Regulatory T cells (Tregs) are essential in tolerizing the maternal immune system toward the semi-allogeneic embryo. In this systematic review, we evaluated the association of levels and function of Tregs in peripheral blood and decidua with recurrent miscarriage (RM), defined as two unexplained miscarriages. We included 18 studies. Ten studies showed a significantly decreased level of Tregs in peripheral blood of non-pregnant women with RM, compared to controls (p < 0.05). In pregnant women with RM, levels of Tregs in the peripheral blood were significantly lower compared to control groups (p = 0.0004), as shown in nine studies. Moreover, seven studies described a decrease of Treg levels in the placenta of pregnant women with RM (p < 0.0001) compared to controls. Accordingly, the median of the relative changes (MRC) between cases and controls in the non-pregnant group (peripheral blood), and the two pregnant groups (peripheral blood and decidua) were -0.18 (-0.27-0), -0.26 (-0.35 to -0.17), and -0.52 (0.63--0.31), respectively. In addition to the assessment of Tregs by phenotype, six out of the 18 included studies investigated the functionality of these cells. These studies showed a lower inhibitory effect of Tregs cells on the proliferation of effector T cells of women with RM compared to fertile women. Also, the expression of IL-10 and TGF-beta was diminished. This systematic review shows that Treg levels and their function are significantly decreased in peripheral blood and decidua of pregnant and non-pregnant women with RM. This underlines the hypothesis that Tregs play a role in the pathogenesis of RM.

中文翻译：

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反复流产和与调节性 T 细胞的关联；系统评价。

调节性 T 细胞 (Tregs) 在使母体免疫系统耐受半同种异体胚胎方面至关重要。在本系统评价中，我们评估了外周血和蜕膜中 Tregs 的水平和功能与复发性流产 (RM) 的关联，RM 定义为两次不明原因的流产。我们纳入了 18 项研究。十项研究表明，与对照组相比，患有 RM 的非孕妇外周血中 Tregs 水平显着降低（p < 0.05）。九项研究表明，在患有 RM 的孕妇中，外周血中 Treg 的水平显着低于对照组（p = 0.0004）。此外，七项研究描述了与对照组相比，RM (p < 0.0001) 孕妇胎盘中 Treg 水平的降低。因此，非妊娠组（外周血）和两个妊娠组（外周血和蜕膜）的病例与对照组的相对变化（MRC）中位数分别为-0.18（-0.27-0）、-0.26（-0.35）到 -0.17) 和 -0.52 (0.63--0.31)，分别。除了通过表型评估 Treg 外，18 项研究中有 6 项研究了这些细胞的功能。这些研究表明，与可育女性相比，Tregs 细胞对 RM 女性效应 T 细胞增殖的抑制作用较低。此外，IL-10 和 TGF-β 的表达也减少了。该系统评价表明，患有 RM 的孕妇和非孕妇的外周血和蜕膜中的 Treg 水平及其功能显着降低。这强调了 Tregs 在 RM 发病机制中发挥作用的假设。