Expression of Fas-ligand in first trimester and term human placental villi

The expression of Fas-ligand (FasL) on trophoblast cells is thought to play a role in immune regulation during human pregnancy. However, there are som e discrepancies in the published data concerning the cell types expressing Fast in the placental villi. Therefore, we examined the expression of Fast on cryosections of first trimester and term placental tissue with three dif ferent anti-sera against Fast, which are in common use. By immunohistochemi stry, all three anti-sera principally gave the same staining result. In the first trimester of pregnancy, villous cytotrophoblast cells underlying the syncytium, as well as all extravillous trophoblast cells of cell columns a nd cell islands, gave a clear, mainly membrane-located staining, whereas th e syncytiotrophoblast, which forms the borderline to the maternal blood flo w, only gave a spot-like reaction in distinct areas. The same result was ob tained with term placental villi; however, in this tissue, the staining of the villous cytotrophoblast cells was less pronounced. From our results, we suggest that in placental villi, an important role of Fast in immune regul ation is not very conclusive because this molecule is mainly expressed on t rophoblast with no access to maternal blood or tissue. This is in contrast to the uterine part of the placenta, where Fast expressing trophoblast cell s are in close contact with apoptotic maternal leukocytes. (C) 2000 Elsevie r Science Ireland Ltd. All rights reserved.