Globoside expression within the human placenta.

This report demonstrates the presence of the neutral glycosphingolipid, globoside, on the villous trophoblast layer of human placenta. Immunoreactivity for globoside which is the receptor used by human parvovirus B19 was strongest in villous trophoblast cells of first trimester placentae, with diminished reactivity in second trimester placentae, and a near lack of staining for the antigen in those of third trimester. This relative reduction in globoside-specific immunoreactivity in placentae of increasing gestational ages was confirmed using thin-layer chromatographic analyses of extracted neutral glycolipids from the syncytiotrophoblast layer and cytotrophoblast cells of first and third trimester placental villi. The presence of globoside on the protective trophoblast layer of the villi provides a potential pathway whereby B19 may be transmitted from an infected mother to the fetus. The virus once across the placental barrier, may gain access to its erythroid precursor target cells within fetal villus capillaries. The observed change found in globoside immunoreactivity correlates well with the observation that fetal outcome is worse when maternal infection occurs during first or second trimester as compared to an infection occurring near term. The reason for this observed difference in fetal outcome may be due not only to the presence of more target cells potentially to infect during the first and second trimesters, but also to the greater number of viral receptors present on the villous trophoblast layer.