Persistence of decidual NK cells and KIR genotypes in healthy pregnant and preeclamptic women: a case-control study in the third trimester of gestation

The central role of natural killer cells in preeclampsia

Preeclampsia (PE) is a disease that is unique to pregnancy and affects multiple systems. It can lead to maternal and perinatal mortality. The precise etiology of PE is unclear. Patients with PE may have systemic or local immune abnormalities. A group of researchers has proposed that the immune communication between the fetus and mother is primarily moderated by natural killer (NK) cells as opposed to T cells, since NK cells are the most abundant immune cells in the uterus. This review examines the immunological roles of NK cells in the pathogenesis of PE. Our aim is to provide obstetricians with a comprehensive and updated research progress report on NK cells in PE patients. It has been reported that decidual NK (dNK) cells contribute to the process of uterine spiral artery remodeling and can modulate trophoblast invasion. Additionally, dNK cells can stimulate fetal growth and regulate delivery. It appears that the count or proportion of circulating NK cells is elevated in patients with or at risk for PE. Changes in the number or function of dNK cells may be the cause of PE. The Th1/Th2 equilibrium in PE has gradually shifted to an NK1/NK2 equilibrium based on cytokine production. An improper combination of killer cell immunoglobulin-like receptor (KIR) and human leukocyte antigen (HLA)-C may lead to insufficient activation of dNK cells, thereby causing PE. In the etiology of PE, NK cells appear to exert a central effect in both peripheral blood and the maternal-fetal interface. To maintain immune equilibrium both locally and systemically, it is necessary to take therapeutic measures directed at NK cells.

HIF1 inhibitor acriflavine rescues early-onset preeclampsia phenotype in mice lacking placental prolyl hydroxylase domain protein 2

Preeclampsia is a serious pregnancy disorder that lacks effective treatments other than delivery. Improper sensing of oxygen changes during placentation by prolyl hydroxylases (PHDs), specifically PHD2, causes placental hypoxia-inducible factor-1 (HIF1) buildup and abnormal downstream signaling in early-onset preeclampsia, yet therapeutic targeting of HIF1 has never been attempted. Here we generated a conditional (placenta-specific) knockout of Phd2 in mice (Phd2-/- cKO) to reproduce HIF1 excess and to assess anti-HIF therapy. Conditional deletion of Phd2 in the junctional zone during pregnancy increased placental HIF1 content, resulting in abnormal placentation, impaired remodeling of the uterine spiral arteries, and fetal growth restriction. Pregnant dams developed new-onset hypertension at midgestation (E9.5) in addition to proteinuria and renal and cardiac pathology, hallmarks of severe preeclampsia in humans. Daily injection of acriflavine, a small molecule inhibitor of HIF1, to pregnant Phd2-/- cKO mice from E7.5 (prior to hypertension) or E10.5 (after hypertension had been established) to E14.5 corrected placental dysmorphologies and improved fetal growth. Moreover, it reduced maternal blood pressure and reverted renal and myocardial pathology. Thus, therapeutic targeting of the HIF pathway may improve placental development and function, as well as maternal and fetal health, in preeclampsia.

Killer-cell immunoglobulin-like receptor/human leukocyte antigen-C combination and 'great obstetrical syndromes' (Review)

Recurrent pregnancy loss (RPL), pre-eclampsia (PE), fetal growth restriction (FGR), and preterm delivery are examples of ‘great obstetrical syndromes’ (GOS). Placental dysfunction is the most common pathogenesis of GOS. In human pregnancies, the effects of uterine natural killer cells involve angiogenesis, promoting the remodeling of uterine spiral artery, and improving the invasion of trophoblast cells. The uNK cells supply killer immunoglobulin-like receptors (KIRs), which come into contact with human leukocyte antigen-C (HLA-C) ligands expressed by extravillous trophoblast cells (EVTs). Numerous studies have investigated the association between GOS and KIR/HLA-C combination. However, the outcomes have not been conclusive. The present review aimed to reveal the association between GOS and KIR/HLA-C combination to screen out high-risk pregnancies, strengthen the treatment of pregnancy complications, and reduce the frequency of adverse maternal and fetal outcomes. It has been reported that a female with a KIR AA genotype and a neonate with a paternal HLA-C2 molecule is more prone to develop GOS and have a small fetus since less cytokines were secreted by uNK cells. Conversely, the combination of KIR BB haplotype (including the activating KIR2DS1) and HLA-C2 can induce the production of cytokines and increase trophoblast invasion, leading to the birth of a large fetus. KIR/HLA-C combinations may be applicable in selecting third-party gametes or surrogates. Detection of maternal KIR genes and HLA-C molecules from the couple could serve as useful markers for predicting and diagnosing GOS.

Decidual Natural Killer Cells: A Good Nanny at the Maternal-Fetal Interface During Early Pregnancy

Decidual natural killer (dNK) cells are the tissue-resident and major subpopulation of NK cells at the maternal-fetal interface. It has been demonstrated that dNK cells play pivotal roles in pregnancy, including keeping maternal-fetal immune tolerance, promoting extravillous trophoblast (EVT) cell invasion, and driving uterine spiral artery remodeling. However, the molecular mechanisms haven't been elucidated until recent years. In this review, we systemically introduce the generation, subsets, and surface or soluble molecules of dNK cells, which are critical for maintaining the functions of dNK cells. Further, new functions of dNK cells including well-controlled cytotoxicity, immunosurveillance and immunotrophism supporting via the cell-cell interaction between dNK cells and EVT cells are mainly focused. The molecular mechanisms involved in these functions are also illustrated. Moreover, pregnancy-associated diseases caused by the dNK cells abnormalities are discussed. It will be important for future investigations about the mechanism of maintenance of pregnancy and parturition and potential clinical applications of dNK cells.

The enrichment of neutrophil extracellular traps impair the placentas of systemic lupus erythematosus through accumulating decidual NK cells

Despite the advances made in the management of pregnancies in women with systemic lupus erythematosus (SLE), the rate of adverse pregnancy outcomes is still higher than that in the general population. In the last few years, neutrophil extracellular traps (NETs) were proven to be detrimental in both autoimmune diseases and placental injury. We investigated whether NETs could be detected in the placentas of pregnant individuals with SLE and explored the relationship between NETs and decidual natural killer cells (dNKs), which comprise the majority of immune cells at the maternal–fetal interface, using clinical samples and animal models. In this study, we found that the infiltration of NETs and dNKs, especially CD56⁺CD16⁺ NK cells, was significantly increased in pregnant individuals with SLE with placental insufficiency. In the murine models of SLE, the number of dNKs was significantly decreased due to the decreased formation of NETs affected by Ly6G. Moreover, the histopathological placental injury was reduced, with a remarkable increase in fetal birth weight. This study shows that NETs may contribute to immunological disorder in the placenta and the pathological changes in pregnancies with SLE, which provides a research basis for further explorations of the mechanism of SLE in placental impairment.

The Maternal-Fetal Interface in Small-for-Gestational-Age Pregnancies Is Associated With a Reduced Quantity of Human Decidual NK Cells With Weaker Functional Ability

Small for gestational age (SGA) refers to a birth weight that is less than the 10th percentile of the mean weight of infants at the same gestational age. This condition is associated with a variety of complications, and a high risk of cardiovascular and cerebrovascular diseases in adulthood. Decidual natural killer (dNK) cells at the maternal–fetal interface have received significant research attention in terms of normal pregnancy or miscarriage; however, data relating to SGA are limited. In this study, we aimed to investigate the characteristics and regulatory role of dNK cells at the maternal–fetal interface in SGA. Using immunofluorescence assays, we found that dNK cells maintained close contact with extra-villous trophoblasts, and the proportion of dNK cells in SGA decreased more than in appropriate for gestational age (AGA). Flow cytometry also showed that there was a significantly lower percentage of dNK cells in SGA (25.01 ± 2.43%) than in AGA (34.25 ± 2.30%) (p = 0.0103). The expression of the inhibitory receptor NKG2A on dNK cells and the secretion levels of both perforin and TGF-β1 from dNK cells were significantly higher in SGA than in AGA, while the cytotoxicity of dNK cells in SGA against K562 cells was attenuated. Compared to AGA, the functional ability of dNK cells in SGA showed significant functional impairment in promoting proliferation, migration, invasion, and tube formation in trophoblast cells or vascular endothelial cells. The abnormal function of dNK cells may affect fetal growth and development, and could therefore participate in the pathogenesis of SGA.

Decreased HLA-C1 alleles in couples of KIR2DL2 positive women with recurrent pregnancy loss

Specific killer cell immunoglobulin-like receptor (KIR) in women with recurrent pregnancy loss (RPL) and HLA ligands in couples invoke a susceptibility to RPL. However, the relationship between KIR2DL2 and its cognate ligand HLA-C1 has not been explored. In this prospective cohort study, 160 Caucasian women with RPL and 99 partners were included. KIR/HLA-C typing, NK assay, Th1/Th2 intracellular cytokine ratios, 25-(OH)-vitamin D level, and the presence of autoantibodies were analyzed. KIR2DL2 positive women (P = 0.023) and their partners (P = 0.017) had lower allele frequencies of HLA-C1 than those of KIR2DL2 negative women. KIR2DL2 positive women had significantly lower genotype frequency of HLA-C1C1 as compared to the North American Caucasian population controls (P < 0.05). In the partners of KIR2DL2 positive women, there was a substantially higher frequency of HLA-C2C2 than controls (P = 0.016). Besides, KIR2DL2 negative women had a higher prevalence of anti-ssDNA antibody as compared with that of KIR2DL2 positive women (P = 0.043). There were no differences in the distribution of HLA-C genotypes based on KIR2DL2, regardless of pregnancy outcome in women with RPL and their partners while on immunomodulation treatment. In conclusion, decreased ligands for inhibitory KIRs (inhKIR) could lead to insufficient inhibition of maternal uterine NK cells toward the trophoblast, thereby contributing to the pathogenesis of RPL. Specific KIR and HLA-C genotyping may predict the reproductive outcome of women with RPL.

Human Term Pregnancy Decidual NK Cells Generate Distinct Cytotoxic Responses

Decidual NK cells (dNK) are the main lymphocyte population in early pregnancy decidual mucosa. Although dNK decrease during pregnancy, they remain present in decidual tissues at term. First trimester dNK facilitate trophoblast invasion, provide protection against infections, and were shown to have many differences in their expression of NKRs, cytokines, and cytolytic capacity compared with peripheral blood NK cells (pNK). However, only limited data are available on the phenotype and function of term pregnancy dNK. In this study, dNK from human term pregnancy decidua basalis and decidua parietalis tissues were compared with pNK and first trimester dNK. Profound differences were found, including: 1) term pregnancy dNK have an increased degranulation response to K562 and PMA/ionomycin but lower capacity to respond to human CMV-infected cells; 2) term pregnancy dNK are not skewed toward recognition of HLA-C, as was previously shown for first trimester dNK; and 3) protein and gene expression profiles identified multiple differences between pNK, first trimester, and term pregnancy dNK, suggesting term pregnancy dNK are a distinct type of NK cells. Understanding the role of dNK throughout pregnancy is of high clinical relevance for studies aiming to prevent placental inflammatory disorders as well as maternal-to-fetal transmission of pathogens.

The Roles of Uterine Natural Killer (NK) Cells and KIR/HLA-C Combination in the Development of Preeclampsia: A Systematic Review

Preeclampsia (PE) is termed as a systemic disease that involves multiple organs; however, the exact etiology is still quite unclear. It is believed that the poor remodeling of uterine spiral arteries triggers PE, thereby causing failed placentation and producing inflammatory factors. The decline of blood flow results in lowering the nutrients and oxygen received by the fetus and augmenting the placental pressure in PE. Decidual immune cells, especially uterine natural killer (uNK) cells, are involved in the process of placentation. Decidual NK (dNK) cells significantly contribute to the vascular remodeling through the secretion of cytokines and angiogenic mediators in normal placental development. The abnormal activation of NK cells in both the peripheral blood and the decidua was counted among the causes leading to PE. The correlation existing between maternal killer cell immunoglobulin-like receptor (KIR) and HLA-C in trophoblast cells constitutes a robust evidence for the genetic etiology of PE. The combinations of the two kinds of gene systems, together with the KIR genotype in the mother and the HLA-C group in her fetus, are likely to exactly decide the pregnancy outcome. The women, who have the inappropriate match of KIR/HLA-C, are likely to be prone to the augmented risk of PE. However, the combinations of KIR/HLA-C in PE undergo ethnic changes. The extensive prospective research works in Europe, Asia, and Africa are required for providing more findings in PE patients.

Uterine natural killer cells: Time for a re-appraisal?

The presence of unusual natural killer cells in human endometrium has been recognized for 30 years, but despite considerable research effort, the in vivo role of uterine natural killer (uNK) cells in both normal and pathological pregnancy remains uncertain. uNK cells may differentiate from precursors present in endometrium, but migration from peripheral blood in response to chemokine stimuli with in situ modification to a uNK cell phenotype is also possible. uNK cells produce a wide range of secretory products with diverse effects on trophoblast and spiral arteries which may play an important role in implantation and early placentation. Interactions with other decidual cell populations are also becoming clear. Recent evidence has demonstrated subpopulations of uNK cells and the presence of other innate lymphoid cell populations in decidua which may refine future approaches to investigation of the role of uNK cells in human pregnancy.

T lymphocytes in the third trimester decidua in preeclampsia

OBJECTIVE

The aim of study was to conduct immunohistochemical quantification of CD3+ and CD8+ decidual lymphocytes in preeclampsia.

METHODS

A study group included 30 cases of preeclampsia and a control group included 20 healthy pregnant women, all delivered by Cesarean section. Samples of placental bed were analyzed after immunohistochemical staining of CD45+, CD3+ and CD8+ cells.

RESULTS

The group with preeclampsia included a significantly higher number of CD3+ (p < 0.01) and CD8+ (p < 0.05) T lymphocytes.

CONCLUSION

It is certain that thebalance dysregulation of T cell of the immune milieu of deciduais of importance in etiopathogenesis and manifestations of preeclampsia.

Genetic Variants in Preeclampsia: Lessons From Studies in Latin-American Populations

Placental vascularization is a tightly regulated physiological process in which the maternal immune system plays a fundamental role. Vascularization of the maternal-placental interface involves a wide range of mechanisms primarily orchestrated by the fetal extravillous trophoblast and maternal immune cells. In a healthy pregnancy, an immune cross-talk between the mother and fetal cells results in the secretion of immunomodulatory mediators, apoptosis of specific cells, cellular differentiation/proliferation, angiogenesis, and vasculogenesis, altogether favoring a suitable microenvironment for the developing embryo. In the context of vasculopathy underlying common pregnancy disorders, it is believed that inefficient invasion of extravillous trophoblast cells in the endometrium leads to a poor placental blood supply, which, in turn, leads to decreased secretion of angiogenic factors, hypoxia, and inflammation commonly associated with preterm delivery, intrauterine growth restriction, and preeclampsia. In this review, we will focus on studies published by Latin American research groups, providing an extensive review of the role of genetic variants from candidate genes involved in a broad spectrum of biological processes underlying the pathophysiology of preeclampsia. In addition, we will discuss how these studies contribute to fill gaps in the current understanding of preeclampsia. Finally, we discuss some trending topics from important fields associated with pregnancy vascular disorders (e.g., epigenetics, transplantation biology, and non-coding RNAs) and underscore their possible implications in the pathophysiology of preeclampsia. As a result, these efforts are expected to give an overview of the extent of scientific research produced in Latin America and encourage multicentric collaborations by highlighted regional research groups involved in preeclampsia investigation.

Number of decidual natural killer cells & macrophages in pre-eclampsia

Background & objectives:

The process of human placentation is complex and still not well understood. This study was aimed to examine the relationship between clinical features of pre-eclampsia and degree of trophoblastic invasion after its immunohistochemical visualization in the context of possible alterations in the number of natural killer (NK) cells and macrophages in the decidua.

Methods:

This prospective study included a study group comprising 30 pregnant women with pre-eclampsia delivered by caesarean section and a control group comprising 20 healthy pregnant women also delivered by caesarean section. Samples of placental bed obtained during caesarean section were analyzed after immunohistochemical labelling CD56⁺ NK cells, CD68⁺ macrophages and cytokeratin 7 trophoblastic cells.

Results:

In pre-eclampsia, there was a significantly lower number of CD56⁺ NK cells in the decidua (P<0.001) and a higher number of CD68⁺ macrophages (P<0.001) compared to control group. In the subgroup of pre-eclampsia with intrauterine growth retardation (IUGR), a significantly greater number of NK cells (P<0.05) was recorded, as well as an increased number of macrophages, but not significantly compared to pre-eclampsia without IUGR. There was no significant difference in the distribution of these cells in the decidua in relation to the severity of pre-eclampsia. CD56⁺ NK cells were significantly less (P<0.05) and macrophages were more (P<0.05) in the group with poor trophoblastic invasion.

Interpretation & conclusions:

Alterations in the number of immune cells in relation to the degree of trophoblastic invasion indicated their role in aetiopathogenesis of pre-eclampsia, while the direct association between their number and severity of pre-eclampsia was not confirmed.

The RNA binding protein IMP3 facilitates tumor immune escape by downregulating the stress-induced ligands ULPB2 and MICB

Expression of the stress-induced ligands MICA, MICB and ULBP 1–6 are up-regulated as a cellular response to DNA damage, excessive proliferation or viral infection; thereby, they enable recognition and annihilation by immune cells that express the powerful activating receptor NKG2D. This receptor is present not exclusively, but primarily on NK cells. Knowledge about the regulatory mechanisms controlling ULBP expression is still vague. In this study, we report a direct interaction of the oncogenic RNA binding protein (RBP) IMP3 with ULBP2 mRNA, leading to ULBP2 transcript destabilization and reduced ULBP2 surface expression in several human cell lines. We also discovered that IMP3 indirectly targets MICB with a mechanism functionally distinct from that of ULBP2. Importantly, IMP3-mediated regulation of stress-ligands leads to impaired NK cell recognition of transformed cells. Our findings shed new light on the regulation of NKG2D ligands and on the mechanism of action of a powerful oncogenic RBP, IMP3.

DOI:http://dx.doi.org/10.7554/eLife.13426.001

Tumor cells differ from healthy cells in many aspects. Importantly, tumor cells have the ability to divide and grow much faster than normal cells. To protect ourselves from full-grown cancers, our bodies have developed a surveillance system: when a tumor cell starts to divide without restraint, “stress-induced” proteins start to appear on its surface. These proteins help the immune system recognize abnormal or damaged cells, allowing the immune cells to eliminate the defective cells.

Despite this system of protection, a tumor cell sometimes manages to avoid having stress-induced proteins placed on its surface, allowing it to remain undetected by the immune system. By studying several different types of human cancer cells, Schmiedel et al. found that a protein called IMP3 is present in cancer cells but not in healthy cells. Further investigation revealed that IMP3 prevents the production of some stress-induced proteins and stops them moving to the cell surface.

Schmiedel et al. also show that the presence of the IMP3 protein in cancer cells causes nearby immune cells to become much less active. This suggests that developing drugs that block the activity of IMP3 could help the immune system to fight back and destroy cancer cells.

DOI:http://dx.doi.org/10.7554/eLife.13426.002

Decidual vascular endothelial cells promote maternal-fetal immune tolerance by inducing regulatory T cells through canonical Notch1 signaling

Adaptation of the maternal immune response to accommodate the semiallogeneic fetus is necessary for pregnancy success. However, the mechanisms by which the fetus avoids rejection despite expression of paternal alloantigens remain incompletely understood. Regulatory T cells (Treg cells) are pivotal for maintaining immune homeostasis, preventing autoimmune disease and fetus rejection. In this study, we found that maternal decidual vascular endothelial cells (DVECs) sustained Foxp3 expression in resting Treg cells in vitro. Moreover, under in vitro Treg cell induction condition with agonistic antibodies and transforming growth factor (TGF)-β, DVECs promoted Treg cell differentiation from non-Treg conventional T cells. Consistent with the promotion of Treg cell maintenance and differentiation, Treg cell-associated gene expression such as TGF-β, Epstein-Barr-induced gene-3, CD39 and glucocorticoid-induced tumor necrosis factor receptor was also increased in the presence of DVECs. Further study revealed that DVECs expressed Notch ligands such as Jagged-1, Delta-like protein 1 (DLL-1) and DLL-4, while Treg cells expressed Notch1 on their surface. The effects of DVECs on Treg cells was inhibited by siRNA-induced knockdown of expression of Jagged-1 and DLL-1 in DVECs. Downregulation of Notch1 in Treg cells using lentiviral shRNA transduction decreased Foxp3 expression in Treg cells. Adoptive transfer of Notch1-deficient Treg cells increased abortion rate in a murine semiallogeneic pregnancy model. Taken together, our study suggests that maternal DVECs are able to maintain decidual Treg cell identity and promote Treg cell differentiation through activation of Notch1 signal pathway in Treg cells and subsequently inhibit the immune response against semiallogeneic fetuses and preventing spontaneous abortion.

Recurrent Pregnancy Loss in Women with Killer Cell Immunoglobulin-Like Receptor KIR2DS1 is Associated with an Increased HLA-C2 Allelic Frequency

PROBLEM

During human pregnancy, the uterine lining is highly populated with killer-immunoglobulin-like receptor (KIR)-expressing NK cells that recognize HLA-C molecules on trophoblast cells. The goal of this study was to analyze the KIR gene contents and frequencies in a N. American cohort of women with RPL of unknown etiology to evaluate whether there is a genetic susceptibility to RPL based on a woman's KIR repertoire and her HLA-C group, as well as the HLA-C group of the partner.

METHOD OF STUDY

The frequencies of KIR and HLA-C1 and HLA-C2 genes were evaluated in 139 Caucasian women with RPL; HLA-C1, and HLA-C2 group genes were analyzed in their partners (n = 42). The gene frequencies were compared with data reported from corresponding populations.

RESULTS

Overall, the frequencies of HLA-C groups and KIR genes and genotypes in RPL cohort resembled the frequencies for US Caucasians. The HLA-C1 and HLA-C2 group distribution was significantly different between women with or without KIR2DS1. Women positive for KIR2DS1 (45.3% of the study cohort) had an increased frequency of its ligand, HLA-C2 (0.5159 versus 0.3684 in KIR2DS1 negative women, P = 0.014).

CONCLUSION

Our results indicate that among KIR2DS1 pos women, the co-expression of HLA-C2 is associated with RPL.

Placenta accreta is associated with decreased decidual natural killer (dNK) cells population: a comparative pilot study

OBJECTIVE

Placenta accreta is a general term describes abnormal adherent placenta to the uterine wall. When the chorionic villi invade the myometrium, the term placenta increta is appropriate. Nowadays, it is one of the increasing causes of materno-fetal morbidities and mortality. The aim of this research was to evaluate density of decidual natural killer cells (dNK, CD56+(bright)) in decidua basalis in patients with placenta accreta.

STUDY DESIGN

We recruited 76 patients from Ain Shams Maternity Hospital between June 2012 to August 2013, they were divided into study subgroup (A) which included 10 patients who underwent cesarean hysterectomy due to unseparated placenta accreta, study subgroup (B) included 16 patients with separated placenta accreta, a comparison group included 25 patients with placenta previa and a control group included 25 patients with normally situated placenta. All patients underwent elective cesarean delivery. Decidual biopsies were taken during the operation. An immunohistochemical staining for (dNK, CD56+(bright)) and a semi quantitative scoring were done. One-way ANOVA and Fisher Exact tests were used for statistical correlation.

RESULTS

The mean dNK cells scores were (0.4±0.5, 1.9±1, 3.3±0.5 and 3.5±0.5) for study subgroups (A), (B) comparison and control groups respectively) with a highly significant statistical difference (P<0.001). There was a significant statistical difference between study subgroups (A) and (B) P=0.002 .There was an insignificant statistical correlation between dNK scores and number of previous uterine scars (P=0.46).

CONCLUSION

These findings suggest that low dNK score was associated with cases of morbidly adherent placenta accreta.

Future directions of clinical laboratory evaluation of pregnancy

In recent years, our understanding of how the immune system interacts with the developing fetus and placenta has greatly expanded. There are many laboratories that provide tests for diagnosis of pregnancy outcome in women who have recurrent pregnancy loss (RPL) or pre-eclampsia. These tests are based on the premise that immune response to the fetus is equivalent to the adaptive immune response to a transplant. New understanding leads to the concept that the activated innate response is vital for pregnancy and this can result in more effective testing and treatment to prevent an abnormal pregnancy in the future. We describe here only three such areas for future testing: one area involves sperm and semen and factors necessary for successful fertilization; another area would determine conditions for production of growth factors necessary for implantation in the uterus; finally, the last area would be to determine conditions necessary for the vascularization of the placenta and growing fetus by activated natural killer (NK) cells (combinations of killer cell immunoglobulin-like receptor (KIR) family genes with HLA-C haplotypes) that lead to capability of secreting angiogenic growth factors. These areas are novel but understanding their role in pregnancy can lead to insight into how to maintain and treat pregnancies with complicating factors.

Interaction of parental KIR and fetal HLA-C genotypes with the risk of preeclampsia

OBJECTIVE

The aim of this study is to investigate whether certain combination of maternal killer cell immunoglobulin-like receptors (KIR) and fetal human leukocyte antigen-C (HLA-C) is risk for preeclampsia in the Chinese Han population.

METHODS

A case-control study was conducted in 47 pregnant women with preeclampsia and 54 normal pregnant women. Twelve KIR genes were genotyped by PCR-sequence-specific primer in mothers. High-resolution HLA-C genotyping was performed in couples and fetuses by a routine sequencing-based typing method.

RESULTS

The frequency of KIR2DS1 was decreased (p = 0.028) and AA genotype was increased (p = 0.017) in preeclampsia compared with controls. More women with KIR AA genotype have fewer C2 genes than their fetuses in preeclampsia than controls.

CONCLUSION

Women with KIR AA genotype and fewer C2 genes than their fetuses were at risk for preeclampsia in the Chinese Han population, supporting that maternal-fetal KIR-HLA-C interaction plays an important role in preeclampsia development.

Upregulation of innate antiviral restricting factor expression in the cord blood and decidual tissue of HIV-infected mothers

Programs for the prevention of mother-to-child transmission of HIV have reduced the transmission rate of perinatal HIV infection and have thereby increased the number of HIV-exposed uninfected (HEU) infants. Natural immunity to HIV-1 infection in both mothers and newborns needs to be further explored. In this study, we compared the expression of antiviral restricting factors in HIV-infected pregnant mothers treated with antiretroviral therapy (ART) in pregnancy (n=23) and in cord blood (CB) (n=16), placental tissues (n=10-13) and colostrum (n=5-6) samples and compared them to expression in samples from uninfected (UN) pregnant mothers (n=21). Mononuclear cells (MNCs) were prepared from maternal and CB samples following deliveries by cesarean section. Maternal (decidua) and fetal (chorionic villus) placental tissues were obtained, and colostrum was collected 24 h after delivery. The mRNA and protein expression levels of antiviral factors were then evaluated. We observed a significant increase in the mRNA expression levels of antiviral factors in MNCs from HIV-infected mothers and CB, including the apolipoprotein B mRNA-editing enzyme 3G (A3G), A3F, tripartite motif family-5α (TRIM-5α), TRIM-22, myxovirus resistance protein A (MxA), stimulator of interferon (IFN) genes (STING) and IFN-β, compared with the levels detected in uninfected (UN) mother-CB pairs. Moreover, A3G transcript and protein levels and α-defensin transcript levels were decreased in the decidua of HIV-infected mothers. Decreased TRIM-5α protein levels in the villi and increased STING mRNA expression in both placental tissues were also observed in HIV-infected mothers compared with uninfected (UN) mothers. Additionally, colostrum cells from infected mothers showed increased tetherin and IFN-β mRNA levels and CXCL9 protein levels. The data presented here indicate that antiviral restricting factor expression can be induced in utero in HIV-infected mothers. Future studies are warranted to determine whether this upregulation of antiviral factors during the perinatal period has a protective effect against HIV-1 infection.

Expression of interferon-γ in decidual natural killer cells from women with hypertensive disorder complicating pregnancy

AIM

Hypertensive disorder complicating pregnancy (HDCP) is one of the most frequent and serious pregnancy-related diseases, which is closely related to disorders of the maternal immune system, especially the local immune microenvironment of the maternal-fetal interface. Uterine decidual natural killer (dNK) cells are the major immune cells in the maternal-fetal interface and they play an important role in establishing and maintaining a normal pregnancy. The aim of this study was to investigate the phenotype and function of dNK cells from women with HDCP.

MATERIAL AND METHODS

Decidual tissues were collected from women with normal pregnancy (normal control group, n = 15 cases) and HDCP (HDCP group, n = 20 cases), respectively. The mononuclear cells were extracted from tissues and flow cytometry (FCM) was utilized to sort out dNK cells. The phenotypes of dNK cells (CD56(bright)CD16⁻CD3⁻ vs CD56(dim)CD16⁺CD3⁻) were detected by FCM. After being co-cultured with Phorbol 12-myristate 13-acetate, ionomycin and monensin, the expression level of interferon (IFN)-γ in the dNK cells was detected by FCM.

RESULTS

The phenotypes of dNK cells from the two groups were dominated by the CD56(bright)CD16⁻CD3⁻ subset, with no significant statistical difference (P < 0.05). The expression level of IFN-γ in the dNK cells from women with HDCP was on a lower trend than those from women with normal pregnancy, having significant statistical difference (P = 0.000 < 0.05).

CONCLUSIONS

Our results indicated that although the phenotype of dNK cells from women with HDCP is of no difference, their functions are abnormal. Impaired cell function leads to a lower expression level of IFN-γ and this may account for one of the pathogeneses of HDCP.

The Placenta in Toxicology. Part II

During pregnancy, the maternal immune system is challenged by the semiallogeneic fetus, which must be tolerated without compromising fetal or maternal health. This review updates the systemic and local immune changes taking place during human pregnancy, including some examples in rodents. Systemic changes are induced by contact of maternal blood with placental factors and include enhanced innate immunity with increased activation of granulocytes and nonclassical monocytes. Although a bias toward T helper (Th2) and regulatory T cell (Treg) immunity has been associated with healthy pregnancy, the relationship between different circulating Th cell subsets is not straightforward. Instead, these adaptations appear most evidently at the fetal–maternal interface, where for instance Tregs are enriched and promote fetal tolerance. Also innate immune cells, that is, natural killer cells and macrophages, are enriched, constituting the majority of decidual leukocytes. These cells not only contribute to immune regulation but also aid in establishing the placenta by promoting trophoblast recruitment and angiogenesis. Thus, proper interaction between leukocytes and placental trophoblasts is necessary for normal placentation and immune adaptation. Consequently, spontaneous maladaptation or interference of the immune system with toxic substances may be important contributing factors for the development of pregnancy complications such as preeclampsia, preterm labor, and recurrent miscarriages.

How does variability of immune system genes affect placentation?

Formation of the placenta is a crucial step in mammalian pregnancy. Apart from its function in ensuring an optimal supply of nutrients and oxygen to the fetus, the placenta is also the interface at which allo-recognition of invading trophoblast cells by the maternal immune system can potentially occur. We summarise here the “state of the art” on how variability of immune system genes that code for major histocompatibility complex (MHC) molecules and natural killer receptors (NKR) may impact on human placentation. MHC and NKR are the most polymorphic human genes. Our recent reports point out that specific combinations of fetal MHC and maternal NKR genes in humans correlate with the risk of pre-eclampsia, recurrent miscarriage (RM) and fetal growth restriction (FGR). Research in this field is still at an early stage and future studies in mouse and humans will be needed before the results can be translated to clinical applications. We discuss our recent work, as well as the opportunities offered by mouse genetics, to understand the cellular and molecular mechanisms underlying immune interactions at the maternal-fetal interface.