Prevalence of Regulatory T-Cell Subtypes in Preeclampsia

CD4+ T cell heterogeneity in gestational age and preeclampsia using single-cell RNA sequencing

A balance between pro-inflammatory decidual CD4+ T cells and FOXP3+ regulatory T cells (FOXP3+ Tregs) is important for maintaining fetomaternal tolerance. Using single-cell RNA-sequencing and T cell receptor repertoire analysis, we determined that diversity and clonality of decidual CD4+ T cell subsets depend on gestational age. Th1/Th2 intermediate and Th1 subsets of CD4+ T cells were clonally expanded in both early and late gestation, whereas FOXP3+ Tregs were clonally expanded in late gestation. Th1/Th2 intermediate and FOXP3+ Treg subsets showed altered gene expression in preeclampsia (PE) compared to healthy late gestation. The Th1/Th2 intermediate subset exhibited elevated levels of cytotoxicity-related gene expression in PE. Moreover, increased Treg exhaustion was observed in the PE group, and FOXP3+ Treg subcluster analysis revealed that the effector Treg like subset drove the Treg exhaustion signatures in PE. The Th1/Th2 intermediate and effector Treg like subsets are possible inflammation-driving subsets in PE.

T cell immunity and the etiology and pathogenesis of preeclampsia

Preeclampsia is more common in nulliparous women, their first pregnancies with a new partner in multiparous women, pregnant women with short duration of cohabitation, and in pregnancies with donor eggs, where the fetus is completely foreign to the mother. The epidemiological study findings strongly suggest that inadequate induction of tolerance to paternal/fetal antigens is involved in the pathogenesis of preeclampsia. This review proposes that preeclampsia may be caused by a reduction in paternal/fetal antigen-specific regulatory T (Treg) cells and decreased PD-1 expression on clonally expanded CD8+ effector memory T (TEM) cells, resulting in a breakdown of mother-to-fetus tolerance. The immune environment of preeclampsia is clearly different from that of recurrent pregnancy loss (RPL). In preeclampsia, cloned Treg cells decreases, and PD-1 expression on cloned CD8+TEM decreased. In RPL, the total number of Treg cells decreased, and the total number of clonally expanded CD8+TEM cells increases. In addition to these changes, increased differentiation of Th17 cells has also been observed in preeclampsia. This change is caused by soluble endoglin, that is increased in preeclampsia, neutralizing TGFβ. These immunological changes make the fetus more susceptible to attacks from maternal T cells.

Immunobiology of pregnancy: from basic science to translational medicine

Embryo implantation failure and spontaneous abortions represent the main causes of infertility in developed countries. Unfortunately, incomplete knowledge of the multiple factors involved in implantation and fetal development keeps the success rate of medically assisted procreation techniques relatively low. According to recent literature, cellular and molecular mechanisms of 'immunogenic tolerance' towards the embryo are crucial to establish an 'anti-inflammatory' state permissive of a healthy pregnancy. In this review we dissect the role played by the immune system in the endometrial-embryo crosstalk, with a particular emphasis towards the fork-head-box-p3 (Foxp3+) CD4+CD25+ regulatory T (Treg) cells and discuss the most recent therapeutic advances in the context of early immune-mediated pregnancy loss.

"To be or not to Be": Regulatory T cells in melanoma

In spite of progresses in the therapy of different malignancies, melanoma still remains as one of lethal types of skin tumor. Melanoma is almost easily treatable by surgery alone with higher overall survival rates when it is diagnosed at early stages. However, survival rates are decreased remarkably upon survival if the tumor is progressed to advanced metastatic stages. Immunotherapeutics have been prosperous in the development of anti-tumor responses in patients with melanoma through promotion of the tumor-specific effector T cells in vivo; nonetheless, suitable clinical outcomes have not been satisfactory. One of the underlying causes of the unfavorable clinical outcomes might stem from adverse effects of regulatory T (Treg) cell, which is a prominent mechanism of tumor cells to escape from tumor-specific immune responses. Evidence shows that a poor prognosis and low survival rate in patients with melanoma can be attributed to a higher Treg cell number and function in these subjects. As a result, to promote melanoma-specific anti-tumor responses, depletion of Treg cells appears to be a promising approach; even though the clinical efficacy of different approaches to attain appropriate Treg cell depletion has been inconsistent. Here in this review, the main purpose is to assess the role of Treg cells in the initiation and perpetuation of melanoma and to discuss effective strategies for Treg cell modulation with the aim of melanoma therapy.

Increased Pro-Inflammatory T Cells, Senescent T Cells, and Immune-Check Point Molecules in the Placentas of Patients With Gestational Diabetes Mellitus

BACKGROUND

Gestational diabetes mellitus (GDM) is the most common metabolic complication of pregnancy. To define the altered pathway in GDM placenta, we investigated the transcriptomic profiles from human placenta between GDM and controls.

METHODS

Clinical parameters and postpartum complications were reviewed in all participants. Differentially expressed canonical pathways were analyzed between the GDM and control groups based on transcriptomic analysis. CD4⁺ T, CD8⁺ T, and senescent T cell subsets were determined by flow cytometry based on staining for specific intracellular cytokines.

RESULTS

Gene ontology analysis revealed that the placenta of GDM revealed upregulation of diverse mitochondria or DNA replication related pathways and downregulation of T-cell immunity related pathways. The maternal placenta of the GDM group had a higher proportion of CD4⁺ T and CD8⁺ T cells than the control group. Interestingly, senescent CD4⁺ T cells tended to increase and CD8⁺ T cells were significantly increased in GDM compared to controls, along with increased programmed cell death-1 (CD274⁺) expression. Programmed death-ligand 1 expression in syncytotrophoblasts was also significantly increased in patients with GDM.

CONCLUSION

This study demonstrated increased proinflammatory T cells, senescent T cells and immune-check point molecules in GDM placentas, suggesting that changes in senescent T cells and immune-escape signaling might be related to the pathophysiology of GDM.

Deep metagenomic characterization of gut microbial community and function in preeclampsia

Preeclampsia (PE) is a pregnancy complication characterized by severe hypertension and multiple organ damage. Gut microbiota has been linked to PE by previous amplicon sequencing studies. To resolve the PE gut microbiota in a higher taxonomy resolution, we performed shotgun metagenomic sequencing on the fecal samples from 40 early-onset PE and 37 healthy pregnant women. We recovered 1,750 metagenome-assembled genomes (representing 406 species) from the metagenomic dataset and profiled their abundances. We found that PE gut microbiota had enriched in some species belonging to Blautia, Pauljensenia, Ruminococcus, and Collinsella and microbial functions such as the bacitracin/lantibiotics transport system, maltooligosaccharide transport system, multidrug efflux pump, and rhamnose transport system. Conversely, the gut microbiome of healthy pregnant women was enriched in species of Bacteroides and Phocaeicola and microbial functions including the porphyrin and chlorophyll metabolism, pyridoxal-P biosynthesis, riboflavin metabolism, and folate biosynthesis pathway. PE diagnostic potential of gut microbial biomarkers was developed using both species and function profile data. These results will help to explore the relationships between gut bacteria and PE and provide new insights into PE early warning.

Immunomodulatory effect of vitamin D on the STATs and transcription factors of CD4+ T cell subsets in pregnant women with preeclampsia

This study evaluated the in vitro modulatory effect of vitamin D (VD) on T cells, by determining the expression of STATs and the transcription factors of each CD4⁺ T cell subsets. Twenty women with preeclampsia (PE) and 20 normotensive pregnant women were studied. Peripheral blood mononuclear cells were cultured with or without VD to analyse the STATs and transcription factors by flow cytometry, and cytokines production by ELISA. The plasma levels of VD were lower in the PE group. Treatment of cells with VD decreased STAT1/STAT4/T-bet, STAT3/RORγt, and increased STAT6/GATA-3 and STAT5/FoxP3 in preeclamptic women. Treatment with VD also decreased the levels of inflammatory cytokines and increased IL-10 and TGF-β. This hormone exerts immunomodulatory effects on the STAT signalling pathway, shifting the inflammatory profiles, Th1/Th17 cells to Th2/Treg profiles, and it can be suggested as a promising strategy to regulate the systemic inflammatory response in PE.

Cellular immune responses in the pathophysiology of preeclampsia

Preeclampsia, defined as new-onset hypertension accompanied by proteinuria occurring at 20 weeks of gestation or later, is a leading cause of perinatal morbidity and mortality worldwide. The pathophysiology of this major multi-systemic syndrome includes defective deep placentation, oxidative stress, endothelial dysfunction, the presence of an anti-angiogenic state, and intravascular inflammation, among others. In this review, we provide a comprehensive overview of the cellular immune responses involved in the pathogenesis of preeclampsia. Specifically, we summarize the role of innate and adaptive immune cells in the maternal circulation, reproductive tissues, and at the maternal-fetal interface of women affected by this pregnancy complication. The major cellular subsets involved in the pathogenesis of preeclampsia are regulatory T cells, effector T cells, NK cells, monocytes, macrophages, and neutrophils. We also summarize the literature on those immune cells that have been less characterized in this clinical condition, such as γδ T cells, invariant natural killer T cells, dendritic cells, mast cells, and B cells. Moreover, we discuss in vivo studies utilizing a variety of animal models of preeclampsia to further support the role of immune cells in this disease. Finally, we highlight the existing gaps in knowledge of the immunobiology of preeclampsia that require further investigation. The goal of this review is to promote translational research leading to clinically relevant strategies that can improve adverse perinatal outcomes resulting from the obstetrical syndrome of preeclampsia.

Regulatory T Cells in Pregnancy Adverse Outcomes: A Systematic Review and Meta-Analysis

Background

Several studies report the role of Regulatory T-cells (Tregs) in the pathophysiology of pregnancy adverse outcomes.

Objective

The aim of this systematic review and meta-analysis was to determine whether there is an association between regulatory T cell levels and pregnancy adverse outcomes (PAOs), including pre-eclampsia and preterm birth (PTB).

Method

Literature searches were conducted in PubMed/MEDLINE, Embase, and Cochrane CENTRAL databases. Inclusion criteria were original articles (clinical trials, case-control studies and cohort studies) comparing Tregs, sampled from the decidua or maternal blood, in healthy pregnant women versus women with pre-eclampsia or PTB. The outcome was standardised mean difference (SMD) in Treg numbers. The tau-squared (Tau²), inconsistency index (I²), and chi-squared (χ²) test quantified heterogeneity among different studies. Analyses were performed in RevMan software V.5.4.0 for Mac using a random-effects model with outcome data reported with 95% confidence intervals (CI). This study was prospectively registered with PROSPERO (CRD42020205469). PRISMA guidelines were followed.

Results

From 4,085 unique studies identified, 36 were included in qualitative synthesis, and 34 were included in quantitative synthesis (meta-analysis). In total, there were 1,783 participants in these studies: healthy controls=964, pre-eclampsia=759, PTB=60. Thirty-two studies compared Tregs in healthy pregnant women and women with pre-eclampsia, and 30 of these sampled Tregs from peripheral blood showing significantly higher Treg numbers in healthy pregnancies (SMD; 1.46; 95% CI, 1.03-1.88; I²=92%). Four studies sampled Tregs from the maternal decidua showing higher Tregs in healthy pregnancies (SMD, 0.76; 95% CI, -0.13-1.65; I²=84%). No difference was found in the number of Tregs between early versus late pre-eclampsia (SMD,-1.17; 95% CI, -2.79-0.44; I²=94%). For PTB, two studies compared Tregs sampled from the peripheral blood with a tendency for higher Tregs in healthy pregnancies but this did not reach significance (SMD, 2.18; 95% CI, -1.34-5.70; I²=96%). Subcohort analysis using Treg analysis (flow cytometry vs. qPCR vs. immunofluorescence tissue staining) showed similar associations.

Conclusion

Lower Tregs in pregnancy, sampled from the maternal peripheral blood, are associated with pre-eclampsia. There is a need for further studies to confirm a relationship between low Tregs and PTB. As the precise mechanisms by which Tregs may mediate pre-eclampsia and PTB remain unclear, further fundamental research is necessary to elucidate the underlying processes and highlight the causative link.

Systematic Review Registration

PROSPERO, identifier CRD42020205469.

T lymphocytes and preeclampsia: The potential role of T-cell subsets and related MicroRNAs in the pathogenesis of preeclampsia

Innate and adaptive immune systems have a crucial role in initiating and progressing some pregnancy disorders such as preeclampsia (PE), which is one of the pregnancy-specific disorders that could result in neonatal and maternal morbidity and mortality. The dysregulation of the spiral artery and inadequate trophoblast invasion lead to PE symptoms through producing various inflammatory cytokines and anti-angiogenic factors from the placenta. T lymphocytes play a special role in the epithelium and stroma of the human endometrium. CD4+ T helper (Th) cells, Th1/Th2, and Th17/T regulatory (Treg) balance mainly contribute to the establishment of a pregnancy-favorable environment. This review examined the dysregulation of some cytokines produced from T cells, the dysregulation of the transcription factors of Th cells, the expression of chemokine receptors on T cells, as well as the effects of some factors including vitamin D on the activity of T cells, and finally, the dysregulation of various miRNAs related to T cells, which could cause PE.

Abnormal expression of the costimulatory molecule B7-H4 in placental chorionic villous and decidual basalis tissues of patients with preeclampsia and HELLP syndrome

BACKGROUND

B7-H4, a checkpoint molecule of the B7 family, regulates a broad spectrum such as T-cell activation, cytokine secretion, tumour progression, and invasion capacities. Our previous data revealed that soluble B7-H4 (sB7-H4) blood serum levels are elevated in women at high risk for the hypertensive pregnancy disorder preeclampsia (PE) in the first trimester, as well as in patients with confirmed early/late-onset PE.

AIM

We here aim to investigate the expression pattern of B7-H4 in placental tissues of PE and HELLP Syndrome versus control group.

METHODS

B7-H4 protein expression and localization were investigated by immunoblotting and co-immunohistochemistry in placental chorionic villous and decidual basalis tissues.

RESULTS

B7-H4 protein was prominently expressed at the cell membrane, in the cytoplasm of the syncytiotrophoblast (STB) and interstitial extravillous trophoblast (EVT). B7-H4 protein levels in placental chorionic villous tissue were significantly higher in women with early-onset/late-onset PE and HELLP, while it was decreased in decidual basalis tissues of early-onset PE and HELLP compared with controls.

CONCLUSION

B7-H4 was inversely expressed in placental chorionic villous and decidual basalis tissues of PE and HELLP patients. The increase in B7-H4 in the STB in PE and HELLP may lead to excessive apical expression and release of soluble B7-H4 in the maternal circulation. In contrast, the decrease in B7-H4 in decidual basalis tissues could be related to the decrease in invasion ability of the EVT in PE. Thus, the current results strongly suggest that B7-H4 is involved in the pathogenesis of PE and HELLP.

The Role of B Cells in PE Pathophysiology: A Potential Target for Perinatal Cell-Based Therapy?

The pathophysiology of preeclampsia (PE) is poorly understood; however, there is a large body of evidence that suggests a role of immune cells in the development of PE. Amongst these, B cells are a dominant element in the pathogenesis of PE, and they have been shown to play an important role in various immune-mediated diseases, both as pro-inflammatory and regulatory cells. Perinatal cells are defined as cells from birth-associated tissues isolated from term placentas and fetal annexes and more specifically from the amniotic membrane, chorionic membrane, chorionic villi, umbilical cord (including Wharton's jelly), the basal plate, and the amniotic fluid. They have drawn particular attention in recent years due to their ability to modulate several aspects of immunity, making them promising candidates for the prevention and treatment of various immune-mediated diseases. In this review we describe main findings regarding the multifaceted in vitro and in vivo immunomodulatory properties of perinatal cells, with a focus on B lymphocytes. Indeed, we discuss evidence on the ability of perinatal cells to inhibit B cell proliferation, impair B cell differentiation, and promote regulatory B cell formation. Therefore, the findings discussed herein unveil the possibility to modulate B cell activation and function by exploiting perinatal immunomodulatory properties, thus possibly representing a novel therapeutic strategy in PE.

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

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

CD25+ FOXP3+ and CD4+ CD25+ cells distribution in decidual departments of women with severe and mild pre-eclampsia: Comparison with healthy pregnancies

PROBLEM

The aim of this study was to quantify and compare the distribution of regulatory CD25⁺ FOXP3⁺ and activated CD4⁺ CD25⁺ T cells in decidua basalis and parietalis of severe and mild pre-eclampsia (PE) to normal healthy pregnancies.

METHOD OF STUDY

Decidual tissue (decidua basalis and parietalis) of 13 women with mild PE, 15 women with severe PE, and 19 women with healthy term pregnancies were analyzed by immunohistochemistry and double immunofluorescence.

RESULTS

The total number of CD25⁺ FOXP3⁺ cells/mm² in decidua basalis was decreased in the severe and mild PE versus normal pregnancy group. The total number of CD4⁺ CD25⁺ cells/mm² in decidua basalis was decreased in the severe PE versus normal pregnancy group. The number of CD25⁺ FOXP3⁺ and CD4⁺ CD25⁺ cells in decidua parietalis was decreased in both PE groups.

CONCLUSION

Our data suggest that immunological changes of PE reflect on decidua basalis and parietalis and emphasize the importance of characterizing T cells in both decidual departments.

Phosphorylated STAT3 inhibited the proliferation and suppression of decidual Treg cells in unexplained recurrent spontaneous abortion

This study aimed to investigate the effects of signal transducer and activators of transcription 3 (STAT3) phosphorylation on the function of decidual regulatory T (Treg) cells in unexplained recurrent spontaneous abortion (URSA) patients and to explore the mechanism of STAT3 in URSA. Treg cells were sorted out from the decidual tissue by magnetic beads. The inhibitor Stattic was utilized to alter the phosphorylation status of STAT3 (pSTAT3) in Treg cells. The proliferation and suppression of Treg cell were detected by flow cytometry, real-time quantitative fluorescent PCR and ELISA. The factors that caused the hyperphosphorylation of Treg cells were detected. Our results showed that the proportion of pSTAT3 cells in the decidual Treg cells of URSA patients was significantly increased. pSTAT3 inhibited the proliferation of Treg cells by downregulating the expression of STAT5 and Foxp3 and increased the number of responder T cells. pSTAT3 decreased the secretion of TGF-β1 and IL-10 in Treg cells. Overexpression of pro-inflammatory cytokines IL-6 and IL-23 stimulated STAT3 phosphorylation in Treg cells. This study suggests that hyperphosphorylation of STAT3 impairs the proliferation, suppression and cytokine secretion of Treg cells, while inhibiting the phosphorylation of STAT3 restores these functions. These findings clarify the role of STAT3 in the pathogenesis of URSA and provide new ideas for the treatment of URSA.

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.

Therapeutic Potential of Regulatory T Cells in Preeclampsia-Opportunities and Challenges

Inflammation is a central feature and is implicated as a causal factor in preeclampsia and other hypertensive disorders of pregnancy. Inflammatory mediators and leukocytes, which are elevated in peripheral blood and gestational tissues, contribute to the uterine vascular anomalies and compromised placental function that characterize particularly the severe, early onset form of disease. Regulatory T (Treg) cells are central mediators of pregnancy tolerance and direct other immune cells to counteract inflammation and promote robust placentation. Treg cells are commonly perturbed in preeclampsia, and there is evidence Treg cell insufficiency predates onset of symptoms. A causal role is implied by mouse studies showing sufficient numbers of functionally competent Treg cells must be present in the uterus from conception, to support maternal vascular adaptation and prevent later placental inflammatory pathology. Treg cells may therefore provide a tractable target for both preventative strategies and treatment interventions in preeclampsia. Steps to boost Treg cell activity require investigation and could be incorporated into pregnancy planning and preconception care. Pharmacological interventions developed to target Treg cells in autoimmune conditions warrant consideration for evaluation, utilizing rigorous clinical trial methodology, and ensuring safety is paramount. Emerging cell therapy tools involving in vitro Treg cell generation and/or expansion may in time become relevant. The success of preventative and therapeutic approaches will depend on resolving several challenges including developing informative diagnostic tests for Treg cell activity applicable before conception or during early pregnancy, selection of relevant patient subgroups, and identification of appropriate windows of gestation for intervention.

Assessment efficacy of neutrophil-lymphocyte ratio and monocyte-lymphocyte ratio in preeclampsia

OBJECTIVE

Abnormal changes in immune-mediated inflammation contribute to the pathogenesis of preeclampsia (PE). We aim to investigate the value of systemic immune inflammation indices-neutrophil-lymphocyte ratio (NLR) and monocyte-lymphocyte ratio (MLR)-to identify and evaluate the prognosis of patients with PE.

METHODS

This study reviewed clinical records of 367 PE patients (162 with mild PE and 205 with severe PE), in addition to a control group of 172 normal pregnancies. Blood cell counts were performed at the first diagnosis of PE, and NLR and MLR were calculated by absolute cell count.

RESULTS

Absolute neutrophil, lymphocyte, and monocyte counts and NLR and MLR values in PE were significantly different from controls, although monocyte counts did not significantly differ between mild and severe PE. Receiver operating characteristics curve (ROC) analysis showed NLR and MLR had better diagnostic accuracy in distinguishing PE from controls [NLR area under the curve (AUC) = 0.70; MLR AUC = 0.78]. Further, NLR was the best predictor of disease severity (AUC = 0.71). Cutoff values of NLR > 4.198 or MLR > 0.325 for control and PE groups or a cutoff value of NLR > 4.182 for PE groups indicated that patients were more likely to encounter preterm delivery, have shorter admission-to-delivery interval, and develop maternal and neonatal complications.

CONCLUSION

Secondary analyses of white blood cell differential count parameters effectively evaluate the systemic inflammatory/immune state. Compared with absolute cell counts, NLR and MLR offer more effective indicators of clinical assessment, disease severity evaluation, and prognosis evaluation of PE.

Involvement of the PD-1/PD-L1 Co-Inhibitory Pathway in the Pathogenesis of the Inflammatory Stage of Early-Onset Preeclampsia

The programmed cell death protein 1 (PD-1) receptor has been reported to downregulate T cell activation effectively via binding to its ligands PD-L1 or PD-L2 in a negative co-stimulatory manner. Little is known about the involvement of PD-1 mediated immunoregulation in pregnancy and in pregnancy-related disorders. In this work, we investigated the possible role of the PD-1 co-stimulatory pathway in the pathogenesis of the clinical phase of early-onset preeclampsia characterized by a systemic maternal inflammatory response. We performed a cross-sectional study for comparative analysis of phenotypic and functional characteristics of peripheral blood mononuclear cells in women with early-onset preeclampsia and third-trimester healthy pregnant controls. According to our findings, enhanced expression of either PD-1 or its ligand PD-L1, or both, on the cell surface of effector cells (T cells, natural killer (NK) cells, natural killer T (NKT)-like cells) and Tregs could be observed, but PD-1 expression did not correlate with effector cells exhaustion. These results suggest the failure of the axis to downregulate Th1 responses, contributing thereby to the exaggerated immunoactivation observed in early-onset preeclampsia.

T cell Subsets in Peripheral Blood of Women with Recurrent Implantation Failure

The objective of this study was to determine whether there are any differences in the T cell composition and the expression of specific factors (i.e., IRF4, TBX21, GATA3, and GITR) of T cells between women with Repeated Implantation Failure (RIF) and fertile women. We observed a decrease in circulating Tregs and exhausted CD8 + T cells in RIF patients when compared to the controls whereas exhausted Treg and Th17 cells were more frequent. Using real-time PCR, we determined that the expression of IRF-4 and TBX21 was significantly elevated in the cases. In contrast, mRNAs encoding GATA3 and GITR were reduced. Furthermore, the expression of some miRNAs involved in T cell differentiation and their target gene candidates were examined in T cells from women with RIF and fertile control women. The patients showed significant up-regulation of miR-25, miR-93, and miR-326. miR-155 and miR-146a demonstrated significant down-regulation in RIF patients. The results revealed that the expression pattern of target genes was in line with data for miRNAs expression from purified Treg and Th17 cells. The findings of real-time PCR analysis provided insights into the genetic pathways underlying this aberration in the proportions of T cell subsets. Our data suggest that a combination of higher pro-inflammatory Th17 and exhausted Treg cells, and lower Treg and exhausted CD8 + T cells may co-exist in the peripheral blood of women with RIF. Moreover, the expression level of transcription factors and miRNAs controlling T cell differentiation may differ in women with RIF influencing pregnancy outcomes in these women.

The imbalance of Th17/Treg axis involved in the pathogenesis of preeclampsia

PROBLEM

Inappropriate activation of the immune system, particularly the imbalance of T-helper type 17 (Th17)/regulatory T (Treg) cells is thought to play considerable roles in preeclampsia (PE). To investigate the probable effects of the adaptive immune system in the pathophysiology of PE, we analyzed the dynamic changes of Th17/Treg cells, cytokines profile, and transcription pattern of Th17/Treg-related genes and microRNAs (miRNAs) in 50 women suffering from PE in comparison with 50 healthy pregnant women.

METHODS

Expressions of cytokines, specific transcription factors, and related miRNAs were measured by real-time polymerase chain reaction (PCR). Enzyme-linked immunosorbent assay (ELISA) was used to test the interleukin (IL)-17, IL-23, IL-6, and IL-10 and transforming growth factor β in serum and supernatant of peripheral blood mononuclear cells (PBMCs). The frequency of Th17 and Treg cells were determined by flow cytometry.

RESULTS

PE patients exhibited a decreased number of Treg cells (p = 0.006), while Th17 cells were increased ( p = 0.004). Forkhead box P3 and IL-10 mRNA expressions were reduced ( p = 0.0001 and 0.0028, respectively), while expressions of retinoic acid receptor-related orphan nuclear receptor γt, IL-17, IL-23, and IL-6 were enhanced ( p < 0.0001, 0.0018, 0.0014, and 0.027, respectively). ELISA results also showed increased levels of IL-6, IL-17, and IL-23 ( p = 0.022, 0.0005, 0.0081, respectively), and decreased levels of IL-10 in the supernatant of PBMCs of PE patients compared with control group ( p = 0.0011). There was significant upregulation of miR-106b and miR-326 ( p = 0.0048 and 0.028, respectively) in PE patients in comparison with the control group.

CONCLUSIONS

These findings suggest that imbalance of Th17/Treg cells, regulated possibly via microRNAs, may be involved in the pathogenesis of PE, emphasizing on the importance of these cells in feto-maternal immune cross-talk.

PD-1/PD-L1 regulates Treg differentiation in pregnancy-induced hypertension

Pregnancy-induced hypertension (PIH) causes significant maternal and fetal morbidity and mortality. A decreased number of regulatory T (Treg) cells is associated with the pathogenesis of PIH. The programmed cell death-1 (PD-1)/PD-ligand 1 (PD-L1) pathway is critical to normal pregnancy (NP) by promoting Treg cell development. However, the relationship between PD-1/PD-L1 and Treg differentiation in PIH has not been fully elucidated. In this study, venous blood was obtained from 20 NP and 58 PIH patients. Peripheral blood mononuclear cells (PBMCs) were isolated from venous blood. The levels of Treg-related cytokines (TGF-β, IL-10, and IL-35) in serum and PBMCs were measured by ELISA. The percentage of Treg cells in PBMCs was assessed by flow cytometry. The mRNA levels of Treg-specific transcription factor Foxp3 in PBMCs, and PD-1 and PD-L1 in Treg cells were detected by qRT-PCR. The protein levels of PD-1 and PD-L1 in Treg cells were evaluated by western blot. The serum levels of TGF-β, IL-10, IL-35, and Foxp3 mRNA expression and CD4⁺CD25⁺ Treg cell percentage in PBMCs were decreased in PIH. Furthermore, a significant increase of PD-1 in Treg cells was found in PIH compared with NP. In addition, PD-L1 Fc, an activator of PD-1/PD-L1 pathway, increased Treg cell percentage, enhanced Foxp3 mRNA expression, and elevated levels of TGF-β, IL-10, and IL-35 in PBMCs. However, anti-PD-L1 mAb exerted a reverse effect. These findings revealed that PD-L1 Fc had a favorable effect on Treg cell differentiation, indicating a potential therapeutic value of PD-1/PD-L1 pathway for PIH treatment.

Inhibition of pregnancy-associated granulocytic myeloid-derived suppressor cell expansion and arginase-1 production in preeclampsia

Myeloid-derived suppressor cells (MDSCs) expand in maternal peripheral blood and cord blood during normal pregnancy to maintain maternal-fetal tolerance. Here we investigated the expansion and function of MDSCs in preeclampsia (PE) patients. Maternal peripheral blood mononuclear cells (PBMCs) and cord blood mononuclear cells (CBMCs) were sampled from healthy pregnant women and PE patients, and analyzed for the frequencies and phenotypes of MDSCs and T cells. Serum levels of key human MDSC effector enzymes were measured using appropriate detection kits. Peripheral blood samples of healthy non-pregnant women were used as controls. We found that normal pregnancy is associated with a significant increase of immunosuppressive MDSCs and regulatory T (Treg) cells. There was no significant difference in the frequency of Treg cells between normal pregnancies and PE patients, but the pregnancy-associated increase of granulocytic MDSCs (G-MDSCs), but not monocytic MDSCs (M-MDSCs), in both PBMCs and CBMCs was markedly inhibited in PE patients. Furthermore, serum levels of Arg-1, an important effector molecule for G-MDSC were significantly reduced in PE patients compared to healthy pregnant women. In conclusion, the lack of G-MDSC expansion is a most notable feature of PE-associated immune-cell alterations, suggesting that restoring G-MDSCs may have the potential to treat PE.

Placental immune state shifts with gestational age

PROBLEM

Placental immunologic functions are implicated in both the maintenance of a healthy pregnancy and the pathogenesis of obstetric complications. Immune populations at the maternal-fetal interface are hypothesized to support fetomaternal tolerance, defend the fetus from infection, and contribute to labor initiation. Despite the many potential roles of placental immune cells in normal and abnormal pregnancy, little is known about placental immune population dynamics over gestation, particularly near parturition.

METHOD OF STUDY

A daily placental immune cell census was established in a murine model by flow cytometry from mid to late gestation and compared to the maternal systemic immune census. Shifts in the placental immune state were further characterized through cytokine ELISAs.

RESULTS

The placental immune census is distinct from the maternal systemic immune census, although the cells are primarily maternal in origin. Near term parturition, the placenta contains fewer CD11c-positive myeloid cells and regulatory T cells, and there is a concurrent decrease in placental IL-9 and IL-35.

CONCLUSION

The immune profile of the placenta demonstrates a decrease in both regulatory immune cell types and cytokines late in gestation. Establishing the placental immune population dynamics over a healthy pregnancy will allow future investigation of placental immune cells during abnormal pregnancy.

Early pregnancy immune biomarkers in peripheral blood may predict preeclampsia

We performed a prospective cohort study in 197 pregnant women. Peripheral blood was collected between 5 and 16 weeks of gestation. Intracellular cytokine analysis and immunophenotype were performed by flow-cytometry. Serum levels of cytokines and chemokines were analyzed by multiplex assay. 86 patients were eligible for the analysis and 10.5% (n=9) developed preeclampsia. Patients with preeclampsia had significantly higher percentage of CD3⁺CD4⁺TNFα⁺ T helper (Th) 1 cells (45.4±10.3 vs 37.1±8.5, P=0.032) and CD3⁺CD4⁺IL17⁺ Th 17 cells (2.4±1.3 vs 1.6±1.1, P=0.029) when compared to those of patients without preeclampsia. CD3⁺CD4⁺CD25⁺CD127^dim/- T regulatory cells (Treg) cells (5.7±1.2% vs 7.0±1.6%, P=0.015) were significantly lower in patients with preeclampsia when compared to those without preeclampsia. Patients with preeclampsia had significantly higher TNFα/IL-10 cell ratio (43.8±10.3 vs 34.3±7.9, P=0.005) and Th17/Treg cell ratio (0.5±0.3 vs 0.2±0.2, P=0.011) when compared to those of patients without preeclampsia. IL-8 and Macrophage inflammatory protein (MIP)-1α serum levels were significantly higher in patients with preeclampsia when compared with patients without preeclampsia (Median=341.0 vs 87.6, U=152, P=0.020 and Median=35.7 vs 17.7, U=120, P=0.029 respectively). Serum MCP-1 levels were significantly lower in patients with preeclampsia when compared with patients without preeclampsia (Median=233.8 vs 390.9, U=183, P=0.021). The logistic regression predictive model combining TNFα/IL-10 ratios, IL-8 and MCP-1 serum levels had the best performance (AUC=0.886, 95%CI 0.8-0.9). We concluded that elevated Th1 and Th17 cell percentages, elevated TNFα/IL-10 and Th17/Treg cell ratios and decreased Treg cell percentages in early pregnancy are associated with preeclampsia.

Characterization of intravascular cellular activation in relationship to subclinical atherosclerosis in postmenopausal women

Objective

Mechanisms and interactions among intravascular cells contributing to development of subclinical atherosclerosis are poorly understood. In women, both menopausal status and pregnancy history influence progression of atherosclerosis. This study examined activation and interactions among blood elements with subclinical atherosclerosis in menopausal women with known pregnancy histories.

Methods

Carotid intima-media thickness (CIMT), as a marker of subclinical atherosclerosis, was measured using B-mode ultrasound in age- and parity-matched women [40 with and 40 without a history of preeclampsia] 35 years after the index pregnancy. Interactions among intravascular cells (38 parameters) were measured by flow cytometry in venous blood. Data analysis was by principal component which retained 7 independent dimensions accounting for 63% of the variability among 38 parameters.

Results

CIMT was significantly greater in women with a history of preeclampsia (P = 0.004). Platelet aggregation and platelet interactions with granulocytes and monocytes positively associated with CIMT in postmenopausal women independent of their pregnancy history (ρ = 0.258, P< 0.05). However, the association of the number of platelets, platelet activation and monocyte-platelet interactions with CIMT differed significantly depending upon pregnancy history (test for interaction, P<0.001).

Conclusion

Interactions among actived intravascular cells and their association with subclinical atherosclerosis differ in women depending upon their pregnancy histories.

The altered PD-1/PD-L1 pathway delivers the 'one-two punch' effects to promote the Treg/Th17 imbalance in pre-eclampsia

The programmed cell death-1 (PD-1)/PD-ligand 1 (PD-L1) pathway is critical for normal pregnancy by promoting regulatory T (Treg) cell development and inhibiting the Th17 response. However, the relationship between the PD-1/PD-L1 pathway and the Treg/Th17 imbalance in pre-eclampsia (PE) is an enigma. In this study, decreased PD-1 and PD-L1 expression and a Treg/Th17 imbalance were observed at the maternal-fetal interface in PE. The regulatory effects of the PD-1/PD-L1 pathway on the Treg and Th17 cell quantities were determined in vitro by targeting T-cell proliferation, differentiation and transdifferentiation. First, decreased PD-1 expression might contribute to a higher Th17 cell frequency by promoting proliferation in PE. Second, the percentages of Treg but not Th17 cells differentiated from peripheral naive CD4⁺ T cells were increased by PD-L1 Fc administration. This effect was accompanied by decreased PI3K/AKT/m-TOR and increased PTEN mRNA expression and was completely reversed by PD-1 blockade. Finally, the percentage of IL-17-producing Treg cells increased and was positively associated with the Th17 cell frequency in PE. Increased RORγt and IL-17 but not Foxp3 and IL-10 mRNA expression by Treg cells was observed with PD-1 blockade. Similar findings occurred when Treg cells were exposed to IL-6/IL-23/IL-1β and were reversed by PD-L1 Fc. Taken together, our findings indicate that the PD-1/PD-L1 pathway contributes to the Treg/Th17 imbalance via 'one-two punch' approaches: (i) promoting Th17 cell proliferation, (ii) inhibiting Treg cell differentiation and (iii) enhancing Treg cell plasticity into Th17 cells in PE. The therapeutic value of PD-L1 Fc for PE treatment will be explored in the future.

The Distribution of Activation Markers and Selectins on Peripheral T Lymphocytes in Preeclampsia

Introduction

Impaired maternal immune tolerance resulting in systemic inflammation plays a pivotal role in the pathogenesis of preeclampsia. Phenotypical changes of monocytes and neutrophil granulocytes have already been studied in preeclampsia, and some studies also included T lymphocyte activation markers; however, the results are controversial and a comprehensive analysis of activation markers is lacking. The characteristics of cellular adhesion molecules in preeclampsia are yet to be described.

Material and Methods

Peripheral blood samples of 18 preeclamptic patients and 20 healthy pregnant women in the third trimester were evaluated using flow cytometry to characterize the cell surface expression of T lymphocyte activation markers and selectins.

Results

We found an elevated ratio of HLA-DR and CD122-, CD62E-, and CD62L-expressing cells among the CD4+ T lymphocytes in PE in comparison to healthy pregnancy. No alterations were found in the prevalence of CD69-, CD25-, and CD62P-expressing lymphocytes and CD11c-expressing monocytes.

Conclusions

Our findings support the role of activated T lymphocytes and specific cell adhesion molecules in the pathogenesis of preeclampsia.

The PD-1/PD-L1 inhibitory pathway is altered in pre-eclampsia and regulates T cell responses in pre-eclamptic rats

The programmed cell death-1(PD-1)/PD-ligand 1 (PD-L1) pathway is critical to immune homeostasis by promoting regulatory T (Treg) development and inhibiting effector T (such as Th17) cell responses. However, the association between the PD-1/PD-L1 pathway and the Treg/Th17 imbalance has not been fully investigated in pre-eclampsia (PE). In this study, we observed an inverse correlation between the percentages of Treg and Th17 cells, and the expression of PD-1 and PD-L1 on the two subsets also changed in PE compared with normal pregnancy. We further explored their relationship in vivo using the L-NG-Nitroarginine Methyl Ester (L-NAME) induced PE-like rat models, also characterized by Treg/Th17 imbalance. Administration of PD-L1-Fc protein provides a protective effects on the pre-eclamptic models, both to the mother and the fetuses, by reversing Treg/Th17 imbalance through inhibiting PI3K/AKT/m-TOR signaling and enhancing PTEN expression. In addition, we also observed a protective effect of PD-L1-Fc on the placenta by reversing placental damages. These results suggested that altered PD-1/PD-L1 pathway contributed to Treg/Th17 imbalance in PE. Treatment with PD-L1-Fc posed protective effects on pre-eclamptic models, indicating that the use of PD-L1-Fc might be a potential therapeutic target in PE treatment.

Regulatory T-cells and preeclampsia: an overview of literature

Regulatory T-cells (Tregs) are key players in successful pregnancy and their deficiencies are implicated in pregnancy complications such as preeclampsia (PE), but the results are inconsistent among studies. This study aims to compile an overview of the studies about the associations of Tregs and PE risk and to provide recommendations for future research. A sensitive search of three databases including PubMed, Scopus and Google scholar (from 1995 to January 9, 2015) identified 636 unique titles. An accurate process of study selection, data extraction and method qualification were independently conducted by authors on retrieved papers. Seventeen papers met the inclusion criteria and were included in quality assessment. Regarding the source of Tregs, 14 studies assessed Tregs in peripheral blood, 2 studies in peripheral blood and decidua and one study in peripheral blood and umbilical cord blood. Despite variation in the combinations of markers and other aspects of the studies designs, remarkable constancy in the results of studies that measured Tregs as CD4+FoxP3+ or CD4+CD25+FoxP3+ cells (but not CD4+CD25(high/low)FoxP3+ markers) was found, which in broad terms showed a shift towards fewer Treg cells in PE. This review revealed an association between lower percentage of circulating CD4+FoxP3+ or CD4+CD25+FoxP3+ Tregs and the risk of PE. Given the above issue and regarding the high consistency of studies on reduction of suppressive activity of Tregs in PE, we have proposed a model in which the Tregs deficiency is a reflection of immune endocrine imbalance, which reverses maternal tolerance and results in development of preeclampsia.

Amniotic mesenchymal cells from pre-eclamptic placentae maintain immunomodulatory features as healthy controls

Pre‐eclampsia (PE) is one of the most severe syndromes in human pregnancy, and the underlying mechanisms of PE have yet to be determined. Pre‐eclampsia is characterized by the alteration of the immune system's activation status, an increase in inflammatory Th1/Th17/APC cells, and a decrease in Th2/Treg subsets/cytokines. Moreover, inflammatory infiltrates have been detected in the amniotic membranes of pre‐eclamptic placentae, and to this date limited data are available regarding the role of amniotic membrane cells in PE. Interestingly, we and others have previously shown that human amniotic mesenchymal stromal cells (hAMSC) possess anti‐inflammatory properties towards almost all immune cells described to be altered in PE. In this study we investigated whether the immunomodulatory properties of hAMSC were altered in PE. We performed a comprehensive study of cell phenotype and investigated the in vitro immunomodulatory properties of hAMSC isolated from pre‐eclamptic pregnancies (PE‐hAMSC), comparing them to hAMSC from normal pregnancies (N‐hAMSC). We demonstrate that PE‐hAMSC inhibit CD4/CD8 T‐cell proliferation, suppress Th1/Th2/Th17 polarization, induce Treg and block dendritic cells and M1 differentiation switching them to M2 cells. Notably, PE‐hAMSC generated a more prominent induction of Treg and higher suppression of interferon‐γ when compared to N‐hAMSC, and this was associated with higher transforming growth factor‐β1 secretion and PD‐L2/PD‐L1 expression in PE‐hAMSC. In conclusion, for the first time we demonstrate that there is no intrinsic impairment of the immunomodulatory features of PE‐hAMSC. Our results suggest that amniotic mesenchymal stromal cells do not contribute to the disease, but conversely, could participate in offsetting the inflammatory environment which characterizes PE.