ORIGINAL ARTICLE: Changes in the Subpopulation of CD25+ CD4+ and FOXP3+ Regulatory T Cells in Decidua with Respect to the Progression of Labor at Term and the Lack of Analogical Changes in the Subpopulation of Suppressive B7-H4+ Macrophages - A Preliminar

Maternal microchimeric cell trafficking and its biological consequences depend on the onset of inflammation at the feto-maternal interface

Microchimerism is defined as the presence of a small population of genetically distinct cells within a host that is derived from another individual. Throughout pregnancy, maternal and fetal cells are known to traffic across the feto-maternal interface and result in maternal and fetal microchimerism, respectively. However, the routes of cell transfer, the molecular signaling as well as the timing in which trafficking takes place are still not completely understood. Recently, the presence of inflammation at the feto-maternal interface has been linked with maternal microchimeric cells modulating organ development in the fetus. Here, we review the current literature and suggest that inflammatory processes at the feto-maternal interface tissues are a physiological prerequisite for the establishment of microchimerism. We further propose a spatio-temporal corridor of microchimeric cell migration to potentially explain some biological effects of microchimerism. Additionally, we elaborate on the possible consequences of a shift in this spatio-temporal corridor, potentially responsible for the development of pathologies in the neonate.

Progestogen-driven B7-H4 contributes to onco-fetal immune tolerance

Immune tolerance mechanisms are shared in cancer and pregnancy. Through cross-analyzing single-cell RNA-sequencing data from multiple human cancer types and the maternal-fetal interface, we found B7-H4 (VTCN1) is an onco-fetal immune tolerance checkpoint. We showed that genetic deficiency of B7-H4 resulted in immune activation and fetal resorption in allogeneic pregnancy models. Analogously, B7-H4 contributed to MPA/DMBA-induced breast cancer progression, accompanied by CD8+ T cell exhaustion. Female hormone screening revealed that progesterone stimulated B7-H4 expression in placental and breast cancer cells. Mechanistically, progesterone receptor (PR) bound to a newly identified -58 kb enhancer, thereby mediating B7-H4 transcription via the PR-P300-BRD4 axis. PR antagonist or BRD4 degrader potentiated immunotherapy in a murine B7-H4+ breast cancer model. Thus, our work unravels a mechanistic and biological connection of a female sex hormone (progesterone) to onco-fetal immune tolerance via B7-H4 and suggests that the PR-P300-BRD4 axis is targetable for treating B7-H4+ cancer.

Melatonin: the placental antioxidant and anti-inflammatory

Melatonin (N-acetyl-5-methoxytryptamine) is an indolamine hormone with many physiological and biological roles. Melatonin is an antioxidant, anti-inflammatory, free radical scavenger, circadian rhythm regulator, and sleep hormone. However, its most popular role is the ability to regulate sleep through the circadian rhythm. Interestingly, recent studies have shown that melatonin is an important and essential hormone during pregnancy, specifically in the placenta. This is primarily due to the placenta's ability to synthesize its own melatonin rather than depending on the pineal gland. During pregnancy, melatonin acts as an antioxidant and anti-inflammatory, which is necessary to ensure a stable environment for both the mother and the fetus. It is an essential antioxidant in the placenta because it reduces oxidative stress by constantly scavenging for free radicals, i.e., maintain the placenta's integrity. In a healthy pregnancy, the maternal immune system is constantly altered to accommodate the needs of the growing fetus, and melatonin acts as a key anti-inflammatory by regulating immune homeostasis during early and late gestation. This literature review aims to identify and summarize melatonin's role as a powerful antioxidant and anti-inflammatory that reduces oxidative stress and inflammation to maintain a favorable homeostatic environment in the placenta throughout gestation.

Effect of B7-H4 downregulation induced by Toxoplasma gondii infection on dysfunction of decidual macrophages contributes to adverse pregnancy outcomes

BACKGROUND

Toxoplasma gondii infection during pregnancy can lead to fetal defect(s) or congenital complications. The inhibitory molecule B7-H4 expressed on decidual macrophages (dMφ) plays an important role in maternal-fetal tolerance. However, the effect of B7-H4 on the function of dMφ during T. gondii infection remains unclear.

METHODS

Changes in B7-H4 expression on dMφ after T. gondii infection were explored both in vivo and in vitro. B7-H4^-/- pregnant mice (pregnant mice with B7-H4 gene knockout) and purified primary human dMφ treated with B7-H4 neutralizing antibody were used to explore the role of B7-H4 signaling on regulating the membrane molecules, synthesis of arginine metabolic enzymes and cytokine production by dMφ with T. gondii infection. Also, adoptive transfer of dMφ from wild-type (WT) pregnant mice or B7-H4^-/- pregnant mice to infected B7-H4^-/- pregnant mice was used to examine the effect of B7-H4 on adverse pregnancy outcomes induced by T. gondii infection.

RESULTS

The results illustrated that B7-H4^-/- pregnant mice infected by T. gondii had poorer pregnancy outcomes than their wild-type counterparts. The expression of B7-H4 on dMφ significantly decreased after T. gondii infection, which resulted in the polarization of dMφ from the M2 toward the M1 phenotype by changing the expression of membrane molecules (CD80, CD86, CD163, CD206), synthesis of arginine metabolic enzymes (Arg-1, iNOS) and production of cytokines (IL-10, TNF-α) production. Also, we found that the B7-H4 downregulation after T. gondii infection increased iNOS and TNF-α expression mediated through the JAK2/STAT1 signaling pathway. In addition, adoptive transfer of dMφ from a WT pregnant mouse donor rather than from a B7-H4^-/- pregnant mouse donor was able to improve adverse pregnancy outcomes induced by T. gondii infection.

CONCLUSIONS

The results demonstrated that the downregulation of B7-H4 induced by T. gondii infection led to the dysfunction of decidual macrophages and contributed to abnormal pregnancy outcomes. Moreover, adoptive transfer of B7-H4⁺ dMφ could improve adverse pregnancy outcomes induced by T. gondii infection.

The immunological role of b7-h4 in pregnant women with sars-cov2 infection

Problem

T‐cells are key players in fighting the coronavirus disease 2019 (COVID‐19). The checkpoint molecule B7‐H4, a member of the B7 family, can inhibit T‐cell activation and proliferation by inhibiting NF‐kb expression. We aimed to elucidate the immunological role of soluble B7‐H4 (sB7‐H4) and B7‐H4 in pregnant women suffered from an acute Sars‐Cov2 infection.

Methods

Expression levels of sB7‐H4 and cytokines were detected by enzyme linked immunosorbent assay. B7‐H4 and cytokines mRNA expression was analyzed by qPCR, and B7‐H4 and NF‐κb (p65) protein levels were investigated by western blot and immunofluorescence staining in placenta chorionic villous and decidual basalis tissues of COVID‐19 affected women and healthy controls.

Results

Fibrinoid necrosis in the periphery of placental villi was increased in the COVID‐19‐affected patients. sB7‐H4 protein in maternal and cord blood serum and IL‐6/IL‐10 were increased while leukocytes were decreased during SARS‐CoV‐2 infection. Serum sB7‐H4 level was increased according to the severity of SARS‐Cov‐2 infection. Cytokines (IL‐6, IL‐18, IL‐1β, TNF‐α), B7‐H4 mRNA and protein in the decidual basalis tissues of COVID‐19‐infected pregnant women were significantly increased compared to healthy controls. IL‐18 and IL‐1β were significantly increased in the placenta chorionic villous samples of COVID‐19 affected patients, while NF‐κb (p65) expression was decreased.

Conclusions

The expression of the immunological marker sB7‐H4 correlated with the severity of COVID‐19 disease in pregnant women. sB7‐H4 and B7‐H4 can be used to monitor the progression of COVID‐19 infection during pregnancy, and for evaluating of the maternal immune status.

Expression of the Costimulatory Molecule B7-H4 in the Decidua and Placental Tissues in Patients with Placental Abruption

B7 homolog 4 protein (B7-H4), a member of the B7 family, is a immunomodulatory membrane protein. The aim of the study was to evaluate the expression of this protein in the decidua and placental tissues in case of placental abruption (PA) compared to cases of retained placental tissue (RPT) and controls. Tissue samples were obtained from 47 patients with PA, 60 patients with RPT, and 41 healthy controls. The samples were stained for B7-H4 expression, analyzed by an expert pathologist, and a semi-quantitative scale was applied. A statistical analysis revealed that the expression of B7-H4 was significantly higher in the decidua in PA samples compared to samples from patients with RPT (p-value < 0.001) and healthy controls (p-value < 0.001). The expression of B7-H4 in the placental chorionic villus was significantly higher in PA samples in relation to samples from healthy controls (p-value < 0.001) but not in relation to RPT samples (p-value = 0.0853). This finding suggests that B7-H4 might play an important role in mechanisms restoring reproductive tract homeostasis. Further research is necessary in regard to the role of B7-H4 in PA.

Preterm Birth in Women With HIV: The Role of the Placenta

Maternal HIV infection is associated with an increased risk of preterm birth (PTB). However, the mechanisms underlying this increased risk in women with HIV remain poorly understood. In this regard, it is well-established that labor is an inflammatory process and premature activation of the pro-inflammatory signals (associated with labor) can result in preterm labor which can subsequently lead to PTB. HIV infection is known to cause severe immune dysregulation within its host characterized by altered immune profiles, chronic inflammation and eventually, the progressive failure of the immune system. The human placenta comprises different immune cell subsets, some of which play an important role during pregnancy including participating in the inflammatory processes that accompany labor. It is therefore plausible that HIV/antiretroviral therapy (ART)-associated immune dysregulation within the placental microenvironment may underlie the increased risk of PTB reported in women with HIV. Here, we review evidence from studies that point toward the placental origin of spontaneous PTB and discuss possible ways maternal HIV infection and/or ART could increase this risk. We focus on key cellular players in the maternal decidua including natural killer cells, CD4+ T cells including CD4+ regulatory T cells, CD8+ T cells as well as macrophages.

Soluble PD-L1 and B7-H4 serum levels during the course of physiological pregnancy

PROBLEM

The aim of this study was to evaluate the soluble programmed death-ligand (sPD-L1) and soluble B7-H4 (sB7-H4) serum concentration levels longitudinal throughout the three trimesters of uncomplicated pregnancies. METHOD OF THE STUDY: sPD-L1 and sB7-H4 levels were determined with enzyme-linked immunosorbent assay (ELISA). The patients (n = 26) were divided into three groups according to the pregnancy trimester. Among 26 women involved in the study 14 had longitudinal sB7-H4 and sPD-L1 measurements in each trimester of pregnancy.

RESULTS

During the course of pregnancy, the sB7-H4 blood serum levels were significant higher in second trimester than in first and third trimester, whereas sPD-L1 levels increased significantly over the course of pregnancy.

CONCLUSION

The highest serum levels of sPD-L1 in the third trimester suggest increasing suppression of maternal immunity throughout pregnancy, whereas elevated sB7-H4 concentration levels in second trimester suggests different profile of T-cell regulation in physiological pregnancy.

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

BACKGROUND

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

AIM

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

METHODS

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

RESULTS

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

CONCLUSION

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

Predictive value of serum soluble B7-H4 in acute pancreatitis

BACKGROUND

Studies reported that soluble B7-H4 (sB7-H4) was significantly related to the progression and prognosis of inflammatory diseases, and whether sB7-H4 is related to the severity and prognosis of acute pancreatitis (AP) timely has not been reported.

MATERIALS AND METHODS

Clinical database data of 446 AP patients were retrospectively collected, and the correlation between the expression serum levels of sB7-H4 with inflammatory factors and prognostic scores was analysed in AP patients.

RESULTS

Soluble B7-H4 was significantly correlated with IL-6, IL-8, TNF-α, PCT, CRP levels and WBC count (P < .01), with correlation coefficients of R = .61, .53, .46, .60, .57 and .47, respectively, and AUCs were 0.905, 0.837, 0.797, 0.858, 0.890, 0.841 and 0.855, respectively. In addition, sB7-H4 was significantly correlated with the Ranson score, APACHE II score and BISAP score (P < .001), with correlation coefficients of R = .58, .63 and .59, respectively. The AUCs of assessing local complications of AP were 0.908, 0.863, 0.785 and 0.844, respectively; assessing organ failure were 0.872, 0.790, 0.796 and 0.857, respectively; and assessing in-hospital mortality were 0.839, 0.821, 0.796 and 0.823, respectively.

CONCLUSIONS

Soluble B7-H4 could be used as a marker for the diagnosis, severity assessment and poor prognosis assessment of AP patients, which may have potential clinical applications.

Maternal and fetal T cells in term pregnancy and preterm labor

Pregnancy is a state of immunological balance during which the mother and the developing fetus must tolerate each other while maintaining sufficient immunocompetence to ward off potential threats. The site of closest contact between the mother and fetus is the decidua, which represents the maternal-fetal interface. Many of the immune cell subsets present at the maternal-fetal interface have been well described; however, the importance of the maternal T cells in this compartment during late gestation and its complications, such as preterm labor and birth, has only recently been established. Moreover, pioneer and recent studies have indicated that fetal T cells are activated in different subsets of preterm labor and may elicit distinct inflammatory responses in the amniotic cavity, leading to preterm birth. In this review, we describe the established and proposed roles for maternal T cells at the maternal-fetal interface in normal term parturition, as well as the demonstrated contributions of such cells to the pathological process of preterm labor and birth. We also summarize the current knowledge of and proposed roles for fetal T cells in the pathophysiology of the preterm labor syndrome. It is our hope that this review provides a solid conceptual framework highlighting the importance of maternal and fetal T cells in late gestation and catalyzes new research questions that can further scientific understanding of these cells and their role in preterm labor and birth, the leading cause of neonatal mortality and morbidity worldwide.

The Role of B7 Family Molecules in Maternal-Fetal Immunity

Pregnancy is a complex but well-arranged process, and a healthy fetus requires immune privilege and surveillance in the presence of paternally derived antigens. Maternal and fetal cells interact at the maternal–fetal interface. The upregulation and downregulation of maternal immunity executed by the leukocyte population predominantly depend on the activity of decidual natural killer cells and trophoblasts and are further modulated by a series of duplex signals. The B7 family, which consists of B7-1, B7-2, B7-H1, B7-DC, B7-H2, B7-H3, B7-H4, B7-H5, BTNL2, B7-H6, and B7-H7, is one of the most characterized and widely distributed signaling molecule superfamilies and conducts both stimulatory and inhibitory signals through separate interactions. In particular, the roles of B7-1, B7-2, B7-H1, and their corresponding receptors in the progression of normal pregnancy and some pregnancy complications have been extensively studied. Together with the TCR–MHC complex, B7 and its receptors play a critical role in cell proliferation and cytokine secretion. Depending on this ligand–receptor crosstalk, the balance between the tolerance and rejection of the fetus is perfectly maintained. This review aims to provide an overview of the current knowledge of the B7 family and its functions in regulating maternal–fetal immunity through individual interactions.

Melatonin Promotes Uterine and Placental Health: Potential Molecular Mechanisms

The development of the endometrium is a cyclic event tightly regulated by hormones and growth factors to coordinate the menstrual cycle while promoting a suitable microenvironment for embryo implantation during the “receptivity window”. Many women experience uterine failures that hamper the success of conception, such as endometrium thickness, endometriosis, luteal phase defects, endometrial polyps, adenomyosis, viral infection, and even endometrial cancer; most of these disturbances involve changes in endocrine components or cell damage. The emerging evidence has proven that circadian rhythm deregulation followed by low circulating melatonin is associated with low implantation rates and difficulties to maintain pregnancy. Given that melatonin is a circadian-regulating hormone also involved in the maintenance of uterine homeostasis through regulation of numerous pathways associated with uterine receptivity and gestation, the success of female reproduction may be dependent on the levels and activity of uterine and placental melatonin. Based on the fact that irregular production of maternal and placental melatonin is related to recurrent spontaneous abortion and maternal/fetal disturbances, melatonin replacement may offer an excellent opportunity to restore normal physiological function of the affected tissues. By alleviating oxidative damage in the placenta, melatonin favors nutrient transfer and improves vascular dynamics at the uterine–placental interface. This review focuses on the main in vivo and in vitro functions of melatonin on uterine physiological processes, such as decidualization and implantation, and also on the feto-maternal tissues, and reviews how exogenous melatonin functions from a mechanistic standpoint to preserve the organ health. New insights on the potential signaling pathways whereby melatonin resists preeclampsia and endometriosis are further emphasized in this review.

Role of Macrophages in Pregnancy and Related Complications

Macrophages (MФs) are the leukocytes produced from differentiation of monocytes and are located in almost all tissues of human body. They are involved in various processes, such as phagocytosis, innate and adaptive immunity, proinflammatory (M1) and anti-inflammatory (M2) activity, depending on the tissue microenvironment. They play a crucial role in pregnancy, and their dysfunction or alteration of polarity is involved in pregnancy disorders, like preeclampsia, recurrent spontaneous abortion, infertility, intrauterine growth restriction, and preterm labor. About 50-60% of decidual leukocytes are natural killer (NK) cells followed by MФs (the second largest population). MФs are actively involved in trophoblast invasion, tissue and vascular remodeling during early pregnancy, besides their role as major antigen-presenting cells in the decidua. These cells have different phenotypes and polarities in different stages of pregnancy. They have also been observed to enhance tumor growth by their anti-inflammatory activity (M2 type) and prevent immunogenic rejection. Targeted alteration of polarity (M1-M2 or vice versa) could be a major focus in the future treatment of pregnancy complications. This review is focused on the role of MФs in pregnancy, their involvement in pregnancy disorders, and decidual MФs as possible therapeutic targets for the treatment of pregnancy complications.

Soluble B7-H4 blood serum levels are elevated in women at high risk for preeclampsia in the first trimester, as well as in patients with confirmed preeclampsia

PROBLEM

B7-H4 negatively regulates T-cell-mediated immunity and might play an important role in preeclampsia (PE). Here, we have investigated the association between PE and maternal soluble B7-H4 (sB7-H4) serum levels and B7-H4 mRNA expression in the placenta.

METHOD OF STUDY

Maternal serum levels of sB7-H4 were determined by enzyme-linked immunosorbent assay in women between 11 and 13 weeks' gestation with elevated risk for PE (n = 48) and women without elevated risk for PE (n = 47). In the third trimester, sB7-H4 serum levels (n = 166) and B7-H4 mRNA expression in the placenta (n = 54) were determined in women with early-onset PE, late-onset PE, fetal growth restriction (FGR), and in healthy controls.

RESULTS

In the first trimester, significant higher levels of sB7-H4 were detected in women at elevated risk for PE compared to women without risk for PE (P < .0001). sB7-H4 has some predictive ability to identify cases with an elevated risk of developing PE with area under the curve (AUC) value of 0.88 (95% CI 0.8-0.94). Using a specificity of 90.0% led to a sensitivity of 47.9% and a threshold of 3.63 ng/mL. In the third trimester, the highest serum levels of sB7-H4 and B7-H4 mRNA expression in the placenta were observed in early-onset PE. Significant higher serum levels of sB7-H4 and B7-H4 mRNA expression in the placenta were observed in women with early-onset PE (P = .01 and P = .006, respectively) and late-onset PE (P = .03 and P = .004, respectively) compared to healthy controls, but not compared to FGR.

CONCLUSION

sB7-H4 is involved in the regulation of immune tolerance in women with PE in the third trimester. In the first trimester of pregnancy, sB7-H4 might serve as a predictive immunological biomarker for women who are at elevated risk of developing PE.

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

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

Soluble CEACAM1 and CEACAM6 are differently expressed in blood serum of pregnant women during normal pregnancy

PROBLEM

CEACAM1 and CEACAM6 belong to the carcinoembryonic antigen (CEA) family and may play an immune-modulatory role during pregnancy. The aim of the study was to determine the blood serum levels of soluble CEACAM1 and CEACAM6 over the course of pregnancy and postpartum.

METHOD OF STUDY

CEACAM1 and CEACAM6 levels were determined with customized in-house Sandwich-enzyme-linked immunosorbent assay (ELISA) systems. The study population (n=125) was divided into four groups according to the pregnancy trimester and postpartum. Additionally, samples of non-pregnant women (n=14) were analyzed.

RESULTS

Serum levels of CEACAM1 in healthy pregnant women were much lower than in non-pregnant women, a difference not seen for CEACAM6. Comparison between the trimesters and postpartum revealed a significant difference in CEACAM1 serum levels. The highest CEACAM1 levels were detected in third trimester. These levels were statistically significantly different from the CEACAM1 levels in first trimester and second trimester. The lowest levels were observed in the second trimester. Postpartum CEACAM1 serum concentrations were slightly lower than in the third trimester, but higher than in the first trimester and significantly higher compared to levels in the second trimester.

CONCLUSION

Decreased concentration of CEACAM1 during the pregnancy suggests its regulatory role in the immune tolerance during the course of pregnancy.

Co-Signaling Molecules in Maternal-Fetal Immunity

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

Regulatory T Cells Show Dynamic Behavior During Late Pregnancy, Delivery, and the Postpartum Period

Regulatory T cells (Tregs) are critical immunomodulators during early pregnancy by preventing maternal T-cell activation against fetal cells. However, how populations of maternal Tregs vary during and after pregnancy in humans is still unclear. Therefore, we investigated Treg subsets in the peripheral blood of pregnant women from late pregnancy through the postpartum period. To accomplish this, the following circulating Treg subsets were analyzed in 43 healthy pregnant women and 35 nonpregnant women by flow cytometry during the third trimester, on the day of delivery, and postpartum: CD4^DimCD25^Hi, CD4⁺CD25^HiFoxp3⁺, and CD4⁺CD25^HiCD127^-/dim. Additionally, the expression levels of the transcription factor Foxp3 in CD4^DimCD25^Hi Treg were analyzed. We have found that CD4^DimCD25^Hi Treg subset significantly decreased in the pregnant women on the day of delivery relative to the third trimester ( P < .05), and that all Treg subsets significantly increased postpartum compared to the third trimester and the day of delivery ( P < .05). Moreover, the Foxp3 expression ratios within the CD4^DimCD25^Hi Treg subset decreased during pregnancy and until delivery compared to those measured in the nonpregnant women and significantly increased postpartum compared to the third trimester and the day of delivery ( P < .05). Thus, despite their established role in offering immunoprotection to the fetus in early pregnancy, the number of circulating Tregs also varies from late pregnancy to the postpartum period. Our results offer an explanation for the possible effects of pregnancy on the clinical outcomes of some autoimmune diseases during the postpartum period.

Immunologic challenges of human reproduction: an evolving story

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

Novel concepts on pregnancy clocks and alarms: redundancy and synergy in human parturition

The signals and mechanisms that synchronize the timing of human parturition remain a mystery and a better understanding of these processes is essential to avert adverse pregnancy outcomes. Although our insights into human labor initiation have been informed by studies in animal models, the timing of parturition relative to fetal maturation varies among viviparous species, indicative of phylogenetically different clocks and alarms; but what is clear is that important common pathways must converge to control the birth process. For example, in all species, parturition involves the transition of the myometrium from a relaxed to a highly excitable state, where the muscle rhythmically and forcefully contracts, softening the cervical extracellular matrix to allow distensibility and dilatation and thus a shearing of the fetal membranes to facilitate their rupture. We review a number of theories promulgated to explain how a variety of different timing mechanisms, including fetal membrane cell senescence, circadian endocrine clocks, and inflammatory and mechanical factors, are coordinated as initiators and effectors of parturition. Many of these factors have been independently described with a focus on specific tissue compartments.In this review, we put forth the core hypothesis that fetal membrane (amnion and chorion) senescence is the initiator of a coordinated, redundant signal cascade leading to parturition. Whether modified by oxidative stress or other factors, this process constitutes a counting device, i.e. a clock, that measures maturation of the fetal organ systems and the production of hormones and other soluble mediators (including alarmins) and that promotes inflammation and orchestrates an immune cascade to propagate signals across different uterine compartments. This mechanism in turn sensitizes decidual responsiveness and eventually promotes functional progesterone withdrawal in the myometrium, leading to increased myometrial cell contraction and the triggering of parturition. Linkage of these processes allows convergence and integration of the gestational clocks and alarms, prompting a timely and safe birth. In summary, we provide a comprehensive synthesis of the mediators that contribute to the timing of human labor. Integrating these concepts will provide a better understanding of human parturition and ultimately improve pregnancy outcomes.

Changes in the Blood Serum Levels of the Costimulatory Soluble B7-H4 Molecule in Pregnant Women During the Peripartal Phase

PROBLEM

B7-H4, a transmembrane protein that negatively regulates T lymphocytes, seems to play a role in the suppression of the im\mune response at the maternal-fetal interface. The aim of this study was to compare the blood serum concentration levels of soluble B7-H4 (sB7-H4) prepartal and postpartal in both women who experienced spontaneous onset of labor and those who underwent elective cesarian section.

METHOD OF STUDY

Blood was obtained from 30 prepartal and postpartal women who delivered at the University Hospital of Essen between 2011 and 2012. These patients were further divided into two subgroups depending on the advancement of labor. The sB7-H4 blood serum concentration levels of the women in the groups were then determined by ELISA (BIOZOL, Eching, Germany).

RESULTS

In women who underwent elective cesarian section, a significant increase in sB7-H4 blood serum concentration levels occurred postpartal, while in women who experienced spontaneous onset of labor, no differences between prepartal and postpartal concentration levels were observed. The sB7-H4 blood serum concentration levels on the day after delivery in the women who experienced spontaneous labor and those who underwent elective cesarian section were comparable; however, higher blood serum concentration levels of sB7-H4 were observed prepartal in women with spontaneous onset of labor compared to those found in the women about to undergo elective cesarian section.

CONCLUSION

These changes in sB7-H4 blood serum concentration levels suggest that this protein is involved in immunological changes associated with the spontaneous onset of labor and post-delivery homeostasis.

Immune cells in the female reproductive tract

The female reproductive tract has two main functions: protection against microbial challenge and maintenance of pregnancy to term. The upper reproductive tract comprises the fallopian tubes and the uterus, including the endocervix, and the lower tract consists of the ectocervix and the vagina. Immune cells residing in the reproductive tract play contradictory roles: they maintain immunity against vaginal pathogens in the lower tract and establish immune tolerance for sperm and an embryo/fetus in the upper tract. The immune system is significantly influenced by sex steroid hormones, although leukocytes in the reproductive tract lack receptors for estrogen and progesterone. The leukocytes in the reproductive tract are distributed in either an aggregated or a dispersed form in the epithelial layer, lamina propria, and stroma. Even though immune cells are differentially distributed in each organ of the reproductive tract, the predominant immune cells are T cells, macrophages/dendritic cells, natural killer (NK) cells, neutrophils, and mast cells. B cells are rare in the female reproductive tract. NK cells in the endometrium significantly expand in the late secretory phase and further increase their number during early pregnancy. It is evident that NK cells and regulatory T (Treg) cells are extremely important in decidual angiogenesis, trophoblast migration, and immune tolerance during pregnancy. Dysregulation of endometrial/decidual immune cells is strongly related to infertility, miscarriage, and other obstetric complications. Understanding the immune system of the female reproductive tract will significantly contribute to women's health and to success in pregnancy.

Regulatory T cells: regulators of life

Pregnancy still represents one of the most fascinating paradoxical phenomena in science. Immediately after conception, the maternal immune system is challenged by the presence of foreign paternal antigens in the semen. This triggers mechanisms of recognition and tolerance that all together allow the embryo to implant and later the fetus to develop. Tolerance mechanisms to maintain pregnancy are of special interest as they defy the classical immunology rules. Several cell types, soluble factors, and immune regulatory molecules have been proposed to contribute to fetal tolerance. Within these, regulatory T cells (Treg) are one of the most studied immune cell populations lately. They are reportedly involved in fetal acceptance. Here, we summarize several aspects of Treg biology in normal and pathologic pregnancies focusing on Treg frequencies, subtypes, antigen specificity, and activity as well as on factors influencing Treg generation, recruitment, and function. This review also highlights the contribution of fetal Treg in tolerance induction and addresses the role of Treg in autoimmune diseases and infections during gestation. Finally, the potential of Treg as a predictive marker for the success of assisted reproductive techniques and for therapeutic interventions is discussed.

Decidual regulatory T cells in placental pathology and pregnancy complications

Regulatory T cells (Tregs) have been identified as immunomodulatory cells, which induce tolerance. Evidence from numerous recent studies implicates these cells as critical for maternal tolerance to the fetal-derived placenta, proper functioning of which is required for normal gestation and growth and development of the fetus in utero. This review focuses on the recent studies of Tregs at the maternal-fetal interface in pregnancy complications, as well as their identification in specific inflammatory lesions in the placenta.

[Immunological analogies between ovarian cancer and pregnancy]

During pregnancy an environment allowing installation of tolerance toward the fetus is set up locally at the materno-fetal interface. Numerous effectors of immunity are involved in this tolerance (NK cell, T cell, Macrophages, dendritic cell). Specific mechanisms during pregnancy attract locally these immunological cells. In the decidua, they are educated toward tolerance. These mechanisms evolve during the pregnancy because at the end of the pregnancy, tolerance is broken to prepare and activate the labor. Ovarian tumors, after having surmounted the immunosurveillance, like trophoblast, chair the installation of a tolerance of their host facilitating the development of the disease. The blocking of these mechanisms of tolerance coupled with activation of mechanisms of defenses offer new perspectives in the treatment of the ovarian cancer. The authors suggest showing the analogies of the tolerance observed during ovarian cancer and pregnancy. The knowledge of the orchestration of the physiological mechanisms observed during pregnancy will offer new therapeutic targets.

Macrophages infiltrate the human and rat decidua during term and preterm labor: evidence that decidual inflammation precedes labor

Preterm delivery is the leading cause of perinatal mortality and morbidity. Current tocolytics target myometrial contractions, a late step in the labor cascade. Identifying earlier events in parturition may lead to more effective therapeutic strategies. We hypothesized that inflammatory events in decidua (the maternal-fetal interface), characterized by leucocyte infiltration, are an early event during term and preterm labor (PTL). Leucocyte abundance in decidua of human pregnancies was quantified following term labor and PTL (idiopathic and infection associated), in conjunction with investigation of temporal inflammatory events in rat uterus during the perilabor period and in PTL induced by mifepristone. In human decidua, macrophage numbers were 4-fold higher in term labor (P < 0.01) and 2.5-fold higher in non-infection-associated PTL (P < 0.05) than in term nonlaboring samples. Neutrophil abundance was unchanged with labor but elevated in PTL with infection (5- to 53-fold increase; P < 0.01). T and NK cells were more abundant in idiopathic PTL than TL (P < 0.05). In rat, decidual macrophage infiltration increased 4.5-fold 12 h prior to labor and remained elevated during labor and early postpartum (P < 0.01). Decidual infiltration preceded that of the myometrium and was 4-fold higher (P < 0.01). In rat PTL, decidual macrophage numbers were also elevated (P < 0.01) and exceeded those of the myometrium (P < 0.05). These studies show for the first time that leucocytes infiltrate decidua during labor at term and preterm, supporting a role for leucocyte-derived inflammatory mediators in decidual activation. In the rat, this occurred prior to labor, suggesting it is an early event during parturition and thus a potential target for intervention.

The presence of B7-H4+ macrophages and CD25+CD4+ and FOXP3+ regulatory T cells in the microenvironment of nasal polyps - a preliminary report

The nasal polyp (NP) seems to represent the end-stage of longstanding inflammation in patients with chronic rhinosinusitis. The aim of our study has been to evaluate the presence of two regulatory cell populations in the microenvironment of NP: CD4+CD25high Foxp3+ (Treg) cells and B7-H4-expressing macrophages. Treg cells are actively able to inhibit T lymphocytes, while the population of B7-H4-expressing macrophages has recently been described as characterized by a regulatory function similar to that of Treg cells. For our study, we evaluated 14 NP tissue samples. The samples were divided into two main groups, eosinophilic (NP) and lymphocytic (NP), according to the predominant type of immune cell infiltration. The presence of Treg cells and B7-H4 positive macrophages in the samples was analyzed by FACS. Treg cells and B7-H4-expressing macrophages were identified in all the examined nasal polyps. The percentages of both Treg cells and of B7H4 positive cells found in the eosinophilic nasal polyps were higher than those found in the lymphocytic nasal polyps. Treg cells and B7H4+ macrophage subpopulations were present in the NP microenvironment and the alterations in their percentages were related to a distinct pattern of immune cell infiltration.

The immunohistochemical analysis of RCAS1, HLA-G, and B7H4-positive macrophages in partial and complete hydatidiform mole in both applied therapeutic surgery and surgery followed by chemotherapy

INTRODUCTION

The suppressive microenvironment developing around the implantating ovum in normal pregnant women may correlate with the development in cancer patients of a suppressive microenvironment of neoplasmatic cells derived from trophoblasts, such as occurs in molar lesions. Macrophages are suitable candidates for mediating not only the balance of the maternal defensive immune responses to external antigens, but also a tolerance to tumor cells. The aim of our study has been to gain information about the expression of RCAS1, B7H4, and HLA-G within the macrophages present in the microenvironment of the molar lesion.

METHODS

We analyzed the immunoreactivity of such antigens as B7H4, RCAS1, and HLA-G on the macrophages present in tissue samples derived from patients on whom curettage was performed after a diagnosis of molar pregnancy. These patients were then divided into two subgroups according to whether or not they required chemotherapy after the surgical procedure.

RESULTS

We observed a statistically significant increase in the RCAS1-positive macrophage infiltration within the microenvironment of the molar lesions in patients with partial hydatidiform mole in comparison with those patients who exhibited complete hydatidiform mole. There were no such differences, however, in the infiltration of HLA-G- and B7H4-positive macrophages between the two groups of patients. Additionally, we showed that RCAS1- and HLA-G-positive macrophages are more distinct in those cases of complete molar pregnancy where chemotherapy was necessary after surgical treatment while no such differences with respect to B7H4-positive macrophages were observed.

CONCLUSION

The immune-suppressive endometrial microenvironment represented by suppressive macrophages may have an influence on the clinical course of hydatidiform mole.

Regulation of costimulatory signal in maternal-fetal immune tolerance

A pregnancy is associated with modifications in the immune status of the mother, but the mechanisms are not well understood. Several observations have indicated that CD28/CTLA-4 and B7-1/B7-2 are involved in the maternal-fetal immune regulation. This review aims to recapitulate our current knowledge concerning the role of CD28/CTLA-4 and B7-1/B7-2 in maternal-fetal immune regulation. Several studies suggest that up-regulation of B7-2 and/or CD28 and/or down-regulation of CTLA-4 are correlated with the occurrence of pregnancy loss. Therefore, an accurate expression of costimulatory molecules at the maternal-fetal interface may ensure that the decidual cells do not elicit a 'danger' signal to the maternal immune system, perhaps instead contributing to the establishment of immune tolerance in vivo. It is showed that costimulation blockade with anti-B7 mAbs results in altered allogeneic T-cell response and overcomes increased maternal rejection to the fetus, which improves fetus growth in the abortion-prone system. These findings suggest that the anti-B7-treated T cells not only function as potent suppresser cells but also exert immunoregulatory effect on the maternal T cells. This procedure might be potentially useful to immunotherapy for human recurrent spontaneous abortion.

The frequency of CD25+CD4+ and FOXP3+ regulatory T cells in ectopic endometrium and ectopic decidua

BACKGROUND

The presence of regulatory T (Treg) cells in human endometrium is crucial for maintaining immunological homeostasis within the uterus. For this study we decided to evaluate the subpopulations of Treg cells in conditions where a disturbance in the immunological equilibrium in ectopic endometrium and decidua has been observed, such as in cases of ovarian endometriosis (involving local immune cell suppression) and ectopic pregnancy (involving an increase in local immune system activity). We then compared these findings to what we observed in the normal eutopic endometrium of women during the secretory phase of the menstrual cycle (with immune cells under individual control).

METHODS

The endometrium tissue samples evaluated in our study were obtained from 47 women during one of two kinds of laparoscopic procedures. 16 of the women underwent laparoscopies due to Fallopian tube pregnancies (EP), and 16 due to ovarian endometrioma, while 15 women made up a control group. The presence of regulatory T cells in these tissue samples was evaluated by FACS.

RESULTS

In our study, the percentages of FOXP3+ cells within the subpopulation of CD4+ T lymphocytes found in the decidua of the patients treated for Fallopian tube pregnancies were statistically significantly lower than both those observed in the ovarian endometriosis tissue samples and those found in the secretory eutopic endometrium samples of the control group.

CONCLUSION

The disturbance in the immunological equilibrium observed in ectopic endometrium and decidua would seem to be related to the alteration in the Treg cell population that occurs in these ectopic tissues.

B7 family molecules as regulators of the maternal immune system in pregnancy

Placental and fetal growth and development are associated with chronic exposure of the maternal immune system to fetally derived, paternally inherited antigens. Because maternal lymphocytes are aware of fetal antigens, active tolerance mechanisms are required to ensure unperturbed progression of pregnancy and delivery of a healthy newborn. These mechanisms of tolerance may include deletion, receptor downregulation, and anergy of fetal antigen-specific cells in lymphoid tissues, as well as regulation at the maternal-fetal interface by a variety of locally expressed immunoregulatory molecules. The B7 family of costimulatory molecules comprises one group of immunoregulatory molecules present in the decidua and placenta. B7 family members mediate both inhibitory and stimulatory effects on T-cell activation and effector functions and may play a critical role in maintaining tolerance to the fetus. Here, we review the known functions of the B7 family proteins in pregnancy.

The immunomodulatory roles of macrophages at the maternal-fetal interface

Macrophages are versatile cells that play a central role in innate and adaptive immunity and participate in a wide variety of biological processes. In the uterine decidua, macrophages represent a major leukocyte subset throughout pregnancy. Here, decidual macrophages exert an immunosuppressive phenotype characterized by abundant production of interleukin (IL)-10 and indoleamine 2,3-dioxygenase activity. Their polarized cytokine secretion pattern has recently been classified as an M2 phenotype. These features of decidual macrophages favor maternal immune tolerance to semiallogenic fetus. In addition, macrophages cooperate with trophoblast cells during the early stages of human pregnancy to support uterine vasculature remodeling by removing apoptotic cells and through the production of proteases that degrade the extracellular matrix. In the peripartum period, macrophages also participate in the regulation of cervical ripening and the initiation of parturition through the production of proinflammatory cytokines and prostaglandin E(2) (PGE(2)). Aberrant activity of uterine macrophages is linked to the pathogenesis of preeclampsia and preterm delivery. Here, we review the immunomodulatory roles of decidual macrophages during pregnancy.