The Fluctuation of Regulatory T Cells during Pregnancy and Obstetrical Complications

Abstract

Background: Regulatory T cells (Tregs) are critical immunomodulators during pregnancy by preventing maternal T-cell activation against fetal cells. However, how characteristics of maternal Tregs vary during pregnancy is still unclear. We analyzed the proportion and phenotypic characteristics of peripheral blood Tregs in normal pregnant women, women with recurrent pregnancy loss (RPL) or gestational diabetes mellitus (GDM), and non-pregnant women.Methods: We investigated the proportion of CD4+ Tregs, CD8+ Tregs and the expression of PD-1, GITR, HLA-G and CTLA-4 on them in the peripheral blood of normal pregnancies during 1st (n = 28), 2nd (n = 43), and 3rd trimester (n = 33); In addition, we evaluated pregnancies in the 1st trimester complicated by RPL (n = 21), in the 2nd (n = 17) and 3rd trimester (n = 28) complicated by GDM. Non-pregnant women (n = 57) were also investigated using flow cytometry.Results: During normal pregnancy, the proportion of CD4+ Tregs in all trimester and CD8+ Tregs in 2nd and 3rd trimester were higher(P ＜ 0.05，respectively) compared with non-pregnancy women. Moreover, the proportion of CD4+ Tregs was higher in 2nd trimester compared to 1st and 3rd trimester (P ＜ 0.01) while the proportion of CD8+ Tregs was higher in 3rd trimester compared to 1st and 2nd trimester (P ＜ 0.05). Compared to non-pregnant studies, the proportion of GITR+/CD8+ Tregs and HLA-G+/CD8+ Tregs in all trimester were higher(P ＜ 0.05, respectively). Moreover, the proportion of PD-1+/CD4+ Tregs, GITR+/CD4+ Tregs, PD-1+/CD8+ Tregs and CTLA-4+/CD8+ Tregs in 3rd trimester were significantly higher compared to 1st, 2nd trimester and non-pregnant group(P ＜ 0.05, respectively).In RPL and GDM groups, the proportions of CD4+ Tregs in all trimesters were decreased while the proportions of CD8+ Tregs in all trimesters were increased compared to normal pregnant group (P ＜ 0.05，respectively).In RPL group, the proportion of PD-1+/CD4+ Tregs, GITR+/CD4+ Tregs and HLA-G+/CD4+ Tregs were decreased compared to 1st trimester normal pregnant group (P ＜ 0.05，respectively). In 2nd trimester GDM group, the proportion of HLA-G+/CD4+ Tregs were decreased compared to 2nd trimester normal pregnant group (P ＜ 0.05，respectively). In 3rd trimester GDM group, the proportion of PD-1+/CD4+ Tregs, GITR+/CD4+ Tregs, PD-1+/CD8+ Tregs, GITR+/CD8+ Tregs and HLA-G+/CD8+Tregs were decreased compared to 3rd trimester normal pregnant group (P ＜ 0.05, respectively).Conclusions: The proportion of CD4+ Tregs and CD8+ Tregs increased during pregnancy, the proportions and subsets of CD4+ Tregs decreased and those of CD8+ Tregs increased in pregnancies complicated by RPL and GDM, indicating that regulatory T cells play a role in pregnancy maintenance, and the abnormal expression of Tregs might be related to the complicated pregnancy.