Peripheral Dendritic Cells and CD4+CD25+Foxp3+ Regulatory T Cells in the First Trimester of Normal Pregnancy and in Women with Recurrent Miscarriage

Abstract

The development of pregnancy is possible due to initiation of immune response in the body of the mother resulting in immune tolerance. Miscarriage may be caused by the impaired maternal immune response to paternal alloantigens located on the surface of trophoblast and fetal cells. The aim of the study was to compare the population of circulating dendritic cells (DCs) and CD4+CD25+Foxp3+ regulatory T cells (TREGs) in the first trimester of a normal pregnancy and in women with recurrent miscarriage and an attempt to determine the relationship between these cells and the role they may play in human reproductive failures. The study was conducted in a group of 33 first trimester pregnant women with recurrent miscarriage and in a group of 20 healthy pregnant women in the first trimester of normal pregnancy. Among mononuclear cells isolated from peripheral blood, the populations of DCs and TREGs were assessed by flow cytometry. The percentage of myeloid DCs and lymphoid DCs showed no significant difference between study and control group. Older maternal age and obesity significantly reduced the pool of circulating myeloid and lymphoid DCs (R=-0.39, p=0.02). In miscarriages the percentage of circulating TREGs was significantly lower compared to normal pregnancies (p=0.003). Among the analysed factors the percentage of TREGs was the most sensitive and the most specific parameter which correlated with the pregnancy loss. The reduction in the population of circulating TREGs suggests immunoregulatory mechanisms disorder in a pregnancy complicated by miscarriage.

Fig 1. Cytometric analysis of myeloid and plasmocytoid dendritic cells among peripheral mononuclear cells in a woman with miscarriage.

The percentage of DCs was assumed among mononuclear cells of the section R1 (Fig 1A). Section R1 was based on FSC and SSC. BDCA-1+CD19- cells from section R2 were rated as circulating mDCs (Fig 1B). BDCA-2+CD123+ cells were rated as circulating pDCs (Fig 1C).

Fig 2. Cytometric analysis of peripheral blood T regulatory cells (CD4+CD25+Foxp3+) of a patient at the 10th week of normal pregnancy.

The evaluation of TREGS percentage was conducted among CD4+ cells in P1 population (Fig 2A). Fig 2B-C show negative controls of the sample. Fig 2D-E show the helper cells (CD4+) expressing CD25 antigen (Fig 2D) and Foxp3 antigen (Fig 2E). Fig 2F shows the population of TREGs cells (CD4+ CD25+ Foxp3+) in the test sample.

Fig 3. Evaluation of mDCs percentage in groups.

Fig 4. Evaluation of pDCs percentage in groups.

Fig 5. Evaluation of TREGs percentage in groups.

Fig 6. Correlation between maternal age and the percentage of mDCs, pDCs and TREGs in patients with miscarriage.

Fig 7. Correlation between body weight (kilograms) and the percentage of mDCs, pDCs, TREGs and mDC/pDC ratio in the study and control group.

Fig 8. ROC curves for risk factors of miscarriage incidence.