Systemic reduction of functionally suppressive CD4dimCD25highFoxp3+ T-regs in human second trimester pregnancy is induced by progesterone and 17 beta-estradiol

• CD4+CD25high regulatory T cells (Tregs) are implicated in maintenance of murine pregnancy. However, reports regarding circulating Treg frequencies in human pregnancy are inconsistent and the functionality and phenotype of these cells in pregnancy have not been clarified. The aim was to determine the frequency, phenotype and function of circulating Tregs in second trimester human pregnancy and the influence of progesterone and 17β-estradiol on Treg phenotype and frequency. Based on expression of Foxp3, CD127 and HLA-DR, as determined by multi-color flow cytometry, we defined a proper CD4dimCD25high Treg population and showed, in contrast to most previous reports, that this population was reduced in second trimester pregnancy. Unexpectedly, Foxp3 expression was decreased in the Treg, as well as in the CD4+ population. These changes could be replicated in an in vitro system resembling the pregnancy hormonal milieu, where 17β-estradiol, and in particular progesterone, induced, in line with the pregnancy situation, a reduction of CD4dimCD25highFoxp3+ cells in PBMC from non-pregnant women. By co-culturing FACS-sorted Tregs and autologous CD4+CD25- responder cells, we showed that Tregs from pregnant women still displayed the same suppressive capacity as non-pregnant women in terms of suppressing IL-2, TNF-α and IFN-γ secretion from responder cells while efficiently producing IL-4 and IL-10. Our findings support the view of hormones, particularly progesterone, as critical regulators of Tregs in pregnancy. Further, we suggest that in the light of the results of this study, early data on circulating Treg frequencies in pregnancy need re-evaluation.

Nyckelord

MEDICINE

MEDICIN

Publikations- och innehållstyp

ref (ämneskategori)

kon (ämneskategori)