Effects of estrogen on CD4(+) CD25(+) regulatory T cell in peripheral blood during pregnancy.

Objective: To investigate the effects of estrogen (E2) level on regulatory T cells (Treg) in peripheral blood during pregnancy.

Methods: A total of 30 healthy non-pregnant women were selected as control group, 90 pregnant women of early, middle and late pregnancy and 30 postpartum women at 1 month after parturition were selected as experimental groups including early pregnancy group, middle pregnancy group and late pregnancy group; the proportions of CD4(+)CD25(+) Treg and CD4(+)CD25(+)CD127(-) Treg among CD4(+)T cells were detected by flow cytometry; the serum estrogen content in peripheral blood was detected by electrochemical immune luminescence method.

Results: E2 level was coincident with the change of Tregs number during pregnancy. The estrogen content in peripheral blood increased gradually from early pregnancy to late pregnancy, then decreased significantly after parturition, and the level at 1 month after parturition down to the level in non- pregnancy group (P>0.05); the level of E2 in pregnancy groups were significantly higher than those in non- pregnancy group (P<0.01); and there were significant differences among early pregnancy group, middle pregnancy group and late pregnancy group (P<0.05). The proportions of CD4(+) CD25(+) Treg and CD4(+) CD25(+) CD127(-) Treg in pregnancy groups were significantly higher than those in non- pregnancy group (P<0.05), but decreased significantly after parturition, and there was no significant difference between non- pregnancy group and postpartum women group (P>0.05); the proportions in middle and late pregnancy groups were significantly higher than those in early pregnancy group (P<0.05), but decreased slightly in late pregnancy group, there was no significant difference between late pregnancy group and middle pregnancy group (P>0.05). There was correlation between Tregs number with estrogen level during pregnancy. The proportion of CD4(+) CD25(+) Treg and CD4(+) CD25(+) CD127(-) Treg were positively correlated with estrogen level.

Conclusions: High proportion of CD4(+) CD25(+) Treg and CD4(+)CD25(+)CD127(-) Treg is closely related to the high level of E2 during pregnancy. It suggested that high level of estrogen may induce an increase of CD4(+) CD25(+) Treg in peripheral blood, and then influence the immune function of pregnant women. The results of this experiment might play an important role of estrogen in immune-modulation during pregnancy.