Immunological regulation and the role of autophagy in preeclampsia

Autophagy is a bulk degradation system that maintains cellular homeostasis by producing energy and/or recycling excess proteins. During early placentation, extravillous trophoblasts invade the decidua and uterine myometrium, facing maternal immune cells, which participate in the immune suppression of paternal and fetal antigens. Regulatory T cells will likely increase in response to a specific antigen before and during early pregnancy. Insufficient expansion of antigen-specific Treg cells, which possess the same T cell receptor, is associated with the pathophysiology of preeclampsia, suggesting sterile systemic inflammation. Autophagy is involved in reducing inflammation through the degradation of inflammasomes and in the differentiation and function of regulatory T cells. Autophagy dysregulation induces protein aggregation in trophoblasts, resulting in placental dysfunction. In this review, we discuss the role of regulatory T cells in normal pregnancies. In addition, we discuss the association between autophagy and regulatory T cells in the development of preeclampsia based on reports on the role of autophagy in autoimmune diseases.

Sex dimorphism and cancer immunotherapy: May pregnancy solve the puzzle?

In the immunoncology era, growing evidence has shown a clear sex dimorphism in antitumor immune response with a potential impact on outcomes upon immunecheckpoint blockade (ICI) in patients with cancer. Sex dimorphism could affect tumor microenvironment composition and systemic anticancer immunity; however, the modifications induced by sex are heterogeneous. From a clinical perspective, six metanalyses have explored the role of sex in cancer patients receiving ICI with conflicting results. Environmental and reproductive factors may further jeopardize the sex-related heterogeneity in anticancer immune response. In particular, pregnancy is characterized by orchestrated changes in the immune system, some of which could be long lasting. A persistence of memory T-cells with a potential fetal-antigen specificity has been reported both in human and mice, suggesting that a previous pregnancy may positively impact cancer development or response to ICI, in case of fetal-antigen sharing from tumor cells. On the other hand, a previous pregnancy may also be associated with a regulatory memory characterized by increased tolerance and anergy towards cancer-fetal common antigens. Finally, fetal-maternal microchimerism could represent an additional source of chronic exposure to fetal antigens and may have important immunological implications on cancer development and ICI activity. So far, the role of pregnancy dimorphism (nulliparous vs parous) in women and the impact of pregnancy-related variables remain largely underexplored in cancer patients. In this review, we summarize the evidence regarding sex and pregnancy dimorphism in the context of immune response and anticancer immunotherapy and advocate the importance of analyzing pregnancy variables on ICIs clinical trials.

Paradoxical expression of NRP1 in decidual stromal and immune cells reveals a novel inflammation balancing mechanism during early pregnancy

OBJECTIVE AND DESIGN

To investigate the balancing mechanisms between decidualization-associated inflammation and pregnancy-related immunotolerance.

MATERIAL OR SUBJECTS

Decidual samples from women with normal pregnancy (n = 58) or unexplained spontaneous miscarriage (n = 13), peripheral blood from normal pregnancy and endometria from non-pregnancy (n = 10) were collected. Primary endometrial stromal cells (ESCs), decidual stromal cells (DSCs), decidual immune cells (DICs) and peripheral blood mononuclear cells (PBMCs) were isolated.

TREATMENT

The plasmid carrying neuropilin-1 (NRP1) gene was transfected into ESC for overexpression. To induce decidualization in vitro, ESCs were treated with a combination of 10 nM estradiol, 100 nM progesterone and 0.5 mM cAMP. Anti-Sema3a and anti-NRP1 neutralizing antibodies were applied to block the ligand-receptor interactions.

METHODS

RNA-seq analysis was performed to identify differentially expressed genes in DSCs and DICs, and NRP1 expression was verified by Western blotting and flow cytometry. The secretion of inflammatory mediators was measured using a multifactor cytometric bead array. The effects of Sema3a-NRP1 pathway on DICs were determined by flow cytometry. Statistical differences between groups were compared using the T test and one way or two-way ANOVA.

RESULTS

Combined with five RNA-seq datasets, NRP1 was the only immune checkpoint changing oppositely between DSCs and DICs. The decreased expression of NRP1 in DSCs allowed intrinsic inflammatory responses required for decidualization, while its increased expression in DICs enhanced tolerant phenotypes beneficial to pregnancy maintenance. DSC-secreted Sema3a promoted immunosuppression in DICs via NRP1 binding. In women with miscarriage, NRP1 was abnormally elevated in DSCs but diminished in decidual macrophages and NK cells.

CONCLUSION

NRP1 is a multifunctional controller that balances the inflammatory states of DSCs and DICs in gravid uterus. Abnormal expression of NRP1 is implicated in miscarriage.

Understanding main pregnancy complications through animal models

Since human pregnancy is an inefficient process, achieving desired and pleasant outcome of pregnancy - the birth of a healthy and fit baby - is the main goal in any pregnancy. Spontaneous pregnancy failure is actually the most common complication of pregnancy and Most of these pregnancy losses are not known. Animal models have been utilized widely to investigate the system of natural biological adaptation to pregnancy along with increasing our comprehension of the most important hereditary and non-hereditary factors that contribute to pregnancy disorders. We use model organisms because their complexity better reproduces the human condition. A useful animal model for the disease should be pathologically similar to the disease conditions in humans. Animal models deserve a place in research because of the ethical limitations that apply to pregnant women's experiments. The present review provides insights into the overall risk factors involved in recurrent miscarriage, recurrent implant failure and preeclampsia and animal models developed to help researchers identify the source of miscarriage and the best research and treatment strategy for women with Repeated miscarriage and implant failure.

Human Leukocyte Antigens in Pregnancy and Preeclampsia

Preeclampsia is a pregnancy-induced hypertensive disorder, the pathophysiology of which includes underlying maternal cardiovascular disease, deficient spiral artery remodeling during placenta development, and inflammatory immune responses at the maternal-fetal interface. Human leukocyte antigens (HLA) are major histocompatibility complex molecules essential for the recognition of foreign antigens that is central to immune defense against pathogens and critical determinants for the immune system discriminating between self and non-self tissues, such as in transplantation. Pregnancy represents a naturally existing “transplantation”, where the maternal immune system must be immunologically tolerant to the developing fetus which is 50% allogeneic. It is then unsurprising that HLA also influence normal pregnancy and pregnancy complications including preeclampsia. Here we review the role of classical and non-classical HLA molecules in influencing normal physiologic function during pregnancy and describe the association of HLA with pathophysiology in preeclampsia.

Next generation of immune checkpoint molecules in maternal-fetal immunity

Successful pregnancy is a unique situation requires the maternal immune system to recognize and tolerate a semi-identical fetus and allow normal invasion of trophoblast cells. Although efforts have been made, the deep mechanisms of the maternal-fetal crosstalk have not yet been fully deciphered. Immune checkpoint molecules (ICMs) are a group of negative modulators of the immune response that avoid immune damage. They have been extensively studied in the fields of oncology and transplantation, while the latest evidence suggests that they are closely associated with pregnancy outcomes via multiple inhibitory mechanisms. Although studies have mostly demonstrated the regulatory role of the well-known PD-1, CTLA-4 at the maternal-fetal interface, what is unique about the newly discovered multiple ICMs remains a mystery. Here, we review the latest knowledge on ICMs, focusing on the first generation of checkpoints (PD-1, CTLA-4) and the next generation (Tim-3, Tigit, Lag-3, VISTA) highlighting their immunoregulatory roles in maternal-fetal tolerance and decidual vascular remodeling, and their involvement in pathological pregnancies. The content covers three aspects: the characteristics they possess, the dynamic expression profile of their expression at the maternal-fetal interface, and their involvement in pathological pregnancy. In immunotherapy strategies for pregnancy complications, upregulation of immune checkpoints may play a role. Meanwhile, the impact on pregnancy outcomes when using ICMs in clinical cancer treatment during pregnancy is a topic worth exploring. These may serve as a guide for future basic research and clinical applications of maternal-fetal immunity.

Immunotherapy for cancer treatment during pregnancy

Immunotherapy has greatly improved outcomes for subgroups of patients with cancer. As indications keep expanding, there is an unmet need to gain a better understanding of the effect of these therapies on pregnancy and fertility. During pregnancy, substantial adaptations occur in the maternal immune system to maintain protection against pathogens while avoiding detrimental reactions to the semi-allogeneic fetus. The pathways involved in the establishment of this fetomaternal tolerance can be hijacked by cancers. Immunotherapies that target these inhibitory pathways, or that directly interact with the regulatory immune cells involved in tolerance mechanisms, might therefore result in complications during pregnancy. Similarly, by activating the patient's immune system with immunotherapy, a broad range of immune-related adverse events can occur that could negatively affect the fetus or impede a future desired pregnancy. This Review summarises preclinical and clinical data related to the use of immunotherapy during pregnancy, including all approved immune checkpoint inhibitors, recombinant cytokines, cell therapies, vaccines, and immunomodulatory drugs.

Immune checkpoints and reproductive immunology: Pioneers in the future therapy of infertility related Disorders?

As co-stimulatory receptors, immune checkpoint molecules are found on the surface of various immune cells and transduce inhibitory signals following ligand binding. The most studied members in this regard include PD-1, TIM-3, and CTLA-4. The physiological part immune checkpoints possess is the prevention of dangerous immune attacks towards self-antigens throughout an immune response, which takes place through the negative regulation of the effector immune cells, through the induction of T-cell exhaustion, for instance. It has recently been suggested that each checkpoint reduces immunoactivation via distinct intracellular mechanisms of signaling. Regulators of immune checkpoints are supposed to participate actively in immune defense mechanisms against infections, preventing autoimmunity, transplantation, and tumor immune evasion. In pregnancy, as an active immunotolerance mechanism which is also natural, the maternal immune system encounters two simultaneous challenges; in addition to accepting the semi-allogeneic fetus, the maternal immune system should also prevent infections. In this regard, the part immune checkpoint molecules possess is particularly interesting. Herein, the current understanding of such part in reproductive immunology is described.

Absorption, distribution, metabolism and excretion of hyaluronic acid during pregnancy: a matter of molecular weight

INTRODUCTION

For many years hyaluronic acid (HA) was mainly used for its hydrating properties. However, new applications have recently arisen, considering the biological properties of HA and its molecular weight. Clinical application of low molecular weight HA (LMW-HA) initially was supported by specific absorption data. The identification of high molecular weight HA (HMW-HA) absorption pathways and the knowledge of its physiological role allowed to evaluate its clinical application. Based on the immunomodulatory properties of HMW-HA and its physiological involvement as signaling molecule, pregnancy represents an interesting context of application.

AREA COVERED

This expert opinion includes in-vitro, in-vivo, ex-vivo and clinical studies on gestational models. It provides an overview of the physiological and the therapeutic role of HMW-HA in pregnancy starting from its metabolism. Indeed, HMW-HA is widely involved in several physiological processes as implantation, immune response, uterine quiescence and cervical remodeling, and therefore is an essential molecule for a successful pregnancy.

EXPERT OPINION

Available evidence suggests that HMW-HA administration can support physiological pregnancy, favoring blastocyst adhesion and development, preventing miscarriage and pre-term birth. For this reason, supplementation in pregnancy should be evaluated.

The role of decidual regulatory T cells in the induction and maintenance of fetal antigen-specific tolerance: Imbalance between regulatory and cytotoxic T cells in pregnancy complications

Fetal antigen-specific tolerance is important for maintaining allogeneic pregnancies. Maternal conventional T cells recognize fetal antigens; however, regulatory T (Treg) cells suppress immune reactions against the fetus. Fetal antigen-specific Treg cells are induced in the decidua upon contact with antigen-presenting cells and extravillous trophoblasts (EVTs). Functional alteration of cytotoxic T cells (CTLs) in the decidua also contributes to maintaining the pregnancy. Reduced, dysfunctional, and imbalanced Treg cell distribution likely contributes to the pathogenesis of pregnancy complications, such as miscarriage and preeclampsia. Recent studies have revealed differences in Treg cell characteristics during preeclampsia and miscarriage. Treg cell reduction in the decidua is likely associated with miscarriage. Insufficient expansion of fetal antigen-specific Treg cells in the decidua probably plays a role in preeclampsia pathogenesis. In addition, the balance between Treg cell-mediated tolerance and functional alteration of CTLs is important. Further investigations of functional molecules in Treg cells will contribute to the development of immunotherapy for pregnancy complications.

Gamma/Delta T Cells in the Course of Healthy Human Pregnancy: Cytotoxic Potential and the Tendency of CD8 Expression Make CD56+ γδT Cells a Unique Lymphocyte Subset

To date, pregnancy is an immunological paradox. The semi-allogenic fetus must be accepted by the maternal immune system, while defense against pathogens and immune surveillance cannot be compromised. Gamma/delta T cells are believed to play an important role in this immunological puzzle. In this study, we analyzed peripheral blood CD56+ γδT cells from pregnant women (1^st, 2^nd, and 3^rd trimester) and non-pregnant women by multicolor flow cytometry. Interestingly, γδT cells represent almost half of CD3+/CD56+ cells. Among γδT cells, the CD56+ population expands in the 2^nd and 3^rd trimester. CD56+ γδT cells maintained a predominantly CD4–/CD8– or CD8+ phenotype, while CD56– γδT cells were in similar rates CD4–/CD8– or CD4+ during pregnancy. Investigation of the lysosomal degranulation marker CD107a revealed a preserved elevated rate of potentially cytotoxic CD56+ γδT cells in pregnancy, while their cytotoxic strength was reduced. Furthermore, CD56+ γδT cells continuously showed a higher prevalence of PD-1 expression. CD56+ γδT cells’ rate of PD-1 increased in the 1^st trimester and decreased hereafter back to normal level. We correlated the cytotoxic potential and the expression of the inhibitory immune checkpoint PD-1 and were able to demonstrate that highly cytotoxic cells within this CD56+ γδT population tend to express PD-1, which might allow the inhibition of these cells after binding its ligand in the placenta. These findings should support the understanding of the complex processes, which ensure the maintenance of pregnancy.

Analysis of TCR Repertoire and PD-1 Expression in Decidual and Peripheral CD8+ T Cells Reveals Distinct Immune Mechanisms in Miscarriage and Preeclampsia

CD8⁺ T cells, the most abundant T cell subset in the decidua, play a critical role in the maintenance of pregnancy. The majority of decidual CD8⁺ T cells have an effector memory phenotype, while those in the peripheral blood display a naive phenotype. An increased amount of highly differentiated CD8⁺ T cells in the decidua indicates local antigen stimulation and expansion, albeit these CD8⁺ T cells are suppressed. In decidual CD8⁺ T cells, co-inhibitory molecules such as PD-1, TIM-3, LAG-3, and CTLA-4 are upregulated, reflecting the suppression of cytotoxicity. Previous studies established the importance of the PD-1/PD-L1 interaction for feto-maternal tolerance. CD8⁺ T cells could directly recognize fetal-specific antigens, such as HLA-C, expressed by trophoblasts. However, although fetal-specific CD8⁺ T cells have been reported, their TCR repertoires have not been identified. In this study, we analyzed the TCR repertoires of effector memory CD8⁺ T cells (CD8⁺ EM cells) and naive CD8⁺ T cells (CD8⁺ N cells) in the decidua and peripheral blood of women with normal or complicated pregnancy and examined PD-1 expression at a single-cell level to verify whether antigen-specific CD8⁺ T cells accumulate in the decidua and to identify immunological differences related to the suppression of antigen-specific CD8⁺ T cells between normal pregnancy, miscarriage, and preeclampsia. We observed that some TCRβ repertoires, which might recognize fetal or placental antigens, were clonally expanded. The population size of clonally expanded CD8⁺ EM cells was higher in the decidua than in the peripheral blood. CD8⁺ EM cells began to express PD-1 during the course of normal pregnancy. We found that the total proportion of decidual CD8⁺ EM cells not expressing PD-1 was increased both in miscarriage and in preeclampsia cases, although a different mechanism was responsible for this increase. The amount of cytotoxic CD8⁺ EM cells increased in cases of miscarriage, whereas the expression of PD-1 in clonally expanded CD8⁺ EM cells was downregulated in preeclampsia cases. These results demonstrated that decidual CD8⁺ EM cells were able to recognize fetal-specific antigens at the feto-maternal interface and could easily induce fetal rejection.

Pregnancy associates with alterations to the host and microbial proteome in vaginal mucosa

Problem

Pregnant women are at increased risk of HIV acquisition, but the biological mechanisms contributing to this observation are not well understood.

Method of Study

Here, we assessed host immune and microbiome differences in the vaginal mucosa of healthy pregnant and non‐pregnant women using a metaproteomics approach. Cervicovaginal lavage (CVL) samples were collected from 23 pregnant and 25 non‐pregnant women.

Results

Mass spectrometry analysis of CVL identified 550 human proteins and 376 bacterial proteins from 11 genera. Host proteome analysis indicated 56 human proteins (10%) were differentially abundant (P < .05) between pregnant and non‐pregnant women, including proteins involved in angiogenesis (P = 3.36E‐3), cell movement of phagocytes (P = 1.34E‐6), and permeability of blood vessels (P = 1.27E‐4). The major bacterial genera identified were Lactobacillus, Gardnerella, Prevotella, Megasphaera, and Atopobium. Pregnant women had higher levels of Lactobacillus species (P = .017) compared with non‐pregnant women. Functional pathway analysis indicated that pregnancy associated with changes to bacterial metabolic pathway involved in energy metabolism, which were increased in pregnant women (P = .035).

Conclusion

Overall, pregnant women showed differences in the cervicovaginal proteome and microbiome that may be important for HIV infection risk.

The novel role of Hippo-YAP/TAZ in immunity at the mammalian maternal-fetal interface: Opportunities, challenges

The Hippo-Yes-associated protein (YAP)/transcriptional co-activator with PDZ-binding motif (TAZ), originally identified as a regulator of tissue generation and tumorigenesis, has been proven to have a pivotal position in immunity. Its multi-faceted roles in regulating immunity cover both intrinsic mechanism of immune cells and the crosstalk with non-immune cells. Survival of the allogeneic embryo in the maternal uterine environment depends on immune tolerance, supported by the highly orchestrated cooperation between decidual immune cells, decidual stromal cells and trophoblasts at the maternal-fetal interface. The abnormal maternal-fetal dialogue is believed to be associated with adverse pregnancy outcomes such as spontaneous pregnancy loss. Recent breakthroughs shed light on the how the Hippo-YAP/TAZ manipulate the decidualization and trophoblast invasion, while further research is needed to integrate and reconcile existing findings of the Hippo-YAP/TAZ in immunity and to extend them at the context of pregnancy. In this review, we summarized the Hippo-YAP/TAZ pathways, detailed the effects of YAP/TAZ on immune cells, and discussed the role of YAP/TAZ at the maternal-fetal interface and the potential of YAP/TAZ on immunity regulation at the context of pregnancy. Given the remarkable effect of therapeutic intervention of YAP/TAZ in cancer and autoimmune diseases, it is worthy to explore the response to YAP/TAZ inhibition in the maternal-fetal immunity. This may provide a new valuable target for therapy of pregnancy loss, or potentially other pregnancy complications.

PDL1 blockage increases fetal resorption and Tfr cells but does not affect Tfh/Tfr ratio and B-cell maturation during allogeneic pregnancy

A successful pregnancy requires sophisticated regulation of uterine microenvironment to guarantee the existence of semi-allogeneic conceptus without immune rejection. T follicular regulatory (Tfr) cells exert a suppressive effect on Tfh-cell expansion, B-cell response, and antibody production. Although accumulating evidence has demonstrated that dysregulations of Tfr cells can bring on various immunological diseases, their immunomodulatory roles during pregnancy still remain unheeded. Herein, we introduced an allogeneic normal-pregnant mouse model and found that CD4⁺CXCR5^hiPD-1^hiFoxp3⁺ Tfr cells were preferentially accumulated in the uterus at mid-gestation and displayed a distinct phenotype. In addition, the absence of PDL1 resulted in increased fetal resorption by favoring Tfr cells accumulation and upregulating PD-1 expression on these cells. However, PDL1 blockade affected neither the ratio of Tfh/Tfr cells nor the maturation and differentiation of B cells. Overall, our results are the first to present a correlation of Tfr cells accumulation with healthy allogeneic pregnancy and PDL1 blockade-induced miscarriage, and to indicate that appropriate assembly of Tfr cells is important for pregnancy maintenance. Since blockade of PD-1-PDL1 pathway leads to more Tfr cells and fetal losses, the reproductive safety must be taken into consideration when PD-1/PD-L1 checkpoint blockade immunotherapy is used in pregnancy.

Immune checkpoint molecules in pregnancy: Focus on regulatory T cells

Regulatory T (Treg) cells are a specialized subpopulation of T cells that plays critical roles in the maintenance of immune homeostasis. Although efforts have been done, their role in human pregnancy is not fully understood. Numerous studies reported the presence of Treg cells throughout gestation by promoting maternal-fetal tolerance and fetal development. Furthermore, Treg population is heterogeneous as it is expressing different immune checkpoint molecules favoring immune suppressive function. Therefore, better understanding of the heterogeneity and function of Treg cells during pregnancy is critical for an effective immune intervention. Latest evidence has shown that several immune checkpoint molecules are closely associated with pregnancy outcome via multiple inhibitory mechanisms. Majority of these studies demonstrated the modulatory effects of immune checkpoint molecules on effector T-cell immunity, but their effects on Treg activation and function are still an enigma. In this review, we emphasize the potential influence of multiple immune checkpoint molecules, including CTLA-4, PD-1, Tim-3, LAG-3, and TIGIT, either in membrane or soluble form, on the function of decidual and peripheral Treg cells during pregnancy. Additionally, we discuss the promising future of targeting Treg cells via immune checkpoint molecules for pregnancy maintenance and prevention of complicated pregnancies.

NOD1 modulates decidual stromal cell function to maintain pregnancy in the early trimester

We sought to explore the functions and modulated factors of NOD1 in normal decidual stromal cells (DSCs) derived from the first trimester pregnancy and whether existed different expression of NOD1 between normal and unexplained recurrent pregnancy loss (URPL) in DSCs. Twenty-six patients with normal pregnancies that required abortion and 12 URPL patients at first trimester were enrolled for the study. As a result, we found lower levels of NOD1 in the DSCs derived from URPL compared with those from normal early trimester pregnancy. Furthermore, increased NOD1 expression in the normal DSCs induced apoptosis and increased monocyte chemotactic protein-1 (MCP-1) and IL-1β (interleukin 1 beta) secretion but decreased their invasion capacity. In addition, several cytokines such as IL-1β, tumour necrosis factor-alpha (TNF-α), interferon-gamma (IFN-γ), and interleukin-17 (IL-17) were present at the maternal-fetal interface in RPL and were found to regulate NOD1 expression in primary DSCs. Our study indicates that RPL may be associated with NOD1 aberrant expression in DSCs, which plays a significant role in maintaining pregnancy via infection control and regulation of immune responses that might affect the pregnancy outcome. We expect that our results will bring more comprehensively understanding about the connection between NOD1 and RPL for researchers.

Exhausted and Senescent T Cells at the Maternal-Fetal Interface in Preterm and Term Labor

Successful pregnancy requires a tightly-regulated equilibrium of immune cell interactions at the maternal-fetal interface (i.e., the decidual tissues), which plays a central role in the inflammatory process of labor. Most of the innate immune cells in this compartment have been well characterized; however, adaptive immune cells are still under investigation. Herein, we performed immunophenotyping of the decidua basalis and decidua parietalis to determine whether exhausted and senescent T cells are present at the maternal-fetal interface and whether the presence of pathological (i.e., preterm) or physiological (i.e., term) labor and/or placental inflammation alter such adaptive immune cells. In addition, decidual exhausted T cells were sorted to test their functional status. We found that (1) exhausted and senescent T cells were present at the maternal-fetal interface and predominantly expressed an effector memory phenotype, (2) exhausted CD4⁺ T cells increased in the decidua parietalis as gestational age progressed, (3) exhausted CD4⁺ and CD8⁺ T cells decreased in the decidua basalis of women who underwent labor at term compared to those without labor, (4) exhausted CD4⁺ T cells declined with the presence of placental inflammation in the decidua basalis of women with preterm labor, (5) exhausted CD8⁺ T cells decreased with the presence of placental inflammation in the decidua basalis of women who underwent labor at term, (6) both senescent CD4⁺ and CD8⁺ T cells declined with the presence of placental inflammation in the decidua basalis of women who underwent preterm labor, and (7) decidual exhausted T cells produced IFNγ and TNFα upon in vitro stimulation. Collectively, these findings indicate that exhausted and senescent T cells are present at the human maternal-fetal interface and undergo alterations in a subset of women either with labor at term or preterm labor and placental inflammation. Importantly, decidual T cell function can be restored upon stimulation.

Immune Checkpoint Molecules in Reproductive Immunology

Immune checkpoint molecules, like CTLA-4, TIM-3, PD-1, are negative regulators of immune responses to avoid immune injury. Checkpoint regulators are thought to actively participate in the immune defense of infections, prevention of autoimmunity, transplantation, and tumor immune evasion. Maternal-fetal immunotolerance represents a real immunological challenge for the immune system of the mother: beside acceptance of the semiallogeneic fetus, the maternal immune system has to be prepared for immune defense mostly against infections. In this particular situation, the role of immune checkpoint molecules could be of special interest. In this review, we describe current knowledge on the role of immune checkpoint molecules in reproductive immunology.

New Paradigm in the Role of Regulatory T Cells During Pregnancy

Semi-allogenic fetuses are not rejected by the maternal immune system because feto-maternal tolerance induced by CD4⁺CD25⁺FoxP3⁺ regulatory T (Treg) cells is established during pregnancy. Paternal antigen-specific Treg cells accumulate during pregnancy, and seminal plasma priming plays an important role in expanding paternal antigen-specific Treg cells in mouse models. Although paternal-antigen specific Treg cells have not been identified in humans, recent studies suggest that antigen-specific Treg cells exist and expand at the feto-maternal interface in humans. Studies have also revealed that reduction of decidual functional Treg cells occurs during miscarriage with normal fetal chromosomal content, whereas insufficient clonal expansion of decidual Treg cells is observed in preeclampsia. In this review, we will discuss the recent advances in the investigation of mechanisms underlying Treg cell-dependent maintenance of feto-maternal tolerance.

The importance of the PD-1/PD-L1 pathway at the maternal-fetal interface

Background

Our goal with this study was to investigate the contribution of PD-1/PD-L1 immune-checkpoint pathway to maternal immunotolerance mechanisms.

Methods

Thirteen healthy pregnant women and 10 non-pregnant controls were involved in this project. PBMCs and DICs were isolated from peripheral blood and from decidual tissues. After the characterization of different immune cell subsets, we used fluorochrome-conjugated monoclonal antibodies to measure the expression level of PD-1, PD-L1, NKG2D, and CD107a molecules by flow cytometry.

Results

We measured significant alternations in the proportion of decidual immune cell subsets compared to the periphery. Elevated PD-1 expression by decidual CD8+ T, CD4+ T, and NKT-like cells were also detected accompanied by the increased PD-L1 expression by decidual CD4+ T, Treg, NKT-like and CD56 + NK cell subsets compared to peripheral blood. The cytotoxic potential was significantly higher in PD-1- decidual immune cells compared to the periphery, however we measured a significantly lower cytotoxicity in the decidual PD-1+ CD8+ T cells compared with the peripheral subsets. An activation receptor NKG2D expression was decreased by the PD-1+ CD8+ T subsets in the first trimester compared to non-pregnant condition but the expression level of the decidual counterparts was significantly elevated compared to the periphery. The cytotoxic potential of decidual PD1/NKG2D double positive CD8+ T cells was significantly decreased compared to the peripheral subsets.

Conclusions

Based on our results we assume that PD-1/PD-L1 pathway might have a novel role in the maintaining of the local immunological environment. Accompanied by NKG2D activating receptor this checkpoint interaction could regulate decidual CD8 Tc cell subsets and may contribute maternal immunotolerance.

Identification of programmed cell death 1 and its ligand in the testicular tissue of mice

PROBLEM

This study aims to determine the expression and localization of programmed cell death 1 (PD-1) and programmed cell death 1 ligand 1 (PD-L1) in the testes of mice at different developmental stages.

METHOD OF STUDY

By means of RT-qPCR, Western blot and immunofluorescence, the expression and localization of PD-1 and PD-L1 were detected in the testicular tissues of mice at different postnatal times: P7, P14, P21, P28, P35, and adulthood. Meanwhile, the level of soluble PD-L1 (sPD-L1) was evaluated by ELISA in the testicular interstitial fluid (IF) of the adult mice, culture supernatants of TM4 cell lines (Sertoli cells lines), and primary Sertoli cells at P14.

RESULTS

Pd-1 mRNA levels were unexpectedly low. From P7 to P21, there was limited PD-1 protein detected while PD-1 was evident at P28 and afterward at significantly higher levels than at P14 and P21 (P < 0.05). Despite being found in the interstitial area at P7, P14, and P21, PD-1 was also detected in the germ cells of the seminiferous tubules after P28. Pd-l1 mRNA exhibited age-related changes, peaking at P21, while PD-L1 protein was constitutively expressed at any stage, specifically localized in the nucleus of Sertoli cells. Moreover, the level of sPD-L1 in IF was significantly higher than that in the culture supernatants of both TM4 and primary Sertoli cells at P14.

CONCLUSIONS

PD-1 and PD-L1 were present in the testicular tissue of adult mice. The expression and localization of PD-1 fluctuated with age, and PD-1 was mainly localized to advanced germ cells, suggesting that it may play a role in spermiogenesis. PD-L1 was constitutively expressed in the nucleus of Sertoli cells, which could secrete sPD-L1 into the testicular interstitial space and thus may be involved in testicular immune privilege.

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.

Suppression of autophagy and HCK signaling promotes PTGS2high FCGR3- NK cell differentiation triggered by ectopic endometrial stromal cells

Impaired NK cell cytotoxic activity contributes to the local dysfunctional immune environment in endometriosis (EMS), which is an estrogen-dependent gynecological disease that affects the function of ectopic endometrial tissue clearance. The reason for the impaired cytotoxic activity of NK cells in an ectopic lesion microenvironment (ELM) is largely unknown. In this study, we show that the macroautophagy/autophagy level of endometrial stromal cells (ESCs) from EMS decreased under negative regulation of estrogen. The ratio of peritoneal FCGR3^- NK to FCGR3⁺ NK cells increases as EMS progresses. Moreover, the autophagy suppression results in the downregulation of HCK (hematopoietic cellular kinase) by inactivating STAT3 (signal transducer and activator of transcription 3), as well as the increased secretion of the downstream molecules CXCL8/IL8 and IL23A by ESCs, and this increase induced the upregulation of FCGR3^- NK cells and decline of cytotoxic activity in ELM. This process is mediated through the depression of microRNA MIR1185-1-3p, which is associated with the activation of the target gene PTGS2 in NK cells. FCGR3^- NK with a phenotype of PTGS2/COX2^high IFNG^low PRF1^low GZMB^low induced by hck knockout (hck^-/-) or 3-methyladenine (3-MA, an autophagy inhibitor)-stimulated ESCs accelerates ESC's growth both in vitro and in vivo. These results suggest that the estrogen-autophagy-STAT3-HCK axis participates in the differentiation of PTGS2^high IFNG^low PRF1^low GZMB^low FCGR3^- NK cells in ELM and contributes to the development of EMS. This result provides a scientific basis for potential therapeutic strategies to treat diseases related to impaired NK cell cytotoxic activity.

ABBREVIATIONS

anti-FCGR3: anti-FCGR3 with neutralizing antibody; Ctrl-ESC: untreated ESCs; CXCL8: C-X-C motif chemokine ligand 8; ectoESC: ESCs from ectopic lesion; ELM: ectopic lesion microenvironment; EMS: endometriosis; ESCs: endometrial stromal cells; eutoESC:eutopic ESCs; HCK: hematopoietic cellular kinase; HCK(OE): overexpression of HCK; IFNG: interferon gamma; IL23A (OE): overexpression of IL23A; KLRK1: Killer cell lectin like receptor K1; MAP1LC3B/LC3B: microtubule-associated protein 1 light chain 3 beta; 3 -MA: 3-methyladenine; 3-MA-ESC: 3-MA-treated ESCs; MIR1185-1-3p⁺: overexpression of HsMIR1185-1-3p; NK: natural killer; normESCs: normal ESCs; Rap-ESC:rapamycin-treated ESCs; PCNA: proliferating cell nuclear antigen; PF: peritoneal fluid; SFKs: SRC family of cytoplasmic tyrosine kinases; si-HCK: silencing of HCK; siIL23A: silencing of IL23A; USCs: uterus stromal cells.

Expression of Programmed Death-Ligand 1 by Human Colonic CD90+ Stromal Cells Differs Between Ulcerative Colitis and Crohn's Disease and Determines Their Capacity to Suppress Th1 Cells

Background and Aims

The role of programmed cell death protein 1 (PD-1) and its ligands in the dysregulation of T helper immune responses observed in the inflammatory bowel disease (IBD) is unclear. Recently, a novel concept emerged that CD90⁺ colonic (myo)fibroblasts (CMFs), also known as stromal cells, act as immunosuppressors, and are among the key regulators of acute and chronic inflammation. The objective of this study was to determine if the level of the PD-1 ligands is changed in the IBD inflamed colonic mucosa and to test the hypothesis that changes in IBD-CMF-mediated PD-1 ligand-linked immunosuppression is a mechanism promoting the dysregulation of Th1 cell responses.

Methods

Tissues and cells derived from Crohn's disease (CD), ulcerative colitis (UC), and healthy individuals (N) were studied in situ, ex vivo, and in culture.

Results

A significant increase in programmed death-ligand 1 (PD-L1) was observed in the inflamed UC colonic mucosa when compared to the non-inflamed matched tissue samples, CD, and healthy controls. UC-CMFs were among the major populations in the colonic mucosa contributing to the enhanced PD-L1 expression. In contrast, PD-L1 expression was decreased in CD-CMFs. When compared to CD-CMFs and N-CMFs, UC-CMFs demonstrated stronger suppression of IL-2, Th1 transcriptional factor Tbet, and IFN-γ expression by CD3/CD28-activated CD4⁺ T cells, and this process was PD-L1 dependent. Similar observations were made when differentiated Th1 cells were cocultured with UC-CMFs. In contrast, CD-CMFs showed reduced capacity to suppress Th1 cell activity and addition of recombinant PD-L1 Fc to CD-CMF:T cell cocultures partially restored the suppression of the Th1 type responses.

Conclusion

We present evidence showing that increased PD-L1 expression suppresses Th1 cell activity in UC. In contrast, loss of PD-L1 expression observed in CD contributes to the persistence of the Th1 inflammatory milieu in CD. Our data suggest that dysregulation of the Th1 responses in the inflamed colonic mucosa of IBD patients is promoted by the alterations in PD-L1 expression in the mucosal mesenchymal stromal cell compartment.

Association of genetic variants of PD1 with recurrent pregnancy loss

Purpose

Programmed cell death 1 (PD1) and PD ligand 1 (PDL1) are speculated to have an important role in maintaining a normal pregnancy and there are also a few reports of an association between the single-nucleotide polymorphisms (SNPs) of PD1 or PDL1 and diseases in humans. The association was examined between the polymorphisms of PD1,PDL1,CTLA4 and recurrent pregnancy loss (RPL).

Methods

The study group consisted of 243 women with two or more pregnancy losses and 176 parous women. The frequency of three SNPs of PD1, two of PDL1, and four of CTLA4 were compared between the patients and controls. Next, the subsequent live birth rates in the patients with RPL with and without risk alleles were examined.

Results

Two SNPs (rs36084323 and rs3481962) of PD1 were found to occur at significantly higher frequencies in the patient group than in the control group. The subsequent live birth rate of the patients with vs. without the risk alleles of rs36084323 and rs3481962 were 83.3% vs. 83.3% and 81.6% vs. 84.0%, respectively.

Conclusion

Variations of the PD1 gene were identified as risk factors for RPL. However, the presence or absence of the PD1 risk alleles had no predictive effect on the subsequent pregnancy outcome.

Maternal Adaptive Immune Cells in Decidua Parietalis Display a More Activated and Coinhibitory Phenotype Compared to Decidua Basalis

The maternal part of the placenta, the decidua, consists of maternal immune cells, decidual stromal cells, and extravillous fetal trophoblasts. In a successful pregnancy, these cell compartments interact to provide an intricate balance between fetal tolerance and antimicrobial defense. These processes are still poorly characterized in the two anatomically different decidual tissues, basalis and parietalis. We examined immune cells from decidua basalis and parietalis from term placentas (n = 15) with flow cytometry. By using multivariate discriminant analysis, we found a clear separation between the two decidual compartments based on the 81 investigated parameters. Decidua parietalis lymphocytes displayed a more activated phenotype with a higher expression of coinhibitory markers than those isolated from basalis and contained higher frequencies of T regulatory cells. Decidua basalis contained higher proportions of monocytes, B cells, and mucosal-associated invariant T (MAIT) cells. The basalis B cells were more immature, and parietalis MAIT cells showed a more activated phenotype. Conventional T cells, NK cells, and MAIT cells from both compartments potently responded with the production of interferon-γ and/or cytotoxic molecules in response to stimulation. To conclude, leukocytes in decidua basalis and parietalis displayed remarkable phenotypic disparities, indicating that the corresponding stromal microenvironments provide different immunoregulatory signals.

Co-Signaling Molecules in Maternal-Fetal Immunity

Physiologically, a successful pregnancy requires the maternal immune system to recognize and tolerate the semiallogeneic fetus, and allow for normal invasion of trophoblasts. Thus, pregnancy complications are considered to be associated with dysfunctional maternal-fetal crosstalk. Co-signaling molecules are a group of cell surface molecules that positively or negatively modulate the immune response. Well studied in the fields of oncology and transplantation, they are also suggested to be involved in maternal-fetal crosstalk. Here, we review the latest knowledge on the expression and function of such co-signaling molecules, highlighting their immunoregulatory roles in maternal-fetal tolerance and decidual vascular remodeling, and their involvement in pathological pregnancies. This review may instruct future basic research on, and clinical applications for, maternal-fetal immunity.

An Ancient Fecundability-Associated Polymorphism Switches a Repressor into an Enhancer of Endometrial TAP2 Expression

Variation in female reproductive traits, such as fertility, fecundity, and fecundability, is heritable in humans, but identifying and functionally characterizing genetic variants associated with these traits has been challenging. Here, we explore the functional significance and evolutionary history of a T/C polymorphism of SNP rs2071473, which we have previously shown is an eQTL for TAP2 and significantly associated with fecundability (time to pregnancy). We replicated the association between the rs2071473 genotype and TAP2 expression by using GTEx data and demonstrated that TAP2 is expressed by decidual stromal cells at the maternal-fetal interface. Next, we showed that rs2071473 is located within a progesterone-responsive cis-regulatory element that functions as a repressor with the T allele and an enhancer with the C allele. Remarkably, we found that this polymorphism arose before the divergence of modern and archaic humans, segregates at intermediate to high frequencies across human populations, and has genetic signatures of long-term balancing selection. This variant has also previously been identified in genome-wide association studies of immune-related disease, suggesting that both alleles are maintained as a result of antagonistic pleiotropy.

Immunologic challenges of human reproduction: an evolving story

Characterization of the implanting human fetus as an allograft prompted a field of research in reproductive immunology that continues to fascinate and perplex scientists. Paternal- or partner-derived alloantigens are present in the maternal host at multiple times during the reproductive process. They begin with exposure to semen, continue through implantation and placentation, and may persist for decades in the form of fetal microchimerism. Changes in maternal immune responses that allow allogenic fertilization and survival of semiallogenic concepti to delivery must be balanced with a continued need to respond appropriately to pathogenic invaders, commensals, cell or tissue damage, and any tendency toward malignant transformation. This complex and sophisticated balancing act is essential for survival of mother, fetus, and the species itself. We will discuss concepts of alloimmune recognition, tolerance, and ignorance as they pertain to mammalian reproduction with a focus on human reproduction, maternal immune modulation, and the very earliest events in the reproductive process, fertilization and implantation.

GD2-specific CAR T Cells Undergo Potent Activation and Deletion Following Antigen Encounter but can be Protected From Activation-induced Cell Death by PD-1 Blockade

Chimeric antigen receptor (CAR) T cells have shown great promise in the treatment of hematologic malignancies but more variable results in the treatment of solid tumors and the persistence and expansion of CAR T cells within patients has been identified as a key correlate of antitumor efficacy. Lack of immunological "space", functional exhaustion, and deletion have all been proposed as mechanisms that hamper CAR T-cell persistence. Here we describe the events following activation of third-generation CAR T cells specific for GD2. CAR T cells had highly potent immediate effector functions without evidence of functional exhaustion in vitro, although reduced cytokine production reversible by PD-1 blockade was observed after longer-term culture. Significant activation-induced cell death (AICD) of CAR T cells was observed after repeated antigen stimulation, and PD-1 blockade enhanced both CAR T-cell survival and promoted killing of PD-L1(+) tumor cell lines. Finally, we assessed CAR T-cell persistence in patients enrolled in the CARPETS phase 1 clinical trial of GD2-specific CAR T cells in the treatment of metastatic melanoma. Together, these data suggest that deletion also occurs in vivo and that PD-1-targeted combination therapy approaches may be useful to augment CAR T-cell efficacy and persistence in patients.

T-cell ligands modulate the cytolytic activity of the CD33/CD3 BiTE antibody construct, AMG 330

Preclinical and emerging clinical studies demonstrate that bispecific T-cell engaging (BiTE) antibody constructs can potently lyse targeted tumor cells, but the determinants for their activity remain incompletely understood. Using human acute myeloid leukemia (AML) cell lines engineered to overexpress individual T-cell ligands, we found that expression of the inhibitory ligands, PD-L1 and PD-L2, reduced the cytolytic activity of the BiTE antibody construct targeting CD33, AMG 330; conversely, expression of the activating ligands, CD80 and CD86, augmented the cytotoxic activity of AMG 330. Consistent with these findings, treatment with an activating antibody directed at the co-stimulatory T-cell receptor, CD28, significantly increased AMG 330-induced cytotoxicity in human AML cell lines. Using specimens from 12 patients with newly diagnosed or relapsed/refractory AML, we found that activation of CD28 also increased the activity of AMG 330 in primary human AML cells (P=0.023). Together, our findings indicate that T-cell ligands and co-receptors modulate the anti-tumor activity of the CD33/CD3 BiTE antibody construct, AMG 330. These findings suggest that such ligands/co-receptors could serve as biomarkers of response and that co-treatment strategies with pharmacological modulators of T-cell receptor signaling could be utilized to further enhance the activity of this targeted therapeutic.

Immunogenicity of decidual stromal cells in an epidermolysis bullosa patient and in allogeneic hematopoietic stem cell transplantation patients

Allogeneic mesenchymal stromal cells (MSCs) are widely used in regenerative medicine, but little is known about their immunogenicity. In this study, we monitored the therapeutic and immunogenic effects of decidual stromal cells (DSCs) from term placentas when used as a therapy for generalized severe junctional epidermolysis bullosa (JEB) (previously termed Herlitz JEB), a lethal condition caused by the lack of functional laminin-332. An 11-month-old JEB patient was treated with five infusions of allogeneic DSCs within a 3-month period. Amniotic membranes (AMs) were applied to severe wounds. After the treatment, wounds started to heal in the middle of the blisters, but the improvements were transient. After two infusions of DSCs, the JEB patient had developed multispecific anti-HLA class-I antibodies. No antibodies to laminin-332 were detected, but the patient had high levels of anti-bovine serum albumin antibodies, which could bind to DSCs. Peripheral blood mononuclear cells (PBMCs) from the patient had a higher proliferative response to DSCs than to third-party PBMCs, which contrasts with the pattern observed in healthy donors. Human DSCs and MSCs induced similar xenoreactivity in mice. Two of 16 allogeneic stem cell-transplanted patients, treated with DSCs for graft-versus-host disease or hemorrhagic cystitis, showed a positive flow cytometric crossmatch test. One patient had anti-HLA antibodies before DSC infusion, whereas the other had no anti-HLA antibodies at any time. AM and DSC infusions may have improved the healing process in the JEB patient, but DSCs appeared to induce anti-HLA antibodies. The risk of alloimmunization by DSCs seems to be low in immunocompromised patients.

Recent Insight into the Role of the PD-1/PD-L1 Pathway in Feto-Maternal Tolerance and Pregnancy

Pregnancy presents a great challenge to the maternal immune system. Given that maternal alloreactive lymphocytes are not depleted during pregnancy, local and/or systemic mechanisms have to serve a central function in altering the maternal immune responses. Regulatory T cells (Tregs) and the PD-1/PD-L1 pathway are both critical in controlling the immune responses. Recent studies have proved the critical function of the PD-1/PD-L1 pathway in regulating the T-cell homeostasis and the peripheral tolerance through promoting the development and function of Tregs, and inhibiting the activation of effector T cells. The function of the PD-1/PD-L1 pathway in feto-maternal interface and pregnancy has been investigated in human and animal models of pregnancy. In this review, we provide recent insight into the role of the PD-1/PD-L1 pathway in regulating T-cell homeostasis, maternal tolerance, and pregnancy-related complications as well as its possible applicability in clinical immunotherapy.

Endometrial stromal cells and decidualized stromal cells: origins, transformation and functions

Decidualization of endometrium, which is characterized by endometrial stromal cell (ESC) decidualization, vascular reconstruction, immune cell recruitment, and plentiful molecule production, is a crucial step for uterus to become receptive for embryo. When implantation takes place, ESCs surround and directly interact with embryo. Decidualized stromal cells (DSCs) are of great importance in endometrial decidualization, having a broad function in regulating immune activity and vascular remodeling of uterus. DSCs are shown to have a higher metabolic level and looser cytoskeleton than ESCs. What's the origin of ESCs and how ESCs successfully transform into DSCs had puzzled scientists in the last decades. Breakthrough had been achieved recently, and many studies had elucidated some of the characters and functions of DSCs. However, several questions still remain unclear. This paper reviews current understanding of where ESCs come from and how ESCs differentiate into DSCs, summarizes some characters and functions of DSCs, analyzes current studies and their limitations and points out research areas that need further investigation.

TLR4 activation enhances the PD-L1-mediated tolerogenic capacity of colonic CD90+ stromal cells

Signaling via programmed death ligand-1 (PD-L1) and PD-L2 is crucial for maintaining peripheral tolerance. CD90(+) myofibroblasts/fibroblasts (CMFs) are major programmed cell death-1 (PD-1) ligand-expressing cells in normal human colonic mucosa. CMFs suppress activated CD4(+) T cell proliferation via PD-1 ligands. It is not known whether signaling through TLRs contribute to the regulation PD-1 ligands on CMFs upon colonic mucosal tolerance. In this study, we demonstrated that stimulation of TLR4 on human CMFs upregulates PD-L1, but not PD-L2, and reinforces CMF-mediated suppression of CD4(+) T cell proliferation and IFN-γ production. TLR4-mediated upregulation of PD-L1 on CMFs involved NF-κB pathways and was JAK2 and MyD88 dependent. MyD88-dependent stimulation of TLR1/2 and TLR5 also upregulated PD-L1 expression on CMFs in culture. PD-L1 expression was drastically decreased in vivo in the colonic mucosa of mice devoid of MyD88. Induction of MyD88 deficiency in CMFs in fibroblast-specific MyD88 conditional knockout mice resulted in a strong increase in a mucosal IFN-γ expression concomitantly with the abrogation of PD-L1 expression in CMFs under homeostasis and epithelial injury induced by dextran sodium sulfate. Together, these data suggest that MyD88-dependent TLR stimulation of CMFs in the normal colonic mucosa may reinforce these cells' anti-inflammatory capacity and thus contribute to the maintenance of mucosal tolerance.

The immune privilege of testis and gravid uterus: same difference?

The fetus in the gravid uterus and the developing spermatogenic cells in the adult testis both comprise special challenges for the host immune system. Protection of the neoantigens of the fetus and male germ cells from immune attack, defined as immune privilege, is fundamental for the propagation of species. Immune privilege is not simply the absence of leukocytes, but involves immune and non-immune cells acting synergistically together at multiple levels to create a unique tolerogenic environment. A number of the pathways are shared by the testis and gravid uterus. Amongst them steroid hormones, namely testosterone in the male and progesterone in the female, seem to function as key molecules that govern the local production of immunoregulatory factors which finally control the overall immune environment.

Maternal CD4⁺ and CD8⁺ T cell tolerance towards a fetal minor histocompatibility antigen in T cell receptor transgenic mice

Tolerance of the maternal immune system in pregnancy is important for successful pregnancy because the semiallogeneic fetus may be subject to antifetal responses. We examined maternal tolerance to the fetus using a murine system in which a model paternally inherited antigen, ovalbumin (OVA), is expressed exclusively in the fetus and placenta. By employing T cell receptor (TCR) transgenic mice specific for major histocompatibility complex class I- or class II-restricted epitopes of OVA (OT-I and OT-II) as mothers, we investigated the fate of fetus-specific CD8⁺ and CD4⁺ T cells, respectively, during gestation. Both OVA-specific CD8⁺ and CD4⁺ T cells displayed an activated phenotype in the peripheral lymphoid tissues of OVA-bred OT-I and OT-II mice, consistent with their encounter of fetal antigen. Whereas a small percentage of OVA-specific CD4⁺ T cells were deleted in the periphery and thymus of OVA-bred OT-II mice, with evidence of TCR downregulation in the remaining T cells, deletion and TCR downregulation were not observed in OVA-bred OT-I mice. Both CD4⁺ and CD8⁺ T cells upregulated inducible costimulator expression in response to the fetal antigen, but only CD4⁺ T cells consistently upregulated the inhibitory receptors programmed cell death 1 and cytotoxic T lymphocyte antigen-4. More regulatory T cells (Tregs) were present in pregnant OVA-bred than in WT-bred OT-II mice, revealing that Tregs expanded specifically in response to the fetal antigen. These data indicate that several mechanisms tolerize fetal antigen-specific maternal CD4⁺ T cells, whereas tolerance of fetal antigen-specific CD8⁺ T cells is less effective. The importance of these mechanisms is underscored by the finding that fetal loss occurs in OVA-bred OT-I but not OT-II mice.

Hyaluronan-CD44 interaction promotes growth of decidual stromal cells in human first-trimester pregnancy

Hyaluronan (HA) and its receptor CD44 are expressed at the maternal-fetal interface, but its role in early pregnancy remains unclear. Here, we found that primary decidual stromal cells (DSCs) continuously secreted HA and expressed its receptor CD44. Pregnancy-associated hormones up-regulated HA synthetase (HAS) 2 transcription and HA release from DSCs. High molecular weight-HA (HMW-HA), but not medium molecular weight (MMW-HA) or low molecular weight (LMW-HA), promoted proliferation and inhibited apoptosis of DSCs in a CD44-dependent manner. The in-cell Western analysis revealed HMW-HA activated PI3K/AKT and mitogen-activated protein kinase (MAPK)/ERK1/2 signaling pathways time-dependently. Blocking these pathways by specific inhibitor LY294002 or U0126 abrogated HMW-HA-regulated DSc proliferation and apoptosis. Finally, we have found that HA content, HA molecular weight, HAS2 mRNA level, and CD44 expression were significantly decreased in DSCs from unexplained miscarriage compared with the normal pregnancy. Collectively, our results indicate that higher level and greater molecular mass of HA at maternal-fetal interface contributes to DSc growth and maintenance of DSCs in human early pregnancy.

Inflammatory and haematological markers in the maternal, umbilical cord and infant circulation in histological chorioamnionitis

BACKGROUND

The relationship between histological chorioamnionitis and haematological and biochemical markers in mothers and infants at delivery, and in infants postnatally, is incompletely characterised. These markers are widely used in the diagnosis of maternal and neonatal infection. Our objective was to investigate the effects of histological chorioamnionitis (HCA) on haematological and biochemical inflammatory markers in mothers and infants at delivery, and in infants post-delivery.

METHODS

Two hundred and forty seven mothers, delivering 325 infants, were recruited at the only tertiary perinatal centre in Western Australia. Placentae were assessed for evidence of HCA using a semi-quantitative scoring system. Maternal high sensitivity C-reactive protein (hsCRP), procalcitonin, and umbilical cord hsCRP, procalcitonin, white cell count and absolute neutrophil count were measured at delivery. In infants where sepsis was clinically suspected, postnatal CRP, white cell count and absolute neutrophil count were measured up to 48 hours of age. The effect of HCA on maternal, cord and neonatal markers was evaluated by multivariable regression analysis.

RESULTS

The median gestational age was 34 weeks and HCA was present in 26 of 247 (10.5%) placentae. Mothers whose pregnancies were complicated by HCA had higher hsCRP (median 26 (range 2-107) versus 5.6 (0-108) mg/L; P<0.001). Histological chorioamnionitis was associated with higher umbilical cord hsCRP (75(th) percentile 2.91 mg/L (range 0-63.9) versus 75(th) percentile 0 mg/L (0-45.6); P<0.001) and procalcitonin (median 0.293 (range 0.05-27.37) versus median 0.064 (range 0.01-5.24) ug/L; P<0.001), with a sustained increase in neonatal absolute neutrophil count (median 4.5 (0.1-26.4)×10(9)/L versus 3.0 (0.1-17.8)×10(9)/L), and CRP up to 48 hours post-partum (median 10 versus 6.5 mg/L) (P<0.05 for each).

CONCLUSION

Histological chorioamnionitis is associated with modest systemic inflammation in maternal and cord blood. These systemic changes may increase postnatally, potentially undermining their utility in the diagnosis of early-onset neonatal infection.

Inflammatory and haematological markers in the maternal, umbilical cord and infant circulation in histological chorioamnionitis

Background

The relationship between histological chorioamnionitis and haematological and biochemical markers in mothers and infants at delivery, and in infants postnatally, is incompletely characterised. These markers are widely used in the diagnosis of maternal and neonatal infection. Our objective was to investigate the effects of histological chorioamnionitis (HCA) on haematological and biochemical inflammatory markers in mothers and infants at delivery, and in infants post-delivery.

Methods

Two hundred and forty seven mothers, delivering 325 infants, were recruited at the only tertiary perinatal centre in Western Australia. Placentae were assessed for evidence of HCA using a semi-quantitative scoring system. Maternal high sensitivity C-reactive protein (hsCRP), procalcitonin, and umbilical cord hsCRP, procalcitonin, white cell count and absolute neutrophil count were measured at delivery. In infants where sepsis was clinically suspected, postnatal CRP, white cell count and absolute neutrophil count were measured up to 48 hours of age. The effect of HCA on maternal, cord and neonatal markers was evaluated by multivariable regression analysis.

Results

The median gestational age was 34 weeks and HCA was present in 26 of 247 (10.5%) placentae. Mothers whose pregnancies were complicated by HCA had higher hsCRP (median 26 (range 2–107) versus 5.6 (0–108) mg/L; P<0.001). Histological chorioamnionitis was associated with higher umbilical cord hsCRP (75^th percentile 2.91 mg/L (range 0–63.9) versus 75^th percentile 0 mg/L (0–45.6); P<0.001) and procalcitonin (median 0.293 (range 0.05–27.37) versus median 0.064 (range 0.01–5.24) ug/L; P<0.001), with a sustained increase in neonatal absolute neutrophil count (median 4.5 (0.1–26.4)×10⁹/L versus 3.0 (0.1–17.8)×10⁹/L), and CRP up to 48 hours post-partum (median 10 versus 6.5 mg/L) (P<0.05 for each).

Conclusion

Histological chorioamnionitis is associated with modest systemic inflammation in maternal and cord blood. These systemic changes may increase postnatally, potentially undermining their utility in the diagnosis of early-onset neonatal infection.

Bacterial LPS differently modulates inflammasome gene expression and IL-1β secretion in trophoblast cells, decidual stromal cells, and decidual endothelial cells

Three Nod-like receptors (NLR family, pyrin domain containing 1/NLRP1, NLR family, pyrin domain containing 3/NLRP3, NLR family, CARD domain containing 4/NLRC4) and the adaptor molecule PYD and CARD domain containing protein/PYCARD are involved in the assembling of multiprotein complexes known as inflammasomes, leading to caspase 1 activation and consequent interleukin (IL)-1β secretion. Considering that inflammasomes are involved in sensing pathogens and in triggering inflammatory and immune response, we hypothesized that they could also act in the placenta as an efficient innate mechanism during pregnancy infections. For this reason the activation of inflammasome was tested in 3 human placental cell populations in the presence of a common gram-negative compound (lipopolysaccharide [LPS]). The transcription of NLRP1, NLRP3, NLRC4, PYCARD, CASP1, and IL1B genes and the secretion of IL-1β were evaluated in human first trimester cytotrophoblasts (CTBs), decidual stromal cells (DSCs), and endothelial cells (DECs) stimulated with LPS. In CTBs and DSCs, LPS induced an augmented expression of CASP1 and IL1B and the specific upregulation of NLRP3 within the 3 NLRs tested. Moreover, LPS induced secretion of IL-1β from CTBs and DSCs. These results suggest the involvement of NLRP3 inflammasome in the placental innate response. The LPS did not affect inflammasome gene transcription and IL-1β production in DECs. Bacterial LPS enhances NLRP3 inflammasome components in trophoblast and DSCs, suggesting that this innate immune complex could play a key role in placental immune defense.

Monocyte chemoattractant protein-1 secreted by decidual stromal cells inhibits NK cells cytotoxicity by up-regulating expression of SOCS3

BACKGROUND

Decidual stromal cells (DSCs) are of particular importance due to their pleiotropic functions during pregnancy. Although previous research has demonstrated that DSCs participated in the regulation of immune cells during pregnancy, the crosstalk between DSCs and NK cells has not been fully elucidated. To address this issue, we investigated the effect of DSCs on perforin expression in CD56(+) NK cells and explored the underlying mechanism.

METHODOLOGY/PRINCIPAL FINDINGS

Flow cytometry analysis showed perforin production in NK cells was attenuated by DSC media, and it was further suppressed by media from DSCs pretreated with lipopolysaccharide (LPS). However, the expression of granzyme A and apoptosis of NK cells were not influenced by DSC media. ELISA assays to detect cytokine production indicated that monocyte chemoattractant protein-1 (MCP-1) in the supernatant of DSCs conditioned culture significantly increased after LPS stimulation. The inhibitory effect of DSC media on perforin was abolished by the administration of anti-MCP-1 neutralizing antibody. Notably, reduced perforin expression attenuated the cytotoxic potential of CD56(+) NK cells to K562 cells. Moreover, Suppressor of cytokine signaling 3 (SOCS3) expression in NK cells was enhanced by treatment with MCP-1, as measured by RT-PCR and western blot. Interestingly, MCP-1-induced perforin expression was partly abolished by the siRNA induced SOCS3 knockdown. Western blot analysis suggested that both NF-κB and ERK/MAPKs pathway were involved in the LPS-induced upregulation of MCP-1 in DSCs.

CONCLUSIONS/SIGNIFICANCE

Our results demonstrate that LPS induces upregulation of MCP-1 in DSCs, which may play a critical role in inhibiting the cytotoxicity of NK cells partly by promoting SOCS3 expression. These findings suggest that the crosstalk between DSCs and NK cells may be crucial to maintain pregnancy homeostasis.

Mesenchymal cells of the intestinal lamina propria

The mesenchymal elements of the intestinal lamina propria reviewed here are the myofibroblasts, fibroblasts, mural cells (pericytes) of the vasculature, bone marrow-derived stromal stem cells, smooth muscle of the muscularis mucosae, and smooth muscle surrounding the lymphatic lacteals. These cells share similar marker molecules, origins, and coordinated biological functions previously ascribed solely to subepithelial myofibroblasts. We review the functional anatomy of intestinal mesenchymal cells and describe what is known about their origin in the embryo and their replacement in adults. As part of their putative role in intestinal mucosal morphogenesis, we consider the intestinal stem cell niche. Lastly, we review emerging information about myofibroblasts as nonprofessional immune cells that may be important as an alarm system for the gut and as a participant in peripheral immune tolerance.