Differences in circulating dendritic cell subtypes in pregnant women, cord blood and healthy adult women

Dendritic Cells and the Establishment of Fetomaternal Tolerance for Successful Human Pregnancy

Pregnancy is a remarkable event where the semi-allogeneic fetus develops in the mother's uterus, despite genetic and immunological differences. The antigen handling and processing at the maternal-fetal interface during pregnancy appear to be crucial for the adaptation of the maternal immune system and for tolerance to the developing fetus and placenta. Maternal antigen-presenting cells (APCs), such as macrophages (Mφs) and dendritic cells (DCs), are present at the maternal-fetal interface throughout pregnancy and are believed to play a crucial role in this process. Despite numerous studies focusing on the significance of Mφs, there is limited knowledge regarding the contribution of DCs in fetomaternal tolerance during pregnancy, making it a relatively new and growing field of research. This review focuses on how the behavior of DCs at the maternal-fetal interface adapts to pregnancy's unique demands. Moreover, it discusses how DCs interact with other cells in the decidual leukocyte network to regulate uterine and placental homeostasis and the local maternal immune responses to the fetus. The review particularly examines the different cell lineages of DCs with specific surface markers, which have not been critically reviewed in previous publications. Additionally, it emphasizes the impact that even minor disruptions in DC functions can have on pregnancy-related complications and proposes further research into the potential therapeutic benefits of targeting DCs to manage these complications.

The Role of Dendritic Cell Subsets in Recurrent Spontaneous Abortion and the Regulatory Effect of Baicalin on It

Recurrent spontaneous abortion (RSA) is a relevant complication of pregnancy. Aberrant dendritic cell (DC) activities and differentiation have been identified to be involved in RSA, but the underlying mechanisms remain unclear. Baicalin from Radix Scutellariae possesses a wide range of pharmacological and biological activities. However, the effect of baicalin on DC function in RSA has not been investigated. Here, we analyzed the changes of peripheral and maternal-fetal interface DC subsets and function in patients and mice with RSA, respectively. Then, we further treated RSA mice with baicalin and analyzed the therapeutic effect and underlying mechanism. We found that DCs from the peripheral blood and decidua of RSA patients and the maternal-fetal of RSA mice were all polarized to conventional DCs, whose proportion was positively correlated with the mice embryo absorption rate. Moreover, DCs from RSA patients and mice showed increased expression of HLA-DR/MHC-II, CD80, and CD86 but decreased expression of CD274 and 33D1. Importantly, baicalin could alleviate embryo resorption of RSA mice by reversing conventional DCs to plasmacytoid DCs and functional molecule expression via inhibiting the STAT5-ID2 pathway. Our research further proved that DCs play an important role in the pathogenesis of RSA and baicalin might be used for treating RSA.

Interactions Between Specific Immune Status of Pregnant Women and SARS-CoV-2 Infection

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the pathogen responsible for the Coronavirus Disease 2019 (COVID-19) global pandemic. Because it is a new and highly contagious coronavirus, most people, especially pregnant women, lack immunity. It is therefore important to understand the interaction between why pregnant women are susceptible to SARS-CoV-2 and the specific immune systems of pregnant women. Here, we provide an overview of the changes that occur in the immune system during pregnancy, the activation and response of the immune system in pregnant women with COVID-19, adverse pregnancy outcomes in pregnant women with COVID-19, and the treatment and prevention of COVID-19 in this population.

Dendritic cells in pregnancy and pregnancy-associated diseases

Dendritic cells (DCs) play a critical immuno-modulating role in pregnancy, which requires the maternal immune system to tolerate semiallogeneic fetus and at the same time to maintain adequate defense against pathogens. DCs interact closely with other immune components such as T cells, natural killer cells and macrophages, as well as the endocrine system to keep a pregnancy-friendly environment. Aberrant DC activities have been related to various pregnancy-associated diseases such as recurrent spontaneous abortion, preterm birth, pre-eclampsia, peripartum cardiomyopathy and infectious pregnancy complications. These findings make DCs an attractive candidate for prevention or therapy on the pregnancy-associated diseases. Here, we review recent findings that provide new insights into the roles of DCs in pregnancy and the related diseases. We also discuss the medical potentials to manipulate DCs in clinics. Whereas this is an emerging area with much work remaining, we anticipate that a better understanding of the role of DCs in maternal-fetal immunotolerance and a therapeutic manipulation of DCs will help women suffering from the pregnancy-associated diseases.

Immunobiological aspects of vaccines in pregnancy: Maternal perspective

Immunization during pregnancy is an efficient strategy to protect both the mother and the newborn infant against infectious pathogens. Pregnant women have an increased susceptibility to severe infections caused by some pathogens, but the mechanisms involved remain poorly understood. Pregnancy is associated with dynamic changes in maternal immune system that are critical for tolerance of the fetus. These changes could also play an important role in shaping maternal immune components that are transferred to the newborn infant following natural infection or vaccination to prevent infectious diseases in early life. As the momentum for maternal immunization is growing, there is a need to increase our understanding of the immunobiology of maternal immunization in order to better prevent infectious diseases in the pregnant women and the young infant.

GNP-GAPDH1-22 nanovaccines prevent neonatal listeriosis by blocking microglial apoptosis and bacterial dissemination

Clinical cases of neonatal listeriosis are associated with brain disease and fetal loss due to complications in early or late pregnancy, which suggests that microglial function is altered. This is believed to be the first study to link microglial apoptosis with neonatal listeriosis and listeriosis-associated brain disease, and to propose a new nanovaccine formulation that reverses all effects of listeriosis and confers Listeria monocytogenes (LM)-specific immunity. We examined clinical cases of neonatal listeriosis in 2013–2015 and defined two useful prognostic immune biomarkers to design listeriosis vaccines: high anti-GAPDH_1-22 titres and tumor necrosis factor (TNF)/interleukin (IL)-6 ratios. Therefore, we developed a nanovaccine with gold glyco-nanoparticles conjugated to LM peptide 1-22 of GAPDH (Lmo2459), GNP-GAPDH_1-22 nanovaccinesformulated with a pro-inflammatory Toll-like receptor 2/4-targeted adjuvant. Neonates born to non-vaccinated pregnant mice with listeriosis, showed brain and vascular diseases and significant microglial dysfunction by induction of TNF-α-mediated apoptosis. This programmed TNF-mediated suicide explains LM dissemination in brains and livers and blocks production of early pro-inflammatory cytokines such as IL-1β and interferon-α/β. In contrast, neonates born to GNP-GAPDH_1–22-vaccinated mothers before LM infection, did not develop listeriosis or brain diseases and had functional microglia. In nanovaccinated mothers, immune responses shifted towards Th1/IL-12 pro-inflammatory cytokine profiles and high production of anti-GAPDH_1–22 antibodies, suggesting good induction of LM-specific memory.

Identifying immune mechanisms mediating the hypertension during preeclampsia

Preeclampsia (PE) is a pregnancy-associated disorder that affects 5-8% of pregnancies and is a major cause of maternal, fetal, and neonatal morbidity and mortality. Hallmark characteristics of PE are new onset hypertension after 20 wk gestation with or without proteinuria, chronic immune activation, fetal growth restriction, and maternal endothelial dysfunction. However, the pathophysiological mechanisms that lead to the development of PE are poorly understood. Recent data from studies of both clinical and animal models demonstrate an imbalance in the subpopulations of CD4+ T cells and a role for these cells as mediators of inflammation and hypertension during pregnancy. Specifically, it has been proposed that the imbalance between two CD4+ T cell subtypes, regulatory T cells (Tregs) and T-helper 17 cells (Th17s), is involved in the pathophysiology of PE. Studies from our laboratory highlighting how this imbalance contributes to vasoactive factors, endothelial dysfunction, and hypertension during pregnancy will be discussed in this review. Therefore, the purpose of this review is to highlight hypertensive mechanisms stimulated by inflammatory factors in response to placental ischemia, thereby elucidating a role.

The role of inflammation in the pathology of preeclampsia

Preeclampsia (PE) affects 5-7% of all pregnancies in the United States and is the leading cause of maternal and prenatal morbidity. PE is associated with hypertension after week 20 of gestation, decreased renal function and small-for-gestational-age babies. Women with PE exhibit chronic inflammation and production of autoantibodies. It is hypothesized that during PE, placental ischaemia occurs as a result of shallow trophoblast invasion which is associated with an immune imbalance where pro-inflammatory CD4(+) T-cells are increased and T regulatory cells (Tregs) are decreased. This imbalance leads to chronic inflammation characterized by oxidative stress, pro-inflammatory cytokines and autoantibodies. Studies conducted in our laboratory have demonstrated the importance of this immune imbalance in causing hypertension in response to placental ischaemia in pregnant rats. These studies confirm that increased CD4(+) T-cells and decreased Tregs during pregnancy leads to elevated inflammatory cytokines, endothelin (ET-1), reactive oxygen species (ROS) and agonistic autoantibodies to the angiotensin II (Ang II), type 1 receptor (AT1-AA). All of these factors taken together play an important role in increasing the blood pressure during pregnancy. Specifically, this review focuses on the decrease in Tregs, and their associated regulatory cytokine interleukin (IL)-10, which is seen in response to placental ischaemia during pregnancy. This study will also examine the effect of regulatory immune cell repopulation on the pathophysiology of PE. These studies show that restoring the balance of the immune system through increasing Tregs, either by adoptive transfer or by infusing IL-10, reduces the blood pressure and pathophysiology associated with placental ischaemia in pregnant rats.

CD8 T cells and dendritic cells: key players in the attenuated maternal immune response to influenza infection

Pregnancy provides a unique challenge for maternal immunity, requiring the ability to tolerate the presence of a semi-allogeneic foetus, and yet still being capable of inducing an immune response against invading pathogens. To achieve this, numerous changes must occur in the activity and function of maternal immune cells throughout the course of pregnancy. Respiratory viruses take advantage of these changes, altering the sensitive balance of maternal immunity, leaving the mother with increased susceptibility to viral infections and increased disease severity. Influenza virus is one of the most common respiratory virus infections during pregnancy, leading to an increased risk of ICU hospitalisations, pneumonia, acute respiratory distress syndrome and even death. Whilst much research has been performed to understand the changes that must take place in maternal immunity during pregnancy, considerable work is still needed to fully comprehend this tremendous feat. To date, few studies have focused on the alterations that occur in maternal immunity during respiratory virus infections. This review highlights the role of dendritic cells (DCs) and CD8 T cells during pregnancy, and the changes that occur in these antiviral cells following influenza virus infections.

Peripheral and endometrial dendritic cell populations during the normal cycle and in the presence of endometriosis

Background

Dysfunctional immune response may be implicated in endometriosis pathogenesis, and dendritic cells (DC) may play greater roles in this response than previously recognized. This study set out to evaluate peripheral blood and endometrial DC population changes in the presence and absence of endometriosis pathology.

Methods

Endometrial (n = 83) and peripheral blood samples (n = 30) were subjected to immunohistochemical techniques and flow cytometry, respectively, to assess DC populations in women with and without endometriosis. Three circulating DC subsets (MDC1, MDC2 and PDC, expressing CD1c, CD303 and CD141), and late-stage mature endometrial DCs (using DC-LAMP antibody) were investigated.

Results

A highly significant reduction in CD1c intensity on MDC1 populations in peripheral blood was observed between normal cycle proliferative and menstrual phases (p = 0.025), but not in women with endometriosis, in whom CD1c intensity was markedly increased at the time of menstruation (p = 0.05). A significant reduction in peripheral blood MDC2 (p = 0.016) and apparent reduction in endometrial DC-LAMP+ DC (trend, p = 0.062) were observed in women with endometriosis compared with controls, consistent with our preliminary DC data.

Conclusions

Cyclical variation in endometrial and circulating DC populations appears to be crucial during normal menstrual cycles and in the establishment of pregnancy. In endometriosis, circulating and endometrial DC populations are significantly dysregulated at a number of levels, and are likely to contribute to inefficient immunological targeting of endometrial fragments shed at menstruation, facilitating their survival and establishment of endometriosis.

Maternal circulating dendritic cell subtypes at delivery and during the 1-year postpartum period

PROBLEM

Dendritic cells (DCs) play an important role in maintaining pregnancy by inducing tolerance toward the fetus. Such an immunologic change in the mother should be restored to normal after delivery, but few studies have reported postpartum maternal immune recovery, in terms of the types circulating DCs.

METHOD OF STUDY

The level of each DC subtype and HLA-DR-positive immunoreactivity of the blood from 29 pregnant women with uncomplicated labor was serially analyzed by flowcytometry at delivery and at 1.5, 6, and 12 months after delivery. DC subtypes were characterized as myeloid, lymphoid, and less differentiated (ldDC). Mean fluorescence intensity (MFI) was evaluated for HLA-DR expression for each DC subtype.

RESULTS

The total number and the percentage of DCs at delivery were lower than those at 12 months postpartum. The ldDC fractions were significantly higher at delivery and at 1.5 months than at 12 months postpartum. The MFI of HLA-DR expression on ldDCs at delivery was lower than that at 12 months postpartum. The myeloid-to-lymphoid DC ratio did not differ over the 1-year postpartum period.

CONCLUSION

The maternal alteration in DCs rapidly normalized within 1.5 months, except for the ldDC fraction, which persisted between 1.5 and 6 months after delivery.

Plasmacytoid dendritic cells and CD8 T cells from pregnant women show altered phenotype and function following H1N1/09 infection

BACKGROUND

Pregnant women are a high-risk group during influenza pandemics. In this study we determined whether plasmacytoid dendritic cells (pDCs) and CD8 T cells from pregnant women display altered activity following in vitro infection with 2009 pandemic swine influenza (H1N1/09).

METHODS

Peripheral blood mononuclear cells (PBMCs) were isolated from pregnant (n = 26) and nonpregnant (n = 28) women. DC subtypes were enumerated from PBMCs. PBMCs were infected with H1N1/09 and CD86, human leukocyte antigen-DR (HLA-DR), and programmed death ligand 1/2 (PDL1/2) measured on pDCs. PD receptor 1 (PD1) was measured on CD8 T cells. Interferon-alpha (IFN-α), interleukin-2 (IL-2), tumor necrosis factor-alpha (TNFα), and IFN-gamma were measured from culture supernatant.

RESULTS

pDC (ie, CD303(+)/CD1c(-) PBMCs) percentages were lower in pregnant compared with nonpregnant women (P < .05). Following H1N1/09 infection, pDCs from pregnant women showed higher expression of CD86 (P < .01), HLA-DR (P < .001), and PDL1 (P < .001) compared with nonpregnant women. Expression of PD1 on CD8 T cells was higher during pregnancy (P < .05). Following H1N1/09 infection, PBMCs from pregnant women displayed reduced IFN-α (P < .01), IL-2 (P < .01), and IFN-γ (P < .01) compared with nonpregnant women. Blocking PDL1 during H1N1/09 infection increased these cytokines during pregnancy (P < .05).

CONCLUSION

Altered maternal cellular antiviral activity is implicated in the increased morbidity during pregnancy following influenza pandemics.

Numerical defect of circulating dendritic cell subsets and defective dendritic cell generation from monocytes of patients with advanced melanoma

The behaviour of circulating dendritic cells (DCs) and DC generation from monocytes in melanoma patients during the progression of disease have not been described. We report a significant decrease in the absolute number of total DCs, which mainly affects plasmacytoid DCs in stage IV. Additionally, monocyte-DC generation is less efficient in advanced stages, resulting in DCs that exhibit increased phagocytic capacity, potentially indicating a less mature state. These findings elucidate aspects of basic tumour-mediated immunosuppression, which may have implications for immunotherapeutic approaches, suggesting that the selection of patients for immunotherapy should also be made on the basis of their immune status.

The Placenta in Toxicology. Part II

During pregnancy, the maternal immune system is challenged by the semiallogeneic fetus, which must be tolerated without compromising fetal or maternal health. This review updates the systemic and local immune changes taking place during human pregnancy, including some examples in rodents. Systemic changes are induced by contact of maternal blood with placental factors and include enhanced innate immunity with increased activation of granulocytes and nonclassical monocytes. Although a bias toward T helper (Th2) and regulatory T cell (Treg) immunity has been associated with healthy pregnancy, the relationship between different circulating Th cell subsets is not straightforward. Instead, these adaptations appear most evidently at the fetal–maternal interface, where for instance Tregs are enriched and promote fetal tolerance. Also innate immune cells, that is, natural killer cells and macrophages, are enriched, constituting the majority of decidual leukocytes. These cells not only contribute to immune regulation but also aid in establishing the placenta by promoting trophoblast recruitment and angiogenesis. Thus, proper interaction between leukocytes and placental trophoblasts is necessary for normal placentation and immune adaptation. Consequently, spontaneous maladaptation or interference of the immune system with toxic substances may be important contributing factors for the development of pregnancy complications such as preeclampsia, preterm labor, and recurrent miscarriages.

Enumeration of human peripheral blood dendritic cells throughout the life

Human aging is associated with immunosenescence, a process characterized by alterations in numerical and functional features of immune system components. Dendritic cells (DCs) are the main antigen-presenting cells, playing a pivotal role in adaptive and innate immunity. Therefore, we investigated the distribution of human circulating DCs throughout the life, in order to contribute to the knowledge of the physiological background underlying the aging of immune system. Cytofluorimetric analysis of peripheral blood samples by all-aged healthy population showed a significant decrease of circulating DCs and of their two main subsets among age. This reduction was limited to the plasmacytoid cell subtype when young and old subjects were analyzed separately. The analysis of circulating Treg cell number in a cohort of the subjects showed a significant reduction with increasing age and a positive significant correlation to myeloid or plasmacytoid absolute numbers. In conclusion, this work provides a large set of data of normal reference values of peripheral blood dendritic cells in healthy population suitable for comparative clinical studies concerning pathological immune dysfunctions.

Dendritic cells in the pathogenesis and treatment of human diseases: a Janus Bifrons?

Dendritic cells (DCs) represent the bridging cell compartment between a variety of nonself antigens (i.e., microbial, cancer and vaccine antigens) and adaptive immunity, orchestrating the quality and potency of downstream immune responses. Because of the central role of DCs in the generation and regulation of immunity, the modulation of DC function in order to shape immune responses is gaining momentum. In this respect, recent advances in understanding DC biology, as well as the required molecular signals for induction of T-cell immunity, have spurred many experimental strategies to use DCs for therapeutic immunological approaches for infections and cancer. However, when DCs lose control over such 'protective' responses - by alterations in their number, phenotype and/or function - undesired effects leading to allergy and autoimmune clinical manifestations may occur. Novel therapeutic approaches have been designed and currently evaluated in order to address DCs and silence these immunopathological processes. In this article we present recent concepts of DC biology and some medical implications in view of therapeutic opportunities.

New adjuvanted vaccines in pregnancy: what is known about their safety?

The recent introduction of oil-in-water emulsions as adjuvants in several pandemic vaccines, such as the H1N1 vaccine, has challenged regulatory authorities to establish their safety in the general population, as well as in specific populations. Pregnant women were advised to be a target group for H1N1 vaccination owing to the risk of this group developing serious complications with this infection. However, the addition of adjuvants to the H1N1 vaccine has initiated a discussion on the safety of adjuvanted vaccines in this special population. Changes in the maternal immune system are essential for acceptance of the fetus and for development of the placenta. The potential effects on pregnancy of interfering with this uniquely adapted immune balance through the induction of proinflammatory reactions such as those induced by adjuvanted vaccines have only been studied rarely. Here, we review the available information and discuss how vaccination may interfere with pregnancy, fetal development and pregnancy outcomes.