title: Shed membrane fragment modulation of CD3-zeta during pregnancy: link with induction of apoptosis.
abstract: Our objective was to identify shed placental plasma membrane fragments in the maternal circulation and determine whether these fragments are capable of down-regulating CD3-zeta chain expression and inducing apoptosis in T lymphocytes. Sera, isolated from the blood of pregnant women at 26-29 weeks gestation that subsequently had uncomplicated term deliveries, were subjected to high exclusion-limit gel chromatography to isolate placental membrane fragments. The placental origin of the fragments was confirmed by the presence of placental-type alkaline phosphates. These shed membrane fragments were further analyzed for the presence of Fas ligand (FasL) and modulation of CD3-zeta expression on cultured T-lymphocytes (Jurkat cells). The ability of the shed membrane fragments to induce apoptosis was assayed using a cell death ELISA. Components associated with Fas-dependent apoptosis (caspase-3, bcl-2 and bax) were characterized using western immunoblot following exposure to serum-derived membrane fragments. Placental membrane fragments were identified in all pregnancy sera, but not in non-pregnant controls. The 41 kDa FasL was identified in membrane fragment isolates and all samples were capable of inducing apoptosis as determined by the ELISA assay. Exposure of T lymphocytes to isolated membrane fragments suppressed the expression of CD3-zeta. The induction of apoptosis correlated with the induction and activation of caspase 3 and the induction of bax. Placenta-derived membrane fragments are detectable in the maternal circulation. These membrane fragment isolates are capable of inducing FasL-mediated apoptosis and down-regulating CD3-zeta expression, which may contribute to the immune tolerance of the fetus.
authors.affiliation: Department of Obstetrics, Gynecology, and Women's Health, University of Louisville School of Medicine, 511 South Floyd Street, MDR 420, Louisville, KY 40292, USA.
authors.forename: Cicek
authors.initials: C
authors.lastname: Gercel-Taylor
authors.forename: Siobhan M
authors.initials: SM
authors.lastname: O'Connor
authors.forename: Garrett K
authors.initials: GK
authors.lastname: Lam
authors.forename: Douglas D
authors.initials: DD
authors.lastname: Taylor
mesh_terms: D017209:Apoptosis; D015153:Blotting, Western; D017252:CD3 Complex / Q000502:physiology*; D053222:Fas Ligand Protein; D005260:Female; D006801:Humans; D007108:Immune Tolerance; D019169:Jurkat Cells; D008562:Membrane Glycoproteins / Q000032:analysis / Q000502:physiology; D010920:Placenta / Q000737:chemistry / Q000276:immunology*; D011247:Pregnancy; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000032:analysis; D019014:fas Receptor / Q000502:physiology
chemical_list: D017252:CD3 Complex; C121704:CD3 antigen, zeta chain; C505661:FASLG protein, human; D053222:Fas Ligand Protein; D008562:Membrane Glycoproteins; D019253:Proto-Oncogene Proteins c-bcl-2; D019014:fas Receptor