Activation of Gonadotropin-releasing Hormone Receptor Impedes the Immunosuppressive Activity of Decidual Regulatory T Cells via Deactivating the Mechanistic Target of Rapamycin Signaling.

Understanding maternal immune tolerance is crucial for the development of therapeutics for immunological pregnancy complications. Decidual regulatory T cells (Tregs) play a pivotal role in the maintenance of maternal immune tolerance. Using a murine allogeneic pregnancy model in the current study, we identified the up-regulation of gonadotropin-releasing hormone receptor (GnRHR) in decidual T cell subsets including CD4+ conventional T cells, CD8+ T cells, and CD4+Foxp3+ Tregs. Using a lentivirus-mediated GnRHR overexpression system and a GnRHR agonist, we found that GnRHR activation decreased the expression of Treg functional molecules such as IL10 (IL-10), IL-35 subunit EBI3 (Ebi3), IL2RA (CD25), TNFRSF18 (GITR), ICOS, and Treg master regulator FOXP3. The functional analysis indicated that GnRHR activation impairs the ability of Tregs to inhibit conventional T cell proliferation. We also revealed that GnRHR activation suppressed the mechanistic target of rapamycin (mTOR) signaling in GnRHR-overexpressing splenic Tregs (Wild type C57BL/6 J background) and decidual Tregs. MHY1485, a potent mTOR activator, effectively abolished the effect of the GnRHR agonist and promoted the immunosuppressive capability of Tregs. Furthermore, in an adoptive transfer model, Treg-specific GnRHR knockdown increased Foxp3 expression in decidual Tregs while decreasing the production of IFN-γ and IL-17 in decidual effector CD4+ T cells and reducing the production of IFN-γ in decidual effector CD8+ T cells. Taken together, the present study unveils a novel mechanism by which the immunosuppressive function of decidual Tregs is modulated, and deepens our understanding of maternal immune tolerance.

Human placental exosomes induce maternal systemic immune tolerance by reprogramming circulating monocytes.

BACKGROUND: The maternal immune system needs to tolerate the semi-allogeneic fetus in pregnancy. The adaptation occurs locally at the maternal-fetal interface as well as systemically through the maternal circulation. Failure to tolerate the paternal antigens may result in pregnancy complications, such as pregnancy loss and pre-eclampsia. However, the mechanism that regulates maternal immune tolerance, especially at the systemic level, is still an enigma. Here we report that the first-trimester placenta-derived exosomes (pEXOs) contribute to maternal immune tolerance by reprogramming the circulating monocytes. RESULTS: pEXOs predominantly target monocytes and pEXO-educated monocytes exhibit an immunosuppressive phenotype as demonstrated by reduced expression of marker genes for monocyte activation, T-cell activation and antigen-process/presentation at the transcriptomic level. They also have a greater propensity towards M2 polarization when compared to the monocytes without pEXO treatment. The inclusion of pEXOs in a monocyte-T-cell coculture model significantly reduces proliferation of the T helper cells and cytotoxic T cells and elevates the expansion of regulatory T cells. By integrating the microRNAome of pEXO and the transcriptomes of pEXO-educated monocytes as well as various immune cell functional assays, we demonstrate that the pEXO-derived microRNA miR-29a-3p promotes the expression of programmed cell death ligand-1, a well-known surface receptor that suppresses the adaptive immune system, by down-regulation of phosphatase and tensin homolog in monocytes. CONCLUSIONS: This is the first report to show how human pEXO directly regulates monocyte functions and its molecular mechanism during early pregnancy. The results uncover the importance of pEXO in regulating the maternal systemic immune response during early pregnancy by reprogramming circulating monocytes. The study provides the basis for understanding the regulation of maternal immune tolerance to the fetal allograft.

Abortion in AhR-knockout mice and fetomaternal immunity.

AhR knockout mice are not completely infertile; however, they do experience decreased litter sizes after repeated pregnancies. This study revealed that the decrease in the number of live births is partly due to fetal deaths leading to miscarriages. Interestingly, fetal mortality was found to be linked only to maternal AhR gene defects and not the fetal genotype. Furthermore, we observed no significant changes in litter sizes in allogenic pregnancy, where AhR-KO female mice were crossed with ICR male mice. The results indicated that the absence of AhR in the dams affected the expression of immune tolerance-related genes in both the placenta and fetus. Specifically, FoxP3 and indoleamine 2,3-dioxygenase-1 (IDO1) mRNA levels were lower in the placentas of AhR-KO dams than in those of wild-type dams. Moreover, there were elevated levels of IL-1ß and IFN-γ mRNA in the placentas of the AhR-KO dams, which indicated increased inflammation. However, the mRNA expression levels of IL-6 and IDO1 were low despite the elevated mRNA levels of IL-1ß and IFN-γ, which may be because AhR is directly involved in IL-6 and IDO1 transcription. These findings imply that in AhR-KO mice, fetal death may be attributed to the disturbance of fetal-maternal immune tolerance as a result of increased inflammation and reduced IDO1 and FoxP3 mRNA levels.

The Protective Effect of Abortion on Preeclampsia: An Analysis of Current Research.

A review of the current literature on preeclampsia (PE) confirms that this pregnancy complication remains a common cause of maternal mortality. Within the last several decades, obstetric and gynecological researchers worldwide have indicated an association between prior abortions and the development of PE. Different studies have debated whether abortion is a protective or risk factor for PE. However, the most current literature demonstrates a stronger likelihood that a positive history of abortions will offer a protective effect against PE. This association has been supported by advancements in the reproductive immunology literature, which states complex fetal and paternal pathological mechanisms help to build maternal immunological tolerance, thus protecting expectant mothers from pregnancy complications. This literature review will compare studies supporting prior abortions offering a protective effect against PE with those stating prior abortions are a risk factor for the development of PE. Additionally, this critical review will discuss the advancements and current understanding of reproductive immunology and how it pertains to this association between positive abortion history and PE.

Establishment of the fetal-maternal interface: developmental events in human implantation and placentation.

Early pregnancy is a complex and well-orchestrated differentiation process that involves all the cellular elements of the fetal-maternal interface. Aberrant trophoblast-decidual interactions can lead to miscarriage and disorders that occur later in pregnancy, including preeclampsia, intrauterine fetal growth restriction, and preterm labor. A great deal of research on the regulation of implantation and placentation has been performed in a wide range of species. However, there is significant species variation regarding trophoblast differentiation as well as decidual-specific gene expression and regulation. Most of the relevant information has been obtained from studies using mouse models. A comprehensive understanding of the physiology and pathology of human implantation and placentation has only recently been obtained because of emerging advanced technologies. With the derivation of human trophoblast stem cells, 3D-organoid cultures, and single-cell analyses of differentiated cells, cell type-specific transcript profiles and functions were generated, and each exhibited a unique signature. Additionally, through integrative transcriptomic information, researchers can uncover the cellular dysfunction of embryonic and placental cells in peri-implantation embryos and the early pathological placenta. In fact, the clinical utility of fetal-maternal cellular trafficking has been applied for the noninvasive prenatal diagnosis of aneuploidies and the prediction of pregnancy complications. Furthermore, recent studies have proposed a viable path toward the development of therapeutic strategies targeting placenta-enriched molecules for placental dysfunction and diseases.

Low molecular weight heparin -induced miRNA changes in peripheral blood mononuclear cells in pregnancies with unexplained recurrent pregnancy loss.

Unexplained recurrent pregnancy loss (uRPL) is a clinical condition for which there is a lack of evidenced-based therapies. However, in clinical practice, low molecular weight heparin (LMWH) has been widely used as an empirical therapy since immune effects have been hypothesized in modulating immune tolerance at the fetal-maternal interface. Epigenetic mechanisms are involved in establishing of immune tolerance, at fetal-maternal interface. To investigate potential induced immune-epigenetic changes at maternal periphery level, which could reflect the maternal-fetal interface condition, seems to open up new therapeutical strategies, since microRNAs circulating in maternal plasma and in peripheral blood mononuclear cells (PBMCs) may be specific and sensitive immunological markers/predictors of adverse pregnancy outcomes such as RPL. Our aim in this pilot study is to evaluate potential LMWH effects on genes regulating immunological response key mechanisms related to maternal-fetal tolerance processes, by studying circulating miRNAs in maternal peripheral blood. We tested a panel of selected miRNAs on three groups: 18 healthy pregnant women, 20 pregnant women affected by uRPL, 18 pregnant women affected by uRPL, treated with LMWH. The majority of differentially expressed miRNAs (miR 374a-5p, 19a-3p, 30e-5p, 128-3p, 155-5p and 200c-3p) were found to be modulated by LMWH, which seems to have a positive function in RPL patients, by bringing patients' values back to those comparable to the control ones. Selected microRNA panels would appear to be an effective clinical tool for uRPL diagnosis and management. LMWH-modified miRNA expression levels could be targets for immunotherapy, as LMWH would appear to restore physiological miRNA levels, which are dysregulated in uRPL.

Role of NLRP7 in Normal and Malignant Trophoblast Cells.

Gestational choriocarcinoma (CC) is an aggressive cancer that develops upon the occurrence of abnormal pregnancies such as Hydatidiform moles (HMs) or upon non-molar pregnancies. CC cells often metastasize in multiple organs and can cause maternal death. Recent studies have established an association between recurrent HMs and mutations in the Nlrp7 gene. NLRP7 is a member of a new family of proteins that contributes to innate immune processes. Depending on its level of expression, NLRP7 can function in an inflammasome-dependent or independent pathway. To date, the role of NLRP7 in normal and in malignant human placentation remains to be elucidated. We have recently demonstrated that NLRP7 is overexpressed in CC trophoblast cells and may contribute to their acquisition of immune tolerance via the regulation of key immune tolerance-associated factors, namely HLA family, ßCG and PD-L1. We have also demonstrated that NLRP7 increases trophoblast proliferation and decreases their differentiation, both in normal and tumor conditions. Actual findings suggest that NLRP7 expression may ensure a strong tolerance of the trophoblast by the maternal immune system during normal pregnancy and may directly affect the behavior and aggressiveness of malignant trophoblast cells. The proposed review summarizes recent advances in the understanding of the significance of NLRP7 overexpression in CC and discusses its multifaceted roles, including its function in an inflammasome-dependent or independent pathways.

Clinical aspects of decidualization / A decidualizáció klinikai vonatkozásai

An essential component of successful conception and pregnancy is decidualization, which involves structural and functional transformation of the endometrium. The process involves structural changes in the uterine mucosa, transformation of spiral arterioles, numerical and functional adaptation of leukocytes in the endometrium and their subsequent migration, and functional and morphological changes in decidual stromal cells. As part of decidualization, trophoblast cells of embryonic origin perform a physiological invasion of maternal tissue to create the placenta. The success of the process is due to the special antigenicity of the trophoblast cells and the immune communication between the graft (fetus) and the host (mother) through hormones, cytokines and multiple receptorligand connections. Disorders of these processes are the basis of several diseases that threaten conception, implantation, and successful pregnancy, such as recurrent miscarriage, preeclampsia, intrauterine retardation, or preterm birth. In this article, we review the anatomical, immunological, and molecular basis of physiological decidualization to address common disorders in the clinical practice of obstetrics that are related to a dysfunctional decidualization.

Myeloid-Derived Suppressor Cells (MDSC) in the Umbilical Cord Blood: Biological Significance and Possible Therapeutic Applications.

Myeloid-derived suppressor cells (MDSCs) represent a heterogeneous population of myeloid cells that suppress immune responses in cancer, infection, and trauma. They mainly act by inhibiting T-cells, natural-killer cells, and dendritic cells, and also by inducing T-regulatory cells, and modulating macrophages. Although they are mostly associated with adverse prognosis of the underlying disease entity, they may display positive effects in specific situations, such as in allogeneic hematopoietic stem cell transplantation (HSCT), where they suppress graft-versus-host disease (GVHD). They also contribute to the feto-maternal tolerance, and in the fetus growth process, whereas several pregnancy complications have been associated with their defects. Human umbilical cord blood (UCB) is a source rich in MDSCs and their myeloid progenitor cells. Recently, a number of studies have investigated the generation, isolation, and expansion of UCB-MDSCs for potential clinical application associated with their immunosuppressive properties, such as GVHD, and autoimmune and inflammatory diseases. Given that a significant proportion of UCB units in cord blood banks are not suitable for clinical use in HSCT, they might be used as a significant source of MDSCs for research and clinical purposes. The current review summarizes the roles of MDSCs in the UCB, as well as their promising applications.

Pro-Inflammatory Signature in Decidua of Recurrent Pregnancy Loss Regardless of Embryonic Chromosomal Abnormalities.

Recurrent pregnancy loss (RPL), especially the unexplained RPL, is associated with the disruption of maternal immune tolerance. However, little is known about the immune status at the decidua of RPL with embryonic chromosomal aberrations. Herein, mass cytometry (CyTOF) was used to interrogate the immune atlas at the decidua which was obtained from 15 RPL women-six with normal chromosome and nine with chromosomal aberrations-and five controls. The total frequency of CCR2-CD11chigh macrophages increased, while CD39high NK cells and CCR2-CD11clow macrophages decrease significantly in RPL when RPLs were stratified, compared with controls. Pro-inflammatory subsets of CD11chigh macrophages increased, while less pro-inflammatory or suppressive subsets decreased statistically in RPL decidua whenever RPLs were stratified or not. However, CD11chigh NK and CD161highCD8+ T cells increased only in RPL with normal chromosome, while the inactivated and naive CD8+/CD4+ T cells were enriched only in RPL with chromosomal aberrations. A pro-inflammatory signature is observed in RPL decidua; however, differences exist between RPL with and without chromosomal abnormalities.

Progesterone decreased indoleamine 2,3-dioxygenase 1(IDO1) expression in early pregnancy chorionic villi and decidua.

Indoleamine 2,3-dioxygenase1(IDO1) is one of the most important proteins in protect the embryos from the mother's immune system during pregnancy. However, the regulation of the protein expression at the maternal-foetal interface is not fully known. We aimed to study the regulation of IDO1 expression by progesterone in villi and decidua of in early pregnancy. Fifty cases of early pregnancy women's villi and decidua were collected. Tissue explants of chorionic villi and the decidua were cultured in media containing in different concentrations of progesterone, in the presence or absence of mifepristone. Western blot analysis and immunofluorescence were used to detect the expression of IDO1 in chorionic villi and decidua in cultured tissues. IDO1 protein was identified in chorionic villi and decidua tissues of normal pregnant women, and the expression of IDO1in the decidua was significantly higher than those in chorionic villi. Progesterone decreased IDO1 expression in early pregnancy chorionic villi and decidua, and mifepristone, as the progesterone inhibitor, reverted this effect. In normal physiological state of pregnancy, progesterone may be involved in the regulation of immune tolerance by negative regulation of IDO1 expression at maternal foetal interface. Progesterone may down-regulate IDO1 expression during early pregnancy.

Placenta-Derived Exosomes as a Modulator in Maternal Immune Tolerance During Pregnancy.

Exosomes are a subset of extracellular vesicles with an average diameter of ~100nm. Exosomes are released by all cells through an endosome-dependent pathway and carry nucleic acids, proteins, lipids, cytokines and metabolites, mirroring the state of the originating cells. The function of exosomes has been implicated in various reproduction processes, such as embryo development, implantation, decidualization and placentation. Placenta-derived exosomes (pEXO) can be detected in the maternal blood as early as 6 weeks after conception and their levels increase with gestational age. Importantly, alternations in the molecular signatures of pEXO are observed in pregnancy-related complications. Thus, these differentially expressed molecules could be the potential biomarkers for diagnosis of the pregnancy-associated diseases. Recent studies have demonstrated that pEXO play a key role in the establishment of maternal immune tolerance, which is critical for a successful pregnancy. To gain a better understanding of the underlying mechanism, we highlighted the advanced studies of pEXO on immune cells in pregnancy.

Mesenchymal stem cells enhance Treg immunosuppressive function at the fetal-maternal interface.

Well-regulated maternal-fetal immune tolerance is a prerequisite for normal pregnancy. Hyperactivated immune cells and overwhelming inflammatory responses trigger adverse gestation outcome, such as recurrent spontaneous abortion (RSA). Local exacerbation of immunomodulatory cells in maternal decidua is a critical event, tightly linked with fetus acceptance. Owning to the notable immunoregulatory potentials, mesenchymal stromal cells (MSCs) and regulatory T cells (Tregs) have been separately reported as promising therapeutic approaches for refractory RSA attributable to certain immune disorders. However, the cross-talk between MSCs and Tregs at the fetal-maternal interface remains poorly understood. Here we revealed, for the first time, that umbilical MSCs could induce expansion of decidual Foxp3+CD4+ T cells with upregulated production of IL-10 and TGF-ß. Meanwhile, MSCs reinforced the immune suppressive functions of decidual Tregs (dTregs). More important, MSCs-instructed dTregs gained enhanced capacity to suppress Th1 and Th17 related inflammatory responses. In vivo data demonstrated that adoptive transfer of MSCs obviously promoted accumulation of Foxp3+ dTregs in lipopolysaccharide (LPS)-induced mice abortion model and spontaneous abortion model (DBA/2-mated female CBA/J mice). Furthermore, MSCs treatment effectively ameliorated absorption rate in both models. This study may offer a new insight for the application of MSCs and Tregs in clinical recurrent miscarriage.

NLRP7 Promotes Choriocarcinoma Growth and Progression through the Establishment of an Immunosuppressive Microenvironment.

The inflammatory gene NLRP7 is the major gene responsible for recurrent complete hydatidiform moles (CHM), an abnormal pregnancy that can develop into gestational choriocarcinoma (CC). However, the role of NLRP7 in the development and immune tolerance of CC has not been investigated. Three approaches were employed to define the role of NLRP7 in CC development: (i) a clinical study that analyzed human placenta and sera collected from women with normal pregnancies, CHM or CC; (ii) an in vitro study that investigated the impact of NLRP7 knockdown on tumor growth and organization; and (iii) an in vivo study that used two CC mouse models, including an orthotopic model. NLRP7 and circulating inflammatory cytokines were upregulated in tumor cells and in CHM and CC. In tumor cells, NLRP7 functions in an inflammasome-independent manner and promoted their proliferation and 3D organization. Gravid mice placentas injected with CC cells invalidated for NLRP7, exhibited higher maternal immune response, developed smaller tumors, and displayed less metastases. Our data characterized the critical role of NLRP7 in CC and provided evidence of its contribution to the development of an immunosuppressive maternal microenvironment that not only downregulates the maternal immune response but also fosters the growth and progression of CC.

Pig Pregnancies after Transfer of Allogeneic Embryos Show a Dysregulated Endometrial/Placental Cytokine Balance: A Novel Clue for Embryo Death?

Pig embryo transfer (ET) is burdened by high embryo mortality, with cytokines playing a significant role in recruitment of immune cells during embryo attachment and placentation. We hereby tested if their levels in endometrium and placenta from sows carrying hemi-allogeneic (artificially inseminated sows; C+ positive control) or allogeneic embryos (sows subjected to ET; ET) during peri-implantation (D18) or post-implantation (D24) are suitable mirrors of embryo rejection or tolerance after ET. Non-pregnant sows (C-) were used as negative controls. A set of cytokines was assayed in the tissues through multiplexed microsphere-based flow cytometry (Luminex xMAP, Millipore. USA). Fewer (58.7%. p < 0.003) conceptuses were recovered at D24 after ET compared to C+ (80.9%); with more than 20% of the ET conceptuses being developmentally delayed. Cytokine levels shifted during implantation. Anti-inflammatory IL-10 levels were significantly (p < 0.05) lower in ET sows compared to C+ at D24 of pregnancy. The C+ controls (carrying hemi-allogeneic embryos) consistently showed higher levels of pro-inflammatory TNF-α, IFN-γ, and IL-2 cytokines at D18 and IL-1α at D24, compared to the ET group. This clear dysregulation of pro- and anti-inflammatory cytokine levels in sows subjected to ET could be associated with an impaired maternal immune tolerance, explaining the high embryonic mortality of ET programs.

Endometrial Cancer Immune Escape Mechanisms: Let Us Learn From the Fetal-Maternal Interface.

The immune escape mechanisms at the base of tumor progression in endometrial cancer mimic immune tolerance mechanisms occurring at the maternal-fetal interface. The biological and immunological processes behind the maternal-fetal interface are finely tuned in time and space during embryo implantation and subsequent pregnancy stages; conversely, those behind cancer progression are often aberrant. The environment composition at the maternal-fetal interface parallels the pro-tumor microenvironment identified in many cancers, pointing to the possibility for the use of the maternal-fetal interface as a model to depict immune therapeutic targets in cancer. The framework of cancer environment signatures involved in immune adaptations, precisely timed in cancer progression, could reveal a specific "immune clock" in endometrial cancer, which might guide clinicians in patient risk class assessment, diagnostic workup, management, surgical and therapeutic approach, and surveillance strategies. Here, we review studies approaching this hypothesis, focusing on what is known so far about oncofetal similarities in immunity with the idea to individualize personalized immunotherapy targets, through the downregulation of the immune escape stage or the reactivation of the pro-inflammatory processes suppressed by the tumor.

First-trimester trophoblasts obtained by chorionic villus sampling maintain tolerogenic and proteomic features in successful pregnancies despite a history of unexplained recurrent pregnancy loss.

PROBLEM: While there are several known causes for recurrent pregnancy loss (RPL), about 50% are unexplained (uRPL), and in these cases, an aberrant immune regulation seems to be involved. Although fetally derived trophoblast cells have a key role in immune regulation, it is difficult to study their immune function during pregnancy, and it is not known whether trophoblast function may be an inherent aberration in uRPL or whether it is associated with the outcome of the current pregnancy. METHOD OF STUDY: Chorionic villus sampling (CVS) was performed for clinical indications at 12 weeks of gestation. Superfluous materials, divided in small explants, were cultured for 20-24 hours, and supernatants (conditioned medium) were collected from 36 women with singleton normal pregnancies, of whom 9 women had a history of RPL. The secreted immune protein profile was measured by proximity extension assay, and the conditioned medium was further used in functional ex vivo models to assess ability to polarize blood monocytes and CD4+ T cells into immune regulatory phenotypes, as detected by flow cytometry. RESULTS: Conditioned medium from chorionic villi, human fetally derived placental tissue, was able to induce a decidual-type of M2-like macrophages, as well as an expansion of Treg cells ex vivo, both in women with uRPL and in control women. The preserved immunological properties were confirmed by a maintained immune protein profile in RPL compared with controls. CONCLUSION: Trophoblasts in an ex vivo model maintain tolerogenic and proteomic profile features in successful pregnancies, despite a previous history of RPL.

Pregnancy persistently affects memory T cell populations.

Pregnancy is an immune challenge to the maternal immune system. The effects of pregnancy on maternal immunity and particularly on memory T cells during and after pregnancy are not fully known. This observational study aims to show the short term and the long term effects of pregnancy on the constitution, size and activation status of peripheral human memory T-lymphocyte populations. Effector memory (EM) and central memory (CM) T-lymphocytes were analyzed using flow cytometry of peripheral blood from 14 nulligravid, 12 primigravid and 15 parous women that were on average 18 months postpartum. The short term effects were shown by the significantly higher CD4+ EM cell and activated CD4+ memory cell proportions in primigravid women compared to nulligravid women. The persistent effects found in this study were the significantly higher proportions of CD4+ EM, CD4+ CM and activated memory T cells in parous women compared to nulligravid women. In contrast to CD4+ cells, activation status of CD8+ memory cells did not differ between the groups. This study shows that pregnancy persistently affects the pre-pregnancy CD4+ memory cell pool in human peripheral blood. During pregnancy, CD4+ T-lymphocytes might differentiate into EM cells followed by persistent higher proportions of CD4+ CM and EM cells postpartum. The persistent effects of pregnancy on memory T cells found in this study support the hypothesis that memory T cells are generated during pregnancy and that these cells could be involved in the lower complication risks in multiparous pregnancies in humans.

Maternal and fetal HLA-G 14 bp gene polymorphism in pregnancy-induced hypertension, preeclampsia, intrauterine growth restricted and normal pregnancies.

OBJECTIVE: Trophoblast expression of Human Leukocyte Antigene-G (HLA-G) is essential for feto-maternal immune tolerance and successful placentation. There is contradicting evidence on the relationship between HLA-G polymorphisms and preeclampsia (PE), intrauterine growth restriction (IUGR) and pregnancy-induced hypertension (PIH). Here, we investigate the association between both maternal and fetal HLA-G 14 bp insertion/deletion polymorphism and obstetrical complications. METHODS: Clinical and genetic data of 282 women/fetuses (31 severe PE, 8 mild PE, 46 IUGR, 42 PIH and 155 controls) were analyzed both individually and jointly under a codominant, a dominant and a recessive model. RESULTS: HLA-G 14 bp polymorphism was not associated with obstetrical complications, considering the mother and fetus genotypes both jointly and individually. CONCLUSIONS: With this study we filled several gaps occurring in previous studies: we analyzed a very well-defined population of PE, PIH and IUGR pregnancies, considering both fetal and maternal HLA-G 14 bp polymorphism, individually and jointly. Our findings showed that fetal and maternal HLA-G 14 bp genotypes are not associated with increased risk for the development of obstetrical complications, suggesting that this polymorphism has no immuno-modulatory role in the development of PE, PIH or IUGR.