Phenotypic characterization of regulatory T cells in the human decidua

Abstract

Pregnancy is a unique situation for the maternal immune system. We have studied and identified a CD4+CD25+ regulatory T (Treg) cell population isolated from the human decidua. This mucosal surface in the uterus is in direct contact with semiallogenic fetal cells. We observed that about 14% of the decidual CD4+ T cells have the CD4+CD25+ phenotype. The decidual CD4+CD25+ T cells expressed high frequency of intracellular CTLA-4 (CTLA-4i). The majority of CD4+CD25+CTLA-4i+ cells were also positive for GITR and OX40, typical markers for human Treg cells. The frequency of CD4+CD25+ T cells in the peripheral blood from pregnant women was found to be increased during the first and second trimester of gestation when compared to nonpregnant controls. Being an important molecule for Treg cells, the role of CTLA-4 in the regulation of indoleamine 2,3-dioxygenase (IDO) expression was also examined. The stimulation with CTLA-4Ig did not increase IDO mRNA expression in CD14+ cells from pregnant women, while IFN-gamma was observed to up-regulate IDO expression. The presence of Treg cells in the human decidua suggests that these cells are important in protecting the fetus from alloreactive immune responses at the maternal-fetal interface.

Fig. 1

Mononuclear cells isolated from term human decidua. Decidual CD4+CD25+ cells were gated and the cell surface and intracellular expression of CTLA-4 was analysed using four-colour staining. GITR and OX40 expression is shown in the decidual Treg cells expressing CD4+CD25+ and intracellular CTLA-4. Representative FACS results are shown from seven individual experiments.

Fig. 2

Frequency of CD4+CD25+ cells is increased in PB CD4+ population from pregnant women during first and second trimester compared to nonpregnant controls. The frequency of PB CD4+CD25+ cells during first trimester is increased also when compared to second and third trimester PB samples. Mean values are shown as bars **P < 0·01, *P < 0·05). PB samples from pregnant women were obtained during the first, second and third trimester of pregnancy.

Fig. 3

The production of IL-10 in PB CD14+ cells from pregnant women after stimulation with CTLA-4Ig or IFN-γ. Cells were cultured for 24 h with CTLA-4Ig (10 µg/ml) or IFN-γ. After the culture concentrations of IL-10 was measured using ELISA. Four individual experiments are shown.