Explore On The Role Of CD4～+CD25～+ Regulatory T Cell In The Maternal-Fetal Tolerance

[Objective] To investigate the shift of the percentage of CD4~+CD25~+ T_r cells at different stage of normal pregnancy, preeclampsia, unexplained recurrent spontaneous abortion (URSA) and in vitro fertilization and embryo transfer (IVF-ET) in peripheral blood of pregnant female or cord blood.To explore the role of CD4~+CD25~+ T_r cells in normal pregnancy.To investigate the expression of the signs of CD4~+CD25~+ T_r cells such as FoxP3, NRP-1 and other immune-related molecules (CXCR4/SDF-1, IDO, CTLA-4, HLA-G etc.) in placenta.To study the effects of estrogen on cell component in vitro mixed cell culture system.[Methods] To measure the shift percentage of CD4~+CD25~+ T cells in the peripheral blood of pregnant women or cord blood by fluorescence-activated cell sorter(FACS) lysis method. To examine the expression of immune-related molecues (FoxP3, NRP-1, IDO, CXCR4/SDF-1, CTLA-4, HLA-G) in placenta/villus by using in situ hybridization, immunohistochemistry, westernblot and RT-PCR or Real-time PCR respectively.Spleen cells from C57BL/6 mouse were stained with carboxyfiuorescein diacetate succinimidyl ester (CFDA-SE, CFSE), then pre-treated BALB/C mouse spleen cells were added, 17-β-dimenformon was added to the mixture, and cultured for other 24 hours. Flow cytometer was employed to analyze the shift of the percentage of CD4~+CD25~+ T_r cells. To detected the expression of FoxP3 mRNA of above mixture by real-time PCR.[Results] The percentage of CD4~+CD25~+ T_r cells of peripheral blood varied during pregnancy, increased in the first trimester, approached the most high level in the second trimester and lowest after labor, which was lower than that of non-pregnant women (P<0.05). The percentage for URSA and preeclampsia was lower than that of normal pregnancy in the same stage respectively (P<0.05). In IVF-ET cases, the percentage of CD4~+CD25~+ T_r cells of the successful cases was significantly higher than that of the failure cases.The expression of FoxP3, NRP-1, IDO, CTLA-4, HLA-G and CXCR4/SDF-1 was detected in placenta/villus. The expressions of these immune-related molecules were similar to that of CD4~+CD25~+ T_r cells.In vitro experiment indicated, in the mixed culture with estrogen, the percentage of CD4~+CD25~+ T_r cells increased, the expression of FoxP3 also increased.[Conclusion] CD4~+CD25~+ T_r cells may play important roles on the normal pregnancy and feto-matemal tolerance.The expression of immune-related molecules in placenta may mediate and contribute to the feto-matemal immune tolerance and normal pregnancy.Abnormal expression of these immune-related molecules in placenta and percentage of CD4~+CD25~+ T_r cells may have related to some abnormal pregnancy, such as URSA and preeclampsia.Estrogen increased the percentage of CD4~+CD25~+ T_r cells and enhanced the expression of FoxP3 in mixed culcure of lymphocytes. Therefore estrogen may maintain the feto-maternal tolerance by regulating the percentage of the CD4~+CD25~+ T_r cells and the expression of FoxP3.