s / Placenta 34 (2013) A1–A99 A75 rate, but clones were significantly smaller. The onset of yolk-sac development was not normal in clones. In addition, later steps differed from the condition in vivo in all three groups in that the yolk-sac was yellowish and juxtaposed with the amnion. Vascularisation of the chorioallantoic membrane was relatively late and low in NT gestations, but normal in the others. Conclusion: In conclusion, the yolk-sac seems to be most vulnerable to morphogenetic alterations. Future studies will focus on gene expression and early vascularisation processes to investigate whether these changes may be responsible for the high incidence of intrauterine mortality, especially in clones. http://dx.doi.org/10.1016/j.placenta.2013.06.220 P2.55. THE PLACENTAL EXPRESSION OF HUMAN LEUKOCYTE ANTIGEN HLA-F AND HLA-E IN EARLY NORMAL PLACENTATION Rinat Hackmon , Lakmini Pinnaduwage , John Kingdom , Gideon Koren , Dan Geraghty , Stephen Lye , Caroline Dunk 4 University of Toronto Department of Obstetrics and Gynecology, Mount Sinai Hospital, Toronto/ON, Canada; University of Toronto Department of Clinical Pharmacolgy, Sick Kids Hospital, Toronto/ON, Canada; University of Toronto Department of Physiology, Toronto/ON, Canada; 4 Samuel Lunenfeld Research Institute, Mount Sinai Hospital, Toronto/ON, Canada; 5 Fred Hutchinson Cancer Research Institute, Clinical Division, Seattle/WA, USA Objective: Human pregnancy is arguably one of the most interesting examples of immune tolerance seen in mammalian biology. A key-organ, the placenta, does not express the classical MHC class I or II antigens, and instead is the single organ tissue expressing simultaneously each of the nonclassical MHC class I antigens on its EVT HLA-E, F, and G, and possibly HLA-C. The function of HLA-F and E in the placental environment is still unknown. Prior results also demonstrated that HLA-F is surface expressed on activated lymphocytes. We hypothesised that HLA-F and E may contribute to the immuno inhibitory response in early placentation. Methods: Immunohistochemistry and RT-PCR were used to examine HLAE and HLA-F expression at different time points of pregnancy. Results: Analysis showed that HLA-F protein expression localised to the syncytiotrophoblast (SYN) cells andwas maximal at 5-7 weeks of gestation and decreased throughout gestation. During the 2nd trimester HLA-F expression was surface expressed, while at term, intracellular. HLA-F protein was expressed in the anchoring cell columns of early 1st trimester placenta and also in invasive interstitial and endovascular EVT within the decidua basalis throughout gestation. HLA-E protein expression was observed in SYN cells and EVT cell columns at 5 weeks gestation and was not detectable from the 7th week until the end of gestation. HLA-F mRNA expression levels showed significant increase across gestation compared to 1st trimester, while HLA-E mRNA levels did not vary. Conclusions: These results support our hypothesis that both surface HLA-F andHLA-Eproteins areexpressed in thehumanplacenta at thehighest levels in early placentation and decrease toward term. This expression of HLA-F suggests a specific role and potential interaction with decidual receptors such as KIR3 2D, that may contribute to immune tolerance of pregnancy. http://dx.doi.org/10.1016/j.placenta.2013.06.221 P2.56. CYTOKINE PROFILE OF CD4+ T-CELLS IN DECIDUA AND CIRCULATION IN 3RD TRIMESTER PREGNANCY Guro Mork Johnsen , Kjetil Tasken , Anne Cathrine Staff 1,4 Department of Obstetrics and Department of Gynaecology, Oslo University Hospital Ulleval, Oslo, Norway; NCMM Centre for Molecular Medicine Norway, Nordic EMBL Partnership, University of Oslo, Oslo, Norway; 3 The Biotechnology Centre of Oslo, University of Oslo, Oslo, Norway; 4 Faculty of Medicine, University of Oslo, Oslo, Norway Objectives: In pregnancy there is a maternal immunologic tolerance toward the semi-allogeneic fetus. Different T-cell subsets and cytokines are important in regulation of this process. Maternal tolerance at the fetalmaternal interface (decidua) has been explained by predominant Th2 immunity. Now, there is an emerging role for regulatory T-cells since they suppress proliferation and cytokine production of different immune cells. Preeclampsia is associated with a pro-inflammatory Th1/Th17 type immunity. Our objective was to analyze Th1/Th2/Th17 cytokines secreted from CD4+ T-cells from decidua and blood from 3rd trimester pregnant women as a basis for investigating possible pathogenic changes in preeclampsia. Methods: Blood and decidua samples were obtained from women with healthy pregnancies or preeclampsia undergoing cesarean section (N1⁄48). PBMCs were isolated from freshly collected blood. Decidua was harvested by vacuum suction from the placental bed after delivery of the placenta, and cells were isolated by enzymatic tissue digestion. CD4+ T-cells were isolated using magnetic bead separation and incubated for 4 days with Tcell activation beads (Miltenyi). Cell supernatants where harvested and cytokine concentrations analyzed using Cytokine Bead Array (BD-Biosciences) for IL-2, IL-4, IL-6, IL-10, TNF, INFg and IL-17A by LSRFortessa flow-cytometer. Results: Preliminary results show that cytokine secretion after stimulation of CD4+ T-cells was lower in cells from decidua compared to blood. The Th1 cytokines IFNg, IL-2 and TNF were highly expressed in CD4+ T-cells from both tissues, while the expression of Th2 cytokine IL-4 and Th17 IL17A was low. Interestingly, the expression of IL-10, an anti-inflammatory cytokine that can be produced by all Th subsets, was significantly higher in circulating than in decidual T-cells. Conclusion: There seems to be a blunted T-cell response in decidua, with reduced cytokine production. These findings add to the notion that there are significant differences between immunological processes in the periphery and the decidua during pregnancy. http://dx.doi.org/10.1016/j.placenta.2013.06.222 P2.57. DECIDUAL NATURAL KILLER CELL RECEPTOR EXPRESSION IS ALTERED IN PREGNANCIES WITH IMPAIRED SPIRAL ARTERY REMODELLING Alison Wallace, Amanda Host, Guy Whitley, Judith Cartwright St George's, University of London, London, UK Objectives: Decidual natural killer (dNK) cells are distinct to peripheral blood (pb) NK cells with regard to both surface receptor expression and function. Decidual NK cells are predominantly CD56brightCD16-, are noncytotoxic and are thought to function primarily through the secretion of cytokines. The role played by dNK cell inhibitory and activating receptors in spiral artery (SA) remodelling is unknown. Uterine artery Doppler resistance index (RI) in the first trimester of pregnancy can be used as a proxy measure of the extent of remodelling of the SA. We have used this technique to identify pregnancies with a high RI, indicative of impaired SA remodelling. Comparisons of the expression of activating and inhibitory receptors on dNK cells from normal RI and high-RI pregnancies were made. Methods: Decidual NK cells were isolated with local ethical approval from first trimester terminations of pregnancy screened by uterine artery Doppler ultrasound. A panel of cell surface receptors was investigated by flow cytometry immediately after dNK cell isolation, and percentage of cells expressing the receptor was measured. The functional outcomes of altered receptor expression were considered. Results: There was no significant difference in expression of the receptors NKp46, NKp30, NKp44, NKG2A, NKG2C, NKG2D, CD160 and KIR2DL2/S2 between dNK cells isolated from high and normal RI pregnancies. However, a greater percentage of dNK cells from normal RI pregnancies