The involvement of HLA-E and -F in pregnancy

Pre-eclampsia: Re-visiting pathophysiology, role of immune cells, biomarker identification and recent advances in its management

Pre-eclampsia (PE) is a hypertension condition that occurs exclusively during pregnancy and has the potential to impact nearly all organ systems. It is estimated to complicate approximately 2-8% of pregnancies worldwide. PE is a prominent medical disorder that poses a significant risk to pregnant mothers and their infants. This review commences by giving the most up-to- date concepts about the pathophysiology of PE. The condition involves atypical infiltration of trophoblast cells into the spiral arteries of the decidua and myometrium, resulting in an insufficient establishment of proper blood flow between the uterus and placenta. The aberrant activation of natural killer (NK) cells in both the peripheral blood and the decidua has been identified as one of the contributing factors to the development of PE. The strong evidence for the genetic etiology of PE is provided by the association between maternal killer cell immunoglobulin-like receptor (KIR) and Human Leukocyte Antigen (HLA-C) in trophoblast cells. Recent observations provide evidence that changes in the expression of anti-angiogenic factors in the placenta are the underlying cause of the clinical symptoms associated with the condition. This review also provides a comprehensive overview of the latest advancements in understanding the underlying causes of PE. It specifically highlights the emergence of new diagnostic biomarkers and their potential implications for therapeutic interventions in managing this medical condition.

Diversity in the HLA-I Recognition of HLA-F Monoclonal Antibodies: HLA-F or HLA-Ib Monospecific, HLA-E or HLA-G Bispecific Antibodies with or without HLA-Ia Reactivity

Previous investigators have used various anti-HLA-F monoclonal antibodies (mAbs) to demonstrate that the tissue distribution of HLA-F is highly restricted. Notably, these mAbs differed in their immunodiagnostic capabilities. Specifically, mAbs Fpep1.1 and FG1 detected HLA-F intracellularly in B cells but not on the cell surface, whereas mAb 3D11 detected HLA-F on the cell surface. The presence of HLA-F on T cells was recognized by mAb FG1 but not by mAb Fpep1.1. mAb 3D11 detected HLA-F on the cell surface of activated B cells and on peripheral blood lymphocytes, but not on the normal cells. Importantly, mAb 3D11 revealed that HLA-F exists as a heavy chain (HC) monomer, rather than as an HC associated with B2m. Although these mAbs are believed to be specific to HLA-F, their monospecificity has not been formally established, which is critical for immunodiagnostic and therapeutic purposes. Previously, we investigated the diversity of HLA class I reactivities of anti-HLA-E mAbs using HLA-I coated multiplex bead assays on a Luminex platform. We reported that more than 80% of the HLA-E mAbs were cross-reactive with other HLA-I molecules, with exceptionally few truly HLA-E-monospecific mAbs. In the present investigation, we generated IgG mAbs against HCs of HLA-F in Balb/C mice and examined the cross-reactivity of anti-HLA-F mAbs with other HLA-I alleles using a multiplex bead assay on the Luminex platform. Beads coated with an array of HLA homo- and heterodimers of different HLA-Ia (HLA-A, HLA-B, and HLA-C) and Ib (HLA-E, HLA-F, and HLA-G) alleles were used to examine the binding of the anti-HLA-F mAbs. Only two mAbs were HLA-F monospecific, and five were HLA-Ib restricted. Several anti-HLA-F mAbs cross-reacted with HLA-E (n = 4), HLA-G (n = 3), HLA-Ia alleles (n = 9), HLA-G and HLA-Ia (n = 2), and HLA-Ib and HLA-Ia (n = 6). This monospecificity and polyreactivity were corroborated by the presence of HLA-F monospecific and HLA-I-shared sequences. This study emphasizes the need to monitor the mono-specificity of HLA-F for reliable immunodiagnostics and passive immunotherapy.

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.

Human Mesenchymal Stem Cell Sheets Improve Uterine Incision Repair in a Rodent Hysterotomy Model

OBJECTIVE

The study aimed to assess the feasibility of creating and transplanting human umbilical cord mesenchymal stem cell sheets applied to a rat model of hysterotomy, and additionally to determine benefits of human umbilical cord mesenchymal stem cell sheet transplantation in reducing uterine fibrosis and scarring.

STUDY DESIGN

Human umbilical cord mesenchymal stem cell sheets are generated by culturing human umbilical cord mesenchymal stem cells on thermo-responsive cell culture plates. The temperature-sensitive property of these culture dishes facilitates normal cell culture in a thin contiguous layer and allows for reliable recovery of intact stem cell sheets without use of destructive proteolytic enzymes.We developed a rat hysterotomy model using nude rats. The rat uterus has two distinct horns: one horn provided a control/untreated scarring site, while the second horn was the cell sheet transplantation site.On day 14 following surgery, complete uteri were harvested and subjected to histologic evaluations of all hysterotomy sites.

RESULTS

The stem cell sheet culture process yielded human umbilical cord mesenchymal stem cell sheets with surface area of approximately 1 cm².Mean myometrial thickness in the cell sheet-transplanted group was 274 μm compared with 191 μm in the control group (p = 0.02). Mean fibrotic surface area in the human umbilical cord mesenchymal stem cell sheet-transplanted group was 95,861 μm² compared with 129,185 μm² in the control group. Compared with control horn sites, cell sheet-transplanted horns exhibited significantly smaller fibrotic-to-normal myometrium ratios (0.18 vs. 0.27, respectively, p = 0.029). Mean number of fibroblasts in cell sheet-transplanted horns was significantly smaller than the control horns (483 vs. 716/mm², respectively, p = 0.001).

CONCLUSION

Human umbilical cord mesenchymal stem cell sheet transplantation is feasible in a rat model of hysterotomy. Furthermore, use of stem cell sheets reduces fibroblast infiltration and uterine scar fibrotic tissue formation during hysterotomy healing, potentially mitigating risks of uterine scar formation.

KEY POINTS

· Stem cell sheet transplanted to hysterotomy promotes myometrial regeneration and reduced fibrotic tissue formation.. · This study demonstrates the feasibility of using human umbilical cord mesenchymal stem cell sheets..

Roles of γδT cells in pregnancy and pregnancy-related complications

A successful pregnancy is a complex and unique process comprised of discrete events, including embryo implantation, placentation, and parturition. To maintain the balance between maternal-fetal immune tolerance and resistance to infections, the maternal immune system must have a high degree of stage-dependent plasticity throughout the period of pregnancy. Innate immunity is the frontline force for the establishment of early anti-infection and tolerance mechanisms in mammals. Belonging to the innate immune system, a subset of T cells called γδT cells (based on γδT cell receptors) are the main participants in immune surveillance and immune defense. Unlike traditional αβT cells, γδT cells are regarded as a bridge between innate immunity and acquired immunity. In this review, we summarize current knowledge on the functional plasticity of γδT cells during pregnancy. Furthermore, we discuss the roles of γδT cells in pathological pregnancies.

Got your mother in a whirl: The role of maternal T cells and myeloid cells in pregnancy

Appropriate development of the placenta is required for healthy pregnancy to occur. After implantation of the fertilized blastocyst, fetal trophoblasts invade the endometrium and myometrium of the mother's uterus to establish placentation. In this process, fetal trophoblasts encounter maternal immune cells. In this review, we focus on the role of maternal T cells and myeloid cells (macrophages, dendritic cells) in pregnancy and their interaction with trophoblasts. To retain immunologic tolerization, trophoblasts evade immune recognition by T cells and produce factors that modulate their phenotype and function. On top of that, the local environment at the maternal-fetal interface favors expansion of regulatory T cells. Macrophages and dendritic cells are essential in maintaining a healthy pregnancy. They produce soluble factors and act as antigen-presenting cells, thereby interacting with T cells. Herein, M2 macrophages, immature dendritic cells, CD4⁺ Th2 cells, and regulatory T cells represent an axis that maintains a local immune tolerant environment. We consider outstanding issues concerning these cell types and their pathways, which need to be addressed in future investigations. Data from recent single-cell sequencing experiments of the placental bed, to study heterogeneity of maternal immune cells and to predict cell-cell interactions, are discussed. Novel ways for long-term culturing of primary trophoblasts allow for cell-cell interaction studies in a functional way. Future directions should include study of the functionality of currently known and newly identified decidual immune cell subsets in healthy and complicated pregnancies, and their interaction with and modulation by trophoblast cells.

Maternal-Fetal Interplay in Zika Virus Infection and Adverse Perinatal Outcomes

During pregnancy, the organization of complex tolerance mechanisms occurs to assure non-rejection of the semiallogeneic fetus. Pregnancy is a period of vulnerability to some viral infections, mainly during the first and second trimesters, that may cause congenital damage to the fetus. Recently, Zika virus (ZIKV) infection has gained great notoriety due to the occurrence of congenital ZIKV syndrome, characterized by fetal microcephaly, which results from the ability of ZIKV to infect placental cells and neural precursors in the fetus. Importantly, in addition to the congenital effects, studies have shown that perinatal ZIKV infection causes a number of disorders, including maculopapular rash, conjunctivitis, and arthralgia. In this paper, we contextualize the immunological aspects involved in the maternal-fetal interface and vulnerability to ZIKV infection, especially the alterations resulting in perinatal outcomes. This highlights the need to develop protective maternal vaccine strategies or interventions that are capable of preventing fetal or even neonatal infection.

Decreased Soluble Human Leukocyte Antigen E Levels in Patients After Allogeneic Hematopoietic Stem Cell Transplantation Are Associated With Severe Acute and Extended Chronic Graft-versus-Host Disease and Inferior Overall Survival

HLA-E is a member of the non-classical HLA molecules and by interaction with activating or inhibitory receptors of NK and T cells, HLA-E can lead to immune activation or suppression context-dependently. Recently, the non-classical HLA molecules gain more attention in the setting of allogeneic hematopoietic stem cell transplantation (HSCT). Most studies so far have focused on the two most frequent genotypes (HLA-E*01:01 and HLA-E*01:03) and investigated their potential association with clinical endpoints of HSCT, like graft-versus-host disease (GvHD), relapse, and overall survival (OS). However, these studies have produced inconsistent results regarding the role of HLA-E and the clinical endpoints after HSCT. We therefore here investigate the amount of soluble HLA-E (sHLA-E) in patients following HSCT and relate this to the clinical endpoints after HSCT. In univariate analysis, we observe a significant association of reduced levels of sHLA-E with severe acute GvHD, extended chronic GvHD and with inferior OS. Using receiver operating characteristic analyses specific thresholds obtained 1, 2, or 3 month(s) after HSCT were identified being indicative for severe acute GvHD, extended chronic GvHD, or inferior OS. In sub-group analyses, this effect can be confirmed in patients not treated with ATG, but is derogated in ATG-treated patients. Notably, we could not detect any association of the course of sHLA-E levels post-HSCT with the three most frequent HLA-E genotypes (HLA-E*01:03/*01:03, HLA-E*01:01/*01:01, HLA-E*01:01/*01:03). However, with regard to 5-year-OS there was an association of HLA-E*01:03 homozygosity with inferior OS. Taking ATG-treatment, recipient and donor HLA-E genotypes into consideration among other well-known risk factors, the sHLA-E status was found as an independent predictor for the development of extended cGvHD and inferior OS following HSCT irrespective of the sHLA-E thresholds. These findings shed some light on the possible impact of reduced sHLA-E levels after HSCT on GvHD and OS. Thus, sHLA-E appears to be a novel promising candidate for the prediction of clinical HSCT outcome with regards to extended cGvHD and OS.

European Patent in Immunoncology: From Immunological Principles of Implantation to Cancer Treatment

The granted European patent EP 2 561 890 describes a procedure for an immunological treatment of cancer. It is based on the principles of the HLA-supported communication of implantation and pregnancy. These principles ensure that the embryo is not rejected by the mother. In pregnancy, the placenta, more specifically the trophoblast, creates an “interface” between the embryo/fetus and the maternal immune system. Trophoblasts do not express the “original” HLA identification of the embryo/fetus (HLA-A to -DQ), but instead show the non-classical HLA groups E, F, and G. During interaction with specific receptors of NK cells (e.g., killer-immunoglobulin-like receptors (KIR)) and lymphocytes (lymphocyte-immunoglobulin-like receptors (LIL-R)), the non-classical HLA groups inhibit these immunocompetent cells outside pregnancy. However, tumors are known to be able to express these non-classical HLA groups and thus make use of an immuno-communication as in pregnancies. If this occurs, the prognosis usually worsens. This patent describes, in a first step, the profiling of the non-classical HLA groups in primary tumor tissue as well as metastases and recurrent tumors. The second step comprises tailored antibody therapies, which is the subject of this patent. In this review, we analyze the underlying mechanisms and describe the currently known differences between HLA-supported communication of implantation and that of tumors.

HLA-G, -E and -F regulatory and coding region variability and haplotypes in the Beninese Toffin population sample

HLA-G/E/F genes exhibit immunomodulatory properties and are expressed in placenta. Little attention has been devoted to the study of these genes in sub-Saharan African populations, which are yet the most diverse. To fill this gap, we evaluated the complete gene variability, approximately 5.1 kb for HLA-G (n = 149), 7.7 kb for HLA-E (n = 150) and 6.2 kb for HLA-F (n = 152) in the remote Beninese Toffin population, using massive parallel sequencing. Overall, 96, 37 and 68 variable sites were detected along the entire HLA-G, -E and -F, respectively, arranged into region-specific haplotypes; i.e., promoter haplotypes (16, 19, and 15 respectively), coding haplotypes (19, 15, and 29 respectively), 3' untranslated region (3'UTR) haplotypes (12, 7 and 2, respectively) and extended haplotypes (33, 31 and 32 respectively). All promoter/coding/3'UTR haplotypes followed the patterns already described in worldwide populations. HLA-E was the most conserved, exhibiting mainly two full-length encoded-molecules (E*01:01 and E*01:03), followed by HLA-F, three full-length proteins (F*01:01, F*01:02 and F*01:03) and HLA-G, four proteins: three full-length (G*01:01, G*01:03 and G*01:04) and one truncated (G*01:05N). Although HLA-G/E/F alleles in the Toffin population were the most frequently observed worldwide, the frequencies of the coding haplotypes were closely similar to those described for other African populations (Guinea-Conakry and Burkina-Faso), when compared to non-African ones (Brazilian), indicating that variable sites along these genes were present in Africa before human dispersion.

An Ancient Fecundability-Associated Polymorphism Creates a GATA2 Binding Site in a Distal Enhancer of HLA-F

Variation in female reproductive traits, such as fertility, fecundity, and fecundability, are heritable in humans, but identifying and functionally characterizing genetic variants associated with these traits have been challenging. Here, we explore the functional significance and evolutionary history of a G/A polymorphism at SNP rs2523393, which is an eQTL for HLA-F and is significantly associated with fecundability (the probability of being pregnant within a single menstrual cycle). We replicated the association between the rs2523393 genotype and HLA-F expression by using GTEx data and demonstrate that HLA-F is upregulated in the endometrium during the window of implantation and by progesterone in decidual stromal cells. Next, we show that the rs2523393 A allele creates a GATA2 binding site in a progesterone-responsive distal enhancer that loops to the HLA-F promoter. Remarkably, we found that the A allele is derived in the human lineage and that the G/A polymorphism arose before the divergence of modern and archaic humans and segregates at intermediate to high frequencies across human populations. Remarkably, the derived A allele is has also been identified in a GWAS as a risk allele for multiple sclerosis. These data suggest that the polymorphism is maintained by antagonistic pleiotropy and a reproduction-health tradeoff in human evolution.

Pre-eclampsia: the role of highly active antiretroviral therapy and immune markers

PURPOSE OF THE REVIEW

This review highlights the role immune cells and markers such as natural killer (NK) cells, cytokines and human leukocyte antigen (HLA-G) play in predisposing HIV-infected women who are on HAART to develop PE, thus contributing to a better understanding and early diagnosis of PE with a subsequent reduction in maternal foetal and neonatal deaths.

RECENT FINDINGS

Pregnant women infected with the Human Immunodeficiency Virus (HIV) have a 25% risk of mother to child transmission. This risk, however, decreases to 2% if the women is on treatment. Highly active antiretroviral therapy (HAART) is the recommended treatment for both pregnant and non-pregnant women infected with HIV. Treatment with HAART is reported to potentiate predisposition to the development of hypertensive disorders of pregnancy such as pre-eclampsia (PE). Pre-eclampsia accounts for 7-10% of abnormal pregnancies worldwide. Studies demonstrate that pregnant women with HIV have PE at lower frequencies than uninfected women, however, the converse is observed upon HAART initiation. HIV-infected women on HAART exhibit a greater tendency to develop PE, emanating from immune reconstitution induced by HAART. There is paucity of information as to the pathogenesis of PE upon HAART initiation and there are, therefore, controversial data as to whether HAART predisposes women to a lower, equal or higher risk of PE development compared to the general population, further investigations on the impact of HIV infection and HAART on the immune response and rate of PE development in HIV infected pregnant women are urgently needed.

Non-classical human leucocyte antigens in ankylosing spondylitis: possible association with HLA-E and HLA-F

OBJECTIVES

Ankylosing spondylitis (AS) is the most prevalent form of spondyloarthritis, with a known genetic association with the HLA-B27 molecule. The aim of this study was to assess the contribution of the HLA-G, HLA-E and HLA-F to AS susceptibility/protection in Portuguese patients with HLA-B27 AS and HLA-B27 unaffected controls.

METHODS

High-resolution typing of HLA-G, HLA-E and HLA-F was performed in 228 patients with HLA-B27 AS and 244 HLA-B27 unaffected controls. Allelic, genotypic and haplotypic frequencies were compared between cohorts. To replicate the results, single nucleotide polymorphisms (SNPs) in HLA-E and HLA-F genes were typed in Australian cohorts. For further confirmation, a group of European-descent patients with AS and unaffected controls were genotyped for Major Histocompatibility Complex SNPs using the Illumina microarray.

RESULTS

In the Portuguese population, no significant differences were found in HLA-G. For HLA-E, a significant difference was detected for the genotype HLA-E*01:01:01/01:03:01 (p=0.009; pc=0.009; OR=0.51), with a protection effect. For HLA-F, significant differences were detected in the allele HLA-F*01:01:02 (p=0.0049; pc=0.0098; OR=0.60) and corresponding SNP rs2075682 (p=0.0004; pc=0.0008; OR=0.53), suggesting protection and in the genotype HLA-F*01:01:01/01:03:01 (p=0.011; pc=0.043; OR=2.00), suggesting a susceptibility effect. Three G-E-F haplotypes with significant differences were detected but occur in a very small number of individuals. The only significant differences detected in the replication studies were for HLA-E rs1059510 in the Australians and for HLA-F rs1736924 in the European-descent cohorts.

CONCLUSION

Our results reveal suggestive AS protective and susceptibility effects from both HLA-E and HLA-F loci, however with population differences. To our knowledge, this is the first study showing association of HLA-F with AS.

HLA-E regulatory and coding region variability and haplotypes in a Brazilian population sample

The HLA-E gene is characterized by low but wide expression on different tissues. HLA-E is considered a conserved gene, being one of the least polymorphic class I HLA genes. The HLA-E molecule interacts with Natural Killer cell receptors and T lymphocytes receptors, and might activate or inhibit immune responses depending on the peptide associated with HLA-E and with which receptors HLA-E interacts to. Variable sites within the HLA-E regulatory and coding segments may influence the gene function by modifying its expression pattern or encoded molecule, thus, influencing its interaction with receptors and the peptide. Here we propose an approach to evaluate the gene structure, haplotype pattern and the complete HLA-E variability, including regulatory (promoter and 3'UTR) and coding segments (with introns), by using massively parallel sequencing. We investigated the variability of 420 samples from a very admixed population such as Brazilians by using this approach. Considering a segment of about 7kb, 63 variable sites were detected, arranged into 75 extended haplotypes. We detected 37 different promoter sequences (but few frequent ones), 27 different coding sequences (15 representing new HLA-E alleles) and 12 haplotypes at the 3'UTR segment, two of them presenting a summed frequency of 90%. Despite the number of coding alleles, they encode mainly two different full-length molecules, known as E*01:01 and E*01:03, which corresponds to about 90% of all. In addition, differently from what has been previously observed for other non classical HLA genes, the relationship among the HLA-E promoter, coding and 3'UTR haplotypes is not straightforward because the same promoter and 3'UTR haplotypes were many times associated with different HLA-E coding haplotypes. This data reinforces the presence of only two main full-length HLA-E molecules encoded by the many HLA-E alleles detected in our population sample. In addition, this data does indicate that the distal HLA-E promoter is by far the most variable segment. Further analyses involving the binding of transcription factors and non-coding RNAs, as well as the HLA-E expression in different tissues, are necessary to evaluate whether these variable sites at regulatory segments (or even at the coding sequence) may influence the gene expression profile.

HLA class Ib in pregnancy and pregnancy-related disorders

The HLA class Ib genes, HLA-E, HLA-F, and HLA-G, were discovered long after the classical HLA class Ia genes. The elucidation of their functions had a modest beginning. However, their basic functions and involvement in pathophysiology and a range of diseases are now emerging. Although results from a range of studies support the functional roles for the HLA class Ib molecules in adult life, especially HLA-G and HLA-F have most intensively been, and were also primarily, studied in relation to reproduction and pregnancy. The expression of HLA class Ib proteins at the feto-maternal interface in the placenta seems to be important for the maternal acceptance of the semi-allogenic fetus. In contrast to the functions of HLA class Ia, HLA-G possesses immune-modulatory and tolerogenic functions. Here, we review an accumulating amount of data describing the functions of HLA class Ib molecules in relation to fertility, reproduction, and pregnancy, and a possible role for these molecules in certain pregnancy complications, such as implantation failure, recurrent spontaneous abortions, and pre-eclampsia. The results from different kinds of studies point toward a role for HLA class Ib, especially HLA-G, throughout the reproductive cycle from conception to the birth weight of the child.

HLA-E allelic genotype correlates with HLA-E plasma levels and predicts early progression in chronic lymphocytic leukemia

BACKGROUND

Human leukocyte antigen-E (HLA-E) is a nonclassical major histocompatibility complex class I molecule that recently came into sharper focus as a putative marker of advanced tumor stages and disease progression. In solid tumors, increased HLA-E expression as well as elevated soluble HLA-E (sHLA-E) plasma levels are associated with a poor prognosis; however, a role for HLA-E in hematologic malignancies remains to be established.

METHODS

The authors analyzed HLA-E alleles and sHLA-E levels in a cohort of 110 individuals with chronic lymphocytic leukemia (CLL).

RESULTS

In patients with CLL, levels of sHLA-E increased with advanced disease stage (P = .01) and decreased after therapy (P = .01). Longitudinal follow-up revealed that both HLA-E*01:03 alleles and high levels of sHLA-E were significantly associated with a requirement for early treatment in patients with CLL (P = .027 and P = .023, respectively). In vitro, sHLA-E inhibited degranulation and interferon-γ production by natural killer (NK) cells when cocultivated with tumor cells. Moreover, sHLA-E loaded onto microspheres induced transforming growth factor-β release by NK cells. Multivariate analysis revealed that the presence of at least 1 HLA-E*01:03 allele was an independent predictor of a requirement for early treatment.

CONCLUSIONS

HLA-E alleles and sHLA-E levels may represent novel biomarkers for early disease progression in patients with CLL. Cancer 2017;123:814-23. © 2016 American Cancer Society.

Is HLA-E a possible genetic marker relevant for natural conception?

BACKGROUND

HLA-E products, class Ib human leukocyte antigens, act in the immunology of human reproduction as modulators of the maternal immune system during pregnancy.

AIMS

To evaluate HLA-E role in the establishment of a viable pregnancy.

MATERIALS & METHODS

HLA-E was genotyped by sequence-based typing (SBT) and analyzed for specific polymorphisms, comparing couples who underwent assisted reproduction treatment (ART) and fertile control couples.

RESULTS

There was a significant difference in HLA-E allele and genotype distributions between ART couples and control couples. The allele HLA-E*01:03 was observed in 63.2% of ART men and in 35.1% of fertile men (P = 0.0032).

CONCLUSION

These results suggest that HLA-E allelic variants may play a role in the modulation of immune responses in the context of the inability of natural conception and establishment of a viable pregnancy.

Distribution of HLA-G extended haplotypes and one HLA-E polymorphism in a large-scale study of mother-child dyads with and without severe preeclampsia and eclampsia

The etiological pathways and pathogenesis of preeclampsia have rendered difficult to disentangle. Accumulating evidence points toward a maladapted maternal immune system, which may involve aberrant placental expression of immunomodulatory human leukocyte antigen (HLA) class Ib molecules during pregnancy. Several studies have shown aberrant or reduced expression of HLA-G in the placenta and in maternal blood in cases of preeclampsia compared with controls. Unlike classical HLA class Ia loci, the nonclassical HLA-G has limited polymorphic variants. Most nucleotide variations are clustered in the 5'-upstream regulatory region (5'URR) and 3'-untranslated regulatory region (3'UTR) of HLA-G and reflect a stringent expressional control. Based on genotyping and full gene sequencing of HLA-G in a large number of cases and controls (n > 900), the present study, which to our knowledge is the largest and most comprehensive performed, investigated the association between the HLA-G 14-bp ins/del (rs66554220) and HLA-E polymorphisms in mother and newborn dyads from pregnancies complicated by severe preeclampsia/eclampsia and from uncomplicated pregnancies. Furthermore, results from extended HLA-G haplotyping in the newborns are presented in order to assess whether a combined contribution of nucleotide variations spanning the 5'URR, coding region, and 3'UTR of HLA-G describes the genetic association with severe preeclampsia more closely. In contrast to earlier findings, the HLA-G 14-bp ins/del polymorphism was not associated with severe preeclampsia. Furthermore, the polymorphism (rs1264457) defining the two nonsynonymous HLA-E alleles, HLA-E*01:01:xx:xx and HLA-E*01:03:xx:xx, were not associated with severe preeclampsia. Finally, no specific HLA-G haplotypes were significantly associated with increased risk of developing severe preeclampsia/eclampsia.

Expression of bovine non-classical major histocompatibility complex class I proteins in mouse P815 and human K562 cells

Major histocompatibility complex class I (MHC-I) proteins can be expressed as cell surface or secreted proteins. To investigate whether bovine non-classical MHC-I proteins are expressed as cell surface or secreted proteins, and to assess the reactivity pattern of monoclonal antibodies with non-classical MHC-I isoforms, we expressed the MHC proteins in murine P815 and human K562 (MHC-I deficient) cells. Following antibiotic selection, stably transfected cell lines were stained with H1A or W6/32 antibodies to detect expression of the MHC-I proteins by flow cytometry. Two non-classical proteins (BoLA-NC1*00501 and BoLA-NC3*00101) were expressed on the cell surface in both cell lines. Surprisingly, the BoLA-NC4*00201 protein was expressed on the cell membrane of human K562 but not mouse P815 cells. Two non-classical proteins (BoLA-NC1*00401, which lacks a transmembrane domain, and BoLA-NC2*00102) did not exhibit cell surface expression. Nevertheless, Western blot analyses demonstrated expression of the MHC-I heavy chain in all transfected cell lines. Ammonium-sulfate precipitation of proteins from culture supernatants showed that BoLA-NC1*00401 was secreted and that all surface expressed proteins where shed from the cell membrane by the transfected cells. Interestingly, the surface expressed MHC-I proteins were present in culture supernatants at a much higher concentration than BoLA-NC1*00401. This comprehensive study shows that bovine non-classical MHC-I proteins BoLA-NC1*00501, BoLA-NC3*00101, and BoLA-NC4*00201 are expressed as surface isoforms with the latter reaching the cell membrane only in K562 cells. Furthermore, it demonstrated that BoLA-NC1*00401 is a secreted isoform and that significant quantities of membrane associated MHC-I proteins can be shed from the cell membrane.

HLA-F coding and regulatory segments variability determined by massively parallel sequencing procedures in a Brazilian population sample

Human Leucocyte Antigen F (HLA-F) is a non-classical HLA class I gene distinguished from its classical counterparts by low allelic polymorphism and distinctive expression patterns. Its exact function remains unknown. It is believed that HLA-F has tolerogenic and immune modulatory properties. Currently, there is little information regarding the HLA-F allelic variation among human populations and the available studies have evaluated only a fraction of the HLA-F gene segment and/or have searched for known alleles only. Here we present a strategy to evaluate the complete HLA-F variability including its 5' upstream, coding and 3' downstream segments by using massively parallel sequencing procedures. HLA-F variability was surveyed on 196 individuals from the Brazilian Southeast. The results indicate that the HLA-F gene is indeed conserved at the protein level, where thirty coding haplotypes or coding alleles were detected, encoding only four different HLA-F full-length protein molecules. Moreover, a same protein molecule is encoded by 82.45% of all coding alleles detected in this Brazilian population sample. However, the HLA-F nucleotide and haplotype variability is much higher than our current knowledge both in Brazilians and considering the 1000 Genomes Project data. This protein conservation is probably a consequence of the key role of HLA-F in the immune system physiology.

Immunomodulation of classical and non-classical HLA molecules by ionizing radiation

Radiotherapy has been employed for the treatment of oncological patients for nearly a century, and together with surgery and chemotherapy, radiation oncology constitutes one of the three pillars of cancer therapy. Ionizing radiation has complex effects on neoplastic cells and on tumor microenvironment: beyond its action as a direct cytotoxic agent, tumor irradiation triggers a series of alterations in tumoral cells, which includes the de novo synthesis of particular proteins and the up/down-regulation of cell surface molecules. Additionally, ionizing radiation may induce the release of "danger signals" which may, in turn lead to cellular and molecular responses by the immune system. This immunomodulatory action of ionizing radiation highlights the importance of the combined use (radiotherapy plus immunotherapy) for cancer healing. Major histocompatibility complex antigens (also called Human Leukocyte Antigens, HLA in humans) are one of those molecules whose expression is modulated after irradiation. This review summarizes the modulatory properties of ionizing radiation on the expression of HLA class I (classical and non-classical) and class II molecules, with special emphasis in non-classical HLA-I molecules.

Association between decreased plasma levels of soluble human leukocyte antigen-G and severe pre-eclampsia

OBJECTIVE

The aim of this study was to investigate the levels of different isoforms of soluble human leukocyte antigen-G (sHLA-G) in maternal plasma during early and late pregnancy, and to investigate the expression of sHLA-G isoforms in women with early or late-onset severe preeclampsia.

METHODS

This prospective, nested, case-control study was performed in 24 early-onset severe preeclamptic, 34 late-onset severe preeclamptic, and 74 uncomplicated pregnant women. Plasma levels of sHLA-G1/5 were measured using ELISA.

RESULTS

Plasma sHLA-G1 levels in women with late-onset severe preeclampsia were markedly lower compared with normal controls (median: 0 vs. 1.22 ng/mL) at the first trimester, and plasma sHLA-G1 levels in women with early-onset severe preeclampsia were markedly lower compared with normal controls at the second (median: 0 vs. 1.24 ng/mL) and third (median: 0 vs. 1.34 ng/mL) trimesters. There was no difference between the late-onset and early-onset groups at three trimesters. As for sHLA-G5, there was no difference in concentrations among the three groups at any time point. However, compared with controls, more women with early- or late-onset severe preeclampsia had undetectable sHLA-G5 levels in the first (71.4% and 76.2% vs. 14.1%), second (75.0% and 73.3% vs. 19.0%), and third (100.0% and 70.4% vs. 14.8%, respectively) trimester (all P<0.05). sHLA-G1 levels in the first (odds ratio [OR]=0.254, 95% confidence interval [CI]=0.109-0.591, P=0.010), second (OR=0.315, 95% CI=0.158-0.627, P=0.001), and third (OR=0.170, 95% CI=0.054-0.533, P=0.002) trimester was a risk factor for severe preeclampsia.

CONCLUSION

Severe preeclampsia was associated with low/undetectable maternal plasma levels of sHLA-G. Low sHLA-G1 levels might be a risk marker for severe preeclampsia.

Reduced pro-inflammatory profile of γδT cells in pregnant patients with rheumatoid arthritis

Background

During pregnancy, many patients with rheumatoid arthritis (RA) experience disease improvement, whereas patients with ankylosing spondylitis often suffer from persistent active disease. Here we investigated whether pregnancy-related changes in disease activity were associated with changes in the proportion and function of γδT cells.

Methods

The study population comprised 55 patients with RA, 31 patients with ankylosing spondylitis, and 35 healthy controls. Among these participants, 28 RA patients, 21 ankylosing spondylitis patients, and 23 healthy controls were investigated once before conception when possible, at each trimester of pregnancy, and at 8 weeks postpartum. Data were compared with age-matched non-pregnant patients to obtain disease-related background. In all subjects, peripheral Vδ1 and Vδ2 T cells were analyzed for cell frequencies, the activation marker CD69, the cytotoxicity markers NKG2D and NKG2A, and the intracellular cytokines tumor necrosis factor (TNF)α, interferon (IFN)γ, interleukin (IL)-17 and IL-10.

Results

Pregnant patients showed a decreased Vδ2/Vδ1 ratio in the third trimester, which resulted from a slightly reduced proportion of Vδ2 cells. Changes in RA disease activity during pregnancy and postpartum were not associated with numerical proportions of γδT cells but with changes of the cell activation marker CD69 on Vδ1 and Vδ2 cells. Only RA patients showed reduced proportions of TNFα-positive Vδ1and Vδ2 cells and IFNγ-positive Vδ2 cells at the third trimester of pregnancy, a finding that was not apparent in the entire population of CD3 T cells. The proportions of IL-17-positive γδT cells and IL-10-positive γδT cells did not differ between pregnant and non-pregnant women of the different groups.

Conclusions

Changes of disease activity in pregnant RA patients were associated with functional changes in both γδT cell subsets. This reduced pro-inflammatory profile of γδT cells might contribute to the immunomodulation resulting in pregnancy-induced improvement of RA.

Electronic supplementary material

The online version of this article (doi:10.1186/s13075-016-0925-1) contains supplementary material, which is available to authorized users.

HLA-E coding and 3' untranslated region variability determined by next-generation sequencing in two West-African population samples

HLA-E is a non-classical Human Leucocyte Antigen class I gene with immunomodulatory properties. Whereas HLA-E expression usually occurs at low levels, it is widely distributed amongst human tissues, has the ability to bind self and non-self antigens and to interact with NK cells and T lymphocytes, being important for immunosurveillance and also for fighting against infections. HLA-E is usually the most conserved locus among all class I genes. However, most of the previous studies evaluating HLA-E variability sequenced only a few exons or genotyped known polymorphisms. Here we report a strategy to evaluate HLA-E variability by next-generation sequencing (NGS) that might be used to other HLA loci and present the HLA-E haplotype diversity considering the segment encoding the entire HLA-E mRNA (including 5'UTR, introns and the 3'UTR) in two African population samples, Susu from Guinea-Conakry and Lobi from Burkina Faso. Our results indicate that (a) the HLA-E gene is indeed conserved, encoding mainly two different protein molecules; (b) Africans do present several unknown HLA-E alleles presenting synonymous mutations; (c) the HLA-E 3'UTR is quite polymorphic and (d) haplotypes in the HLA-E 3'UTR are in close association with HLA-E coding alleles. NGS has proved to be an important tool on data generation for future studies evaluating variability in non-classical MHC genes.

Impact of human leukocyte antigen molecules E, F, and G on the outcome of transplantation

BACKGROUND

HLA class I molecules are divided into classic (Ia) and nonclassic (Ib). Nonclassic HLA molecules (E, F, and G) have acquired relevance owing to their immunomodulatory properties and possible repercussions for induction of tolerance in organ transplantation. The objective of this study was to identify the impact of these molecules on transplant success or failure.

METHODS

A systematic review of literature was performed with the use of MeSH terms in Pubmed. Clinical trials, randomized clinical trials, case-control studies, and reviews from the past 15 years were included.

RESULTS

HLA-E*0103/E*0103 genotype is associated with lower risk of graft-versus-host disease, decreased mortality, and greater disease-free survival after bone marrow transplantation. There were no significant associations between HLA-F and clinical outcomes in any of the studies. Elevated serum levels of HLA-G were associated with a lower incidence of rejection in hepatic and renal transplantation during the 1st year and lower T-cell response after bone marrow, liver, and kidney transplantation. Detection of mRNA of HLA-G1 was also associated with less graft rejection.

CONCLUSIONS

Current literature suggests that nonclassic HLA Ib molecules play an important role in immunotolerance in organ transplantation; however, more studies are required to predict outcomes related to specific genotypes.

Infection of human amniotic and endothelial cells by Japanese encephalitis virus: Increased expression of HLA-F

Productive infection of human amniotic and endothelial cell lines with Japanese encephalitis virus (JEV) was established leading to the induction of NFκB and HLA-F, a non-classical MHC molecule. Induction of the HLA-F gene and protein in JEV-infected cells was shown to be NFκB dependent since it was blocked by inhibitors of NFκB activation. ShRNA targeting lentivirus-mediated stable knockdown of the p65 subunit of NFκB inhibited JEV-mediated induction of HLA-F both in the amniotic cell line, AV-3 as well as the human brain microendothelial cell line, HBMEC. The induction of HLA-F by treatment of AV-3 with TNF-α was also inhibited by ShRNA mediated knockdown of NFκB. TNF-α treatment of HEK293T cells that were transfected with reporter plasmids under the control of HLA-F enhancer A elements resulted in significant transactivation of the luciferase reporter gene. NFκB-mediated induction of HLA-F following JEV infection and TNF-α exposure is being suggested for the first time.

Sera from early-onset, severely preeclamptic women directly modulate HLA-E expression in the EA.hy296 endothelial cell line

The expression of endothelial HLA-E in the context of the systemic inflammatory response observed in preeclampsia has not been established. An experimental study was designed to determine the effect of the sera of pregnant women on the expression of HLA-E in EA.hy296 endothelial cells. First, measurements of protein fractions were performed in sera from early-onset, severely preeclamptic women without HELLP syndrome, in which there was no significant difference in total proteins between the groups, but a reduced level of plasma albumin and an increase in α1-globulin were observed in both groups of pregnant women compared with non-pregnant women. Measurements of colloid osmotic pressure (COP) using a recalculated albumin/globulin ratio formula determined only a significant decrease in COP in all pregnant groups compared with non-pregnant women. The expression of membrane HLA-E was increased in EA.hy296 endothelial cells stimulated with sera of early-onset, severely preeclamptic women, while recombinant interferon-γ (IFN-γ) significantly reduced the expression of membrane HLA-E. Pro-inflammatory cytokines were measured by Luminex in the serum samples, and increased levels of tumor necrosis factor (TNF) and decreased levels of IFN-γ were observed in early-onset, severe preeclampsia compared with normal pregnancy. Moreover, soluble HLA-E was detected in these serum samples by Western blot and ELISA, but no significant difference was found. This raises the possibility that a systemic inflammatory response promotes a compensatory mechanism of COP balance in severe preeclampsia by release of inflammation-induced factors, including endothelial HLA-E. Evidence is now provided regarding HLA-E expression by EA.hy296 cells.

HLA-G as a tolerogenic molecule in transplantation and pregnancy

HLA-G is a nonclassical HLA class I molecule. In allogeneic situations such as pregnancy or allograft transplantation, the expression of HLA-G has been related to a better acceptance of the fetus or the allograft. Thus, it seems that HLA-G is crucially involved in mechanisms shaping an allogeneic immune response into tolerance. In this contribution we focus on (i) how HLA-G is involved in transplantation and human reproduction, (ii) how HLA-G is regulated by genetic and microenvironmental factors, and (iii) how HLA-G can offer novel perspectives with respect to therapy.

A critical role of non-classical MHC in tumor immune evasion in the amphibian Xenopus model

Non-classical class Ib (class Ib) genes are found in all jawed vertebrates, including the amphibian Xenopus, which possesses at least 20 distinct Xenopus non-classical class Ib genes (XNCs). As an immune evasion strategy, tumors often downregulate surface expression of classical major histocompatibility complex class Ia molecules. In contrast, cancers commonly express class Ib molecules, presenting an alternative for tumor immune recognition. We characterized a novel XNC, XNC10, functionally similar to CD1d from a class Ia-deficient thymic lymphoid tumor (15/0), which grows aggressively in Xenopus LG-15 cloned animals. To investigate the roles of XNC10 in antitumor immunity, we generated stable 15/0-transfectants with silenced XNC10 mRNA and protein expression. Notably, XNC10 silencing resulted in acute tumor rejection by naturally class Ia-deficient syngeneic tadpoles, with greater potency of rejection in tumors with more efficient XNC10 knockdown. In vivo killing assays shows that the rejection of XNC10-deficient tumors is due to a cell-mediated cytotoxic immune response elicited by the tadpole host. Importantly, priming enhances XNC10-deficient tumor rejection. Flow cytometry reveals that XNC10-deficient tumor rejection is associated with an accumulation of XNC10-restricted invariant T cells and conventional CD8 T cells as well as other leukocytes. Similarly, semisolid tumor grafts in tadpoles also exhibit leukocytes infiltration. These findings suggest that XNC10 allows the 15/0-tumor to escape immune recognition and class Ia-independent cytotoxicity, thus emphasizing the critical roles of class Ibs in tumor immunity.

Immune balance at the foeto-maternal interface as the fulcrum of reproductive success

Viviparity has many evolutionary advantages but brings with it the problem of the semi-allogeneic foetus having to coexist with the mother for the duration of pregnancy. In species with haemochorial placentation this problem is particularly evident as foetal trophoblast cells are extensively intermingled with maternal tissue and are directly exposed to maternal blood. Fascinating adaptations on both the foetal and maternal side have allowed for this interaction to be re-directed away from an immune rejection response not only towards immunotolerance, but in fact towards actively supporting reproductive success. Recent data have shown that some of these remarkable adaptations are conserved between mice and humans. Thus, a subset of trophoblast cells that is directly exposed to the maternal uterine environment shares the feature of expressing an unusual antigen repertoire on their surface. Paternal antigens can be recognized by maternal immune cells, in particular uterine natural killer cells that express cognate receptors, to regulate the extensive remodelling events that take place at the implantation site. Detailed genetic dissection experiments in the mouse have further demonstrated the direct impact of antigenic dissimilarity on foetal growth. With the availability of inbred strains, in vitro culture systems of trophoblast stem cells, and in-depth genetic, genomic and epigenomic data the mouse will be a valuable model system to study the intricate immune crosstalk at the foeto-maternal boundary. These insights will pave the way towards unravelling the mutual and synergistic interactions between trophoblast and its surrounding maternal environment, and in doing so help understand pregnancy pathologies.

Suppression of natural killer cell cytotoxicity in postpartum women: time course and potential mechanisms

Little is known about the recovery of the immune system from normal pregnancy and whether the postpartum period is a uniquely adapted immune state. This report extends previous observations from our group of decreased natural killer (NK) cell cytotoxicity in the postpartum period. NK cytotoxicity was measured from 1 week through 9 months postpartum. In addition, NK cytotoxicity was assayed in the presence or absence of pooled plasmas collected from either postpartum or nonpostpartum women. Samples of cells were stained for inhibitory receptors and analyzed by flow cytometry. NK cytotoxicity remained decreased in postpartum women compared to controls through the first 6 postpartum months, returned to normal levels by 9 months, and remained normal at 12 months. NK cytotoxicity during the first 6 months was further inhibited by the addition of pooled plasma to NK cultures from postpartum women, but the addition of pooled plasma from the control group did not affect that group's NK cultures. There were differences in inhibitory receptor staining between the two groups, with decreased CD158a and CD158b and increased NKG2A expression on postpartum NK cells during the first 3 postpartum months. These data suggest that NK cytotoxicity postpartum inhibition lasts 6 months and is influenced by unidentified postpartum plasma components. The effect may also involve receptors on NK cells.

Isolation and characterization of CD276+/HLA-E+ human subendocardial mesenchymal stem cells from chronic heart failure patients: analysis of differentiative potential and immunomodulatory markers expression

Mesenchymal stem cells (MSCs) are virtually present in all postnatal organs as well as in perinatal tissues. MSCs can be differentiated toward several mature cytotypes and interestingly hold potentially relevant immunomodulatory features. Myocardial infarction results in severe tissue damage, cardiomyocyte loss, and eventually heart failure. Cellular cardiomyoplasty represents a promising approach for myocardial repair. Clinical trials using MSCs are underway for a number of heart diseases, even if their outcomes are hampered by low long-term improvements and the possible presence of complications related to cellular therapy administration. Therefore, elucidating the presence and role of MSCs that reside in the post-infarct human heart should provide essential alternatives for therapy. In the current article we show a novel method to reproducibly isolate and culture MSCs from the subendocardial zone of human left ventricle from patients undergoing heart transplant for post-infarct chronic heart failure (HSE-MSCs, human subendocardial mesenchymal stem cells). By using both immunocytochemistry and reverse transcriptase-polymerase chain reaction (RT-PCR), we demonstrated that these cells do express key MSCs markers and do express heart-specific transcription factors in their undifferentiated state, while lacking strictly cardiomyocyte-specific proteins. Moreover, these cells do express immunomodulatory molecules that should disclose their further potential in immune modulation processes in the post-infarct microenvironment. Another novel datum of potentially relevant interest is the expression of cardiac myosin heavy chain at nucclear level in HSE-MSCs. Standard MSCs trilineage differentiation experiments were also performed. The present paper adds new data on the basic biological features of heart-resident MSCs that populate the organ following myocardial infarction. The use of heart-derived MSCs to promote in-organ repair or as a cellular source for cardiomyoplasty is a fascinating and challenging task, which deserves further research efforts.

HLA-E expression in cervical adenocarcinomas: association with improved long-term survival

BACKGROUND

Cervical cancer is the third most common cancer in women worldwide. The most common histopathological subtype is cervical squamous cell carcinoma (SCC, 75-80%), followed by adenocarcinoma (AC) and adenosquamous carcinoma (ASC; together 15-20%). Rising incidence rates of AC have been observed relative and absolute to SCC and evidence is accumulating that cervical AC is a distinct clinical entity. Cervical SCC, ASC, and AC are caused by a persistent infection with high-risk human papillomavirus (HPV) and failed control of the immune system plays a pivotal role in the carcinogenesis of all three histopathological subtypes. Human leukocyte antigen E (HLA-E), a non-classical HLA class Ib molecule, plays an important role in immune surveillance and immune escape of virally infected cells. In this study we investigated HLA-E expression in three well-defined cohorts of cervical AC, ASC, and SCC patients, and determined whether HLA-E expression was associated with histopathological parameters and patient survival.

METHODS AND RESULTS

HLA-E expression was assessed by immunohistochemistry on formalin-fixed, paraffin-embedded tissue sections of 79 SCC, 38 ASC, and 75 AC patients. All patients included were International Federation of Gynaecology and Obstetrics stage I-II and underwent radical hysterectomy with lymphadenectomy as primary treatment. Significant differences between the histopathological subgroups were detected for age distribution, HPV positivity, HPV type distribution, tumour size, tumour infiltration depth, lymph-vascular space invasion, and adjuvant radiotherapy. High expression of HLA-E was found in 107/192 (56%) cervical carcinomas, with significantly more overexpression in cervical AC compared to SCC and ASC (37/79 SCC, 18/38 ASC, and 52/75 AC; P = 0.010). High HLA-E expression in cervical AC was associated with favourable long term disease-specific and recurrence-free survival (P = 0.005 and P = 0.001, respectively).

CONCLUSION

High expression of HLA-E occurred in the majority of all histopathological subtypes of cervical cancer; especially in cervical AC. High HLA-E expression in cervical AC was associated with improved patient survival. This study also highlights the importance of careful evaluation of cervical carcinomas to distinguish histopathological subtypes. In the future, insight into the biological behaviour and distinct molecular carcinogenetic processes of the AC, ASC, and SCC subtypes may contribute to the development of more tumour-specific treatment strategies.

Innate immunity, decidual cells, and preeclampsia

Preeclampsia (PE) manifested by hypertension and proteinuria complicates 3% to 8% of pregnancies and is a leading cause of fetal-maternal morbidity and mortality worldwide. It may lead to intrauterine growth restriction, preterm delivery, and long-term sequelae in women and fetuses, and consequently cause socioeconomic burden to the affected families and society as a whole. Balanced immune responses are required for the maintenance of successful pregnancy. Although not a focus of most studies, decidual cells, the major resident cell type at the fetal-maternal interface, have been shown to modulate the local immune balance by interacting with other cell types, such as bone marrow derived-immune cells, endothelial cells, and invading extravillous trophoblasts. Accumulating evidence suggests that an imbalanced innate immunity, facilitated by decidual cells, plays an important role in the pathogenesis of PE. Thus, this review will discuss the role of innate immunity and the potential contribution of decidual cells in the pathogenesis of PE.

The role of classical and non-classical HLA class I antigens in human tumors

In human tumors alterations in the surface expression and/or function of the major histocompatibility complex (MHC) class I antigens are frequently found and equip neoplastic cells with mechanisms to escape immune control. The aberrant expression of HLA class I molecules can be caused by structural alterations or dysregulations of genes encoding the classical HLA class I antigens and/or components of the HLA class I antigen processing machinery (APM). The dysregulation of APM components could occur at the epigenetic, transcriptional or post-transcriptional level. In some malignancies these abnormalities are significantly associated with a higher tumor staging, grading, disease progression and a reduced survival of patients as well as a failure to CD8(+) T cell-based immunotherapies. In addition to HLA class I abnormalities, expression of the non-classical HLA-G antigen is often induced in tumors, which could be mediated by various microenvironmental factors. Interestingly, soluble HLA-G serum and plasma levels have been useful markers for the prediction of some malignancies. The biological consequence of HLA-G expression or sHLA-G is an escape from T and NK cell-mediated recognition. Thus, alterations of non-classical and classical HLA class I antigens and components of the antigen processing pathway provide tumor cells with different mechanisms to inactivate immune responses resulting in tumor growth and evasion from host immune surveillance.

Epigenetic code and self-identity

Epigenetics is a new and expanding science that studies the chromatin-based regulation of gene expression. It is achieving considerable importance, especially with regard to developmental mechanisms that drive cell and organ differentiation, as well as in all those biological processes that involve response and adaptation to environmental stimuli. One of the most interesting biological questions concerning animals, especially human beings, is the ability to distinguish self from nonself. This ability has developed throughout evolution, both as the main function of the immune system, which defends against attack by foreign organisms and at the level of consciousness of oneself as an individual, one of the highest functions of the brain that enables social life. Here we will attempt to dissect the epigenetic mechanisms involved in establishing these higher functions and describe some alterations of the epigenetic machinery responsible for the impairment of correct self-recognition and self-identity.

Immunology of pregnancy

The conceptual framework for reproductive immunology was put in place over 50 years ago when the survival of the fetal semi-allograft within an immunocompetent mother was first considered. During this time, a number of paradigms have emerged and the mechanisms receiving current attention are those related to immune tolerance, such as regulatory T-cells and indoleamine 2,3,-dioxygenase, and innate immunity, such as natural killer cells, trophoblast debris and inflammation. A key consideration is the temporal and spatial variation in any of these pathways (e.g. implantation v. parturition). As fetally derived trophoblasts are the semi-allogeneic cells with which the maternal immune system comes into contact, understanding the immune response to these cells is critical. There is much interest in the immunological pathways that support a healthy pregnancy and how they might be perturbed in adverse pregnancy outcomes. Additionally, there is increasing awareness that antenatal determinants of the immune function of pregnant women and their offspring have consequences for health and disease in childhood and beyond. Changes in maternal diet over recent decades coincide with the increasing prevalence of allergic and other immune-mediated diseases, and the modification of maternal diet has emerged as a strategy for disease prevention. Approaches undergoing trial at numerous sites around the world include dietary supplementation with fish oil and/or probiotics. Understanding the underlying mechanisms of any positive effect on disease outcomes should reveal further novel strategies for disease prevention.

Epigenetic mechanisms regulate MHC and antigen processing molecules in human embryonic and induced pluripotent stem cells

Background

Human embryonic stem cells (hESCs) are an attractive resource for new therapeutic approaches that involve tissue regeneration. hESCs have exhibited low immunogenicity due to low levels of Mayor Histocompatibility Complex (MHC) class-I and absence of MHC class-II expression. Nevertheless, the mechanisms regulating MHC expression in hESCs had not been explored.

Methodology/Principal Findings

We analyzed the expression levels of classical and non-classical MHC class-I, MHC class-II molecules, antigen-processing machinery (APM) components and NKG2D ligands (NKG2D-L) in hESCs, induced pluripotent stem cells (iPSCs) and NTera2 (NT2) teratocarcinoma cell line. Epigenetic mechanisms involved in the regulation of these genes were investigated by bisulfite sequencing and chromatin immunoprecipitation (ChIP) assays. We showed that low levels of MHC class-I molecules were associated with absent or reduced expression of the transporter associated with antigen processing 1 (TAP-1) and tapasin (TPN) components in hESCs and iPSCs, which are involved in the transport and load of peptides. Furthermore, lack of β2-microglobulin (β2m) light chain in these cells limited the expression of MHC class I trimeric molecule on the cell surface. NKG2D ligands (MICA, MICB) were observed in all pluripotent stem cells lines. Epigenetic analysis showed that H3K9me3 repressed the TPN gene in undifferentiated cells whilst HLA-B and β2m acquired the H3K4me3 modification during the differentiation to embryoid bodies (EBs). Absence of HLA-DR and HLA-G expression was regulated by DNA methylation.

Conclusions/Significance

Our data provide fundamental evidence for the epigenetic control of MHC in hESCs and iPSCs. Reduced MHC class I and class II expression in hESCs and iPSCs can limit their recognition by the immune response against these cells. The knowledge of these mechanisms will further allow the development of strategies to induce tolerance and improve stem cell allograft acceptance.

The hidden maternal-fetal interface: events involving the lymphoid organs in maternal-fetal tolerance

The genetic disparity between the mother and fetus has long enticed immunologists to search for mechanisms of maternal tolerance to fetal antigens. The study of antigen-specific tolerance in murine and human pregnancy has gained new momentum in recent years through the focus on antigen-presenting cells, uterine lymphatics and fetal antigen-specific maternal T cell responses. In mice, we now know that these responses occur within the secondary lymphoid structures as they can be conveniently tracked through the use of defined, often transgenic fetal antigens and maternal T cell receptors. Although the secondary lymphoid organs are sites of both immunization and tolerization to antigens, the immunological processes that occur in response to fetal antigens during the healthy pregnancy must invariably lead to tolerance. The molecular properties of these maternal-fetal tolerogenic interactions are still being unraveled, and are likely to be greatly influenced by tissue-specific microenvironments and the hormonal milieu of pregnancy. In this article, we discuss the events leading to antigen-specific maternal tolerance, including the trafficking of fetal antigens to secondary lymphoid organs, the properties of the antigen-presenting cells that display them to maternal T lymphocytes, and the nature of the ensuing tolerogenic response. Experimental data generated from human biological specimens as well as murine transgenic models are considered.

Mycobacterium tuberculosis peptides presented by HLA-E molecules are targets for human CD8 T-cells with cytotoxic as well as regulatory activity

Tuberculosis (TB) is an escalating global health problem and improved vaccines against TB are urgently needed. HLA-E restricted responses may be of interest for vaccine development since HLA-E displays very limited polymorphism (only 2 coding variants exist), and is not down-regulated by HIV-infection. The peptides from Mycobacterium tuberculosis (Mtb) potentially presented by HLA-E molecules, however, are unknown. Here we describe human T-cell responses to Mtb-derived peptides containing predicted HLA-E binding motifs and binding-affinity for HLA-E. We observed CD8(+) T-cell proliferation to the majority of the 69 peptides tested in Mtb responsive adults as well as in BCG-vaccinated infants. CD8(+) T-cells were cytotoxic against target-cells transfected with HLA-E only in the presence of specific peptide. These T cells were also able to lyse M. bovis BCG infected, but not control monocytes, suggesting recognition of antigens during mycobacterial infection. In addition, peptide induced CD8(+) T-cells also displayed regulatory activity, since they inhibited T-cell proliferation. This regulatory activity was cell contact-dependent, and at least partly dependent on membrane-bound TGF-beta. Our results significantly increase our understanding of the human immune response to Mtb by identification of CD8(+) T-cell responses to novel HLA-E binding peptides of Mtb, which have cytotoxic as well as immunoregulatory activity.