Membrane progesterone receptors in human regulatory T cells: a reality in pregnancy

Abstract

Objective - To provide evidence of the existence of membrane progesterone receptor alpha (mPRa) on regulatory T cells (Treg) in peripheral blood during pregnancy, postulating a possible explanation for the effect of progesterone on preterm birth. Design Cross-sectional study. Setting - Tertiary Obstetric Department in a University Hospital. Population - Healthy pregnant women. Methods - Treg cells from peripheral blood samples were studied by flow cytometry using multiple monoclonal antibody expression. Main outcome measures - Evaluate the number and percentage of CD4+CD25highCD127low, the number and percentage of Treg cells among the total CD4+ T cells, and the percentage and mean fluorescence intensity (MFI) of mPRa in that population, using several gating strategies. Results - 43 peripheral blood samples were collected from healthy women during pregnancy, whose median gestational age was 28.7 7.1 (16–40) weeks. The percentage of CD4+ in the total lymphocytes was 43% (32–51) and the percentage of CD4+CD25highCD127low was 4.8% (1.6–5.9), with only 45% (16–72) of those cells expressing the intracellular marker FoxP3 (Treg cell pool). We confirmed the existence of mPRa in that specific population because 8.0% (2.02–33) of the Treg cells were marked with the specific monoclonal antibody, with an mPRa+ MFI of 719 (590–1471). Conclusions - This research shows that Treg cells express mPRa during pregnancy, which might play an important role in immune modulation by progesterone.