The evaluation of the endogenous melatonin impact on regulatory T cells functional activity during pregnancy

Regulatory T lymphocytes (Treg) play an important role in the physiological course of pregnancy providing the formation of peripheral tolerance. The paper presents data of the ability of the epiphyseal hormone melatonin to regulate the differentiation of this T cell subpopulation during gestation. The subjects of the study were leukocytes of women in I and Ш trimester of pregnancy as well as leukocytes of healthy non-pregnant women of reproductive age. The level and activity of Treg were evaluated ex vivo and in vitro in response to polyclonal activation (anti-CD3/CD28) by expression of the differentiation marker of the Treg - transcription factor FoxP3 by flow cytometry and by the production of the key cytokine of these cells - TGFp by ELISA. The contribution of endogenous melatonin in the regulation of Treg was determined by cultivation of lymphocytes in the presence of autologous serum against the background of blockade of melatonin-dependent signals using the inhibitor of membrane melatonin receptors (MT1 / MT2). It was shown that the differentiation process was differently regulated by endogenous melatonin in pregnant and non-pregnant women. An increase of the percentage of CD4+FoxP3+ T cells was observed only in non-pregnant cells under the polyclonal activation (anti-CD3/CD28), and this increase did not cancel by the blockade of melatonin-dependent signals. In pregnant women Treg differentiation depended on MT1/MT2-mediated signals.