The adhesion molecule CEACAM1 (CD66a, C-CAM, BGP) is specifically expressed by the extravillous intermediate trophoblast

CEACAM1 (CD66a, C-CAM, BGP) is an adhesion molecule of the carcinoembryonic antigen family which has been shown to be normally expressed at the apical pole of epithelial cells, including the apical pole of endometrial surface and glandular epithelia, The purpose of the present study was to investiga te its expression pattern at the maternal-fetal interface, and thus to dete rmine whether CEACAM1 could be implicated in the human implantation process , For this purpose, we performed immuohistochemistry using the 4D1/C2 monoc lonal antibody (mAb) as well as flow cytometry and Western blot on isolated trophoblast populations, On the maternal side of the maternal-fetal interf ace, CEACAM1 was present in epithelial cells of pregnancy endometrium as we ll as in small endometrial vessels, whereas it was absent from decidual cel ls, On the fetal side, CEACAM1 was strongly expressed by the extravillous ( intermediate) trophoblast at the implantation site, as well as by extravill ous trophoblast cells with invasive phenotype in primary culture, as shown by now cytometry and Western blot. Expression was also observed in placenta l villous core vessels but was absent from both villous cyto- and syncytiot rophoblasts throughout the pregnancy. We conclude that, given its specific expression pattern, CEACAM1 can be a useful marker for extravillous interme diate trophoblast and might be functionally implicated in mediating trophob last/endometrial and/or trophoblast/endothelial interactions during the tro phoblastic invasion of the endometrium.