained with anti-α2,6-ST and SNA, and SNA reaction products were primarily observed in the basal and suprabasal layers of the stratified epithelia rather than in the more differentiated upper layers. In view of the vivid reactivity of anti-α2,6- ST in the decidual cells of the placenta, it seems likely that α2,6-ST expression is under hormonal control.