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

The impact of pregnancy on future health in Rheumatoid Arthritis: A systematic review of the literature

OBJECTIVES

To assess whether obstetric history predicts future rheumatoid arthritis (RA) diagnosis, severity, and/or maternal health beyond the immediate postpartum period.

METHODS

A systematic literature search was conducted on 01/07/24 (PubMed, Embase); PROSPERO ID CRD42024559893. Primary research examining health outcomes in RA-affected females, stratified on obstetric history pre- or post-RA onset, were selected for inclusion. Studies of overlapping cohorts were included if differing exposures/outcomes reported.

RESULTS

Out of 3333 articles screened, 95 studies were selected. Future health outcomes analysed included RA diagnosis (n = 66 studies), severity (n = 11), cardiovascular disease (n = 2), immunity (n = 9), and microchimerism (n = 7). Parity/gravidity (n = 67), infertility (n = 7), and pregnancy loss (n = 22) were not reliable predictors of subsequent RA. High parity (n = 2) was linked to increased cardiovascular disease risk in RA-affected females. Both pre-eclampsia (n = 4) and delivery of a low birthweight infant (n = 2) were associated with RA diagnosis/severity. A trend suggested increased RA risk after preterm birth (n = 3) and severe hyperemesis gravidarum (n = 3), but not for gestational diabetes (n = 1). No significant differences in post-translational modification of serum proteins were noted beyond 6 months postpartum, though persistent differences in anti-HLA antibodies and microchimerism were observed.

CONCLUSIONS

Research indicates that parity, gravidity, infertility, and pregnancy loss do not adversely affect RA development. Conversely, low birthweight delivery was associated with RA diagnosis and severity, while pre-eclampsia correlated with subsequent RA diagnosis. Differences in immune responses, as indicated by anti-HLA and microchimerism, may indicate immune sensitisation relevant to RA pathogenesis. The predictive impact of pre-eclampsia and gestational diabetes on cardiovascular health in RA-affected females remains unstudied.

Tregs in pregnancy with type 1 diabetes mellitus: pilot study

OBJECTIVE

Pregnancy in women with type 1 diabetes mellitus has been associated with adverse outcomes due to persistent hyperglycemia and impaired maternal-fetal interactions. Regulatory T cells seem to exert a critical role in this process. Pregnancy can change the profile of Treg cells and affect the outcome of pregnancy; therefore, our purpose was to characterize the profile of regulatory T cells in the peripheral blood of pregnant and nonpregnant (controls) women with type 1 diabetes mellitus.

METHODS

This prospective case-control study recruited 36 women with type 1 diabetes mellitus, 16 pregnant and 20 nonpregnant. Peripheral blood samples were collected in the three trimesters of pregnancy and only once in the control group. Flow cytometry was used to assess peripheral blood T subpopulations: CD3+, CD4+, CD8+, CD4+ Treg (CD4+CD25+CD127-FOXP3+), and CD8+ Treg (CD8+CD25+FOXP3). In addition, the expression of CD4+CD25high and CD4+CD25low was analyzed.

RESULTS

Compared to controls, the pregnant women (regardless of the trimester) presented a lower percentage of TCD4+CD25high, TCD4+CD25low, and CD8 Treg (CD8+CD25+FOXP3+). Moreover, a higher percentage of total TCD8+ lymphocytes was observed in pregnant women than in controls.

CONCLUSION

This study reported changes in the circulating Treg cell profile that seem to be associated with pregnancy in type 1 diabetes mellitus patients and pregnancy outcomes.

A comprehensive review of the roles of T-cell immunity in preeclampsia

Preeclampsia (PE) is an obstetrical disorder that occurs after the 20th week of gestation. It is recognized as one of the "Great Obstetrical Syndromes" and principally contributes to maternal morbidity and mortality. PE has been associated with a range of immune disorders, including a preponderance of T helper (Th) 1 over Th2 cells and imbalanced levels of Th17 and T regulatory cells (Tregs). During pregnancy, T cells safeguard the placenta against immune rejection and aid embryo implantation while involved in pregnancy complications, such as PE. Promoting alloantigen-specific Treg cells is a potential preventive and therapeutic strategy for PE. However, ensuring the safety of mothers and infants is of the utmost importance since the risk-benefit ratio of reproductive and obstetric conditions differs significantly from that of immune diseases that pose a life-threatening risk. In this review, we systematically summarize the roles of T-cell immunity in the peripheral blood, reproductive tissues, and at the maternal-fetal interface of PE patients. Furthermore, the recent therapeutic approaches centered on targeting T cell immunity in PE are critically appraised.

Regulatory B-Cells Are Associated Negatively With Regulatory T-Cells and Positively With Cytokines in Peripheral Blood of Pregnant Women

PROBLEM

Regulatory B-cells (Bregs, CD19+CD24hiCD38hi) are a specialized B-cell subset that suppresses immune responses and potentially contribute to the maintenance of an immune-privileged environment for fetal development during pregnancy. However, little is known about the surrounding immunological environment of Bregs in gestational physiology. The relationship of regulatory T-cells (Tregs, CD4+CD25hiCD127loFoxP3+) to Bregs in coordinating immunoregulation during pregnancy is unknown. We aimed to determine whether peripheral concentrations of Bregs and/or PD-L1-expressing Bregs correlated with Tregs and cytokines during pregnancy.

METHOD

Peripheral blood samples were obtained from 29 pregnant women at mean 12 weeks' gestation. Participants were age ≥ 18, self-identified as Latina/Hispanic, and N = 12 primigravid. Peripheral blood mononuclear cells were isolated, stained, and analyzed by flow cytometry to determine percentages of Tregs from CD4+ T-cells and five Treg subsets defined by immune checkpoint markers, and Bregs and PD-L1+ Bregs from total B-cells. Levels of 13 cytokines were measured on a Meso Scale Discovery multiplex platform.

RESULTS

Bregs positively correlated with pro-inflammatory cytokine interleukin (IL)-6. PD-L1+ Bregs positively correlated with T-cell suppressive cytokine IL-10. PD-L1+ Bregs negatively correlated with Tregs and Helios+, CTLA-4+, PD-1+, TIGIT+, and TIM3+ Tregs. For primigravida, PD-L1+ Bregs correlated positively with IL-10 and negatively with Helios+ and TIGIT+ Tregs. For multigravida, PD-L1+ Bregs correlated positively with IL-8 and negatively with Helios+, CTLA-4+, PD-1+, and TIGIT+ Tregs.

CONCLUSIONS

This study provides insight into the immunosuppressive role of Bregs and PD-L1+ Bregs during human pregnancy. Our results suggest that PD-L1+ Bregs can employ suppressive mechanisms to limit pro-inflammatory responses in primigravida.

Reduced number of regulatory T cells in maternal circulation precede idiopathic spontaneous preterm labor in a subset of patients

BACKGROUND

Accumulating evidence suggests that spontaneous preterm labor is a syndrome caused by multiple pathological processes. The breakdown of maternal-fetal tolerance has been proposed as a key mechanism of idiopathic spontaneous preterm labor, often viewed as a chronic inflammatory process resulting from the maternal immune system's impaired tolerance of the fetus from early pregnancy. Regulatory T cells are crucial for maintaining maternal-fetal tolerance. Even a partial reduction in their levels can disrupt this tolerance, leading to adverse pregnancy outcomes such as preterm labor. Given the complexity of the T lymphocyte-mediated immune response, identifying candidate signaling pathways involved in maternal-fetal tolerance is challenging. However, current literature highlights the importance of the functional and developmental markers FoxP3, CD45RA, Helios, and CD39 due to their immunosuppressive abilities essential for maintaining pregnancy.

OBJECTIVE

This study aimed to determine whether changes in numbers of selected regulatory T cell subpopulations in the first trimester are associated with subsequent spontaneous preterm labor.

STUDY DESIGN

This prospective study enrolled 43 women with early singleton pregnancies, excluding those with autoimmune diseases, diabetes mellitus (type 1, type 2), primary hypertension, or who had been treated with vaginal progesterone prior to sample collection. We analyzed regulatory T cell subpopulations in maternal circulation using the DURAClone IM T cell kit, focusing on the following subsets: CD4+CD25+FoxP3+, CD4+CD25+FoxP3+CD45RA, CD4+CD25+FoxP3+Helios+, and CD4+CD25+FoxP3+CD39-.

RESULTS

Among the participants, 7 experienced spontaneous preterm labor between the 23rd and 33rd weeks of gestation, while 36 delivered at term. The preterm group showed a significant reduction in numbers of all analyzed regulatory T cell subpopulations: CD4+CD25+FoxP3+ (median 0.0410×10ˆ9/L vs median 0.0550×10ˆ9/L, P=.0217), CD4+CD25+FoxP3+CD45RA- (median 0.0310×10ˆ9/L vs median 0.0420×10ˆ9/L, P=.0216), CD4+CD25+FoxP3+Helios+ (median 0.0270×10ˆ9/L vs median 0.0370×10ˆ9/L, P=.0260), CD4+CD25+FoxP3+CD39- (median 0.0300×10ˆ9/L vs median 0.0420×10ˆ9/L, P=.0427).

CONCLUSION

Early first trimester alterations in specific regulatory T cell subpopulations, including diminished levels of CD4+CD25+FoxP3+, CD4+CD25+FoxP3+CD45RA-, CD4+CD25+FoxP3+Helios+, and CD4+CD25+FoxP3+CD39-, are associated with idiopathic spontaneous preterm labor. These findings suggest that early changes in these lymphocyte subpopulations may be linked to spontaneous preterm birth. This highlights the need for further research to understand the mechanisms underlying regulatory T-cell dynamics and their impact on pregnancy outcomes.

SARS-CoV-2 infection elucidates features of pregnancy-specific immunity

Pregnancy is a risk factor for increased severity of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and other respiratory infections, but the mechanisms underlying this risk are poorly understood. To gain insight into the role of pregnancy in modulating immune responses at baseline and upon SARS-CoV-2 infection, we collected peripheral blood mononuclear cells and plasma from 226 women, including 152 pregnant individuals and 74 non-pregnant women. We find that SARS-CoV-2 infection is associated with altered T cell responses in pregnant women, including a clonal expansion of CD4-expressing CD8+ T cells, diminished interferon responses, and profound suppression of monocyte function. We also identify shifts in cytokine and chemokine levels in the sera of pregnant individuals, including a robust increase of interleukin-27, known to drive T cell exhaustion. Our findings reveal nuanced pregnancy-associated immune responses, which may contribute to the increased susceptibility of pregnant individuals to viral respiratory infection.

The Immunomodulatory Role of Regulatory T Cells in Preterm Birth and Associated Pregnancy Outcomes

Spontaneous preterm birth (sPTB), defined as live birth before 37 weeks of gestational age, is associated with immune dysregulation and pro-inflammatory conditions that profoundly impact newborn health. The question of immune integrity at the maternal-foetal interface is a focus of recent studies centring not only sPTB but the conditions often affiliated with this outcome. Regulatory T cells (Tregs) play a critical anti-inflammatory role in pregnancy, promoting foetal tolerance and placentation. Due to this gestational role, it is hypothesised that decreased or dysfunctional Tregs may be implicated in cases of sPTB. This review examines studies comparing Treg presence in healthy term pregnancies and those with sPTB-associated conditions. Conflicting findings across different conditions and within sPTB itself have been identified. However, notable findings from the research indicate increased proinflammatory cytokines in pregnancies suffering from premature rupture of membranes (pPROM), chorioamnionitis, infection, preeclampsia, and gestational diabetes (GDM). Additionally, reduced Treg levels were identified in preeclampsia, GDM, and pPROM as well as chorioamnionitis presenting with increased Treg dysfunctionality. Treg deficiencies may contribute to health issues in preterm newborns. Current sPTB treatments are limited, underscoring the potential of in utero therapies targeting inflammation, including T cell interventions. Future research aims to establish consensus on the role of Tregs in sPTB and associated conditions and advancing understanding of mechanisms leading to Treg deficiencies in adverse pregnancy outcomes.

The rebalancing of the immune system at the maternal-fetal interface ameliorates autism-like behavior in adult offspring

Maternal immune activation (MIA) is critical for imparting neuropathology and altered behaviors in offspring; however, maternal-fetal immune cell populations have not been thoroughly investigated in MIA-induced autism spectrum disorders (ASDs). Here, we report the single-cell transcriptional landscape of placental cells in both PBS- and poly(I:C)-induced MIA dams. We observed a decrease in regulatory T (Treg) cells but an increase in the M1 macrophage population at the maternal-fetal interface in MIA dams. Based on the Treg-targeting approach, we investigate an immunoregulatory protein, the helminth-derived heat shock protein 90α (Sjp90α), that induces maternal Treg cells and subsequently rescues the autism-like behaviors in adult offspring. Furthermore, in vivo depletion of maternal macrophages attenuates placental inflammatory reaction and reverses behavioral abnormalities in adult offspring. Notably, Sjp90α induces CD4+ T cell differentiation via scavenger receptor A (SR-A) on the macrophage in vitro. Our findings suggest a maternal Treg-targeted approach to alleviate MIA-induced autism-like behavior in adult offspring.

Maternal Soluble Programmed Death Ligand-1 (sPD-L1) and T-regulatory Cells (Tregs) Alteration in Preeclampsia: A Cross-Sectional Study From Eastern India

Background Studies have shown that aberrant reactions of the immune system play an important role in the pathogenesis of preeclampsia. The immune checkpoint molecules programmed cell death protein 1/programmed death-ligand 1 (PD-1/PD-L1) system and the T-regulatory cells (Tregs) system are decisive in the regulation of immune responses and can be the target molecules in preeclampsia. In this study, an attempt has been made to evaluate the soluble PD-L1 (sPD-L1) in the serum of preeclampsia cases and correlate it with Tregs and inflammatory markers to have an insight into the link between these immunomodulatory molecules in the pathogenesis of preeclampsia. Materials and methods Ten normal fertile women, 20 trimester-matched normal pregnancy cases, and 20 preeclampsia cases were enrolled in the study. Serum sPD-L1, transforming growth factor beta 1 (TGF-β1), and IL-6 were measured by enzyme-linked immunosorbent assay (ELISA). High-sensitive C-reactive protein (hsCRP) was estimated using a clinical biochemistry autoanalyzer. Tregs were evaluated using flow cytometry. Results and discussion The immune checkpoint molecule PD-L1 inversely correlated with Tregs in preeclampsia cases. Associated inflammation was seen by raised IL-6 and hsCRP. The breakdown of immunological tolerance is mainly caused by the dysregulating the Tregs/Th17 balance, which leads to conditions of autoimmunity and chronic inflammatory disorders. PD-L1 can be the link between this immunological misbalance. Conclusion Our study, showing an increase in sPD-L1 and TGF and a decrease in Tregs with an increase in inflammatory markers like IL-6 and hsCRP levels in preeclampsia, has potential implications for early diagnosis and management of the condition. PD-L1 and Tregs can be target molecules for early management of preeclampsia.

Characteristics and functions of memory regulatory T cells in normal pregnancy cycle and pregnancy complications

Regulatory T cells (Tregs) are activated and expanded after exposure to fetal-specific (paternal) antigens. A proportion of Tregs differentiate into memory Tregs (mTregs), exhibiting immune memory function and exerting more potent immunosuppression than naive Tregs (nTregs). However, it is unclear how mTregs are regulated during normal and pathological pregnancies (e.g., gestational diabetes mellitus (GDM) and preeclampsia (PE)). In this study, PD-1, HLA-G, and HLA-DR expressions on memory CD4+ T cells, naive CD4+ T cells, Tregs, mTregs, and nTregs in healthy non-pregnant women (n=20), healthy first (n=20), second (n=20), and third-trimester women (n=20), postpartum women (n=20), GDM (n=20), and PE patients (n=20) were analyzed. The proportion of mTregs out of Tregs was increased (P<0.05) in the first trimester compared with that in non-pregnancy and reduced in the second and third trimesters. The proportions of PD-1+ Tregs and mTregs were significantly increased during the first trimester compared to those of non-pregnancy (P<0.01), reached their maximum in the second trimester. Moreover, the proportions of HLA-G+ memory CD4+ T cells, Tregs, and mTregs were increased in the first and second trimesters (P<0.01), reached their maximum in the third trimester. GDM patients were characterized by significantly lower percentages of PD-1+ and HLA-G+ mTregs (P<0.01), while PE patients were characterized by significantly lower percentages of HLA-G+ mTregs (P<0.01), compared with the healthy third-trimester women. In general, as demonstrated by this study, mTregs increase in number and enhance maternal-fetal immunoregulation during pregnancy, and their dysfunction can result in pregnancy complications such as GMD or PE.

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.

The Role of Regulatory T Cells and Their Therapeutic Potential in Hypertensive Disease of Pregnancy: A Literature Review

Hypertensive disorders of pregnancy (HDP), including preeclampsia (PE) and gestational hypertension (GH), are major causes of maternal and foetal morbidity and mortality. This review elucidates the role of regulatory T cells (Tregs) in the immunological aspects of HDP and explores their therapeutic potential. Tregs, which play a critical role in maintaining immune homeostasis, are crucial in pregnancy to prevent immune-mediated rejection of the foetus. The review highlights that Tregs contribute to immunological adaptation in normal pregnancy, ensuring foetal acceptance. In contrast, HDP is associated with Treg dysfunction, which is marked by decreased numbers and impaired regulatory capacity, leading to inadequate immune tolerance and abnormal placental development. This dysfunction is particularly evident in PE, in which Tregs fail to adequately modulate the maternal immune response against foetal antigens, contributing to the pathophysiology of the disorder. Therapeutic interventions aiming to modulate Treg activity represent a promising avenue for HDP management. Studies in animal models and limited clinical trials suggest that enhancing Treg functionality could mitigate HDP symptoms and improve pregnancy outcomes. However, given the multifactorial nature of HDP and the intricate regulatory mechanisms of Tregs, the review explores the complexities of translating in vitro and animal model findings into effective clinical therapies. In conclusion, while the precise role of Tregs in HDP is still being unravelled, their central role in immune regulation during pregnancy is indisputable. Further research is needed to fully understand the mechanisms by which Tregs contribute to HDP and to develop targeted therapies that can safely and effectively harness their regulatory potential for treating hypertensive diseases of pregnancy.

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.

Phenotypic characterisation of regulatory T cells in patients with gestational diabetes mellitus

Gestational diabetes mellitus (GDM) is a common complication that occurs during pregnancy. Emerging evidence suggests that immune abnormalities play a pivotal role in the development of GDM. Specifically, regulatory T cells (Tregs) are considered a critical factor in controlling maternal-fetal immune tolerance. However, the specific characteristics and alterations of Tregs during the pathogenesis of GDM remain poorly elucidated. Therefore, this study aimed to investigate the changes in Tregs among pregnant women diagnosed with GDM compared to healthy pregnant women. A prospective study was conducted, enrolling 23 healthy pregnant women in the third trimester and 21 third-trimester women diagnosed with GDM. Participants were followed up until the postpartum period. The proportions of various Treg, including Tregs, mTregs, and nTregs, were detected in the peripheral blood of pregnant women from both groups. Additionally, the expression levels of PD-1, HLA-G, and HLA-DR on these Tregs were examined. The results revealed no significant differences in the proportions of Tregs, mTregs, and nTregs between the two groups during the third trimester and postpartum period. However, GDM patients exhibited significantly reduced levels of PD-1+ Tregs (P < 0.01) and HLA-G+ Tregs (P < 0.05) in the third trimester compared to healthy pregnant women in the third trimester. Furthermore, GDM patients demonstrated significantly lower levels of PD-1+ mTregs (P < 0.01) and HLA-G+ (P < 0.05) mTregs compared to healthy pregnant women in the third trimester. Overall, the proportion of Tregs did not exhibit significant changes during the third trimester in GDM patients compared to healthy pregnant women. Nevertheless, the observed dysregulation of immune regulation function in Tregs and mTregs may be associated with the development of GDM in pregnant women.

Regulatory T-cell phenotypes in prenatal psychological distress

BACKGROUND

Experiencing symptoms of psychological distress during pregnancy is common and has been linked to dysregulated immune functioning. In this context, immunoregulatory function is especially relevant because of its crucial role in establishment and maintenance of healthy pregnancy. However, little research has examined associations between women's prenatal psychological distress and immunoregulatory biomarkers. We investigated how symptoms of depression, anxiety, and stress relate to circulating levels of regulatory T-cells (Tregs).

MATERIALS AND METHODS

Pregnant Latina women were assessed at around 12 weeks of pregnancy (N = 82). These assessments included blood draws and self-report questionnaires assessing symptoms of depression, state anxiety, pregnancy-related anxiety, and perceived stress. Flow cytometry on PBMCs was used to quantify circulating Tregs, defined as CD3+CD4+CD25hiCD127loFoxP3+, and subpopulations positive for one of the following intra- or extracellular markers, CD45RA, CTLA-4, Helios, PD-1, TIM-3, and TIGIT. We collected 82 samples at 12 weeks. Multivariable linear regressions tested for associations between symptoms of psychological distress and Treg concentrations, adjusted for gestational age.

RESULTS

State anxiety symptoms at 12 weeks were negatively associated with parent Treg cell levels (b = -4.02, p = 0.023) and subpopulations Helios+ (b = -3.29, p = 0.019) and TIM3+ (b = -3.17, p = 0.008). Perceived stress was negatively associated with the PD-1+ subpopulation at 12 weeks (b = -4.02, p = 0.023). Depression was not related to Tregs or the subpopulations.

CONCLUSION

Our observation that symptoms of anxiety and stress are related to tolerogenic immunology suggests a possible biomechanism explaining correlations of maternal mood disorders with adverse outcomes for mothers and offspring.

Memory regulatory T cells in pregnancy

Pregnancy requires the process of maternal immune tolerance to semi-allogeneic embryos. In contrast, an overreactive maternal immune system to embryo-specific antigens is likely to result in the rejection of embryos while damaging the invading placenta, such that the likelihood of adverse pregnancy outcomes can be increased. Regulatory T cells (Tregs) are capable of suppressing excessive immune responses and regulating immune homeostasis. When stimulating Tregs, specific antigens will differentiate into memory Tregs with long-term survival and rapid and powerful immune regulatory ability. Immunomodulatory effects mediated by memory Tregs at the maternal-fetal interface take on critical significance in a successful pregnancy. The impaired function of memory Tregs shows a correlation with various pregnancy complications (e.g., preeclampsia, gestational diabetes mellitus, and recurrent pregnancy losses). However, the differentiation process and characteristics of memory Tregs, especially their role in pregnancy, remain unclear. In this study, a review is presented in terms of memory Tregs differentiation and activation, the characteristics of memory Tregs and their role in pregnancy, and the correlation between memory Tregs and pregnancy complications. Furthermore, several potential therapeutic methods are investigated to restore the function of memory Tregs in accordance with immunopathologies arising from memory Tregs abnormalities and provide novel targets for diagnosing and treating pregnancy-associated diseases.

Th1 or Th2 cytokines are correlated with Tregs and T cell subsets and pregnancy outcomes in patients with autoimmune thyroid disease during early, middle, late pregnancy, and postpartum period

Autoimmune thyroid disease (AITD) is a T lymphocytes-mediated autoimmune disorder affecting pregnant women. The current study sought to determine the correlations between T helper-1 (Th1)/T helper-2 (Th2) cytokines and regulatory T cells (Tregs) and T cell subsets and pregnancy outcomes in AITD patients during early pregnancy (T1), middle pregnancy (T2), late pregnancy (T3), and postpartum period (PP). A total of 60 patients with Graves' disease, 60 patients with Hashimoto's thyroiditis, and 30 healthy pregnant women were initially enrolled in the study. Thyroid hormones and antibodies, Th1 or Th2 cytokines, transforming growth factor-β, Tregs, CD4+ T helper cells (CD4+), CD8+ T helper cells (CD8+) levels were determined by means of Maglumi2000 automatic chemiluminescence instrument, enzyme-linked immunosorbent assay, and flow cytometry. Our findings demonstrated higher IFN-γ and IL-2 levels, along with lower IL-4, IL-10, TGF-β, Treg, and CD4+/CD8+ levels in AITD patients during T1, T2, T3, and PP. Furthermore, the TGF-β, Treg, and CD4+/CD8+ levels were lower in the IFN-γ/IL-2 high expression group but higher in the IL-4/IL-10 high expression group. The IFN-γ and IL-2 levels were higher, while IL-4 and IL-10 level were lower in AITD patients with adverse pregnancy outcomes. Lastly, Th1 cytokines were higher and Th2 cytokines were lower in AITD patients and elicited correlation with Tregs and CD4+/CD8+ levels. Collectively, our findings highlighted that up-regulation of Th1 cytokines may increase the percentage of adverse pregnancy outcomes in AITD patients.

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.

The Molecular Mechanisms of HLA-G Regulatory Function on Immune Cells during Early Pregnancy

Human leukocyte antigen-G (HLA-G) is a non-classical human major histocompatibility complex (MHC-I) molecule with the membrane-bound and soluble types. HLA-G is primarily expressed by extravillous cytotrophoblast cells located at the maternal-fetal interface during pregnancy and is essential in establishing immune tolerance. This review provides a comprehensive understanding of the multiple molecular mechanisms by which HLA-G regulates the immune function of NK cells. It highlights that HLA-G binds to microRNA to suppress NK cell cytotoxicity and stimulate the secretion of growth factors to support fetal growth. The interactions between HLA-G and NK cells also activate senescence signaling, promoting spiral artery remodeling and maintaining the balance of maternal-fetal immune responses. In addition, HLA-G can inhibit the function of decidual T cells, dendritic cells, and macrophages. Overall, the interaction between trophoblast cells and immune cells mediated by HLA-G plays a crucial role in understanding immune regulation at the maternal-fetal interface and offers insights into potential treatments for pregnancy-related diseases.

Pre-Eclampsia: From Etiology and Molecular Mechanisms to Clinical Tools-A Review of the Literature

Pre-eclampsia is a severe pregnancy-related complication that manifests as a syndrome with multisystem involvement and damage. It has significantly grown in frequency during the past 30 years and could be considered as one of the major causes of maternal and fetal morbidity and mortality. However, the specific etiology and molecular mechanisms of pre-eclampsia are still poorly known and could have a variety of causes, such as altered angiogenesis, inflammations, maternal infections, obesity, metabolic disorders, gestational diabetes, and autoimmune diseases. Perhaps the most promising area under investigation is the imbalance of maternal angiogenic factors and its effects on vascular function, though studies in placental oxidative stress and maternal immune response have demonstrated intriguing findings. However, to determine the relative importance of each cause and the impact of actions aiming to significantly reduce the incidence of this illness, more research is needed. Moreover, it is necessary to better understand the etiologies of each subtype of pre-eclampsia as well as the pathophysiology of other major obstetrical syndromes to identify a clinical tool able to recognize patients at risk of pre-eclampsia early.

Placenta autophagy is closely associated with preeclampsia

The pathogenesis of preeclampsia (PE) is complex and placental internal homeostasis is regulated by cellular autophagy. However, there are fewer studies related to the role of placental autophagy in the pathogenesis of PE. The GSE75010 and GSE10588 datasets were downloaded from the gene expression omnibus (GEO) database. In the GSE75010 (test cohort), 103 differentially expressed genes (DEGs) were screened using "Limma" package, and 281 PE characteristic genes were screened by weighted gene coexpression network analysis (WGCNA). Combined with the autophagy gene set, a total of 5 autophagy-related hub genes were obtained. Three biomarkers (HK2, PLOD2, and TREM1) were then further screened by random forest(RF) model and least absolute shrinkage and selection operator(LASSO) algorithm as diagnostic of PE. In the unsupervised consensus clustering analysis, HK2, PLOD2, and TREM1 may be synergistically involved in hypoxia-induced autophagy and hypoxia-inducible factor 1(HIF-1) signaling pathway to induce PE. In addition, we constructed and evaluated a nomogram model for PE diagnosis using these three key diagnostic biomarkers, and the results showed that the model had significantly excellent predictive power (AUC values of GSE75010 and GSE10588 datasets were 0.869 and 0.876, respectively). In terms of immune infiltration, a higher proportion of T cells CD8, and a lower proportion of Macrophages M2 were found in PE placentas compared to normal tissue, and high expression of HK2, PLOD2, and TREM1 were accompanied by low levels of Macrophages M2 infiltration. HK2, PLOD2, and TREM1 may be associated with the development of pre-eclampsia, and their mechanisms of action in preeclampsia need to be further investigated.

Inflammation in preterm birth: Novel mechanism of preterm birth associated with innate and acquired immunity

Preterm birth (PB) is the most-frequent complication occurring during pregnancy, with a significant impact on neonatal morbidity and mortality. Chorioamnionitis (CAM), the neutrophil infiltration into chorioamniotic membranes, is a major cause of PB. However, several cases of PB have also been reported without apparent pathogenic infection or CAM. Such cases are now attributed to "sterile inflammation." The concept of sterile inflammation has already attracted attention in various diseases, like cardiovascular diseases, diabetes, and autoimmune diseases; recently been discussed for obstetric complications such as miscarriage, PB, gestational hypertension, and gestational diabetes. Sterile inflammation is induced by alarmins, such as high-mobility group box 1 (HMGB1), interleukins (IL-33 and IL-1α), and S100 proteins, that are released by cellular damage without apparent pathogenic infection. These antigens are recognized by pattern-recognition receptors, expressed mainly on antigen-presenting cells of decidua, placenta, amnion, and myometrium, which consequently trigger inflammation. In reproduction, these alarmins are associated with the development of various pregnancy complications, including PB. In this review, we have summarized the development of PB related to acute CAM, chronic CAM, and sterile inflammation as well as proposed a new mechanism for PB that involves innate immunity, acquired immunity, and sterile inflammation.

Perinatal derivatives: How to best validate their immunomodulatory functions

Perinatal tissues, mainly the placenta and umbilical cord, contain a variety of different somatic stem and progenitor cell types, including those of the hematopoietic system, multipotent mesenchymal stromal cells (MSCs), epithelial cells and amnion epithelial cells. Several of these perinatal derivatives (PnDs), as well as their secreted products, have been reported to exert immunomodulatory therapeutic and regenerative functions in a variety of pre-clinical disease models. Following experience with MSCs and their extracellular vesicle (EV) products, successful clinical translation of PnDs will require robust functional assays that are predictive for the relevant therapeutic potency. Using the examples of T cell and monocyte/macrophage assays, we here discuss several assay relevant parameters for assessing the immunomodulatory activities of PnDs. Furthermore, we highlight the need to correlate the in vitro assay results with preclinical or clinical outcomes in order to ensure valid predictions about the in vivo potency of therapeutic PnD cells/products in individual disease settings.

Inflammation in Preeclampsia: Genetic Biomarkers, Mechanisms, and Therapeutic Strategies

Objective

Preeclampsia is a common and serious complication of pregnancy, posing a threat to maternal and fetal safety due to the lack of effective biomarkers and treatment strategies. This study aimed to identify potential biomarkers that can be used to predict preeclampsia and identify the molecular mechanisms of preeclampsia pathogenesis and drug prediction at the transcriptome level.

Methods

We analyzed differential expression genes (DEGs) in preeclampsia and non-preeclampsia groups in the GSE75010 dataset, cross-linking with extracted inflammatory response-related genes to obtain differentially expressed inflammation-related genes (DINRGs). Enrichment analysis and protein-protein interaction (PPI) networks were constructed to understand the functions and enrichment pathways. Machine learning models were used to identify key genes associated with preeclampsia and build a nomogram in the training set, which was validated in the validation set. The R package RcisTarget was used to predict transcription factors, and Cytoscape was used to construct miRNA-mRNA pathways, which could identify the molecular mechanisms. Then, we conducted molecular docking of the obtained key genes INHBA (inhibin subunit beta A), OPRK1 (opioid receptor kappa 1), and TPBG (trophoblast glycoprotein), as well as predicted transcription factors with drug molecules. Additionally, the CIBERSORT method explored the differences in immune cell infiltration between preeclampsia and non-preeclampsia samples based on the GSE75010 dataset.

Results

A total of 69 DINRGs associated with preeclampsia patients were screened. INHBA, OPRK1, and TPBG were the key genes based on machine learning models. A nomogram for prediction was further constructed, and the receiver operating curves (ROCs) showed good performance. Based on the transcriptome level of key genes, we proposed that RELA-miR-548K/miR-1206-TPBG may be a potential RNA regulatory pathway regulating the progression of early preeclampsia. Molecular docking suggested the effectiveness of curcumin in the treatment of preeclampsia. Additionally, regulatory T cells (Tregs) and resting mast cells were significantly different between the two groups.

Conclusion

In summary, we identified three key inflammation-associated genes, namely INHBA, OPRK1, and TPBG, which can be used as potential genetic biomarkers for preeclampsia prediction and treatment, and established a nomogram as a predictive model. Additionally, we provided insights into the mechanisms of preeclampsia development at the transcriptome level and performed corresponding drug predictions.

At Embryo Implantation Site IL-35 Secreted by Trophoblast, Polarizing T Cells towards IL-35+ IL-10+ IL-4+ Th2-Type Cells, Could Favour Fetal Allograft Tolerance and Pregnancy Success

We investigated the role of rhIL-35, at low concentrations compatible with those produced by human trophoblast cells (less than 1 ng/mL), on human T helper (Th) cell functions and the presence of decidual IL-35-producing Th cells in human pregnancy. We found that human trophoblast cells produced IL-35 but not IL-4 or IL-10. RhIL-35, at concentrations produced by human trophoblasts, polarized T cells towards IL-35+, IL-10+, IL-4+ Th2-type cells and to Foxp3+ EBI3+ p35+ T reg cells producing IL-35 but not IL-10 and IL-4. Moreover, rhIL-35 at low concentrations did not suppress the proliferation of Th cells but stimulated IL-4 and IL-10 production by established Th clones. In particular, Th1-type clones acquired the capacity to produce IL-4. In addition, purified human trophoblast cell supernatants containing IL-35 upregulated IL-4 and IL-10 production by Th clones. Finally, IL-35+, IL-10+, IL-4+ Th2-type cells, which were found to be induced by low concentrations of IL-35 compatible with those produced by human trophoblasts, are exclusively present in the decidua of a successful pregnancy and at the embryo implantation site, suggesting their stringent dependence on trophoblast cells. Thus, the proximity of Th cells to IL-35-producing trophoblasts could be the determining factor for the differentiation of IL-35+, IL-10+, IL-4+ Th2-type cells that are crucial for human pregnancy success.

Associations of FOXP3 gene polymorphisms with susceptibility and severity of preeclampsia: A meta-analysis

OBJECTIVE

FOXP3 single nucleotide polymorphisms (SNPs) were recently elucidated to influence the development of preeclampsia (PE), but the results on this issue still remained controversial. Thus, a meta-analysis was implemented to systematically investigate the roles of FOXP3 SNPs in PE.

METHODS

Eligible publications were identified by retrieving relevant electronic databases. Meanwhile, the association intensity was estimated by calculating odds ratios (ORs) and 95% confidence intervals (CIs) in various genetic models.

RESULTS

Totally eight investigations involving 3446 subjects were enrolled in the final meta-analysis. The AC and AC + CC genotypes of FOXP3 rs3761548 were related to the susceptibility of PE in over-dominant (OR = 1.19, 95%CI = 1.02-1.38, P = 0.03) and recessive (OR = 0.59, 95% CI: 0.36-0.97, P = 0.04) models. Furthermore, correlation between rs2232365 and PE was observed in recessive model (GG vs. GA + AA) (OR = 0.79, 95%CI: 0.65-0.97, P = 0.03). Moreover, rs2232365 GA and GG + GA genotypes were associated with the severity of PE. However, rs4824747, rs3761547 and rs2280883 polymorphisms had no significant impact on PE susceptibility.

CONCLUSIONS

FOXP3 rs3761548 and rs2232365 SNPs influenced the PE susceptibility and therefore may be potential biomarkers for prediction of PE risk.

Reconsideration of the Role of Regulatory T Cells during Pregnancy: Differential Characteristics of Regulatory T Cells between the Maternal-Fetal Interface and Peripheral Sites and between Early and Late Pregnancy

Regulatory T (Treg) cells play an important role in implantation of the embryo and maintenance of pregnancy after allogeneic mating. Implantation failure, miscarriage, and preeclampsia are associated with decreased numbers of Treg cells or with dysfunctional Treg cells. Treg cells are classified into naturally occurring Treg (nTreg) cells or thymus-derived Treg (tTreg) cells that differentiate in the thymus and induce tolerance to self-antigens, while induced Treg (iTreg) or peripheral Treg (pTreg) cells differentiate in the periphery and induce transient tolerance to foreign antigens. Memory nTreg or iTreg cells were recently reported to accumulate in the uterus during early pregnancy and contribute to the establishment of pregnancy. Miscarriage is characterized by the downregulation of the total numbers of Treg cells rather than a downregulation of the numbers of paternal/fetal antigen-specific Treg cells. In addition to the volume of paternal/fetal antigen-specific CD8+ T cells, the number of paternal/fetal antigen-specific Treg cells, which protect the fetus/placenta against maternal immune cell attack, increases after the second trimester of pregnancy. Clonal Treg cells which are surrogate markers of paternal/fetal antigen-specific Treg cells in humans may be involved in the development of preeclampsia during the mid- to late pregnancy stage, as evidenced by their downregulation in the decidua of preeclamptic cases. This review summarizes recent findings on Treg cells and discusses the roles, in the maintenance of pregnancy, of different types of Treg cells such as paternal/fetal antigen-specific Treg, pregnancy-associated memory Treg, nTreg (or tTreg), and iTreg (or pTreg cells).