Alteration of Th17 and Foxp3+ regulatory T cells in patients with unexplained recurrent spontaneous abortion before and after the therapy of hCG combined with immunoglobulin

Helper T cells: A potential target for sex hormones to ameliorate rheumatoid arthritis? (Review)

Rheumatoid arthritis (RA) is a chronic autoimmune inflammatory disease whose etiology is not fully understood. Defective peripheral immune tolerance and subsequent mis‑differentiation and aberrant infiltration of synovium by various immune cells, especially helper T (Th) cells, play an important role in the development of RA. There are significant sex differences in RA, but the results of studies on the effects of sex hormones on RA have been difficult to standardize and hormone replacement therapy has been limited by the potential for serious side effects. Existing research has amply demonstrated that cellular immune responses are largely determined by sex and that sex hormones play a key role in Th cell responses. Based on the aforementioned background and the plasticity of Th cells, it is reasonable to hypothesize that the action of sex hormones on Th cells will hopefully become a therapeutic target for RA. The present review discussed the role of various Th cell subsets in the pathogenesis of RA and also explored the role of sex hormones on the phenotype and function of these aberrantly regulated immune cells in RA as well as other pathologic effects on RA.

Enhancing endometrial receptivity: the roles of human chorionic gonadotropin in autophagy and apoptosis regulation in endometrial stromal cells

Inadequate endometrial receptivity often results in embryo implantation failure and miscarriage. Human chorionic gonadotropin (hCG) is a key signaling molecule secreted during early embryonic development, which regulates embryonic maternal interface signaling and promotes embryo implantation. This study aimed to examine the impact of hCG on endometrial receptivity and its underlying mechanisms. An exploratory study was designed, and endometrial samples were obtained from women diagnosed with simple tubal infertility or male factor infertile (n = 12) and recurrent implantation failure (RIF, n = 10). Using reverse transcription-quantitative PCR and western blotting, luteinizing hormone (LH)/hCG receptor (LHCGR) levels and autophagy were detected in the endometrial tissues. Subsequently, primary endometrial stromal cells (ESCs) were isolated from these control groups and treated with hCG to examine the presence of LHCGR and markers of endometrial receptivity (HOXA10, ITGB3, FOXO1, LIF, and L-selectin ligand) and autophagy-related factors (Beclin1, LC3, and P62). The findings revealed that the expressions of receptivity factors, LHCGR, and LC3 were reduced in the endometrial tissues of women with RIF compared with the control group, whereas the expression of P62 was elevated. The administration of hCG to ESCs specifically activated LHCGR, stimulating an increase in the endometrial production of HOXA10, ITGB3, FOXO1, LIF and L-selectin ligands. Furthermore, when ESCs were exposed to 0.1 IU/mL hCG for 72 h, the autophagy factors Beclin1 and LC3 increased within the cells and P62 decreased. Moreover, the apoptotic factor Bax increased and Bcl-2 declined. However, when small interfering RNA was used to knock down LHCGR, hCG was less capable of controlling endometrial receptivity and autophagy molecules in ESCs. In addition, hCG stimulation enhanced the phosphorylation of ERK1/2 and mTOR proteins. These results suggest that women with RIF exhibit lower levels of LHCGR and compromised autophagy function in their endometrial tissues. Thus, hCG/LHCGR could potentially improve endometrial receptivity by modulating autophagy and apoptosis.

Immunogenetic Role of IL17A Polymorphism in the Pathogenesis of Recurrent Miscarriage

Interleukin-17A (IL17A) is a proinflammatory cytokine and is assumed to play an important role in fetal rejection. In order to evaluate the potential role of IL17A polymorphism in the pathogenesis of recurrent miscarriage (RM), serum IL17A levels were estimated by ELISA. Single-nucleotide polymorphism was assessed by polymerase chain reaction-restriction fragment-length polymorphism (PCR-RFLP) using gene-specific primers and the EcoNI restriction enzyme. Serum IL17A levels were nonsignificantly (p > 0.5) low in RM patients compared with the control group. IL17A gene amplification by PCR yielded the undigested product of 815 bp, and its digestion with EcoNI enzyme produced 815, 529, 286, and 270 bp fragments for the GG genotype; 529, 286, and 270 bp fragments for the GA genotype; and 529 and 286 bp fragments for the AA genotype. The genotype frequency between the RM and control groups exhibited a significant difference (p = 0.001), whereas no significant difference was observed between allele frequencies in the two groups (p = 0.0954). These data suggest that the IL17A gene polymorphism exhibits no significant effect on IL17A gene expression. However, it significantly decreases and increases RM risk in the homozygous and recessive models, suggesting its potential pregnancy-protecting and -harming roles in the AA and GA + GG genotypes, respectively.

Does Intrauterine Injection of hCG Improve IVF Outcome? A Systematic Review and a Meta-Analysis

Various interventions have been proposed to improve embryo implantation in IVF. Among these, intrauterine injections of human chorionic gonadotropin seem to have promising results. Consequently, we conducted a review and meta-analysis to assess IVF outcomes by comparing couples who underwent intrauterine hCG injection transfer versus those who underwent embryo transfer with intrauterine injection of placebo, or without any additional intervention. The primary outcome was the clinical pregnancy rate. Secondary outcomes were the implantation rate, miscarriage rate, and live birth rate. A meta-analysis was conducted using the random effects model, while bias within studies was detected using the Cochrane risk of bias tool. Ectopic pregnancies and stillbirths were also assessed. The clinical pregnancy (RR 1.38, 95% CI 1.17−1.62, p < 0.0001) and implantation rate (RR 1.40, 95% CI 1.12−1.75, p = 0.003) were significantly higher in women who underwent hCG injection than in the control group. These significant effects persisted only in women who underwent cleavage-stage embryo transfer. No significant differences between groups were observed in the other secondary outcomes. In conclusion, our systematic review and meta-analysis demonstrate that intrauterine injection of hCG could be a valuable approach in women who undergo cleavage-stage embryo transfer. Given the lack of data about the live birth rate, caution should be exercised in interpreting these data.

Human chorionic gonadotropin promotes murine Treg cells and restricts pregnancy-harmful proinflammatory Th17 responses

An equilibrium between proinflammatory and anti-inflammatory immune responses is essential for maternal tolerance of the fetus throughout gestation. To study the participation of fetal tissue-derived factors in this delicate immune balance, we analyzed the effects of human chorionic gonadotropin (hCG) on murine Treg cells and Th17 cells in vitro, and on pregnancy outcomes, fetal and placental growth, blood flow velocities and remodeling of the uterine vascular bed in vivo. Compared with untreated CD4⁺CD25⁺ T cells, hCG increased the frequency of Treg cells upon activation of the LH/CG receptor. hCG, with the involvement of IL-2, also interfered with induced differentiation of CD4⁺ T cells into proinflammatory Th17 cells. In already differentiated Th17 cells, hCG induced an anti-inflammatory profile. Transfer of proinflammatory Th17 cells into healthy pregnant mice promoted fetal rejection, impaired fetal growth and resulted in insufficient remodeling of uterine spiral arteries, and abnormal flow velocities. Our works show that proinflammatory Th17 cells have a negative influence on pregnancy that can be partly avoided by in vitro re-programming of proinflammatory Th17 cells with hCG.

The association of AT-III and D-Dimer with unexplained recurrent spontaneous abortion and their diagnostic value for prethrombotic state

OBJECTIVE

This study aimed to investigate the role of antithrombin III (AT-III) and D-dimer (D-Dimer) in patients with unexplained recurrent spontaneous abortion (URSA); Methods: Sixty pregnant women with URSA (AEP group), 80 non-pregnant women with a history of URSA (ANP group), 50 healthy women in early pregnancy (NEP group) and 50 healthy non-pregnant women (NNP group) were retrospectively enrolled. Their serum AT-III and D-Dimer levels were measured. The patients in the ANP group were divided into three subgroups according to the number of miscarriages: 3 miscarriages (32 cases), 4 miscarriages (22 cases), and >4 miscarriages (26 cases), and the differences in serum AT-III and D-Dimer levels among these subgroups were compared. The patients in the AEP group were monitored for changes in AT-III and D-Dimer levels, and finally the diagnostic value of AT-III and D-Dimer levels were calculated for the prethrombotic state of URSA.

RESULTS

(1) AT-III and D-Dimer levels differed significantly among the 4 groups (P<0.05); (2) As the number of miscarriages increased, D-Dimer levels elevated and AT-III levels decreased, with significant differences among three subgroups (P<0.05); (3) As the treatment proceeded, patients in AEP and ANP groups showed a tendency for a gradual increase in AT-III levels and a significant decrease in D-Dimer levels, with significant differences before and after treatment (P<0.05); (4) The diagnostic AUC of AT-III and D-Dimer in the prediction of prethrombotic state of URSA were 0.8922 (95% CI=0.8026-0.9819, P<0.0001) and 0.8776 (95% CI=0.7643-0.9909, P<0.0001).

CONCLUSION

AT-III and D Dimer levels are closely associated with URSA. The results of this study have preliminarily confirmed the feasibility of applying AT-III and D Dimer to screen the prethrombotic state of URSA, and their clinical application will help provide a reference for determining the cause of miscarriage in the infertile population with URSA and facilitate successful pregnancy.

Human Chorionic Gonadotropin and Early Embryogenesis: Review

Human chorionic gonadotropin (hCG) has four major isoforms: classical hCG, hyperglycosylated hCG, free β subunit, and sulphated hCG. Classical hCG is the first molecule synthesized by the embryo. Its RNA is transcribed as early as the eight-cell stage and the blastocyst produces the protein before its implantation. This review synthetizes everything currently known on this multi-effect hormone: hCG levels, angiogenetic activity, immunological actions, and effects on miscarriages and thyroid function.

T helper cell immunity in pregnancy and influence on autoimmune disease progression

Pregnancy presents the maternal immune system with a unique immunological challenge since it has to defend against pathogens while tolerating paternal allo-antigens expressed by fetal tissues. T helper (Th) cells play a central role in modulating immune responses and recent advances have defined distinct contributions of various Th cell subsets throughout each phase of human pregnancy, while dysregulation in Th responses show association with multiple obstetrical complications. In addition to localized decidual mechanisms, modulation of Th cell immunity during gestation is mediated largely by oscillations in sex hormone concentrations. Aberrant Th cell responses also underlie several autoimmune disorders while pregnancy-induced changes in the balance of Th cell immunity has been shown to exert favorable outcomes in the progression Th1 and Th17 driven autoimmune conditions only to be followed by post-partal exacerbations in disease.

Regulatory effect of daphnetin on the balance of Th17 and Treg cells in the peripheral blood mononuclear cells from patients with unexplained recurrent pregnancy loss

Introduction

There has a close relationship between the balance of T helper 17 (Th17) cells and Foxp3+ regulatory T cells (Treg) and unexplained recurrent pregnancy loss (URPL). The present study is to investigate the regulatory effect of daphnetin, which is extracted from Daphne odora Var, on the balance of Th17 and Treg cells in the peripheral blood mononuclear cells (PBMCs) from patients with URPL.

Material and methods

PBMCs were isolated from 35 pregnant women with URPL and 35 women with normal early pregnancies, respectively and treated with daphnetin for three days. Flow cytometry was performed to measure the proportions of Th17 and Treg cells. The level of expression of IL-6, TGF-β1 and IL-2 were detected using enzyme-linked immunosorbent assay (ELISA) and the level of expression of FoxP3, RORγt, signal transducers and activators of transcriotion 3 (STAT3) and STAT5 were detected by RT-PCR.

Results

The concentrations of Th17-type cytokines IL-2 were significantly decreased in the URPL group after treatment (p < 0.01). Treg-type cytokines such as TGF-β1 and IL-6 were significantly increased after treatment (p < 0.01). At the same time, daphnetin may induce a decrease in the ratio of RORγt to Foxp3 and a Treg cell bias, which would be beneficial for pregnancy maintenance. Futhermore the expression level of STAT3 were higher in the URPL patients whereas STAT5 were lower than those in the control subjects.

Conclusions

In conclusion, daphnetin may have regulatory effect on the balance of Th17 and Treg cells in the peripheral blood mononuclear cells from patients with URPL.

Is there a Role of Intravenous Immunoglobulin in Immunologic Recurrent Pregnancy Loss?

Recurrent pregnancy loss (RPL) commonly refers to three or more miscarriages that occur before 20 weeks of pregnancy. The immunological cause of RPL could be either an auto- or alloimmune-related event or both. Because of the discovery of immunological abnormalities in RPL patients in clinical practice, several immunomodulatory therapies were introduced to maintain the immune balance at the maternal-fetal interface. Intravenous immunoglobulin (IVIg) is one of the immunomodulators. In recent years, several studies have analyzed the therapeutic effect of IVIg on RPL patients with antiphospholipid syndrome (APS) or unexplained RPL. However, their results are controversial. IVIg can be used in RPL patients with APS who have previously failed in other treatments. It is recommended that IVIg infusion could be considered used before conception in RPL patients who have cellular immune abnormalities such as increased natural killer (NK) cell counts, NK cell cytotoxicity, or increased T helper (Th)1/Th2 ratio, depending on the cut-off values of each hospital. The aim of this review was to summarize the mechanisms, efficacy, pharmacokinetics, and side effects associated with passive immunization using IVIg in immunologic RPL, according to the literature published in recent years. We hope that more obstetricians will be able to understand the timing and indication of IVIg properly in immunologic RPL patients and effectively enhance pregnancy outcomes for mothers and neonates.

Elevated Neurokinin-1 Receptor Expression in Uterine Products of Conception Is Associated With First Trimester Miscarriages

Background

Miscarriage is a common complication of early pregnancy, mostly occurring in the first trimester. However, the etiological factors and prognostic and diagnostic biomarkers are not well known. Neurokinin-1 receptor (NK-1R) is a receptor of tachykinin peptide substance P (SP) and has a role in various pathological conditions, cancers, but its association with miscarriages and significance as a clinicopathological parameter are not studied. Accordingly, the present study aimed to clarify the localization and expression for NK-1R in human retained products of conception (POC). The role of NK-1R is not known in miscarriages.

Materials and Methods

NK-1R expression was assessed in POC and normal placental tissues by immunohistochemistry. Three- to four-micrometer-thin sections of formalin-fixed paraffin-embedded tissues were used for this purpose. Tissues were processed and then immunohistochemically stained with NK-1R antibody. Brain tissue was used as control for antibody. Protein expression was evaluated using the nuclear labeling index (%). Tissues were counterstained with 3,3'-diaminobenzidine (DAB), and microscopy was performed at 10×, 20×, and 40× magnifications.

Results

Ten human POC tissues and 10 normal placental tissues were studied by immunohistochemistry to demonstrate the localization of NK-1R. The expression of NK-1R protein was high in all the cases of both groups. NK-1R expression showed no notable differences among different cases of miscarriages as well as normal deliveries at full term regardless of the mother's age and gestational age at which the event occurred. Statistically, no difference was found in both groups, which is in agreement with our hypothesis and previous findings.

Conclusion

The expression of NK-1R was similar in all the cases, and it was intense. It shows that dysregulation of NK-1R along with its ligand SP might be involved in miscarriages and also involved in normal delivery. Our results provide fundamental data regarding this anti-NK-1R strategy. Thus, the present study recommends that SP/NK-1R system might, therefore, be considered as an emerging and promising diagnostic and therapeutic strategy against miscarriages. Hence, we report for the first time the expression and localization of NK-1R in POC. We suggest NK-1R antagonist in addition to the immunoglobulins and human chorionic gonadotropin to diagnose and treat spontaneous miscarriages.

Analysis of chromosomes and the T helper 17 and regulatory T cell balance in patients with recurrent spontaneous abortion

The present study investigated the genetic etiology and possible immunological pathogenesis of recurrent spontaneous abortion by analyzing chromosome abnormalities, and the balance between T helper 17 (Th17) and regulatory T (Treg) cells. A total of 54 patients with recurrent spontaneous abortion were selected. The villus and decidual tissues, and peripheral venous blood were collected from each patient. Villus chromosome analysis was performed by high-throughput gene sequencing. Flow cytometry was used to detect Th17 and Treg cells in patients without chromosome abnormalities (n=30) and the control group (normal pregnancy; n=32). Immunoglobulin (IG) combined with human chorionic gonadotropin hormone (HCG) treatment was given to patients without chromosome abnormalities (n=30). Changes in the expression levels of Th17 and Treg cells before and after treatment were compared with patients with successful pregnancy (n=18). Before treatment, compared with the control group, the proportion of Th17 cells in peripheral blood and decidual tissue was increased and the proportion of Treg cells decreased. After treatment, compared with patients before treatment, the proportion of Th17 cells decreased and Treg cells increased, and the Th17 and Treg cells balance was reversed with a biased towards Treg cells. The present results suggested that the Th17 and Treg cell immune imbalance may be an important immune factor in recurrent spontaneous abortion. IG combined with HCG therapy may improve pregnancy outcomes by reversing the imbalance between Th17 and Treg cells.

Human Chorionic Gonadotrophin: New Pleiotropic Functions for an "Old" Hormone During Pregnancy

Human chorionic gonadotrophin (hCG) is the first specific molecule synthesized by the embryo. hCG RNA is transcribed as early as the eight-cell stage, and the blastocyst produces the protein before its implantation. hCG in the uterine microenvironment binds with its cognate receptor, luteinizing hormone/choriogonadotropin receptor (LHCGR), on the endometrial surface. This binding stimulates leukemia inhibitory factor (LIF) production and inhibits interleukin-6 (IL-6) production by epithelial cells of the endometrium. These effects ensure essential help in the preparation of the endometrium for initial embryo implantation. hCG also effects angiogenic and immunomodulatory actions as reported in many articles by our laboratories and other ones. By stimulating angiogenesis and vasculogenesis, hCG provides the placenta with an adequate maternal blood supply and optimal embryo nutrition during the invasion of the uterine endometrium. The immunomodulatory properties of hCG are numerous and important for programming maternal immune tolerance toward the embryo. The reported effects of hCG on uterine NK, Treg, and B cells, three major cell populations for the maintenance of pregnancy, demonstrate the role of this embryonic signal as a crucial immune regulator in the course of pregnancy. Human embryo rejection for hCG-related immunological reasons has been studied in different ways, and a sufficient dose of hCG seems to be necessary to maintain maternal tolerance. Different teams have studied the addition of hCG in patients suffering from recurrent miscarriages or implantation failures. hCG could also have a beneficial or a negative impact on autoimmune diseases during pregnancy. In this review, we will discuss the immunological impacts of hCG during pregnancy and if this hormone might be used therapeutically.

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.

Human chorionic gonadotropin promotes recruitment of regulatory T cells in endometrium by inducing chemokine CCL2

Human chorionic gonadotropin (hCG) can attract regulatory T cells (Tregs) into the fetal-maternal interface regulating maternal immune tolerance in pregnancy. The objective of this study was to investigate whether hCG recruits the Tregs into endometrium by inducing chemokines. The number of Tregs in the endometrium was analyzed by immunohistochemistry. The expression of CCL2 was analyzed in vivo and in vitro with hCG stimulation. CD4+CD25+ Tregs were isolated from peripheral blood for Tregs migration assay with hCG, CCL2 siRNA and CCR2 antagonist stimulation. Our results showed that the number of endometrial Tregs in RIF patients was significantly decreased (9.4 ± 5.3 vs. 23.1 ± 3.1, P < 0.01), while intrauterine infusion of 2000 IU hCG increased the endometrial Tregs (18.6 ± 9.8 vs. 9.4 ± 5.3, P < 0.05) and CCL2 expression (0.21 ± 0.01 vs. 0.17 ± 0.01, P < 0.01). Horn injecting with 10 IU hCG also increased the endometrial Tregs in pseudopregnant mice (46 ± 16.8 vs. 7 ± 4.3, P < 0.01). Furthermore, the CCL2 protein and mRNA levels were significantly increased in human endometrial stromal cells (hESCs) with the stimulation of hCG. Migration assays showed that hESCs with hCG stimulation promoted Tregs migration (2597 ± 833.2 vs. 1115 ± 670.7, P < 0.05), while the number of migrated Tregs significantly decreased with CCL2 siRNA (1061 ± 105.4 vs. 2598 ± 294.7, P < 0.05) or CCR2 antagonist (356.7 ± 138.8 vs. 2597 ± 833.2, P < 0.05) treatment. In conclusion, intrauterine perfusion of hCG might promote the recruitment of Tregs into endometrium by inducing chemokine CCL2.

Human Chorionic Gonadotropin-Mediated Immune Responses That Facilitate Embryo Implantation and Placentation

Human chorionic gonadotropin (hCG) serves as one of the first signals provided by the embryo to the mother. Exactly at the time when the first step of the implantation process is initiated and the blastocyst adheres to the maternal endometrium, the embryonic tissue starts to actively secrete hCG. Shortly thereafter, the hormone can be detected in the maternal circulation where its concentration steadily increases throughout early pregnancy as it is continuously released by the forming placenta. Accumulating evidence underlines the critical function of hCG for embryo implantation and placentation. hCG not only regulates biological aspects of these early pregnancy events but also supports maternal immune cells in their function as helpers in the establishment of an adequate embryo-endometrial relationship. In view of its early presence in the maternal circulation, hCG has the potential to influence both local uterine immune cell populations as well as peripheral ones. The current review aims to summarize recent literature on the participation of innate and adaptive immune cells in embryo implantation and placentation with a specific focus on their regulation by hCG.

Bidirectional regulation between 1st trimester HTR8/SVneo trophoblast cells and in vitro differentiated Th17/Treg cells suggest a fetal-maternal regulatory loop in human pregnancy

Problem

During normal pregnancy, delicate crosstalk is established between fetus‐derived trophoblasts and maternal immune cells to ensure maternal‐fetal tolerance and successful placentation. Dysfunction in these interactions has been highly linked to certain pregnancy complications.

Method of study

Naïve CD4⁺T cells were cultivated with or without 1st trimester derived trophoblast cell line HTR8/SVneo cells in the absence or presence of T helper 17 (Th17) or regulatory (Treg)cell‐inducing differentiation conditions. After 5 days of co‐culture, HTR8/SVneo cells and CD4⁺T cells were harvested and analyzed using flow cytometry.

Results

CD4⁺T cells exposed to HTR8/SVneo cells showed enhanced induction of CD4⁺Foxp3⁺Treg cells with strong expression of TGF‐β1 and inhibitory molecules (cytotoxic T lymphocyte‐associated protein‐4 [CTLA‐4], T‐cell immunoglobulin mucin‐3 [Tim‐3], and programmed cell death‐1 [PD‐1]). Though not effecting Th17 differentiation, exposure to HTR8/SVneo cells promoted increased expression of proliferative and apoptotic markers on Th17 cells. Co‐culture with Th0 cells, or differentiated Th17 or Treg cells, down‐regulated Caspase‐3 and MMP‐9 (but not MMP‐2) expression in HTR8/SVneo cells, while promoting Ki67 expression.

Conclusions

HTR8/SVneo cells regulated maternal CD4⁺T‐cell differentiation, resulting in the expansion of immunosuppressive Treg cells, while CD4⁺T cells might promote the growth, and control the invasiveness of HTR8/SVneo cells. Thus, a bidirectional regulatory loop might exist between trophoblasts and maternal immune cell subsets, thereby promoting harmonious maternal‐fetal crosstalk.

Advances in Understanding the Immune Imbalance between T-Lymphocyte Subsets and NK Cells in Recurrent Spontaneous Abortion

Recurrent spontaneous abortion is a global problem, and unexplained recurrent abortion triggered by immunological factors is an important focus of current research. Helper T lymphocytes (Th cells) and regulatory T lymphocytes (Treg cells) are central in human immune regulation and play a complex role in pregnancy. Natural killer cells (NK cells) exist in the endometrium and cooperate with T lymphocytes to create immune tolerance at the maternal-fetal interface, which is essential for successful pregnancy. This review has analyzed studies on Th17 cell, Treg cell and NK cell dysfunction and cellular imbalances which may contribute to unexplained recurrent spontaneous abortion to suggest a possible direction for future immunotherapies.

Modulatory effect of intravenous immunoglobulin on Th17/Treg cell balance in women with unexplained recurrent spontaneous abortion

Recurrent spontaneous abortion (RSA) is a growing problem worldwide. In a majority of cases, the cause remains unknown but there is increasing evidence that immunologic factors play an important role. Intravenous immunoglobulin (IVIg) therapy has been proposed to have immune modulatory effects and therefore been applicable for the treatment of patients with RSA. Although its efficacy is still controversial, several recent studies suggest that IVIg treatment may improve pregnancy outcomes. CD4⁺ T cells and their related cytokines play an important role in maternal-fetal immune regulation, and an imbalance of Th17/Treg cell ratio has been proposed as a cause for RSA. We review the scientific evidence supporting a modulatory effect of IVIg on Th17/Treg cell balance and discuss the potential mechanisms how IVIg might enhance Treg cells function. We propose that correction of Th17/Treg cell dysregulation could be one of the mechanisms that can explain the positive therapeutic effects of IVIg therapy. Consequently, selecting patients with abnormal Th17/Treg cell ratios could increase the success of IVIg therapy.

Human Chorionic Gonadotropin as a Pivotal Endocrine Immune Regulator Initiating and Preserving Fetal Tolerance

The pregnancy hormone, human chorionic gonadotropin (hCG), is crucially involved in processes such as implantation and placentation, two milestones of pregnancy whose successful progress is a prerequisite for adequate fetal growth. Moreover, hCG determines fetal fate by regulating maternal innate and adaptive immune responses allowing the acceptance of the foreign fetal antigens. As one of the first signals provided by the embryo to its mother, hCG has the potential to regulate very early pregnancy-driven immune responses, allowing the establishment and preservation of fetal tolerance. This mini review focuses on how hCG modulates the adaptive arm of the immune system including dendritic cells as key regulators of adaptive immune responses.