Abstract
Aim To investigate the changes in the maternal immune system at term pregnancy, we studied the expression of natural cytotoxicity receptors (NCRs) and the cytokine production of NK cells in term placenta decidua and peripheral blood. Methods Term decidua and peripheral blood were taken from patients undergoing elective cesarean section. The lymphocytes were separated using density gradient centrifugation (DGC) from peripheral blood and were separated from decidua using DGC after enzyme digestion. These cells were stained with FITC anti-CD56 and Per-CP anti-CD3 monoclonal antibodies, and the NCRs were stained with PE-conjugated anti-NKG2D, NKp46, NKp30, and NKp44 monoclonal antibodies. Cytokines, including IFN-γ, TNF-α, IL-10, and TGF-β, were stained and then analyzed by flow cytometry. Results There were fewer cells positive for NKG2D, NKp46, and NKp30 among CD56+CD3- cells in deciduas than in peripheral blood, but the percentages of NKp44-positive cells in CD56+CD3- lymphocytes in deciduas tended to be higher. Conclusion The decreased expression of some NCRs in deciduas may be related to decreased cytotoxicity at term pregnancy, but the increased expression of NKp44 may affect the increased cytokine production in the decidua. Similarly, the expression of NCRs in the decidua may be connected to the maintenance of pregnancy at term.
Highlights
In successful pregnancy, there are many mechanisms by which the fetus avoids rejection by the maternal immune system [1]
It has been reported that the cytotoxic activity of natural killer (NK) cell is depressed during pregnancy and that the suppression of cytotoxicity is multifactorial and may include both cellular and humoral elements [2]
To investigate the changes in the immune system in term normal pregnancy, we first analyzed the subtypes of NK cells in peripheral blood and decidua during normal pregnancy; we analyzed the expression of natural cytotoxicity receptors (NCRs) on the CD56+CD3- NK cell; and, we evaluated cytokine production in the peripheral blood and decidua in term pregnancy
Summary
There are many mechanisms by which the fetus avoids rejection by the maternal immune system [1]. It has been reported that the cytotoxic activity of natural killer (NK) cell is depressed during pregnancy and that the suppression of cytotoxicity is multifactorial and may include both cellular and humoral elements [2]. Uterine decidual cells have depressed NK cytotoxicity [3,4,5]. It has been reported that the killer inhibitory receptors (KIR) in uterine NK cells play a role in maintaining a normal pregnancy. HLA-G, as one of the HLA class I antigens, is expressed in extravillous trophoblasts, and NK cytotoxicity is suppressed by stimulation of KIR by HLA-G [6]. The elements of suppressed cytotoxicity have not been evaluated well
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