Human chorionic gonadotropin and IL-35 contribute to the maintenance of peripheral immune tolerance during pregnancy through mediating the generation of IL-10+ or IL-35+ Breg cells

Intrauterine administration of peripheral blood mononuclear cells helps manage recurrent implantation failure by normalizing dysregulated gene expression including estrogen-responsive genes in mice

BACKGROUND

Intrauterine peripheral blood mononuclear cell (PBMC) therapy for recurrent implantation failure (RIF) has been reported to improve embryo implantation by acting on the endometrium. However, the exact mode of action of PBMC on the endometrium of patients with RIF remains unclear. In addition, the differences in the therapeutic effects of PBMC therapy with and without human chorionic gonadotropin (hCG) are unknown. Therefore, in this study, we investigated the changes in the endometrium during the implantation phase induced by PBMC administration and the differences in the efficacy of this therapy with and without hCG using a mouse model of implantation failure (IF).

METHODS

IF model was established by the subcutaneous administration of low-dose RU486. Pregnant mice were randomly divided into five groups: control, IF, culture medium, PBMC, and PBMC-hCG (the latter three groups were IF model mice with intrauterine administration). The pregnancy rate and the number and size of implantation sites were recorded during early pregnancy (day 7.5). Uteri from the preimplantation phase (evening of day 3.5) were collected and analyzed using RNA-sequencing (RNA-seq).

RESULTS

The pregnancy rate, the number of implantation sites, and the number of normal-sized implantation sites were significantly decreased in the IF model and were improved in the medium, PBMC, and PBMC-hCG groups. RNA-seq data showed that PBMC treatment normalized the expression of the majority of dysregulated genes in the endometrium during the preimplantation phase in the IF model, especially the overexpression of estrogen-activated genes. In addition, PBMC treatment increased the expression of local glucocorticoid receptors and suppressed the expression of inflammation-related genes, whereas no significant changes in blood estradiol and glucocorticoid levels were observed. These changes were more pronounced in the PBMC-hCG group and were consistent with the pregnancy outcomes.

CONCLUSIONS

Intrauterine administration of PBMC before embryo implantation promoted embryo implantation in the IF mouse model, and hCG enhanced pregnancy outcomes. PBMC modulated steroid receptor expression and suppressed inflammation and excessive estrogen action.

The Protective Effect of Esculentoside A on MPL/lpr Mice by Upregulating the Expression of CD19+IL-35+Breg Cells and Interleukin-35

INTRODUCTION

Esculentoside A (EsA) is one of the main components of the traditional Chinese medicine Phytolacca esculenta. The possible mechanism of action of EsA in the treatment of lupus nephritis (LN) was explored by observing the effects of EsA on CD19+ IL-35+regulatory B (IL-35+Breg) cells.

METHODS

Twenty-four MRL/lpr mice were randomly divided into control, EsA, and EsA+IL-12p35 antibody groups. Mice were administered the respective treatments intraperitoneally once a day for 4 weeks. The urine protein/creatinine ratio (UPCR) and blood creatinine (Cr) and IL-35, IL-10, and IL-17 expression levels were measured. Body and spleen weight were measured to calculate the splenic index (SI). Flow cytometry was performed to determine the proportion of CD19+ IL-35+ Breg cells in the spleen. Hematoxylin-eosin and PASM-Masson staining of renal tissues were performed, and the "Austin" acute index (AI) system for LN was determined.

RESULTS

The most severe conditions were seen in mice in the control group, with the highest UPCR, Cr, and IL-17 levels and SI and AI scores; the most severe renal histopathology, and the lowest proportion of CD19+ IL-35+ Breg cells and IL-35 and IL-10 levels. This was followed by the EsA+IL-12p35 antibody group. The EsA group had the lowest UPCR, Cr, and IL-17 levels and SI and AI scores; the mildest renal lesions; and the highest proportion CD19+ IL-35+ Breg cells and IL-35 and IL-10 levels.

CONCLUSION

EsA delayed the progression of LN by promoting the proliferation of CD19+ IL-35+ Breg cells, upregulating the expression of IL-35, and decreasing the secretion of IL-17.

B cells: roles in physiology and pathology of pregnancy

B cells constitute a diverse and adaptable immune cell population with functions that can vary according to the environment and circumstances. The involvement of B cells in pregnancy, as well as the associated molecular pathways, has yet to be investigated. This review consolidates current knowledge on B cell activities and regulation during pregnancy, with a particular focus on the roles of various B cell subsets and the effects of B cell-derived factors on pregnancy outcomes. Moreover, the review examines the significance of B cell-associated autoantibodies, cytokines, and signaling pathways in relation to pregnancy complications such as pregnancy loss, preeclampsia, and preterm birth.

Association between Dietary Inflammatory Index and Hyperemesis Gravidarum

(1) Background: Diet holds a pivotal position in exacerbating or ameliorating chronic inflammation, which has been implicated in the pathogenesis of hyperemesis gravidarum (HG). However, no study has explored the association between dietary inflammatory potential and HG. This study aimed to investigate the potential correlation between following a pro-inflammatory diet and the likelihood of developing HG. (2) Methods: A total of 2033 Chinese pregnant women (mean age: 31.3 ± 3.4 years) were included in this cross-sectional study from April 2021 to September 2022 as part of the China Birth Cohort Study (CBCS). Dietary inflammatory index (DII) scores with 23 food components were constructed through dietary intakes collected via a reliable 108-item semi-quantitative food frequency questionnaire. HG was defined as a pregnancy-unique quantification of emesis (PUQE) score ≥13 points, severe nausea and vomiting leading to weight loss ≥5%, or being hospitalized for treatment due to the disease. The relationship between DII and HG was conducted utilizing binary logistic regression and restricted cubic spline regression. (3) Results: Overall, 8.2% (n = 167) of study participants had HG. The DII scores ranged from -4.04 to 3.82. After adjusting for potential confounders, individuals with the highest tertile of DII score had a higher risk of HG (OR = 1.65, 95% CI: 1.04, 2.62, Ptrend = 0.032). Such an association was stronger in those with pre-pregnancy overweight/obesity (Pinteraction = 0.018). (4) Conclusions: A higher DII score, which serves as a marker for a diet promoting inflammation, is correlated with an elevated risk of developing HG. This finding suggests that dietary recommendations for HG should focus on minimizing the DII through incorporating foods abundant in anti-inflammatory components.

Immunological mechanisms of tolerance: Central, peripheral and the role of T and B cells

T and B cells are key components of the adaptive immune system. Through their immune properties and their interactions with other immune cells and cytokines around them, they build a complex network to achieve immune tolerance and maintain homeostasis of the body. This is achieved through mechanisms of central and peripheral tolerance, both of which are associated with advantages and disadvantages. For this reason, the immune system is tightly regulated and their dysregulation can result in the subsequent initiation of various diseases. In this review, we will summarize the roles played by T cells and B cells within immune tolerance with specific examples in the context of different diseases that include allergic disease. In addition, we will also provide an overview on their suitability as biomarkers of allergen-specific immunotherapy.

Increased IL-10-competent regulatory B cells in the decidua of early human pregnancy

Regulatory B cells (Bregs) may play a pivotal role in maintaining human pregnancy. For the first time, to the best of our knowledge, this study noted that cell percentages of CD24hiCD38hi Bregs and CD24hiCD27+ Bregs, which can potentially produce IL-10, are increased in human decidua compared with the mid-luteal phase endometrium. In each case of decidua, the correlation between Bregs and dendritic cell (DC) or natural killer (NK) cell expression was further explored. A positive correlation between the percentage of CD24hiCD38hi Bregs and CD123-CD11c+ myeloid DCs (mDCs) was noted. Furthermore, a significant positive correlation was also observed between the percentage of CD24hiCD27+ Bregs and CD94+CD56brightCD16- suppressive NK cells. These findings regarding decidual Bregs deepen the understanding of the harmonious immunological microenvironment that sustains early human pregnancy.

Bone marrow mesenchymal stem cells repress renal transplant immune rejection by facilitating the APRIL phosphorylation to induce regulation B cell production

Bone marrow mesenchymal stem cells (BMSCs) exert pivotal roles in suppressing immune rejection in organ transplantation. However, the function of BMSCs on immune rejection in renal transplantation remains unclear. This study aimed to evaluate the effect and underlying mechanism of BMSCs on immune rejection in renal transplantation. Following the establishment of the renal allograft mouse model, the isolated primary BMSCs were injected intravenously into the recipient mice. Enzyme-linked immunosorbent assay, flow cytometry, hematoxylin-eosin staining, and Western blot assays were conducted to investigate BMSCs' function in vivo and in vitro. Mechanistically, the underlying mechanism of BMSCs on immune rejection in renal transplantation was investigated in in vivo and in vitro models. Functionally, BMSCs alleviated the immune rejection in renal transplantation mice and facilitated B cell activation and the production of IL-10⁺ regulatory B cells (Bregs). Furthermore, the results of mechanism studies revealed that BMSCs induced the production of IL-10⁺ Bregs by facilitating a proliferation-inducing ligand (APRIL) phosphorylation to enhance immunosuppression and repressed renal transplant rejection by promoting APRIL phosphorylation to induce IL-10⁺ Bregs. BMSCs prevent renal transplant rejection by facilitating APRIL phosphorylation to induce IL-10⁺ Bregs.

Postpartum hepatitis and host immunity in pregnant women with chronic HBV infection

In order to develop immune tolerant to the fetal, maternal immune system will have some modification comparing to the time before pregnancy. Immune tolerance starts and develops at the maternal placental interface. In innate immunity, decidual natural killer (dNK) cells, macrophages and dendritic cells play a key role in immue tolerance. In adaptive immunity, a moderate increase of number and immune inhibition function of regulatory T cells (Treg) are essential for immune tolerance. The trophoblast cells and immune cells expressing indoleamine 2,3-dioxygenase (IDO), the trophoblast cells expressing HLA-G, and Th1/Th2 shifting to Th2 dominant and Th17/Treg shifting to Treg domiant are in favor of maternal fetal immune tolerance. Steroids (estrogen and progesterone) and human chorionic gonadotropin (HCG) also participate in immune tolerance by inducing Treg cells or upregulating immunosuppressive cytokines. Most of the patients with chronic HBV infection are in the "HBV immune tolerance period" before pregnancy, and the liver disease is relatively stable during pregnancy. In chronic HBV infection women, after delivery, the relative immunosuppression in vivo is reversed, and Th1 is dominant in Th1/Th2 and Th17 is dominant in Th17/Treg balance. After delivery, the number of Treg decrease and NK cells increase in quantity and cytotoxicity in peripheral blood. Liver NK cells may cause liver inflammation through a non-antigen specific mechanism. After delivery, the number of CD8+ T cells will increase and HBV specific T cell response recovers from the disfunction in pregnancy. Under the background of postpartum inflammation, the rapid decrease of cortisol after delivery, and especially the enhancement of HBV specific T cell response induced by HBV DNA and cytokines, are the main reasons for postpartum hepatitis. HBeAg positive, especially HBeAg<700 S/CO, and HBV DNA>3-5Log10IU/ml are risk factors for postpartum hepatitis. Antiviral treatment in late pregnancy can reduce the incidence of mother to child transmission (MTCT) in chronic HBV infection women. Chronic HBV infection women have hepatitis both during pregnancy and more often in 12 weeks postpartum. It is generally agreed that postpartum hepatitis is mild symptoms and self-limited. Delaying drug withdrawal to 48 weeks can increase the seroconversion rate of HBeAg in delivery women with elevated alanine aminotransferase (ALT) in pregnancy.

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

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

Interleukin-35 promotes Breg expansion and interleukin-10 production in CD19+ B cells in patients with ankylosing spondylitis

OBJECTIVE

IL-35 is a potent immunosuppressive and anti-inflammatory cytokine, consisting of a p35 subunit and an Epstein-Barr virus-induced gene 3 (EBI3) subunit, which suppresses CD4⁺ effector T cell proliferation and promotes regulatory T cell (Treg) expansion. However, the effects of IL-35 on regulatory B cells (Bregs) in ankylosing spondylitis (AS) have not been explored. The present study aimed (i) to measure serum IL-35 levels and the percentages of Bregs in the peripheral blood of patients with AS and (ii) to explore their relationships in the pathogenesis of AS.

METHODS

A total of 77 patients with AS (AS group), including 47 inactive AS and 30 active AS cases, and 59 healthy controls (HCs) were enrolled into this study. The serum levels of IL-35 and IL-10 were detected by ELISA, and the mRNA levels of p35 and EBI3 were measured by RT-qPCR. The percentages of CD19⁺CD24^hiCD38^hi and CD19⁺CD24^hiCD27⁺ Bregs and IL-35 receptor (IL-12Rβ2, IL-27Rα and gp130), IL-10, p-STAT1, p-STAT3, and p-STAT4 in CD19⁺ B cells were detected by flow cytometry. The correlations between IL-35 levels and percentages of Bregs were analyzed by determining Pearson's correlation coefficient. The effect of IL-35 on Bregs was determined by mix-culture of recombinant (r) IL-35 with peripheral blood mononuclear cells (PBMCs).

RESULTS

The serum IL-35 and IL-10 levels, p35 and EBI3 mRNA levels, and the percentages of CD19⁺CD24^hiCD38^hi and CD19⁺CD24^hiCD27⁺ Bregs were significantly lower in AS patients than those in HCs. In addition, the percentages of CD19⁺CD24^hiCD38^hi and CD19⁺CD24^hiCD27⁺ Bregs in active AS patients were significantly lower than those in inactive AS patients. The serum IL-35 levels were positively correlated with the percentages of CD19⁺CD24^hiCD38^hi and CD19⁺CD24^hiCD27⁺ Bregs in AS patients. IL-12Rβ2 and IL-27Rα, but not gp130 subunit, were expressed in CD19⁺ B cells in AS patients. RIL-35 could effectively promote CD19⁺CD24^hiCD38^hi Breg expansion and IL-10 production. Meanwhile, rIL-35 also promoted the expression of IL-12Rβ2 and IL-27Rα and the phosphorylation of STAT1 and STAT3 in CD19⁺ B cells.

CONCLUSION

These results demonstrated that reduced IL-35 production may be associated with Bregs defects in AS patients. RIL-35 induced the proliferation of CD19⁺CD24^hiCD38^hi Bregs and IL-10 production, suggesting that IL-35 may serve as a reference for further investigation to develop novel treatments for AS. Key Points • Our study investigated the effects of IL-35 on Bregs in AS patients. • We found the serum IL-35, IL-10 levels, and the percentages of CD19⁺CD24^hiCD38^hi and CD19⁺CD24^hiCD27⁺ Bregs were significantly lower in AS patients. • The serum IL-35 levels were positively correlated with the percentages of CD19⁺CD24^hiCD38^hi and CD19⁺CD24^hiCD27⁺ Bregs in AS patients. • Recombinant IL-35 could effectively promote CD19⁺CD24^hiCD38^hi Breg expansion and IL-10 production.

Interleukin-35 in autoimmune dermatoses: Current concepts

Interleukin-35 (IL-35) is a lately observed cytokine and is part of the IL-12 cytokine family. IL-35 includes two subunits, p35 and Epstein-Barr virus-induced gene 3, and activates subsequent signaling pathways by binding to receptors to mediate signal transduction, thereby modulating the immunoregulatory functions of T cells, B cells, macrophages, and other immune cell types. Although there is currently limited research on the roles of IL-35 in human autoimmunity, many studies have demonstrated that IL-35 may mediate immunosuppression. Therefore, it plays an essential role in some autoimmune dermatoses, including systemic lupus erythematosus, psoriasis, systemic sclerosis, and dermatomyositis. We will introduce the structure and biological characteristics of IL-35 and summarize its effects on the occurrence and development of autoimmune dermatoses in this article. It is suggested that IL-35 is a possible target for therapy in the aforementioned diseases.

How neuroactive factors mediates immune responses during pregnancy: An interdisciplinary view

Pregnancy, from insemination to parturition, is a highly complex but well-orchestrated process that requires various organs and systems to participate. Immune system and neuroendocrine system are important regulators in healthy pregnancy. Dozens of neuroactive factors have been detected in human placenta, whether they are locally secreted or circulated. Among them, some are vividly studied such as corticotropin-releasing hormone (CRH), human chorionic gonadotropin (hCG), transforming growth factor-β (TGF-β), progesterone and estrogens, while others are relatively lack of research. Though the neuroendocrine-immune interactions are demonstrated in some diseases for decades, the roles of neuroactive factors in immune system and lymphocytes during pregnancy are not fully elucidated. This review aims to provide an interdisciplinary view on how the neuroendocrine system mediate immune system during pregnancy process.

Immunosuppressive Mechanisms of Regulatory B Cells

Regulatory B cells (Bregs) is a term that encompasses all B cells that act to suppress immune responses. Bregs contribute to the maintenance of tolerance, limiting ongoing immune responses and reestablishing immune homeostasis. The important role of Bregs in restraining the pathology associated with exacerbated inflammatory responses in autoimmunity and graft rejection has been consistently demonstrated, while more recent studies have suggested a role for this population in other immune-related conditions, such as infections, allergy, cancer, and chronic metabolic diseases. Initial studies identified IL-10 as the hallmark of Breg function; nevertheless, the past decade has seen the discovery of other molecules utilized by human and murine B cells to regulate immune responses. This new arsenal includes other anti-inflammatory cytokines such IL-35 and TGF-β, as well as cell surface proteins like CD1d and PD-L1. In this review, we examine the main suppressive mechanisms employed by these novel Breg populations. We also discuss recent evidence that helps to unravel previously unknown aspects of the phenotype, development, activation, and function of IL-10-producing Bregs, incorporating an overview on those questions that remain obscure.

Regulatory B Cells: Dark Horse in Pregnancy Immunotherapy?

There are many unanswered questions surrounding the function of immune cells and how they interact with the reproductive system to support successful pregnancy or contribute to pregnancy pathologies. While the role of immune cells such as uterine natural killer and dendritic cells, and more recently regulatory T cells has been established, the role of another major immune cell population, the B cell, and particularly the regulatory B cells, is relatively poorly understood. This review outlines what is known about B-cell subsets in the context of pregnancy, what constitutes a regulatory B cell and what role they may play, particularly during early pregnancy. Lastly, we discuss why immunotherapies for the treatment of pregnancy disorders is not widely progressed clinically and speculate on the potential of functional regulatory B cells as the basis of novel immunotherapeutic approaches for the treatment of immune-based pregnancy pathologies.

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.

Medawar's Paradox and Immune Mechanisms of Fetomaternal Tolerance

Brazilian-born British biologist Dr. Peter Medawar played an integral role in developing the concepts of immunologic rejection and tolerance, which led to him receiving the Nobel Prize "for the discovery of acquired immunologic tolerance" and eventually made organ transplantation a reality. However, at the time of his early work in tolerance, a paradox to his theories was brought to his attention; how was pregnancy possible? Pregnancy resembles organ transplantation in that the fetus, possessing paternal antigens, is a semi-allogeneic graft that can survive without immunosuppression for 9 months. To answer this question, Medawar proposed three hypotheses of how a mother supports her fetus in utero, now known as "Medawar's Paradox." The mechanisms that govern fetomaternal tolerance are still incompletely understood but may provide critical insight into how to achieve immune tolerance in organ transplantation. Here, we review current understanding of the immune factors responsible for fetomaternal tolerance during pregnancy and discuss the potential implications for advances in transplantation science.

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.