The Study Of Biological Characteristic Of NK Cells And NK Cells Before And After The Onset Of Normal Labour

Background:In normal pregnancy, there were immunotolerance between mother's immune system with paternal fetal , though many factors play a part in it. Recent years, many study display that NK cells and NKT cells play an impotant roles in fetal-maternal interface, they produce large amounts of both Th1 and Th2 cytokines, and regulate immune responses by modulating T helper type 1/type 2 (Th1/Th2) balance. In pregnancy, hemiallogeneic fetal spared from attack by the maternal immune system. There were Th2-dominance by different mechanisms constitute a distinct immunologic microenvironment inside maternal-fetal interface to maintenance successful pregnancy. Recent study has concentrated on the role of immune balance with some disease of pregnancy(include recurrent spontaneous abortion, intrahepatic cholestasis of pregnancy, gestational hypertension, the onset of labour, et al) , and suggested that innate immune system including NK cells and NKT cells might play an important role in pregnancy progression. The mechanisms of onset of human parturition are very complicated, despite important advances in our understanding of the mechanism of human parturition, more study were concentrate on histology and immunology. Recent research on maternal-fetal interface has been proposed,the main content is composed of maternal uterus deciduas and fetal trophoblast,γδT cells,NK cells,NKT cells,CTL and secreted cytokine are composed of special immunological microenvironment on at the maternal-fetal interface , which is crucial for embryo implantation,gestational maintenance,disease of pregnancy and the onset of labour.Recent research on maternal-fetal interface has been proposed,the main content is composed of maternal uterus deciduas and fetal trophoblast,all kinds of cells and secreted cytokine are composed of special immunological microenvironment on at the maternal-fetal interface, which is crucial for embryo implantation and gestational maintenance. Decidual NK cells begin to increase from secretary phase,which peaks in early pregnancy when dNK cells comprise about 70% of resident lymphocytes and tightly touch with the invading trophoblasts. With the development of human pregnancy, the percentage of dNK cells then fall off. Recent study also proposed, the NKT cells also enrich in maternal-fetal interface, there were many TCRαβ+CDl61+ NKT cells(II NKT cells,non-iNKT cell)in human decidual and play an important role on generate Th2 bias.To further shed light on the immunological mechanisms of onset of labour, we focus our attention on local immune reactions at the maternal-fetal interface and system immunity reactions before and after onset of labour in normal late preganacy. We study the percentage and the phenotype natural killer cells/ natural T killer cells in the deciduas and peripheral blood, the change of Th1/Th2 cytokine levels of peripheral blood mononudear cells before and after onset of labour, to futher investigate the change of Th1/Th2 cytokine levels in peripheral blood NK cells and NKT cells, so that we can investigate whether the change of biological characteristic of NK cells and NKT cells play an important role in the onset of labour. Undoubtedly, elucidation of immunologic microenvironment at maternal-fetal interface with the onset of labour must be an original pathway to investigate the mechanism of delivery.Objective:To detect the change of NK cells and NKT cells in decidual and peripheral blood,to compare the percentage,phenotype,Th1/Th2 cytokine secretion between normal late pregnant women undergoing elective caesarean sections before the onset of labour (caesarean group, 34 cases) or after normal vaginal delivery (delivery group, 32 cases),which Can help us to further discover the importance of NK cells,NKT cells and immunotolerance local immune reactions at the maternal-fetal interface before and after the onset of normal labour.Methods:1) Decidual tissue and peripheral blood were collected from healthy women undergoing elective caesarean sections before the onset of labour (caesarean group, 34 cases) or after normal vaginal delivery (delivery group, 32 cases), PBMC were centrifugated using a standard gradient sedimentation technique cell suspensions were prepared by an electromechanical dispersal method and centrifugated using a standard gradient sedimentation technique. Mononuclear cells were analysed for contents of NK cells,NKT cells and NKG2A/NKG2D expression with flow cytometry analysis.2) Flow cytometry was used to detect the expression of intracellular Th1,Th2 ctyokines IFN-γand IL-4 in NK cells,NKT cells and CD3+ cells of peripheral blood.3) The method of RT-PCR was used to detect the mRNA expression of CXCR4 in placenta tissue and decidual tissue.Results:1) The contents of NK cells and NKT cells in decidual were significantly higher in cases of elective cesarean section than in cases of vaginal delivery, while the contents of NK cells and NKT cells in peripheral blood were significantly lower in cases of elective cesarean section than in cases of vaginal delivery. The contents of NK cells and NKT cells are higher in decidual in both groups.2) Compared with cesarean groups, the proportion of CD56+NKG2A+ cells,CD56+NKG2D+ cells,the expression of NKG2A/NKG2D of NK cells in decidual were lower in cases of vaginal delivery, whereas the expression of NKG2A/NKG2D of NKT cells is no significant deviation in two groups .3) In peripheral blood, compared with cesarean groups, the proportion of CD56+NKG2A+ cells,the expression of NKG2A of NK cells is lower but the proportion of CD56+NKG2D+ cells,the expression of NKG2D of NK cells and NKG2A/NKG2D of NKT cells were higher in delivery group.4) The contents of Th1 cells in peripheral blood is higher in cases of vaginal delivery, the difference is significantly. The expression of intracellular Th1/Th2 cytokines IFN-γand IL-4 were significantly high in NK cells and NKT cells in cases of vaginal delivery.IFN-γand IL-4 are the most important cytokines in regulating Th1/Th2 immunological balance,suitable quantity of which play an important role in regulating immunological balance at fetal-maternal interface.5) Decidual and placentas tissue had high expression of CXCR4, which may contact with transmigration of NK cells and NKT cells in cesarean group.Conclusions:NK cells and NKT cells in decidual and peripheral blood are the important natural lymphocytes,whose percentage,phenotype,Th1/Th2 cytokine secretion are obviously different before and after the onset of labour,NK cells and NKT cells propotion is higher in peripheral blood after the onset of labour. There were Th1-dominance by different mechanisms constitute a distinct immunologic microenvironment inside maternal-fetal interface contact with the onset of labour. From the above results,we conclude that redistribution of NK cells and NKT cells include the receptor expression,biological effect play all important role in regulating immunological tolerance at fetal-maternal interface and system immunity, and induction delivery.