Expression Of Human Leucocyte Antigen E In Human Normal And Pathological Pregnancy And The Regulating Effect Of Progesterone On Its Transcription

How the fetal–placental unit, a semi-allograft, escapes maternal immune rejection during pregnancy is a fundamental question in reproductive immunology. Placental trophoblast cells must play an essential role, since they are the only cells of this unit which come into direct contact with maternal tissue at the interface. These cells express neither HLA class I nor class II antigens, but express the non-classical class I antigen-G,-E and -F specifically. Until now, it has been widely explored on the researches of HLA-G. However, the expressions and mechanisms of HLA-E and -F remain unclear. In this study, the expressions and localization of HLA-E were investigated in normal pregnancy and pregnancy related diseases such as hypertensive disorder complicating pregnancy and trophoblastic diseases.It is well-known that the successful pregnancy requires a number of immune modulation factors from both mother and fetus. Progesterone has been suggested to be an important immune modulator during pregnancy for many years. The concentration of progesterone in maternal blood is distinguishably high during pregnancy. Functions attributed to progesterone in pregnancy include triggering suppressor T-cell generation, blocking cytotoxic T-cell activity, reducing natural killer cell activity, inducing lymphocyte blocking proteins and modifying the cytokine response, stimulation of growth and differentiation of the endometrium to allow for implantation, inhibition of myometrial contractions, and induction of immune tolerance to the fetus, reducing the rejection to the trophoblast cell, and finally protecting the embryo. However, the exact mechanisms by which progesterone induces immune tolerance are not well characterized. It was reported that the progesterone can up-regulate the expression of HLA-G gene. On the basis of this finding, it was boldly hypothesized that the mechanism of progesterone inducing immune tolerance might be through modulation of the gene expression of placental non-classical class I antigen.To evaluate the hypothesis, we studied the effects of progesterone on non-classical class I antigen gene expression in cultured isolated first trimester extravillous cytotrophoblasts by RT-PCR. It will be further assessed that the function and mechanism of non-classical class I antigens and progesterone involve in the maintenance of immune tolerance.PartⅠExpression of human leucocyte antigen E in human normal and pathological pregnancyExperiment One Expression of human leucocyte antigen E in human normal and hypertensive disorder complicating pregnancyObjective To investigate the expression and significance of human leucocyte antigen E (HLA-E) protein in normal and hypertensive disorder complicating pregnancy. Methods Six subjects were recruited in this study, who were in normal first-, second- or third- trimester pregnancy, or suffered from hypertensive disorder complicating pregnancy, respectively. Immunohistochemistry method was applied to detect the different expression of HLA-E protein in villi and decidua in each case.Results At each stage of normal pregnancy, HLA-E was found weakly expressed in all kinds of trophoblasts, including cytotrophoblast and syncytotrophoblast. In decidua, it was mainly expressed in the extravillous trophoblast invading the decidua and glandular epithelium. Moreover, its expression increased from the second trimester to full term. However, its expression was obviously decreased in both placenta and decidua tissues from hypertensive disorder complicating pregnant women in contrast to normal pregnant women.Conclusion In the first trimester, the expression of HLA-E might involve in embryo implantation. The enhancement of its expression from the second trimester to full term might play a role in sustaining pregnancy. The low expression of HLA-E protein might participate in the process of hypertensive disorder complicating pregnancy.Experiment Two Expression and significance of HLA-E protein in hydatidiform mole, invasive hydatidiform mole and choriocarcinoma Objective To investigate the expression and significance of the human leucocyte antigen protein E (HLA-E) in hydatidiform mole, invasive hydatidiform mole and choriocarcinoma tissues.Methods Immunohistochemical method was applied to detect the expressions of HLA-E protein in early villus, hydatidiform mole, invasive hydatidiform mole and choriocarcinoma tissues.Results In early villus, HLA-E protein mainly expressed in trophoblastic cells of external villus. The expression of HLA-E protein increased gradiently in the order of normal villus, hydatidiform mole, invasive hydatidiform mole and choriocarcinoma, and the differences among them were statistically significant (P<0.001).Conclusion The expression of HLA-E protein may relate to the invasiveness of trophoblast and malignant changes of trophoblastic cells. PartⅡThe regulating effect of progesterone on the transcription of the non-classical human leukocyte antigenExperiment One Isolation, purification and primary culture of the EVCTs from human first trimester chorionic villiObjective To establish a simple,convenient and practical method in terms of isolation, purification and primary culture of human EVCTs from human first trimerster chorionic villi.Methods The human first trimerster chorionic villis were obtained and digested with trypsin, purified by lymphocyte separating solution. Electron microscopy was used to reveale the morphology characteristics of the EVCTs, and the purity of these cells were identified by immunohistochemical staining.Results The proportion of the positive cells could reach at 90%. Moreover, they specifically exhibited positive staining for HLA-G.Conclusion This convenient and economical method can be successfully used to isolate the pure extravillous cytotrophoblasts.Experiment Two The regulation effect of progesterone on transcription of the non-classical human leukocyte antigenObjective To explore the potential effects of progesterone on the gene expression of HLA-G,-E and -F.Methods Cultured first trimester EVCTs were treated with progesterone and its antagonist mifepristone. The transcription levels of HLA-G,-E and -F genes were detected by RT-PCR.Results HLA-G,-E,-F mRNA in extravillous cytotrophoblasts were significantly elevated by incubation of 100ng/ml progesteron(eP<0.05). The effect of progesterone can be completely inhibited by co-incubation with mifepristone at the same concentrations.Conclusion Progesterone has an up-regulatory effect on HLA-G,-E,-F gene expression in first trimester trophoblasts in vitro.