Expression of Fas/Fas ligand by decidual leukocytes in hydatidiform mole

Complete hydatidiform moles are entirely paternally derived and, therefore, represent a complete intrauterine allograft that might be expected to prov oke an altered maternal immune response compared with that of normal pregna ncy. Uterine decidua contains a large leukocyte population, of which 10%-20 % are T lymphocytes. Fas ligand (FasL) expression by placental trophoblast may induce apoptosis of Fas+ lymphocytes, thereby facilitating immune toler ance and survival of the molar trophoblast. Our previous studies have shown an increase in activated CD4+ decidual T cells in molar pregnancy compared with normal pregnancy. This study was designed to characterize and quantit ate Fas/FasL expression by decidual leukocytes in complete and partial hyda tidiform mole compared with that in normal early pregnancy using single and double immunohistochemical labeling (i.e., avidin-biotin-peroxidase and av idin biotin-alkaline phosphatase). A significant increase was found in Fas and FasL expression by decidual CD4+ T cells in complete (Fas+, P = 0.0106; FasL+, P = 0.0081) and partial (Fas+, P = 0.0131; FasL+, P = 0.0051),hydat idiform moles, as was a significant decrease in Fas expression by decidual CD8+ T cells in complete (P = 0.0137) and partial (P = 0.0202) hydatidiform mole compared with normal early pregnancy. The implications of altered Fas /FasL status of decidual T-cell subsets in hydatidiform mole are also discu ssed.