Natural killer (NK) cells are present in large populations at the maternal-fetal interface during early pregnancy. However, the role of NK cells in fetal growth is unclear. Here, we have identified a CD49aEomes subset of NK cells that secreted growth-promoting factors (GPFs), including pleiotrophin and osteoglycin, in both humans and mice. The crosstalk between HLA-G and ILT2 served as a stimulus for GPF-secreting function of this NK cell subset. Decreases in this GPF-secreting NK cell subset impaired fetal development, resulting in fetal growth restriction. The transcription factor Nfil3, but not T-bet, affected the function and the number of this decidual NK cell subset. Adoptive transfer of induced CD49aEomes NK cells reversed impaired fetal growth and rebuilt an appropriate local microenvironment. These findings reveal properties of NK cells in promoting fetal growth. In addition, this research proposes approaches for therapeutic administration of NK cells in order to reverse restricted nourishments within the uterine microenvironment during early pregnancy.

Natural killer (NK) cells accumulate at the maternal-fetal interface in large numbers, but their exact roles in successful pregnancy remain poorly defined. Here, we provide evidence that T H 17 cells and local inflammation can occur at the maternal-fetal interface during natural allogenic pregnancies. We found that decidual NK cells promote immune tolerance and successful pregnancy by dampening inflammatory T H 17 cells via IFN-γ secreted by the CD56 bright CD27 + NK subset. This NK-cell-mediated regulatory response is lost in patients who experience recurrent spontaneous abortions, which results in a prominent T H 17 response and extensive local inflammation. This local inflammatory response further affects the regulatory function of NK cells, leading to the eventual loss of maternal-fetal tolerance. Thus, our data identify NK cells as key regulatory cells at the maternal-fetal interface by suppressing T H 17-mediated local inflammation.regulatory NK cells | fetomaternal tolerance D uring pregnancy, allogeneic fetal cells invade the maternal decidua but they are protected from the maternal immune system. This invasion of extraembryonic trophoblasts does not harm gestation during normal pregnancy; it establishes tolerance at the maternal-fetal interface (1), (2), although the mechanism of such tolerance is not clear. In addition, inflammatory responses induced by a variety of mechanisms can result in embryo loss, but mild inflammation can be effectively controlled through regulatory mechanisms to maintain successful pregnancy (3). Thus, suppression of strong inflammatory responses is essential to ensure normal pregnancy (4, 5), although the mechanisms involved in regulating local inflammation without compromising overall maternal immunity during a successful pregnancy remain unknown.Multiple mechanisms are potentially involved in promoting immune tolerance during pregnancy. For example, T H 2 cytokine polarization (6-9), the expression of the Fas ligand on trophoblast cells (10), and the inhibition of complement activation (11) are crucial for ensuring tolerance at the maternal-fetal interface. In addition, a delicate balance exists between inhibitory (PD-L1, Stat3, and TGF-β1) and stimulatory (CD80 and CD86) signals during the establishment of immune privilege (12-18). Furthermore, studies have shown that galectin-1 (19) and indoleamine 2,3-dioxygenase (20) play pivotal roles in maternal-fetal tolerance. Several types of immune cells, such as CD4 + CD25 + regulatory T cells, are also essential in the generation of maternal-fetal tolerance in mice and humans (7,(21)(22)(23)(24). Furthermore, natural killer (NK) T cells and immature dendritic cells have been reported to promote the expansion of Treg cells that confer protection of the fetus (19).Despite considerable progress, many questions remain unanswered. The most striking feature at the maternal-fetal interface is the accumulation of NK cells, which account for ∼60-90% of immune cells in the decidua in humans during early pregnancy (25)(26)(27)(28)(29) and a...

Human Th17 cells may play a major role in rejecting conceptus antigens and therefore may be harmful to the maintenance of pregnancy. The data also suggest that Treg cells are beneficial to pregnancy. There may exist a balance of Th17/Treg in normal pregnancy.

Maintaining homeostasis of the decidual immune microenvironment at the maternal–fetal interface is essential for placentation and reproductive success. Although distinct decidual immune cell subpopulations have been identified under normal conditions, systematic understanding of the spectrum and heterogeneity of leukocytes under recurrent miscarriage in human deciduas remains unclear. To address this, we profiled the respective transcriptomes of 18,646 primary human decidual immune cells isolated from patients with recurrent pregnancy loss (RPL) and healthy controls at single-cell resolution. We discovered dramatic differential distributions of immune cell subsets in RPL patients compared with the normal decidual immune microenvironment. Furthermore, we found a subset of decidual natural killer (NK) cells that support embryo growth were diminished in proportion due to abnormal NK cell development in RPL patients. We also elucidated the altered cellular interactions between the decidual immune cell subsets in the microenvironment and those of the immune cells with stromal cells and extravillous trophoblast under disease state. These results provided deeper insights into the RPL decidual immune microenvironment disorder that are potentially applicable to improve the diagnosis and therapeutics of this disease.

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Endometriosis, a pathological condition in which the endometrium grows outside the uterus, is one of the most common causes of female infertility; it is diagnosed in 25–40% of infertile women. The mechanism by which endometriosis affects the fertility of females remains largely unknown. We examined the ultrastructure of oocytes from patients with minimal or mild endometriosis and control females undergoing in vitro fertilization (IVF) treatment by transmission electron microscopy (TEM) to investigate the physiological significance of oocyte quality for patients with minimal or mild endometriosis. The TEM results revealed that the oocytes from women with minimal or mild endometriosis exhibited abnormal mitochondrial structure and decreased mitochondria mass. Quantitative real time PCR analysis revealed that the mitochondrial DNA copy number was significantly reduced in the oocytes from women with minimal or mild endometriosis compared with those of the control subjects. Our results suggest that decreased oocyte quality because of impaired mitochondrial structure and functions probably an important factor affecting the fertility of endometriosis patients.

Abundant decidual natural killer (dNK) cells at the maternal-fetal interface are important during early pregnancy. However, functional subsets of dNK cells remain poorly understood. We describe a CD49a+PBX homeobox 1 (PBX1)+ dNK cell subset that promotes fetal development in humans and mice. The expression of PBX1 in dNK cells is up-regulated via the activated AKT1 pathway through the interaction of major histocompatibility complex G with the immunoglobulin-like transcript 2 receptor. PBX1 drives pleiotrophin and osteoglycin transcription in dNK cells, further promoting fetal development. Decreased PBX1 expression or the PBX1G21S mutant correlated with fetal growth restriction and pregnancy failure in patients with unexplained recurrent spontaneous abortion (URSA). Inactivation of Pbx1 in mouse dNK cells impairs fetal development by decreasing growth-promoting factors from CD49a+PBX1+ dNK cells. Impairment of PBX1 in dNK cells has positive correlation with URSA pathogenesis and may provide a potential marker for this condition.

BackgroundAnti-nuclear antibodies (ANA) are suspected of having relevance to adverse reproductive events.MethodsThis study aims to investigate the potential effect of ANA on IVF/ICSI outcome and the therapeutic role of prednisone plus low-dose aspirin (P + A) adjuvant treatment in ANA + patients. The first IVF/ICSI cycles without P + A of sixty-six ANA + women were enrolled as the ANA + group, and the 233 first IVF/ICSI cycles of matched ANA- women served as the ANA- group. The ANA + group was divided into the Titre < =1:320 subgroup and the Titre > 1:320 subgroup. Twenty-one ANA + women with adverse outcomes in their first cycles (ANA + cycles without P + A) received P + A adjuvant treatment for three months before the second IVF/ICSI cycle (ANA + cycles with P + A). The clinical characteristics and the IVF/ICSI outcomes were compared, respectively, between 1) the ANA + group and the ANA- group, 2) the Titre < =1:320 subgroup and the Titre > 1:320 subgroup, and 3) the ANA + cycles without P + A and the ANA + cycles with P + A.ResultsNo significant differences were observed between each of the two-group pairs in the clinical characteristics. The ANA + group exhibited significantly lower MII oocytes rate, normal fertilisation, pregnancy and implantation rates, as well as remarkably higher abnormal fertilisation and early miscarriage rates. The Titre < =1:320 subgroup’s IVF/ICSI outcomes were as poor as those of the Titre > 1:320 subgroup. After the P + A adjuvant treatment, the number of two pro-nuclei, perfect embryos and available embryos, and the implantation rate increased significantly.ConclusionsThese observations suggest that ANA could exert a detrimental effect on IVF/ICSI outcome that might not be titre-dependent, and P + A adjuvant treatment could be useful for ANA + patients. This hypothesis should be verified in further prospective randomised studies.