Maternal inflammation regulates fetal emergency myelopoiesis.

Neonates are highly susceptible to inflammation and infection. Here, we investigate how late fetal liver (FL) mouse hematopoietic stem and progenitor cells (HSPCs) respond to inflammation, testing the hypothesis that deficits in the engagement of emergency myelopoiesis (EM) pathways limit neutrophil output and contribute to perinatal neutropenia. We show that fetal HSPCs have limited production of myeloid cells at steady state and fail to activate a classical adult-like EM transcriptional program. Moreover, we find that fetal HSPCs can respond to EM-inducing inflammatory stimuli in vitro but are restricted by maternal anti-inflammatory factors, primarily interleukin-10 (IL-10), from activating EM pathways in utero. Accordingly, we demonstrate that the loss of maternal IL-10 restores EM activation in fetal HSPCs but at the cost of fetal demise. These results reveal the evolutionary trade-off inherent in maternal anti-inflammatory responses that maintain pregnancy but render the fetus unresponsive to EM activation signals and susceptible to infection.

Human chorionic gonadotrophin indirectly activates peripheral γδT cells to produce interleukin-10 during early pregnancy.

BACKGROUNDS: The immunomodulatory properties of human chorionic gonadotrophin (hCG) have been identified to be critical for successful pregnancy. However, the effects of hCG on peripheral γδT cells during early pregnancy have not been reported previously. METHODS: We cocultured the purified γδT cells and peripheral blood mononuclear cells (PBMCs) with early pregnancy-relevant hCG concentrations and investigated the changes in the immune functional characteristics of γδT cells via flow cytometry assays. RESULTS: The ratios of CD69+ and IL-10+ γδT cells were increased in early pregnant women compared to nonpregnant women. γδT cells expressed low levels of the mannose receptor (CD206) instead of the classical hCG/LH receptor for hCG. The direct treatment of purified γδT cells with early pregnancy-relevant hCG concentrations may have no significant effects on their immune functions. Interestingly, when PBMCs were treated with the same broad range of hCG concentrations, the ratios of CD69+ and IL-10+ γδT cells to total γδT cells were significantly increased. CONCLUSION: Certain early pregnancy-relevant hCG concentrations could enhance the ratios of peripheral CD69+ and IL-10+ γδT cells, contributing to the activation of γδT cells and immunological tolerance during early pregnancy. However, these affects may not be strongly mediated by direct ligand-receptor interactions and they may highly depend on immune microenvironment. Our novel observations propose a perspective into the endocrine-immune dialog that exists between the fetus and maternal immune cells.

Reproductive Immunology and Pregnancy 3.0.

This Special Issue, the third dedicated to reproductive immunology and pregnancy, is another review of the latest trends in research topics in this field [...].

Reproductive outcomes after pregnancy-induced displacement of preexisting microchimeric cells.

Pregnancy confers partner-specific protection against complications in future pregnancy that parallel persistence of fetal microchimeric cells (FMcs) in mothers after parturition. We show that preexisting FMcs become displaced by new FMcs during pregnancy and that FMc tonic stimulation is essential for expansion of protective fetal-specific forkhead box P3 (FOXP3)-positive regulatory T cells (Treg cells). Maternal microchimeric cells and accumulation of Treg cells with noninherited maternal antigen (NIMA) specificity are similarly overturned in daughters after pregnancy, highlighting a fixed microchimeric cell niche. Whereas NIMA-specific tolerance is functionally erased by pregnancy, partner-specific resiliency against pregnancy complications persists in mothers despite paternity changes in intervening pregnancy. Persistent fetal tolerance reflects FOXP3 expression plasticity, which allows mothers to more durably remember their babies, whereas daughters forget their mothers with new pregnancy-imprinted immunological memories.

Immunology of Pregnancy and Systemic Consequences.

Pregnancy is an immunological paradox, with renowned Nobel Prize winning transplantation biologist Sir Peter Brian Medawar being the first to introduce this concept back in 1953. This concept considers how the maternal immune system can tolerate the developing fetus, which is 50% antigenically foreign to the uterus. There have been significant advances in our understanding of the immune system in regulating fertility, pregnancy and in complications of these, and what was once considered a paradox can be seen as a highly evolved system. Indeed, the complexity of the maternal-fetal interface along with our ever-advancing knowledge of immune cells and mediators means that we have a better understanding of these interactions, with gaps still present.  This chapter will summarise the key aspects of the role of the immune system at each stage of pregnancy and highlight the recent advances in our knowledge.

Cases of RhD variants RhD*DAU2/DAU6 and RhD*weak D type 4.1 in pregnant women in Saudi Arabia.

The D antigen is one of the most immunogenic and clinically significant antigens of the Rh blood group system due to its various genotypes that encode for more than 450 different variants. Accurate RhD typing and D variant identification is crucial specially in prenatal screening during pregnancy. Women with RhD -ve phenotype are eligible to Rh immune globulin (RhIG) prophylaxis for the prevention of anti-D alloimmunization and hemolytic disease of the fetus and newborn (HDFN). However, there are some women who possess RhD variant alleles, who are mistakenly grouped as RhD positive and considered not eligible for RhIG prophylaxis, putting them at risk of anti-D alloimmunization and consequently leading to HDFN during subsequent pregnancies. Here, we describe  two cases of RhD variants DAU2/DAU6 and Weak D type 4.1 in obstetric patients who were grouped as RhD +ve with negative antibody screening during routine serologic  testing. Weak/Partial D molecular analysis using genomic DNA Red Cell Genotyping (RCG) revealed that both patients had RhD variants, one of which DAU2/DAU6 allele associated with anti-D alloimmunization. According to routine testing neither patients received RhIG or transfusion. In this case report we document to our knowledge the first reported cases of RhD variants among pregnant women in Saudi Arabia.

The differential expression of toll like receptors and RIG-1 in the placenta of neonates with in utero infections.

Novel biomarkers of in utero infections are needed to help guide early therapy. The toll like receptors (TLRs) and retinoic acid-inducible gene 1 (RIG-1) are proteins involved in the initial reaction of the innate immune system to infectious diseases. This study tested the hypothesis that a panel of TLRs and RIG-1 in the placenta could serve as an early biomarker of in utero infections. The TLRs and RIG-1 expression as determined by immunohistochemistry was scored in 10 control placentas (normal delivery or neonatal damage from known non-infectious cause), 8 placentas from documented in utero bacterial infection, and 7 placentas from documented in utero viral infections blinded to the clinical information. The non-infected placentas showed the following profile: no expression (TLR1, TLR3, TLR4, TLR7, TLR8), moderate expression (TLR2), and strong expression (RIG-1). The bacterial and viral infection cases shared the following profile: no to mild expression (TLR 2, TLR7, and RIG1), moderate expression (TLR4), and strong expression (TLR1, TLR3, and TLR8). The histologic findings in the chorionic villi were equivalent in the infected cases and controls, underscoring the need for molecular testing by the surgical pathologist when in utero infection is suspected. The results suggest that a panel of TLRs/RIG-1 analyses can allow the pathologist and/or clinician to diagnose in utero infections soon after birth. Also, treatments to antagonize the effects of TLR1, 3, and 8 may help abrogate in utero neonatal damage.

A Zika virus-specific IgM elicited in pregnancy exhibits ultrapotent neutralization.

Congenital Zika virus (ZIKV) infection results in neurodevelopmental deficits in up to 14% of infants born to ZIKV-infected mothers. Neutralizing antibodies are a critical component of protective immunity. Here, we demonstrate that plasma IgM contributes to ZIKV immunity in pregnancy, mediating neutralization up to 3 months post-symptoms. From a ZIKV-infected pregnant woman, we isolated a pentameric ZIKV-specific IgM (DH1017.IgM) that exhibited ultrapotent ZIKV neutralization dependent on the IgM isotype. DH1017.IgM targets an envelope dimer epitope within domain II. The epitope arrangement on the virion is compatible with concurrent engagement of all ten antigen-binding sites of DH1017.IgM, a solution not available to IgG. DH1017.IgM protected mice against viremia upon lethal ZIKV challenge more efficiently than when expressed as an IgG. Our findings identify a role for antibodies of the IgM isotype in protection against ZIKV and posit DH1017.IgM as a safe and effective candidate immunotherapeutic, particularly during pregnancy.

IL-10: A bridge between immune cells and metabolism during pregnancy.

Energy metabolism plays a crucial role in the immune system. In addition to providing vital energy for cell growth, reproduction and other cell activities, the metabolism of nutrients such as glucose and lipids also have significant effects on cell function through metabolites, metabolic enzymes, and changing metabolic status. Interleukin-10 (IL-10), as a pleiotropic regulator, can be secreted by a diverse set of cells and can also participate in regulating the functions of various cells, thereby playing an essential role in the formation and maintenance of immune tolerance in pregnancy. Studies on the regulatory effects and mechanisms of IL-10 on immune cells are extensive; however, research from a metabolic perspective is relatively negligible. Here, we have discussed old and new data on the relationship between IL-10 and metabolism. The data show that alterations in cellular metabolism and specific metabolites regulate IL-10 production of immune cells. Moreover, IL-10 regulates immune cell phenotypes and functions by modulating oxidative phosphorylation and glycolysis. This review summarizes some earlier observations regarding IL-10 and its relationship with immune cells in pregnancy, and also presents recent research on the link between IL-10 and metabolism, highlighting the potential relationship between IL-10, immune cells, and energy metabolism during pregnancy.

Uterine Deletion of Bmal1 Impairs Placental Vascularization and Induces Intrauterine Fetal Death in Mice.

Recently, it was demonstrated that the expression of BMAL1 was decreased in the endometrium of women suffering from recurrent spontaneous abortion. To investigate the pathological roles of uterine clock genes during pregnancy, we produced conditional deletion of uterine Bmal1 (cKO) mice and found that cKO mice could receive embryo implantation but not sustain pregnancy. Gene ontology analysis of microarray suggested that uterine NK (uNK) cell function was suppressed in cKO mice. Histological examination revealed the poor formation of maternal vascular spaces in the placenta. In contrast to WT mice, uNK cells in the spongiotrophoblast layer, where maternal uNK cells are directly in contact with fetal trophoblast, hardly expressed an immunosuppressive NK marker, CD161, in cKO mice. By progesterone supplementation, pregnancy could be sustained until the end of pregnancy in some cKO mice. Although this treatment did not improve the structural abnormalities of the placenta, it recruited CD161-positive NK cells into the spongiotrophoblast layer in cKO mice. These findings indicate that the uterine clock system may be critical for pregnancy maintenance after embryo implantation.

Pregnancy enables antibody protection against intracellular infection.

Adaptive immune components are thought to exert non-overlapping roles in antimicrobial host defence, with antibodies targeting pathogens in the extracellular environment and T cells eliminating infection inside cells1,2. Reliance on antibodies for vertically transferred immunity from mothers to babies may explain neonatal susceptibility to intracellular infections3,4. Here we show that pregnancy-induced post-translational antibody modification enables protection against the prototypical intracellular pathogen Listeria monocytogenes. Infection susceptibility was reversed in neonatal mice born to preconceptually primed mothers possessing L. monocytogenes-specific IgG or after passive transfer of antibodies from primed pregnant, but not virgin, mice. Although maternal B cells were essential for producing IgGs that mediate vertically transferred protection, they were dispensable for antibody acquisition of protective function, which instead required sialic acid acetyl esterase5 to deacetylate terminal sialic acid residues on IgG variable-region N-linked glycans. Deacetylated L. monocytogenes-specific IgG protected neonates through the sialic acid receptor CD226,7, which suppressed IL-10 production by B cells leading to antibody-mediated protection. Consideration of the maternal-fetal dyad as a joined immunological unit reveals protective roles for antibodies against intracellular infection and fine-tuned adaptations to enhance host defence during pregnancy and early life.

Biological Characteristics of HLA-G and Its Role in Solid Organ Transplantation.

Organ transplantation is a lifesaving option for patients with advanced diseases. Rejection is regarded as one of the most severe risk factors post-transplantation. A molecule that contributes to immune tolerance and resisting rejection is human leukocyte antigen (HLA)-G, which belongs to the non-classical major histocompatibility complex class (MHC) I family. HLA-G was originally found to play a role during pregnancy to maintain immune tolerance between mother and child. It is expressed in the placenta and detected in several body fluids as soluble factor as well as different membrane isoforms on cells. Recent findings on HLA-G show that it can also play multifaceted roles during transplantation. This review will explain the general characteristics and biological function of HLA-G and summarize the views supporting the tolerogenic and other roles of HLA-G to better understand its role in solid organ transplantation (SOT) and its complications. Finally, we will discuss potential future research on the role of HLA-G in prevention, diagnosis, and treatment in SOT.

Pregnancy tailors endotoxin-induced monocyte and neutrophil responses in the maternal circulation.

OBJECTIVE: To comprehensively characterize monocyte and neutrophil responses to E. coli and its product [lipopolysaccharide (LPS) or endotoxin] in vitro during pregnancy. MATERIAL OR SUBJECTS: Peripheral blood was collected from pregnant women during the third trimester (n = 20) and from non-pregnant women (n = 20). METHODS: The number, phagocytic activity, and reactive oxygen species (ROS) production of peripheral monocytes and neutrophils were investigated using flow cytometry. The phenotypes of peripheral monocytes and neutrophils after acute or chronic LPS stimulation were also determined using flow cytometry. Cytokine profiles were quantified for LPS-stimulated peripheral blood mononuclear cells (PBMCs) and a whole blood TruCulture® system using a multiplex immunoassay. RESULTS: Increased number, phagocytic activity, and ROS production capacity of monocytes and neutrophils were found in pregnant compared to non-pregnant women. Additionally, specific subsets of pro-inflammatory monocytes (IL-6+CD14+ or MIP-1α+CD14+ cells) and neutrophils (IL-1ß+CD15+ or MIP-1ß+CD15+ cells) were increased in pregnant women in response to acute LPS stimulation. Moreover, distinct subsets of intermediate-activated monocytes expressing CD142, IL-6, and IL-1RA were increased in pregnant women upon chronic LPS stimulation. Last, pregnant women displayed a different cytokine profile than non-pregnant women in LPS-stimulated PBMCs and in whole blood. CONCLUSIONS: Pregnancy tailors the immune responses of circulating monocytes and neutrophils to endotoxin, a Gram-negative bacterial product.

Establishment of fetomaternal tolerance through glycan-mediated B cell suppression.

Discrimination of self from non-self is fundamental to a wide range of immunological processes1. During pregnancy, the mother does not recognize the placenta as immunologically foreign because antigens expressed by trophoblasts, the placental cells that interface with the maternal immune system, do not activate maternal T cells2. Currently, these activation defects are thought to reflect suppression by regulatory T cells3. By contrast, mechanisms of B cell tolerance to trophoblast antigens have not been identified. Here we provide evidence that glycan-mediated B cell suppression has a key role in establishing fetomaternal tolerance in mice. B cells specific for a model trophoblast antigen are strongly suppressed through CD22-LYN inhibitory signalling, which in turn implicates the sialylated glycans of the antigen as key suppressive determinants. Moreover, B cells mediate the MHC-class-II-restricted presentation of antigens to CD4+ T cells, which leads to T cell suppression, and trophoblast-derived sialoglycoproteins are released into the maternal circulation during pregnancy in mice and humans. How protein glycosylation promotes non-immunogenic placental self-recognition may have relevance to immune-mediated pregnancy complications and to tumour immune evasion. We also anticipate that our findings will bolster efforts to harness glycan biology to control antigen-specific immune responses in autoimmune disease.

Th17/Regulatory T cells ratio evolution: A prospective study in a group of healthy pregnant women.

During pregnancy, the maternal immune system is challenged to tolerate a semi-allogenic fetus. A shift toward a tolerogenic profile is essential to ensure a healthy fetal and placental development. One of the most important mechanisms involved in the maternal immune tolerance towards the fetal antigens is expressed in the activity of the regulatory T (Treg) and Th17 cells. The behavior and equilibrium of these two T lymphocyte populations were rarely studied in normal healthy pregnancies through the beginning of gestation to the postpartum period. We conducted a prospective longitudinal observational study where peripheral blood lymphocyte subsets were analyzed in each trimester of pregnancy and postpartum period in a group of healthy pregnant women. Our study observed a consistent reduction in peripheric Treg cell count through all pregnancy while the Th17 cell count remained stable. The Th17/Treg ratio increases significantly throughout pregnancy to the postpartum period. These changes could be justified by the migration of the immunotolerant Treg cells to the maternal decidua and lead to the establishment of a systemic pro-inflammatory profile by the end of pregnancy. This data could explain why systemic syndromes like preeclampsia develop in susceptible women during the second half of pregnancy or why many autoimmune disorders flourish in the first weeks postpartum.

Placental galectins regulate innate and adaptive immune responses in pregnancy.

Introduction: Galectins are master regulators of maternal immune responses and placentation in pregnancy. Galectin-13 (gal-13) and galectin-14 (gal-14) are expressed solely by the placenta and contribute to maternal-fetal immune tolerance by inducing the apoptosis of activated T lymphocytes and the polarization of neutrophils toward an immune-regulatory phenotype.Furthermore, their decreased placental expression is associated with pregnancy complications, such as preeclampsia and miscarriage. Yet, our knowledge of the immunoregulatory role of placental galectins is incomplete. Methods: This study aimed to investigate the effects of recombinant gal-13 and gal-14 on cell viability, apoptosis, and cytokine production of peripheral blood mononuclear cells (PBMCs) and the signaling pathways involved. Results: Herein, we show that gal-13 and gal-14 bind to the surface of non-activated PBMCs (monocytes, natural killer cells, B cells, and T cells) and increase their viability while decreasing the rate of their apoptosis without promoting cell proliferation. We also demonstrate that gal-13 and gal-14 induce the production of interleukin (IL)-8, IL-10, and interferon-gamma cytokines in a concentration-dependent manner in PBMCs. The parallel activation of Erk1/2, p38, and NF-ĸB signaling evidenced by kinase phosphorylation in PBMCs suggests the involvement of these pathways in the regulation of the galectin-affected immune cell functions. Discussion: These findings provide further evidence on how placenta-specific galectins assist in the establishment and maintenance of a proper immune environment during a healthy pregnancy.

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

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

The New Old CD8+ T Cells in the Immune Paradox of Pregnancy.

CD8+ T cells are the most frequent T cell population in the immune cell compartment at the feto-maternal interface. Due to their cytotoxic potential, the presence of CD8+ T cells in the immune privileged pregnant uterus has raised considerable interest. Here, we review our current understanding of CD8+ T cell biology in the uterus of pregnant women and discuss this knowledge in relation to a recently published immune cell Atlas of human decidua. We describe how the expansion of CD8+ T cells with an effector memory phenotype often presenting markers of exhaustion is critical for a successful pregnancy, and host defense towards pathogens. Moreover, we review new evidence on the presence of long-lasting immunological memory to former pregnancies and discuss its impact on prospective pregnancy outcomes. The formation of fetal-specific memory CD8+ T cell subests in the uterus, in particular of tissue resident, and stem cell memory cells requires further investigation, but promises interesting results to come. Advancing the knowledge of CD8+ T cell biology in the pregnant uterus will be pivotal for understanding not only tissue-specific immune tolerance but also the etiology of complications during pregnancy, thus enabling preventive or therapeutic interventions in the future.

HLA-G/sHLA-G and HLA-G-Bearing Extracellular Vesicles in Cancers: Potential Role as Biomarkers.

As a non-classic major histocompatibility complex (MHC) class I molecule, human leukocyte antigen G (HLA-G) is expressed in fetal-maternal interface and immunoprivileged site only in healthy condition, and in pathological conditions such as cancer, it can be de novo expressed. It is now widely accepted that HLA-G is a key molecule in the process of immune escape of cancer cells, which is ubiquitously expressed in the tumor environment. This raises the possibility that it may play an adverse role in tumor immunity. The expression level of HLA-G has been demonstrated to be highly correlated with clinical parameters in many tumors, and its potential significance in the diagnosis and prognosis of cancer has been postulated. However, because HLA-G itself has up to seven different subtypes, and for some subtypes, detected antibodies are few or absent, it is hard to evaluate the actual expression of HLA-G in tumors. In the present work, we described (a) the structure and three main forms of HLA-G, (b) summarized the mechanism of HLA-G in the immune escape of tumor cells, (c) discussed the potential role of HLA-G as a tumor marker, and reviewed (d) the methods for detecting and quantifying HLA-G.