FIG. 1.

Expression of the HERV-W Env glycoprotein at the apical syncytiotrophoblast microvillus membrane. (A) Detection of the Env glycoprotein with the 6A2B2 monoclonal antibody on the external face of the syncytiotrophoblast (brown arrows) on term and 13-week normal placenta sections. (B) Double labeling on a serial section of a 10-week-gestation normal placenta with anti-Env (upper and lower image, brown arrows) and antidesmoplakin (lower image, red arrow) antibodies. Desmoplakin, a protein of the desmosomiale plaque involved in intercellular junctions, is absent from the syncytiotrophoblast fused tissue and lines the plasmatic membranes of the cytotrophoblasts. Note the presence of maternal red blood cells (Mrbc) in the intervillous space.