Expression of the nonclassic histocompatibility antigen HLA-G by preeclamptic placenta

A Novel Paradigm for Non-Invasive Prenatal Genetic Screening: Trophoblast Retrieval and Isolation from the Cervix (TRIC)

As the prevalence of pregnancies with advanced maternal age increases, the risk of fetal chromosomal abnormalities is on the rise. Therefore, prenatal genetic screening and diagnosis have become essential elements in contemporary obstetrical care. Trophoblast retrieval and isolation from the cervix (TRIC) is a non-invasive procedure that can be utilized for prenatal genetic diagnosis. The method involves the isolation of fetal cells (extravillous trophoblasts) by transcervical sampling; along with its non-invasiveness, TRIC exhibits many other advantages such as its usefulness in early pregnancy at 5 weeks of gestation, and no interference by various fetal and maternal factors. Moreover, the trophoblast yields from TRIC can provide valuable information about obstetrical complications related to abnormal placentation even before clinical symptoms arise. The standardization of this clinical tool is still under investigation, and the upcoming advancements in TRIC are expected to meet the increasing need for a safe and accurate option for prenatal diagnosis.

Single-cell RNA-seq reveals developmental deficiencies in both the placentation and the decidualization in women with late-onset preeclampsia

Preeclampsia (PE) is a leading cause of maternal and fetal morbidity and mortality. Although increasing lines of evidence suggest that both the placenta and the decidua likely play roles in the pathogenesis of PE, the molecular mechanism of PE remains elusive partly because of the heterogeneity nature of the maternal-fetal interface. In this study, we perform single-cell RNA-seq on the placenta and the decidual from patients with late-onset PE (LOPE) and women in normal pregnancy. Analyses of single-cell transcriptomes reveal that in LOPE, there are likely a global development deficiency of trophoblasts with impaired invasion of extravillous trophoblasts (EVT) and increased maternal immune rejection and inflammation in the placenta, while there are likely insufficient decidualization of decidual stromal cells (DSC), increased inflammation, and suppressed regulatory functions of decidual immune cells. These findings improve our understanding of the molecular mechanisms of PE.

The Relationship between Obesity and Pre-Eclampsia: Incidental Risks and Identification of Potential Biomarkers for Pre-Eclampsia

Obesity has been steadily increasing over the past decade in the US and worldwide. Since 1975, the prevalence of obesity has increased by 2% per decade, unabated despite new and more stringent guidelines set by WHO, CDC, and other public health organizations. Likewise, maternal obesity has also increased worldwide over the past several years. In the United States, pre-pregnancy rates have increased proportionally across all racial groups. Obesity during pregnancy has been directly linked to obstetric complications including gestational diabetes, HTN, hematomas, pre-eclampsia, and congenital defects. In the particular case of pre-eclampsia, the incidence rate across the globe is 2.16%, but the condition accounts for 30% of maternal deaths, and a robust body of evidence underscored the relationship between obesity and pre-eclampsia. More recently, attention has focused on the identification of reliable biomarkers predictive of an elevated risk for pre-eclampsia. The aim of this literature review is to elucidate the relationship between obesity and these predictive biomarkers for future prediction and prevention of pre-eclampsia condition in women at risk.

Acute Atherosis Lesions at the Fetal-Maternal Border: Current Knowledge and Implications for Maternal Cardiovascular Health

Decidua basalis, the endometrium of pregnancy, is an important interface between maternal and fetal tissues, made up of both maternal and fetal cells. Acute atherosis is a uteroplacental spiral artery lesion. These patchy arterial wall lesions containing foam cells are predominantly found in the decidua basalis, at the tips of the maternal arteries, where they feed into the placental intervillous space. Acute atherosis is prevalent in preeclampsia and other obstetric syndromes such as fetal growth restriction. Causal factors and effects of acute atherosis remain uncertain. This is in part because decidua basalis is challenging to sample systematically and in large amounts following delivery. We summarize our decidua basalis vacuum suction method, which facilitates tissue-based studies of acute atherosis. We also describe our evidence-based research definition of acute atherosis. Here, we comprehensively review the existing literature on acute atherosis, its underlying mechanisms and possible short- and long-term effects. We propose that multiple pathways leading to decidual vascular inflammation may promote acute atherosis formation, with or without poor spiral artery remodeling and/or preeclampsia. These include maternal alloreactivity, ischemia-reperfusion injury, preexisting systemic inflammation, and microbial infection. The concept of acute atherosis as an inflammatory lesion is not novel. The lesions themselves have an inflammatory phenotype and resemble other arterial lesions of more extensively studied etiology. We discuss findings of concurrently dysregulated proteins involved in immune regulation and cardiovascular function in women with acute atherosis. We also propose a novel hypothesis linking cellular fetal microchimerism, which is prevalent in women with preeclampsia, with acute atherosis in pregnancy and future cardiovascular and neurovascular disease. Finally, women with a history of preeclampsia have an increased risk of premature cardiovascular disease. We review whether presence of acute atherosis may identify women at especially high risk for premature cardiovascular disease.

Late-onset intrauterine growth restriction and HHV-6 infection: A pilot study

Late-onset Intrauterine growth restriction (IUGR) refers to impaired growth and development of the fetus, characterized by placental morphological abnormalities that affect the fetus's supply of nutrients. Human leukocyte antigen-G (HLA-G) is physiologically expressed during pregnancy, but decreased in normal placenta during the last weeks of gestation possibly inducing childbirth. Several viruses involved in congenital infection, such as herpesviruses, exploit HLA-G expression as an immune-escape mechanism. To date, despite different congenital herpetic infections having been associated with late IUGR, no direct implication of Human herpesvirus 6 (HHV-6) infection has been reported. We evaluated HLA-G expression and HHV-6 infection in 11 placentas from late-onset IUGR newborns and 11 placentas from uncomplicated pregnancies by histopathological and immunohistochemistry analysis. We found higher levels of HLA-G expression and HHV-6 presence in IUGR placenta samples compared with control placenta samples. We report HHV-6 staining in IUGR placenta samples, characterized by high HLA-G expression. These preliminary data suggest a possible involvement of HHV-6 infection in HLA-G deregulation that might affect vessel remodeling and prevent the correct pregnancy outcome in the IUGR condition.

Pregnancy and postpartum levels of circulating maternal sHLA-G in preeclampsia

Preeclampsia is a leading cause of maternal and offspring mortality and morbidity, and predicts increased future cardiovascular disease risk. Placental dysfunction and immune system dysregulation are likely key pathophysiological factors. Soluble human leukocyte antigen G (sHLA-G) may dampen the specific immune response towards placental trophoblasts. Previous studies have shown low sHLA-G levels in preeclampsia, but postpartum, levels are unknown. Furthermore, the relationship between sHLA-G and sFlt-1 and PlGF, placental function markers, is unknown. We hypothesized that low maternal sHLA-G during pregnancy would be associated with placental dysfunction, including preeclampsia, gestational hypertension, and dysregulated sFlt-1 and PlGF, and that sHLA-G would remain decreased following preeclampsia. We included 316 pregnant women: 58 with early-onset preeclampsia (<34 weeks' gestation), 81 with late-onset preeclampsia (≥34 weeks' gestation), 25 with gestational hypertension, and 152 normotensive controls. Postpartum (1 or 3 years), we included 321 women: 29 with early-onset preeclampsia, 98 with late-onset preeclampsia, 57 with gestational hypertension, and 137 who were normotensive during their index pregnancies. In pregnancy, plasma sHLA-G was significantly lower both in the early- and late-onset preeclampsia groups compared to controls. In women with preeclampsia or gestational hypertension, sHLA-G was inversely correlated with serum sFlt-1. Postpartum, plasma sHLA-G levels were significantly higher in women who had had early-onset preeclampsia compared to controls. Our results support that sHLA-G may be important for placental function. Unexpectedly, sHLA-G was elevated up to 3 years after early-onset preeclampsia, suggesting an excessively activated immune system following this severe preeclampsia form, potentially contributing to future cardiovascular disease risk.

NKG2A/CD94 Is a New Immune Receptor for HLA-G and Distinguishes Amino Acid Differences in the HLA-G Heavy Chain

Natural killer (NK) cell therapies are a tool to antagonize a dysfunctional immune system. NK cells recognize malignant cells, traffic to a tumor location, and infiltrate the solid tumor. The immune checkpoint molecule human leukocyte antigen (HLA)-G is upregulated on malignant cells but not on healthy surrounding cells, the requirement of understanding the basis of receptor mediated events at the HLA-G/NK cell interface becomes obvious. The NK cell receptors ILT2 and KIR2DL4 have been described to bind to HLA-G; however, their differential function and expression levels on NK cell subsets suggest the existence of an unreported receptor. Here, we performed a ligand-based receptor capture on living cells utilizing sHLA-G*01:01 molecules coupled to TriCEPS and bound to NK cells followed by mass spectrometric analyses. We could define NKG2A/CD94 as a cognate receptor of HLA-G. To verify the results, we used the reciprocal method by expressing recombinant soluble heterodimeric NKG2A/CD94 molecules and used them to target HLA-G*01:01 expressing cells. NKG2A/CD94 could be confirmed as an immune receptor of HLA-G*01:01. Despite HLA-G is marginal polymorphic, we could previously demonstrate that the most common allelic subtypes HLA-G*01:01/01:03 and 01:04 differ in peptide repertoire, their engagement to NK cells, their catalyzation of dNK cell proliferation and their impact on NK cell development. Continuing these studies with regard to NKG2A/CD94 engagement we engineered recombinant single antigen presenting K562 cells and targeted the surface expressed HLA-G*01:01, 01:03 or 01:04 molecules with NKG2A/CD94. Specificity and sensitivity of HLA-G*01:04/NKG2A/CD94 engagement could be significantly verified. The binding affinity decreases when using K562-G*01:03 or K562-G*01:01 cells as targets. These results demonstrate that the ligand-receptor assignment between HLA-G and NKG2A/CD94 is dependent of the amino acid composition in the HLA-G heavy chain. Understanding the biophysical basis of receptor-mediated events that lead to NK cell inhibition would help to remove non-tumor reactive cells and support personalized mild autologous NK cell therapies.

Could circRNA be a new biomarker for pre-eclampsia?

Pre-eclampsia is a devastating complication of pregnancy which is characterized by hypertension and proteinuria in pregnant women. Pre-eclampsia is important as it is the leading cause of death. Moreover, untreated pre-eclampsia might lead to other lethal complications, for both fetus and mother. Pre-eclampsia can also affect the quality of life in affected women. Despite a large number of risk factors for pre-eclampsia, these risk factors are able to detect just 30% of women who are susceptible to pre-eclampsia. Heterogeneous manifestations of pre-eclampsia necessitate the discovery of potential biomarkers required for its early detection. Circular RNAs (circRNAs) are a type of RNA which are more abundant, specific, and highly organized compared with other types of RNA. Accordingly, circRNAs have been suggested as one of the potential biomarkers for different diseases. Recently, researchers have shown interest in the effects of circRNAs in pre-eclampsia, although the current evidence is limited. The majority of obstetricians are probably not aware of circRNAs as a useful biomarker. Here, we aimed to summarize recent supporting evidence and assess the mechanisms by which circRNAs are involved in pre-eclampsia.

Mitochondria and Coenzyme Q10 in the Pathogenesis of Preeclampsia

Hypertensive disorders during pregnancy constitute one of the main causes of maternal and perinatal morbidity and mortality across the world and particularly in developing countries such as Ecuador. However, despite its impact on public health, the primary pathophysiological processes involved are yet to be elucidated. It has been proposed, among other theories, that an abnormal placentation may induce an endothelial dysfunction, which is ultimately responsible for the final clinical manifestations. Mitochondria, particularly from trophoblastic cells, are responsible for the production of energy, which is extremely important for normal placentation. The malfunction in this supply of energy may produce higher levels of free radicals. In both production of energy and free radicals, coenzyme Q10 (CoQ10) plays a crucial role in electron transport. As such, the role of CoQ10 in the genesis and prevention of preeclampsia has become the focus of a number of research groups, including that of the authors. Developing an in-depth understanding of these mechanisms might allow us to design new and feasible strategies with which we can reduce preeclampsia, particularly in the Latin-American countries.

Preeclampsia: Disease biology and burden, its management strategies with reference to India

Preeclampsia is the cause of significant maternal and fetal mortality and morbidity. It is characterized by new-onset hypertension and proteinuria after 20 weeks of gestation. Preeclamptic women and children born from preeclamptic pregnancies are at greater risk to develop severe cardiovascular complications and metabolic syndromes later in life. The incidence of preeclampsia is estimated to be seven times higher in developing countries as compared to the developed countries. This review summarizes the pathophysiology of preeclampsia, emerging new hypothesis of its origin, risk factors that make women susceptible to developing preeclampsia and the potential of various biomarkers being studied to predict preeclampsia. The health care of developing countries is continuously challenged by substantial burden of maternal and fetal mortality. India despite being a fast developing country, is still far behind in achieving the required maternal mortality rates as per Millennium Development Goals set by the World Health Organization. Further, this review discusses the prevalence of preeclampsia in India, health facilities to manage preeclampsia, current guidelines and protocols followed and government policies to combat this complication in Indian condition.

Trophoblast retrieval and isolation from the cervix: origins of cervical trophoblasts and their potential value for risk assessment of ongoing pregnancies

BACKGROUND

Early during human development, the trophoblast lineage differentiates to commence placentation. Where the placenta contacts the uterine decidua, extravillous trophoblast (EVT) cells differentiate and invade maternal tissues. EVT cells, identified by expression of HLA-G, invade into uterine blood vessels (endovascular EVT), as well as glands (endoglandular EVT), and open such luminal structures towards the intervillous space of the placenta. Endoglandular invasion diverts the contents of uterine glands to the intervillous space, while glands near the margin of the placenta that also contain endoglandular EVT cells open into the reproductive tract. Cells of the trophoblast lineage have thus been recovered from the uterine cavity and endocervical canal. An emerging non-invasive technology [trophoblast retrieval and isolation from the cervix (TRIC)] isolates and examines EVT cells residing in the cervix to explore their origin, biology and relationship to pregnancy and fetal status.

OBJECTIVE AND RATIONALE

This review explores the origins and possible uses of trophoblast cells obtained during ongoing pregnancies (weeks 5-20) by TRIC. We hypothesize that endoglandular EVT cells at the margins of the expanding placenta enter the uterine cavity and are carried together with uterine secretion products to the cervix where they can be retrieved from a Papanicolaou (Pap) smear. The advantages of TRIC for investigation of human placentation and prenatal testing will be considered. Evidence from the literature, and from archived in utero placental histological sections, is presented to support these hypotheses.

SEARCH METHODS

We used 52 out of 80 publications that appeared between 1966 and 2017 and were found by searching the PubMed and Google Scholar databases. The studies described trophoblast invasion of uterine vessels and glands, as well as trophoblast cells residing in the reproductive tract. This was supplemented with literature on human placental health and disease.

OUTCOMES

The literature describes a variety of invasive routes taken by EVT cells at the fetal-maternal interface that could displace them into the reproductive tract. Since the 1970s, investigators have attempted to recover trophoblast cells from the uterus or cervix for prenatal diagnostics. Trophoblast cells from Pap smears obtained at 5-20 weeks of gestation have been purified (>95% β-hCG positive) by immunomagnetic isolation with nanoparticles linked to anti-HLA-G (TRIC). The isolated cells contain the fetal genome, and have an EVT-like expression profile. Similar EVT-like cells appear in the lumen of uterine glands and can be observed entering the uterine cavity along the margins of the placenta, suggesting that they are the primary source of cervical trophoblast cells. Cells isolated by TRIC can be used to accurately genotype the embryo/fetus by targeted next-generation sequencing. Biomarker protein expression quantified in cervical trophoblast cells after TRIC correlates with subsequent pregnancy loss, pre-eclampsia and fetal growth restriction. A key remaining question is the degree to which EVT cells in the cervix might differ from those in the basal plate and placental bed.

WIDER IMPLICATIONS

TRIC could one day provide a method of risk assessment for maternal and fetal disease, and reveal molecular pathways disrupted during the first trimester in EVT cells associated with placental maldevelopment. As perinatal interventions emerge for pregnancy disorders and inherited congenital disorders, TRIC could provide a key diagnostic tool for personalized precision medicine in obstetrics.

Comparison of single nucleotide polymorphisms in the 3' untranslated region of HLA-G in placentas between spontaneous preterm birth and preeclampsia

OBJECTIVE

To compare single nucleotide polymorphisms (SNPs) in the 3'-untranslated region (3'UTR) of human leukocyte antigen (HLA)-G in placentas between spontaneous preterm birth and preeclampsia pregnancies.

RESULTS

Placental samples matched for gestational age were obtained from 20 cases of spontaneous preterm births and 19 cases of preeclampsia. Genomic deoxyribonucleic acid was extracted from placenta tissue and the 3'UTR region of HLA-G was amplified via polymerase chain reaction. Nine SNPs were analyzed by direct Sanger sequencing. There was no significant difference in gestational age at delivery or birth weight between two groups. And there were no significant differences in the allele and phenotype frequencies between two groups.

Shift in Expression of HLA-G mRNA Spliceforms in Pregnancies Complicated by Preeclampsia

OBJECTIVE

Despite emerging data on the in vitro modulatory effects of trophoblast-associated human leukocyte antigen G (HLA-G), its in vivo function needs to be determined. Immunohistochemical studies show a decrease in protein expression of trophoblast HLA-G in preeclampsia. Such a decrease in protein might be the consequence of a shift in HLA-G mRNA spliceform patterns. In an exploratory pilot study we determined trophoblast HLA-G mRNA spliceform distribution in preeclampsia.

METHODS

Placental samples were collected immediately after cesarean delivery from pregnancies complicated by preeclampsia or the syndrome hemolysis, elevated liver enzymes, and low platelet count (HELLP) and uncomplicated normotensive pregnancies as controls. HLA-G mRNA spliceform distribution was analyzed using a semiquantitative reverse transcriptase polymerase chain reaction procedure.

RESULTS

Analysis of HLA-G spliceform distribution showed a significant increase in frequency of the G5 form encoding for a soluble HLA-G molecule in preeclampsia. This increase in G5 form was not found in pregnancies complicated by HELLP.

CONCLUSION

The increased frequency in the expression of the HLA-G G5 spliceform may play a role in the pathophysiology of preeclampsia, in particular through a recently suggested effect of this soluble HLA-G molecule on remodeling of the spiral arteries.

HLA Class Ib Molecules and Immune Cells in Pregnancy and Preeclampsia

Despite decades of research, the highly prevalent pregnancy complication preeclampsia, “the disease of theories,” has remained an enigma. Indeed, the etiology of preeclampsia is largely unknown. A compiling amount of studies indicates that the pathological basis involves a complex array of genetic predisposition and immunological maladaptation, and that a contribution from the mother, the father, and the fetus is likely to be important. The Human Leukocyte Antigen (HLA)-G is an increasing focus of research in relation to preeclampsia. The HLA-G molecule is primarily expressed by the extravillous trophoblast cells lining the placenta together with the two other HLA class Ib molecules, HLA-E and HLA-F. Soluble isoforms of HLA-G have been detected in the early endometrium, the matured cumulus–oocyte complex, maternal blood of pregnant women, in umbilical cord blood, and lately, in seminal plasma. HLA-G is believed to be involved in modulating immune responses in the context of vascular remodeling during pregnancy as well as in dampening potential harmful immune attacks raised against the semi-allogeneic fetus. In addition, HLA-G genetic variants are associated with both membrane-bound and soluble forms of HLA-G, and, in some studies, with preeclampsia. In this review, a genetic contribution from the mother, the father, and the fetus, together with the presence and function of various immune cells of relevance in pregnancy are reviewed in relation to HLA-G and preeclampsia.

A combination of single nucleotide polymorphisms in the 3'untranslated region of HLA-G is associated with preeclampsia

Reduced expression of human leukocyte antigen-G (HLA-G) has been linked to onset of preeclampsia. Associations have also been reported between preeclampsia and single nucleotide polymorphisms (SNP) in the 3'-untranslated region (UTR) of the HLA-G gene. However, there are conflicting results between studies. This studied examined whether a SNP, by itself or in combination with other SNPs, in the 3'UTR of the HLA-G gene is associated with an increased risk of preeclampsia. Placenta samples were obtained from 47 preeclamptic and 68 control cases. DNA was extracted, and the 3'UTR was sequenced and analyzed for nine polymorphisms using different genetic models of inheritance. Four of these polymorphisms have never been analyzed for an association with preeclampsia. Disputing existing reports, preeclamptic cases were suggestively associated with a G/G-genotype at SNP +3187 (p<0.05). Several SNP combinations were more prevalent in preeclampsia cases. Following corrections for multiple testing, one SNP combination (+3027C/C and +3187G/G) was significantly more prevalent in preeclampsia cases using co-dominant, additive, and dominant models (p<0.001). Taken together with the current literature, the data suggests that HLA-G 3'UTR SNP-pair associations, and not individual SNPs, could be useful in a predictive test for the susceptibility to preeclampsia.

Pre-eclampsia: pathophysiology, diagnosis, and management

The incidence of pre-eclampsia ranges from 3% to 7% for nulliparas and 1% to 3% for multiparas. Pre-eclampsia is a major cause of maternal mortality and morbidity, preterm birth, perinatal death, and intrauterine growth restriction. Unfortunately, the pathophysiology of this multisystem disorder, characterized by abnormal vascular response to placentation, is still unclear. Despite great polymorphism of the disease, the criteria for pre-eclampsia have not changed over the past decade (systolic blood pressure > 140 mmHg or diastolic blood pressure ≥ 90 mmHg and 24-hour proteinuria ≥ 0.3 g). Clinical features and laboratory abnormalities define and determine the severity of pre-eclampsia. Delivery is the only curative treatment for pre-eclampsia. Multidisciplinary management, involving an obstetrician, anesthetist, and pediatrician, is carried out with consideration of the maternal risks due to continued pregnancy and the fetal risks associated with induced preterm delivery. Screening women at high risk and preventing recurrences are key issues in the management of pre-eclampsia.

Placental dysferlin expression is reduced in severe preeclampsia

Dysferlin (DYSF) and myoferlin (MYOF), members of the ferlin family of membrane proteins, are co-expressed in human placental syncytiotrophoblast (STB). Although the role of these ferlin proteins in the placenta has yet to be established, it has been suggested that DYSF and MYOF may contribute to the stability of the apical STB plasma membrane. The release of STB-derived cellular debris increases in the setting of preeclampsia (PE), suggesting relative destabilization of the hemochorial interface. To test whether PE was associated with alterations in placental expression of DYSF and/or MYOF, a cross-sectional study was performed using specimens of villous placenta collected form women with severe PE (n=10) and normotensive controls (n=10). DYSF and MYOF expression were examined using quantitative real-time RT-PCR, immunoblotting, and immunofluorescence labeling of tissue specimens. Placental DYSF expression was 57% lower at the mRNA level (p=0.03) and 38% lower at the protein level (p=0.026) in severe PE as compared to normotensive subjects. There were no differences in placental MYOF protein or mRNA expression between these groups. No appreciable changes in the distribution of DYSF or MYOF within placental villi was observed in PE relative to control specimens. We conclude that DYSF expression is reduced in severe PE relative to gestational age-matched controls. As DYSF has a role in membrane repair, these data suggest a role for DYSF in the stability of the apical STB plasma membrane and may account, at least in part, for the increased shedding of microparticles from this membrane in PE.

A single base-pair mutation in the 3'-untranslated region of HLA-G mRNA is associated with pre-eclampsia

Human leukocyte antigen-G (HLA-G) is a non-classical class I HLA molecule that is expressed by extravillous cytotrophoblast cells. This protein may play a critical role in the protection of cytotrophoblasts from maternal immune response, allowing these semi-allogeneic cells to invade the uterus unimpeded. We have demonstrated that diminished placental HLA-G expression is associated with pre-eclampsia. In order to explore fundamental mechanisms underlying this reduced HLA-G expression in pre-eclampsia, we looked for, and found by sequences analysis, a single base-pair mutation in the HLA-G gene 3'-untranslated region (3'UTR) adjacent to an AUUUA motif. This mutation is significantly associated with pre-eclampsia, the severe form being more strongly associated with homozygosity for this mutation than the mild form. Since the null allele was discovered in the HLA-G mRNA 3'UTR adjacent to an AUUUA motif, we also examined the effect of this mutation on HLA-G mRNA stability, and found that half-lives of HLA-G mRNA with the mutation were significantly shorter than without the mutation. These data provide evidence that this mutation could be one of the fundamental mechanisms for lower levels of placental HLA-G protein expression in patients with pre-eclampsia.

Soluble HLA-G and control of angiogenesis

In this review, we summarize the results of a number of our recent in vitro and in vivo experiments demonstrating that, in addition to the immunoregulatory functions, soluble HLA-G molecules also affect endothelial cell activity. We have found that soluble HLA-G1 (also designated HLA-G5) inhibits endothelial cell proliferation, migration and tubule formation, and this occurred through binding to the CD160 receptor and via an apoptotic pathway. Moreover, we have demonstrated that soluble HLA-G1 blocks in vivo rabbit corneal neoangiogenesis. Although it cannot be excluded that other soluble HLA class I molecules may have similar effects, as soluble forms of HLA-G are being produced by trophoblast cells at the maternal-fetal interface during early gestation, we discuss how such anti-angiogenic properties of soluble HLA-G1 may locally influence uterine vascular remodeling.

The role of the immune system in preeclampsia

Recent data demonstrate that an altered immune response may play a key role in the development of preeclampsia. Some epidemiological findings and animal models support this idea. In this article, we review the innate immune system and adaptive immune system in preeclampsia and discuss the pathophysiology of preeclampsia from an immunological viewpoint. The most characteristic immunological finding in preeclampsia is the activation of both the innate and adaptive immune system. Activated neutrophils, monocytes, and NK cells initiate inflammation which induce endothelial dysfunction, and activated T cells may support inadequate tolerance during pregnancy. The cytokine profile in preeclampsia shows that the production of type 1 cytokines, which induce inflammation, is dominant while the production of type 2 cytokines, which regulates inflammation, is suppressed. Furthermore, the immunoregulatory system is down-regulated in preeclampsia and persistent inflammation reduces regulatory T cell function. Therefore, systematical immunoactivation may be one cause of preeclampsia.

Novel risk factor in gastroschisis: Change of paternity

In recent years, an increase in the rate of gastroschisis has been documented in several countries throughout the world. Based on accumulating evidence that a maternal immunologic response to a novel set of paternal antigens may be involved in risk for several adverse pregnancy outcomes, including preeclampsia, reduced birth weight, and preterm delivery, we tested the hypothesis that a pregnancy following a change in fathers (change in paternity) may be a risk factor for gastroschisis. Using a case-control design, we compared the prevalence of change in paternity with the index pregnancy in 102 mothers of isolated gastroschisis cases to the prevalence of change in paternity in 117 mothers of non-malformed infants and 78 mothers of infants with neural tube defects or oral clefts. In a multivariate analysis, the adjusted odds of change in paternity in multigravid case mothers were 7.81 times higher (95% Confidence interval 2.80-21.88) relative to multigravid mothers of malformed and non-malformed controls combined, after adjustment for maternal age. These data suggest that maternal immune factors may play a role in the cause of gastroschisis. Further research is needed to corroborate these findings and to elucidate possible immunologic mechanisms involved in the pathogenesis of gastroschisis.

Mechanisms regulating cytotrophoblast invasion in normal pregnancy and pre-eclampsia

The placental bed underlies the placenta and includes the decidua basalis and underlying myometrium containing the uterine spiral arteries. For successful human haemochorial placentation, the placental bed spiral arteries must undergo considerable alterations. These physiological modifications are thought to be brought about by the interaction of invasive cytotrophoblast with the spiral artery vessel wall. Failure of spiral artery transformation is thought to play an important role in the sequence of events that gives rise to pre-eclampsia. The mechanisms that control human trophoblast invasion in normal, let alone abnormal pregnancy, are still poorly understood. Much of the information on the early physiological changes within the placental bed comes from studies on intact hysterectomy specimens.(1) Details of such events in late pregnancy and in pregnancies complicated by pre-eclampsia and fetal growth restriction are principally derived from the study of placental bed biopsies taken at Caesarean section. The methods of sampling the placental bed have been reviewed elsewhere.(2) Many investigators have relied on in vitro models of trophoblast invasion. In vitro models can be extremely useful in dissecting out some of these processes but may be open to artefacts. The mechanisms underlying normal and failed trophoblast invasion appear to be complex. In this manuscript the mechanisms that control the invasion of trophoblast into the decidua and myometrium are reviewed. Along with this is a review of the purported mechanisms underlying failed spiral artery transformation. Particular emphasis has been placed on topics that have been best studied.

Maternal human leukocyte antigen-G polymorphism is not associated with pre-eclampsia in a Chinese Han population

Pre-eclampsia is a multisystem disorder of pregnancy and remains the leading cause of both maternal and fetal morbidity and mortality in many countries. Despite extensive studies, the underlying mechanisms still remain unknown. Besides its restricted expression in the tissues of placenta and its function in regulating immune suppression and in ensuring successful invasion of placental tissues into maternal deciduas, it has been postulated that HLA-G may play a role in modulation of immune tolerance at the fetal-maternal interface. Aberrant HLA-G expression may result in pregnancy disorders that are associated with poor invasion of extravillous cytotrophoblast into maternal spiral arteries, such as pre-eclampsia. Studies have shown that pre-eclampsia is largely under genetic control, but genetic mechanisms underlying the disorder have yet to be determined. In the current study, we focus on the potential role of HLA-G polymorphism in the pathogenesis of pre-eclampsia. Samples were obtained from Chinese Han primiparous women with pre-eclampsia and irrelative normal women, and case-matched placentas were genotyped for the HLA-G polymorphism in the exons 2, 3, and 4, and the 14-base-pair (bp) insertion/deletion polymorphism in the 3'-untranslated region of exon 8 was analyzed separately. The frequency of HLA-G polymorphism in these samples was not significantly different from those of normal controls, indicating that maternal HLA-G polymorphism is not associated with the risk for pre-eclampsia in this Chinese Han population. However, the maternal 14-bp insertion/deletion polymorphism is ethnically different.

HLA-G and immune tolerance in pregnancy

Multiple mechanisms underlie the surprising willingness of mothers to tolerate genetically different fetal tissues during pregnancy. Chief among these is the choice of HLA-G, a gene with few alleles, rather than the highly polymorphic HLA-A and -B genes, for expression by the placental cells that interface directly with maternal blood and tissues. Novel aspects of this major histocompatibility complex class Ib gene include alternative splicing to permit production of membrane and soluble isoforms, deletions that dampen responses to interferons, and a shortened cytoplasmic tail that affects expression at the cell surface. Placental cells migrating into the maternal uterus synthesize both membrane and soluble isoforms, which interact with inhibitory receptors on leukocytes such as ILT2 and ILT4. Cytotoxic T lymphocytes either die or reduce production of one of their major coreceptor/activator cell surface molecules, CD8; natural killer cells are immobilized and mononuclear phagocytes are programmed into suppressive modes characterized by high production of anti-inflammatory cytokines. The idea that placental HLA-G proteins facilitate semiallogeneic pregnancy by inhibiting maternal immune responses to foreign (paternal) antigens via these actions on immune cells is now well established, and the postulate that the recombinant counterparts of these proteins may be used as powerful tools for preventing immune rejection of transplanted organs is gaining in popularity.

Report of the Wet Workshop for Quantification of Soluble HLA-G in Essen, 2004

Membrane-anchored and soluble human leukocyte antigen HLA-G (sHLA-G) molecules exert strong inhibiting signals after interaction with their cognate receptors ILT2 (CD85j), ILT4 (CD85d), and KIR2DL4 (CD158d) that are differentially expressed by natural killer cells, T cells, and antigen-presenting cells. These inhibitory functions can become operative in conditions in which such immune cells try to attack viral infected or tumor cells. Recently, clinical studies showed that sHLA-G molecules are also relevant in the prediction of allograft acceptance after heart transplantation, liver-kidney cotransplantation, and the successful implantation and development of embryos after in vitro fertilization. In view of this diagnostic potential, reliable methods for the measurement of sHLA-G molecules in various body fluids are of interest. Thus, the aims of the Wet Workshop for measurement of sHLA-G held in Essen, Germany (at the Institute of Immunology October 18-20, 2004) were to select and validate HLA-G-specific enzyme-linked immunosorbent assay (ELISA) formats and purified standard HLA-G proteins, which can be easily generated and used as consensual references. To this end, the antibody combinations monoclonal antibody (mAb) MEM-G/9 (capture) + anti-beta2m (detection) and the mAb 5A6G7 (capture) + mAb W6/32 (detection) were chosen in an ELISA format for the simultaneous determination of shed HLA-G1 + soluble HLA-G5 (sHLA-G1 + HLA-G5) and for the exclusive detection of HLA-G5 molecules, respectively. As standard, protein HLA-G5 molecules were purified from insect SF9 cells coinfected by HLA-G5 + human beta2m and characterized for their antigenic determinants. A total of 24 members in 13 teams participated in the 3-day sHLA-G Wet Workshop. All workshop materials, protocols, standard reagents, and samples were provided to each team by the organizers. The Wet-Workshop results clearly demonstrated that (1) the HLA-G5 standard reagent was equally detected by both ELISA formats; (2) sHLA-G1 + G5 and HLA-G5 molecules, respectively, were specifically detected by the two ELISA formats; and (3) both ELISA formats measure reproducibly the amounts of sHLA-G. The comparison of the two ELISA results obtained evidenced that in healthy donors sHLA-G1 molecules can exist in body fluids besides HLA-G5. Moreover, a novel soluble HLA-G structure can be predicted that is recognized by the mAb 5A6G7 + mAb W6/32 antibody combination, but not by the one of mAb MEM-G/9 + anti-beta2m.

Low plasma HLA-G protein concentrations in early gestation indicate the development of preeclampsia later in pregnancy

OBJECTIVE

The aim of this study was to determine whether circulating HLA-G levels, early in pregnancy, predict the subsequent development of preeclampsia (PE).

STUDY DESIGN

Plasma samples, collected longitudinally during the first, second, and third trimesters, from 12 PE patients and 12 matched control patients were tested for HLA-G protein using a validated sandwich ELISA.

RESULTS

First and second trimester HLA-G levels in PE were significantly lower than in control patients (first trimester, 1.25 microg/mL vs 1.95 microg/mL, P=.029; second trimester, 1.11 microg/mL vs 1.90 microg/mL, P=.024).

CONCLUSION

Our results indicate that HLA-G levels in plasma from women who subsequently develop PE are lower than control patients, as early as the first trimester. This suggests that determination of circulating HLA-G protein concentration may be useful as an early predictor for the development of PE.

Immunogenetic Determinants of Preeclampsia and Related Pregnancy Disorders

OBJECTIVE

We sought to systematically review the impact of immunogenetic factors, specifically human leukocyte antigen (HLA) allele frequencies, maternal homozygosity, couple sharing, and maternal-fetal sharing, on the risk of preeclampsia and intrauterine growth restriction.

DATA SOURCES

A computerized search of PubMed databases from 1975 to 2003 was performed with the terms "preeclampsia," "eclampsia," "intrauterine growth restriction," and "human leukocyte antigens" and limited to studies of human subjects in English. No restrictions were placed on study design. All bibliographies were cross-referenced to identify additional pertinent studies.

METHODS OF STUDY SELECTION

Titles and abstracts were reviewed carefully. Observational and basic science research studies were selected if their main objective was to assess the relationship of any aspect of HLA genotypes with preeclampsia and related disorders of pregnancy.

TABULATION, INTEGRATION, AND RESULTS

Data were abstracted and tabulated from 22 original research studies. Meta-analytic techniques were not performed owing to variations in disease and exposure definitions as well as research methodologies. Studies that examined maternal, paternal, and fetal HLA allele frequencies, maternal homozygosity, and couple sharing yielded inconsistent results. Although the cumulative evidence points to the HLA-DR locus (particularly DR4) as a correlate of preeclampsia, it remains unclear whether any specific HLA allele, haplotype, or susceptibility gene in linkage disequilibrium with the HLA region is responsible. Although genetic evidence is suggestive of gene-gene interaction between mother and fetus, few studies have evaluated the influence of maternal-fetal HLA sharing.

CONCLUSION

In the early 1990s, HLA genotypes were dismissed as possible etiologic factors for preeclampsia, based on studies that are heterogeneous with respect to study design, outcome, and exposure assessment. Many of these studies did not take into account the interactions between maternal, paternal, and infant genotypes. Thus, adequately powered studies designed specifically to assess the effect of maternal-fetal HLA sharing on risk of preeclampsia are needed.

Association of human leucocyte antigen sharing with recurrent spontaneous abortions

An estimated 15% of clinically recognized pregnancies abort spontaneously. Recurrent spontaneous abortion (RSA) is defined as three or more consecutive miscarriages conceived with the same partner in the absence of uterine, genetic or autoimmune abnormalities. Evidence points to human leucocyte antigens (HLA) as playing a role in the successful development of the foetus. In particular, HLA compatibility is more prevalent in couples experiencing reproductive failure, especially RSA couples, compared to fertile couples. According to the immunological hypothesis, an adequate immune response is necessary for proper implantation of the embryo; conversely, a depressed response of maternal lymphocytes to the stimulation by paternal antigens because of HLA sharing can result in disorders, such as RSA. The genetic hypothesis implicates homozygosity for recessive lethal alleles in linkage disequilibrium with specific HLA haplotypes. The specificity of HLA alleles or haplotypes responsible for or linked to other RSA susceptibility genes remains unclear. In this study, we identified 40 observational studies (32 case-control, five cohort, one cross-sectional, one case series and one basic science) that examined the associations between HLA and RSA, focusing on HLA allele couple and maternal-foetal sharing, and the special role of HLA-G. We sought to identify consistent findings among studies examining similar questions. Evidence remains divided concerning the role of HLA allele couple sharing. Of major concern is the focus of many studies on couple sharing as a proxy measure of maternal-foetal sharing. Therefore, adequately powered studies are needed, which employ standard case definitions and reproducible methodologies to directly assess the role of maternal-foetal HLA sharing on the risk of RSA.

HLA-G protein concentrations in maternal serum and placental tissue are decreased in preeclampsia

OBJECTIVE

The aim of this study were to determine whether soluble human leukocyte antigen-G protein levels in serum and/or human leukocyte antigen protein in placental tissues differ between women with preeclampsia versus uncomplicated pregnancies. Study design human leukocyte antigen-G levels were determined with the use of a specific enzyme-linked immunosorbent assay in 20 subjects with preeclampsia and 14 normal control subjects.

RESULTS

Both serum and placental human leukocyte antigen-G levels were decreased significantly in the preeclampsia group (median, 0.026 microg/mL in serum; median, 0.026 microg/mg protein in placenta), in comparison with normal pregnant women (median, 0.093 microg/mL in serum; median, 0.088 microg/mg protein in placenta; P=.0112 and P=.0406, respectively). There was a significant correlation between serum and placental human leukocyte antigen-G levels (r=0.603; P=0.0002).

CONCLUSION

The reduced expression of placental human leukocyte antigen-G and reduced release of this protein into the maternal circulation in preeclampsia may alter the maternal-fetal immune relationship and thus be involved in the cause of this disorder.

[The role of HLA-G expression in the embryo during implantation]

HLA-G is a non-classical major histocompatibility complex class I molecule, whose tissue distribution is mainly restricted to the placenta. HLA-G expression in the placenta is found mainly in extravillous cytotrophoblast that invades décidual tissue and maternal spiral arteries as well as villous cytotrophoblast (soluble form). Its function contributes to modulate local placental immunity during pregnancy: it is an immunosuppressive molecule inducing apoptosis of activated CD8(+) T cells and down-modulating CD4(+) T cell proliferation. HLA-G also modulates cytokine secretion of NK cells upon interaction with specific receptors. Soluble HLA-G1 may also contribute to the control of implantation.

HLA-G, pre-eclampsia, immunity and vascular events

Pre-eclampsia, one of the main complications in pregnancy, is characterised by shallow cytotrophoblast invasion of decidua as well as by vascular endothelial cell dysfunction, leading to a poor perfusion of placenta. A striking feature of pre-eclamptic pregnancies is that expression of HLA-G protein is reduced in term placentas compared with normal pregnancy. How such HLA-G deficient expression may be related to the pre-eclamptic pathology is unknown. Here, we review the major structural characteristics of HLA-G and some of its functions that have been recently characterised. Soluble HLA-G1 isoform down-regulates both CD8(+) and CD4(+) T cell reactivity. HLA-G also modulates innate immunity by binding to several NK and/or decidual receptors, inducing particular cytokine secretion. HLA-G was shown to be less susceptible to human cytomegalovirus-derived US protein down-modulation. Finally, soluble HLA-G1 down-regulates endothelial cell proliferation and migration. In view of these different HLA-G properties, we will briefly discuss how defective HLA-G function may contribute to the low trophoblast invasion and vascular abnormalities observed in pre-eclamptic placentas.

Pre-term birth and severe pre-eclampsia are not associated with altered expression of HLA on human trophoblasts

PROBLEM

The unusual pattern of human leukocyte antigen (HLA) expression on human trophoblasts could play an important role in successful pregnancy outcome. To determine whether alterations in HLA expression are associated with pregnancy abnormalities we have investigated expression of these antigens on chorionic and extravillous cytotrophoblasts.

METHODS

Frozen tissue sections of placenta and fetal membranes were collected after pre-term spontaneous delivery, severe pre-eclampsia pre-term Caesarean section, normal term delivery and term Caesarean section. HLA expression was analyzed by immunohistochemistry.

RESULTS

We did not observe differences in the expression of HLA on chorionic and extravillous cytotrophoblasts in pregnancy abnormalities. However, we noted higher expression levels of HLA class Ia molecules in amnion epithelial cells in pre-term deliveries. Furthermore, in severe pre-eclampsia the number of extravillous cytotrophoblast islands were elevated when compared with pre-term deliveries.

CONCLUSIONS

No alterations in expression of HLA class Ia, HLA-G and HLA class II on human trophoblasts in pregnancy abnormalities were seen.

HLA-G Molecules: from Maternal–Fetal Tolerance to Tissue Acceptance

Over the past few years, HLA-G, the non-classical HLA class I molecule, has been the center of investigations that have led to the description of its specific structural and functional properties. Although located in the HLA class I region of chromosome six, the HLA-G gene may be distinguished from other HLA class I genes by its low polymorphism and alternative splicing that generates seven HLA-G proteins, whose tissue-distribution is restricted to normal fetal and adult tissues that display a tolerogeneic function toward both innate and acquired immune cells. We review these points, with special emphasis on the role of HLA-G in human pathologies, such as cancer, viral infection, and inflammatory diseases, as well as in organ transplantation.

The expressions of intracellular cytokines in the lymphocytes of preeclamptic patients

PURPOSE

The objective of the study was to investigate the intracellular expressions of T helper 1 (Th1) and Th2 cytokines in peripheral blood T lymhocytes and natural killer (NK) cells of patients with preeclampsia and women with uncomplicated pregnancy.

METHOD OF STUDY

Blood samples were taken from 20 patients with preeclampsia and 16 healthy pregnant women. Mononuclear cells were isolated from peripheral blood and stimulated for 5 hr at 37 degrees C and 5% CO2. Next, the cells were stained with antibodies against surface markers of T-cell subsets and NK cells. After fixation and permeabilization processes, the cells were stained with antibodies against intracellular cytokines--interleukin-2 (Il-2) and interferon-gamma (IFN-gamma) as well as Il-10 and Il-4. The intracellular expressions of Th1 and Th2 cytokines were determined using the flow cytometric method. Statistical analysis was performed using Mann-Whitney U-test.

RESULTS

We found that in patients with preeclampsia the expressions of Il-2 were significantly higher when compared with women with uncomplicated pregnancy. Furthermore, in the group of patients with preeclampsia the expressions of Il-2 were higher in T CD 8+ lymphocytes than in T CD4+ cells. The expressions of IFN-gamma did not differ in CD4+ cells and CD8+ cells in both studied groups but they were higher in NK cells in the study group. The expressions of Il-10 were lower in lymphocytes of preeclamptic patients when compared with controls. The expressions of Il-4 did not differ in both studied groups.

CONCLUSIONS

These results suggest that in patients with preeclampsia there is Th1/Th2 imbalance, with predominant Th1 immunity.

Preeclampsia. Part 2: experimental and genetic considerations

Preeclampsia-eclampsia is still one of the leading causes of maternal and fetal morbidity and mortality. Despite active research for many years, the etiology of this disorder exclusive to human pregnancy is an enigma. Recent evidence suggests there may be several underlying causes or predispositions leading to the signs of hypertension, proteinuria, and edema, findings that allow us to make the diagnosis of the "syndrome" of preeclampsia. Despite improved prenatal care, severe preeclampsia and eclampsia still occur. Although understanding of the pathophysiology of these disorders has improved, treatment has not changed significantly in over 50 years. Although postponement of delivery in selected women with severe preeclampsia improves fetal outcome to a degree, this is not done without risk to the mother. In the United States, magnesium sulfate and hydralazine are the most commonly used medications for seizure prophylaxis and hypertension in the intrapartum period. The search for the underlying cause of this disorder and for a clinical marker to predict those women who will develop preeclampsia-eclampsia is ongoing, with its prevention the ultimate goal. This review began with the clinical and pathophysiologic aspects of preeclampsia-eclampsia (Part 1). Now, in Part 2, the experimental observations, the search for predictive factors, and the genetics of this disorder are reviewed.

Cytokine secretion by decidual lymphocytes in transient hypertension of pregnancy and pre-eclampsia

BACKGROUND

Transient hypertension (TH) and preeclampsia (PE) are believed to have different pathophysiology. However, 15-25% of pregnant women initially diagnosed as having TH develop PE. To clarify the immuno-pathogenetical connections between the two syndromes, we studied the pattern of T helper cell (Th)1/Th2 cytokine balance disturbances existing inside maternal decidua in normal pregnancy (NP) and pregnancies complicated with TH and PE.

METHODS

Third-trimester decidual tissue was obtained by curettage of uterine cavity during elective caesarean sections in NP (n = 11), TH (n = 17) and PE (n = 21) patients. Cell suspensions were prepared by an electromechanical dispersal method and centrifugated using a standard gradient sedimentation technique. Isolated lymphocytes were placed in medium (RPMI 1640, 10% fetal calf serum, L-glutamine, penicillin, streptomycin) and cultured for 72 h with or without mitogen phytohaemaglutinine (PHA). The enzyme-linked immunosorbent assay method was used for estimation of interleukin (IL)-2, IL-4, IL-6, IL-10, IL-12 and interferon-gamma (IFN-gamma) in culture supernatant.

STATISTICAL ANALYSIS

The Kruskal-Wallis and the Mann-Whitney U tests were used (p < 0.05).

RESULTS

Both spontaneous and PHA-stimulated secretion of Th2-type cytokines IL-6 and IL-10 was decreased in PE patients compared with TH and NP patients. The concentration of Th1-type cytokine IFN-gamma was increased in patients suffering both from TH and PE.

CONCLUSION

On the base of decidual cytokine secretion, both PE and TH are syndromes of local Th1/Th2 cytokine balance disturbances as compared with NP, and TH seems to be an intermediate step to PE.

Regulation of trophoblast invasion: from normal implantation to pre-eclampsia

Conversion of the maternal spiral arteries into larger competent vessels is one of the essential steps in the development of the normal placenta. This process is apparently dependent on the invasion by trophoblasts of the sub-endometrial area and the spiral arteries. Preeclampsia is characterized by shallow trophoblast invasion and unconverted narrow spiral arteries. This leads to fetal hypoxia that causes endothelial injury that eventually manifest as maternal hypertension, edema, and proteinuria. The following steps have been shown to be involved in the breakthrough of the trophoblasts from the uterine cavity into the decidua and the spiral arteries: trophoblast targeting, adhesion, and detachment from the extracellular matrix (ECM), invasion of the ECM and maternal vessels by proteolysis. Abnormal expression and activity of these molecules may explain in part some of the molecular mechanisms leading to abnormal placentation and the development of preeclampsia.

Is antigen presentation the primary function of HLA-G?

Human histocompatibility leukocyte antigen (HLA)-G is an antigen-presenting molecule. This review discusses the possibility that this might not be its primary function. HLA-G indeed modulates innate immunity by interacting with immunoglobulin-like receptors and by regulating HLA-E expression and its subsequent interaction with CD94/NKG2 receptors. HLA-G also down-modulates both CD8(+) and CD4(+) T-cell responsiveness.

The expression and concentrations of Fas/APO-1 (CD95) antigen in patients with severe pre-eclampsia

PROBLEM

Apoptosis has been proposed as a mechanism for maintaining homeostasis in the immune system. Activated lymphocytes are removed by a Fas/FasL-mediated programmed cell death process called activation induced cell death (AICD). The aim of the study was to investigate surface Fas antigen (APO-1, CD95) expression on T lymphocytes and NK cells and also soluble Fas antigen concentrations in pre-eclamptic patients and healthy pregnant women.

MATERIALS AND METHODS

Sixteen pre-eclamptic patients and 18 healthy pregnant women were studied. Peripheral blood lymphocytes were isolated, labeled by direct staining with anti-CD95 monoclonal antibodies and analyzed using the flow cytometric method. Furthermore, the concentrations of soluble CD95 molecule in serum of patients with severe pre-eclampsia and women with uncomplicated pregnancy were measured using ELISA method.

RESULTS

We found that Fas antigen expression and fluorescence intensity on T CD8+ lymphocytes were higher in patients with severe pre-eclampsia in comparison with healthy pregnant women (P<0.05). Furthermore, the concentrations of soluble CD95 molecule were higher in the group of pre-eclamptic patients when compared to controls (P<0.001).

CONCLUSIONS

These findings suggest that T CD8+ lymphocytes in patients with severe pre-eclampsia can be activated. Moreover, higher concentrations of soluble CD95 antigen can suggest altered possibilities to undergo Fas/FasL-mediated activation induced cell death process of lymphocytes in severe pre-eclampsia.

Analysis of the role of HLA-G in preeclampsia

Preeclampsia (PE) is a multisystem disorder of human pregnancy, occurring in 5%-10% of all population births and represents the leading cause of both fetal and maternal morbidity and mortality in pregnancy. Although the disorder only becomes clinically apparent late in pregnancy, the underlying pathology indicates that invasion of fetal trophoblasts into maternal spiral arteries during early pregnancy is shallow or absent in PE. A large number of epidemiologic studies have been carried out and they demonstrate that the disorder is highly heritable and occurs with a high incidence in all populations. Studies have shown that PE is largely under genetic control, but the mode of its inheritance remains unclear. Genetic studies have been carried out using both large scale linkage analysis and candidate gene approaches; however, the genetic mechanisms underlying the disorder have yet to be determined. We focus on the potential role of HLA-G, a nonclassical class I HLA located on chromosome 6, which appears to be a key component in trophoblast invasion. We examine the hypothesis that HLA-G may have a key role in both genetic susceptibility to, and pathogenesis of, PE.

HLA-G has a concentration-dependent effect on the generation of an allo-CTL response

Human leucocyte antigen (HLA) -G is expressed on trophoblast cells during pregnancy, suggesting a role in protection of the semiallogeneic fetus. Published data suggest that HLA-G protects a cell against natural killer cell lysis. It has been hypothesized that HLA-G may also protect the fetus by preventing allo-cytotoxic T lymphocyte (CTL) responses. To test this hypothesis, we assayed the effects of various concentrations of purified HLA-G on CTL response in a mixed lymphocyte culture (MLC) system. We found that concentrations > or =0.1 microg/ml of HLA-G suppressed the allo-CTL response by 30-100% over the control, but, paradoxically, concentrations of 0.01-0.05 microg/ml of HLA-G augmented the allo-CTL response by 25-50% over the control. Concentrations < or = 0.001 microg/ml HLA-G had no effect. Addition of HLA-G to preprimed allo-CTL effector cells did not affect their killing ability. Allo-CTL suppressive doses of HLA-G induced a T helper type 2 (Th2) cytokine response, whereas allo-CTL-enhancing doses of HLA-G induced a Th1-type cytokine response. HLA-G purified from first-trimester placenta does not affect allo-proliferative responses nor does it alter the percentage of CD4+ or CD8+ T cells in MLCs. These findings support a potential role for HLA-G-mediated suppression of allo-CTL formation in normal pregnancies. In addition, the effects observed at lower concentrations of HLA-G may have interesting implications for the condition of pre-eclampsia in which concentrations of this HLA class I molecule are reduced.

A null mutation in HLA-G is not associated with preeclampsia or intrauterine growth retardation

Modulation of the expression of genes of the major histocompatibility complex (MHC) in tissues at the maternal-fetal interface almost certainly plays a role in successful development of the semi-allogeneic fetus. While expression of the classical class I genes (HLA-A, B, C) is low to non-existent at this site, the non-classical molecule, HLA-G, is expressed uniquely in fetal cells at the maternal-fetal interface. The recent demonstration that homozygotes for a deletion mutation in exon 3 (1597DeltaC) of HLA-G do not express the full-length HLA-G1 isoforms indicates a potential reduction in expression of this isoform in heterozygotes. If the full-length isoform of HLA-G (i.e. HLA-G1) contributes to proper invasion of maternal spiral arteries by extravillous cytotrophoblast, then 1597DeltaC heterozygotes could be at increased risk for disorders of trophoblast invasion. Two populations, infants with intrauterine growth retardation (IUGR) and infants of preeclamptic (PE) mothers, were genotyped for the 1597DeltaC polymorphism. The frequency of 1597DeltaC in these samples was not significantly different from healthy controls, suggesting that heterozygotes for this deletion mutation are not at significantly increased risk for PE or IUGR (P = 0.727 and 0.803, respectively).

T helper 1- and T helper 2-type cytokine imbalance in pregnant women with pre-eclampsia

OBJECTIVES

The purpose of our study was to investigate T helper 1/T helper 2 balance in pregnant women with pre-eclampsia.

STUDY DESIGN

18 patients with pre-eclampsia and 20 healthy pregnant women were included in the study. Peripheral blood mononuclear cells (PBMC) were stimulated with phytohaemagglutinin (PHA) for 48 h. Cytokine: interleukin-2 (11-2), interferon-gamma (IFN-gamma) and interleukin-10 (I1-10) concentrations in culture supernatants were determined using the ELISA method. Statistical analysis was performed using a standard non-parametric Mann-Whitney U-test.

RESULTS

We found that in pre-eclamptic patients PHA-stimulated 11-2 and IFN-y production was significantly higher (P<0.001) and I1-10 production significantly lower (P<0.005) in comparison with the control group.

CONCLUSION

These results could suggest that there is Th1/Th2 imbalance in pre-eclamptic patients with predominant Th1-type immunity.