Regulatory T Cells Play a Role in a Subset of Idiopathic Preterm Labor/Birth and Adverse Neonatal Outcomes

Preterm Birth in African American Women: A Multi-Omic Pilot Study in Early Pregnancy

Preterm birth (PTB; <37 weeks completed gestation) is a devastating problem affecting over 13 million live births worldwide. In the U.S., African Americans experience significantly higher rates of PTB compared to non-Hispanic Whites. PTB disparities have been linked to social determinants of health (e.g., socioeconomic status, discrimination). However, the biological underpinnings related to these associations are unclear. DNA methylation (DNAm) is subject to environmental influences, and DNAm modifications are known to affect gene expression. Using a multi-omic approach, we examined differences in combined DNA methylation (DNAm) and messenger RNA (mRNA) transcriptomic data from 20 pregnant African American women (12 PTB; 8 term birth) early in pregnancy (8-18 weeks gestation). We found that the HLA-DQB2 gene was both differentially methylated (cg12296550; p = .02) and differentially expressed (p = .014; log2FC = 2.5) between women with PTB and term birth. Gene expression analysis showed HLA-DQB2 and HLA-DRB4 (p = .028; log2FC = -3.6) were the two most highly expressed genes. HLA-DQB2 expressed higher in PTB and HLA-DRB4 expressed higher in term birth. However, no genes remained significant (p < .05) after Bonferroni correction. HLA-DRB4 and AKR1C1 were identified as a potential biomarkers in dimensionality reduction models and are also important to immune function and allogenic breakdown. Altered gene expression may lead to inflammatory imbalances or allogenic intolerance resulting in PTB. This study provides proof-of-concept evidence for the feasibility and importance of future multi-omics studies with larger populations to further explore the genes and pathways identified here.

The single-cell immune profile throughout gestation and its potential value for identifying women at risk for spontaneous preterm birth

Precisely timed immune adaptations, observed in the maternal circulation, underpin the notion of an immune clock of human pregnancy that supports its successful progression and completion at delivery. This immune clock is divided into three immunological phases, with the first phase starting at the time of conception and implantation, shifting into the second phase that supports homeostasis and tolerance throughout pregnancy, and culminating in the last phase of labor and parturition. Disruptions of this immune clock are reported in pregnancy complications such as spontaneous preterm birth. However, our understanding of the immune clock preceding spontaneous preterm birth remains scattered. In this review, we describe the chronology of maternal immune cell adaptations during healthy pregnancies and highlight its disruption in spontaneous preterm birth. With a focus on single-cell cytometric, proteomic and transcriptomic approaches, we review recent studies of term and spontaneous preterm pregnancies and discuss the need for future prospective studies aimed at tracking pregnancies longitudinally on a multi-omic scale. Such studies will be critical in determining whether spontaneous preterm pregnancies progress at an accelerated pace or follow a preterm-intrinsic pattern when compared to those delivered at term.

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

BACKGROUND

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

OBJECTIVE

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

STUDY DESIGN

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

RESULTS

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

CONCLUSION

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

The loss of dNK1/2 and EVT1 cells at the maternal-fetal interface is associated with recurrent miscarriage†

Recurrent miscarriage is a chronic and heterogeneous pregnancy disorder lacking effective treatment. Alterations at the maternal-fetal interface are commonly observed in recurrent miscarriage, with the loss of certain cell subpopulations believed to be a key cause. Through single-cell sequencing of recurrent miscarriage patients and healthy donors, we aim to identify aberrancy of cellular features in recurrent miscarriage tissues, providing new insights into the research. Natural killer cells, the most abundant immune cells in the decidua, are traditionally classified into dNK1, dNK2, and dNK3. In this study, we identified a new subset, dNK1/2, absent in recurrent miscarriage tissues. This subset was named because it expresses biomarkers of both dNK1 and dNK2. With further analysis, we discovered that dNK1/2 cells play roles in immunoregulation and cytokine secretion. On the villous side of the interface, a notable decrease of extravillous trophoblast cells was identified in recurrent miscarriage tissues. We clustered extravillous trophoblasts into EVT1 (absent in recurrent miscarriage) and EVT2 (retained in recurrent miscarriage). Pseudotime analysis revealed distinct differentiation paths, identifying CCNB1, HMGB1, and NPM1 as EVT1 biomarkers. Additionally, we found that EVT1 is involved in the regulation of cell death, while EVT2 exhibited more angiogenic activity. Cell communication analysis revealed that interaction between EVT1 and dNK1/2 mediates chemotaxis and endothelial cell regulation, crucial for spiral artery remodeling. The loss of this interaction may impair decidualization, which is associated with recurrent miscarriage. In summary, we propose that the loss of dNK1/2 and EVT1 cells is a significant pathological feature of recurrent miscarriage.

SUMMARY SENTENCE

The communication between EVT1 and dNK1/2 mediated the chemotaxis of EVT1 and facilitated regulation of endothelial cell death, initiating spiral artery remodeling. The loss of this specific cellular interaction may result in impaired decidualization, leading to recurrent miscarriage.

Pre-pregnancy obesity is associated with an altered maternal metabolome and reduced Flt3L expression in preterm birth

Mechanisms linking pre-pregnancy obesity to increased preterm birth risk are unclear. Here, we examined the impact of pre-pregnancy obesity on metabolites, Fms-related tyrosine kinase 3 ligand (Flt3L), and proinflammatory cytokine profiles in preterm birth. We used cytokine bead array, ELISA and Gas Chromatography-Mass Spectrometry (GC-MS) to determine cytokine and metabolite profiles in maternal and cord blood samples from 124 pregnant women in Australia, who gave birth at term (n = 86) or preterm (n = 38). Besides the expected variations in birth weight and gestational age, all demographic characteristics, including pre-pregnancy body mass index, were similar between the term and preterm birth groups. Mothers in the preterm birth group had reduced Flt3L (P = 0.002) and elevated IL-6 (P = 0.002) compared with term birthing mothers. Among mothers who gave birth preterm, those with pre-pregnancy obesity had lower Flt3L levels (P = 0.02) compared with lean mothers. Flt3L and IL-6 were similar in cord blood across both groups, but TNFα levels (P = 0.02) were reduced in preterm newborns. Metabolomic analysis revealed significant shifts in essential metabolites in women with pre-pregnancy obesity, some of which were linked to preterm births. Our findings suggest that maternal pre-pregnancy obesity alters the metabolome and reduces Flt3L expression, potentially increasing risk of preterm birth.

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

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

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

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

To boldly go where no microRNAs have gone before: spaceflight impact on risk for small-for-gestational-age infants

In the era of renewed space exploration, comprehending the effects of the space environment on human health, particularly for deep space missions, is crucial. While extensive research exists on the impacts of spaceflight, there is a gap regarding female reproductive risks. We hypothesize that space stressors could have enduring effects on female health, potentially increasing risks for future pregnancies upon return to Earth, particularly related to small-for-gestational-age (SGA) fetuses. To address this, we identify a shared microRNA (miRNA) signature between SGA and the space environment, conserved across humans and mice. These miRNAs target genes and pathways relevant to diseases and development. Employing a machine learning approach, we identify potential FDA-approved drugs to mitigate these risks, including estrogen and progesterone receptor antagonists, vitamin D receptor antagonists, and DNA polymerase inhibitors. This study underscores potential pregnancy-related health risks for female astronauts and proposes pharmaceutical interventions to counteract the impact of space travel on female health.

The vaginal immunoproteome for the prediction of spontaneous preterm birth: A retrospective longitudinal study

Background

Preterm birth is the leading cause of neonatal morbidity and mortality worldwide. Most cases of preterm birth occur spontaneously and result from preterm labor with intact (spontaneous preterm labor [sPTL]) or ruptured (preterm prelabor rupture of membranes [PPROM]) membranes. The prediction of spontaneous preterm birth (sPTB) remains underpowered due to its syndromic nature and the dearth of independent analyses of the vaginal host immune response. Thus, we conducted the largest longitudinal investigation targeting vaginal immune mediators, referred to herein as the immunoproteome, in a population at high risk for sPTB.

Methods

Vaginal swabs were collected across gestation from pregnant women who ultimately underwent term birth, sPTL, or PPROM. Cytokines, chemokines, growth factors, and antimicrobial peptides in the samples were quantified via specific and sensitive immunoassays. Predictive models were constructed from immune mediator concentrations.

Results

Throughout uncomplicated gestation, the vaginal immunoproteome harbors a cytokine network with a homeostatic profile. Yet, the vaginal immunoproteome is skewed toward a pro-inflammatory state in pregnant women who ultimately experience sPTL and PPROM. Such an inflammatory profile includes increased monocyte chemoattractants, cytokines indicative of macrophage and T-cell activation, and reduced antimicrobial proteins/peptides. The vaginal immunoproteome has improved predictive value over maternal characteristics alone for identifying women at risk for early (<34 weeks) sPTB.

Conclusions

The vaginal immunoproteome undergoes homeostatic changes throughout gestation and deviations from this shift are associated with sPTB. Furthermore, the vaginal immunoproteome can be leveraged as a potential biomarker for early sPTB, a subset of sPTB associated with extremely adverse neonatal outcomes.

Funding

This research was conducted by the Perinatology Research Branch, Division of Obstetrics and Maternal-Fetal Medicine, Division of Intramural Research, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, U.S. Department of Health and Human Services (NICHD/NIH/DHHS) under contract HHSN275201300006C. ALT, KRT, and NGL were supported by the Wayne State University Perinatal Initiative in Maternal, Perinatal and Child Health.

Predicting Spontaneous Preterm Birth Using the Immunome

Throughout pregnancy, the maternal peripheral circulation contains valuable information reflecting pregnancy progression, detectable as tightly regulated immune dynamics. Local immune processes at the maternal-fetal interface and other reproductive and non-reproductive tissues are likely to be the pacemakers for this peripheral immune "clock." This cellular immune status of pregnancy can be leveraged for the early risk assessment and prediction of spontaneous preterm birth (sPTB). Systems immunology approaches to sPTB subtypes and cross-tissue (local and peripheral) interactions, as well as integration of multiple biological data modalities promise to improve our understanding of preterm birth pathobiology and identify potential clinically actionable biomarkers.

Immune cells at the feto-maternal interface: Comprehensive characterization and insights into term labor

Immune cells at the feto-maternal interface play an important role in pregnancy; starting at implantation, maintenance of pregnancy, and parturition. The role of decidual immune cells in induction of labor still needs to be understood. Published reports on this topic show heterogeneity in methods of cell isolation, assay, analysis and cellular characterization making it difficult to collate available information in order to understand the contribution of immune cells at term leading to parturition. In the present study, available literature was reviewed to study the differences in immune cells between the decidua basalis and decidua parietalis, as well as between immune cells in term and preterm labor. Additionally, immune cells at the decidua parietalis were isolated from term not in labor (TNL) or term in labor (TL) samples and characterized via flow cytometry using a comprehensive, high-dimensional antibody panel. This allowed a full view of immune cell differences without combining multiple studies, which must include variation in isolation and analysis methods, for more conclusive data. The ratio of cells found in decidua parietalis in this study generally matched those reported in the literature, although we report a lower percentage of natural killer (NK) cells at term. We report that CD4 expression on CD8- NK cells decreased in term labor compared to not in labor samples, suggesting that natural killer cells may be migrating to other sites during labor. Also, we report a decrease in CD38 expression on CD8+ CD57+ T cells in labor, indicative of cytotoxic T cell senescence. Our study provides a comprehensive status of immune cells at the decidua-chorion interface at term.

CD4+ T cell heterogeneity in gestational age and preeclampsia using single-cell RNA sequencing

A balance between pro-inflammatory decidual CD4+ T cells and FOXP3+ regulatory T cells (FOXP3+ Tregs) is important for maintaining fetomaternal tolerance. Using single-cell RNA-sequencing and T cell receptor repertoire analysis, we determined that diversity and clonality of decidual CD4+ T cell subsets depend on gestational age. Th1/Th2 intermediate and Th1 subsets of CD4+ T cells were clonally expanded in both early and late gestation, whereas FOXP3+ Tregs were clonally expanded in late gestation. Th1/Th2 intermediate and FOXP3+ Treg subsets showed altered gene expression in preeclampsia (PE) compared to healthy late gestation. The Th1/Th2 intermediate subset exhibited elevated levels of cytotoxicity-related gene expression in PE. Moreover, increased Treg exhaustion was observed in the PE group, and FOXP3+ Treg subcluster analysis revealed that the effector Treg like subset drove the Treg exhaustion signatures in PE. The Th1/Th2 intermediate and effector Treg like subsets are possible inflammation-driving subsets in PE.

Preterm birth, a consequence of immune deviation mediated hyperinflammation

Preterm birth represents a multifaceted syndrome with intricacies still present in our comprehension of its etiology. In the context of a semi-allograft, the prosperity from implantation to pregnancy to delivery hinges on the establishment of a favorable maternal-fetal immune microenvironment and a successful trilogy of immune activation, immune tolerance and then immune activation transitions. The occurrence of spontaneous preterm birth could be related to abnormalities within the immune trilogy, stemming from deviation in maternal and fetal immunity. These immune deviations, characterized by insufficient immune tolerance and early immune activation, ultimately culminated in an unsustainable pregnancy. In this review, we accentuated the role of both innate and adaptive immune reason in promoting spontaneous preterm birth, reviewed the risk of preterm birth from vaginal microbiome mediated by immune changes and the potential of vaginal microbiomes and metabolites as a new predictive marker, and discuss the changes in the role of progesterone and its interaction with immune cells in a preterm birth population. Our objective was to contribute to the growing body of knowledge in the field, shedding light on the immunologic reason of spontaneous preterm birth and effective biomarkers for early prediction, providing a roadmap for forthcoming investigations.

Immunological regulation and the role of autophagy in preeclampsia

Autophagy is a bulk degradation system that maintains cellular homeostasis by producing energy and/or recycling excess proteins. During early placentation, extravillous trophoblasts invade the decidua and uterine myometrium, facing maternal immune cells, which participate in the immune suppression of paternal and fetal antigens. Regulatory T cells will likely increase in response to a specific antigen before and during early pregnancy. Insufficient expansion of antigen-specific Treg cells, which possess the same T cell receptor, is associated with the pathophysiology of preeclampsia, suggesting sterile systemic inflammation. Autophagy is involved in reducing inflammation through the degradation of inflammasomes and in the differentiation and function of regulatory T cells. Autophagy dysregulation induces protein aggregation in trophoblasts, resulting in placental dysfunction. In this review, we discuss the role of regulatory T cells in normal pregnancies. In addition, we discuss the association between autophagy and regulatory T cells in the development of preeclampsia based on reports on the role of autophagy in autoimmune diseases.

Association between Preconception Dietary Fiber Intake and Preterm Birth: The Japan Environment and Children's Study

Preterm birth (PTB) is a leading cause of neonatal morbidity and mortality. Therefore, this study aimed to determine whether preconception dietary fiber intake is associated with PTB. This was a prospective cohort Japan Environmental and Children's Study (JECS). The study population comprised 85,116 singleton live-birth pregnancies from the JECS database delivered between 2011 and 2014. The participants were categorized into five groups based on their preconception dietary fiber intake quintiles (Q1 and Q5 were the lowest and highest groups, respectively). Multiple logistic regression analysis was performed to determine the association between preconception dietary fiber intake and PTB. Multiple logistic regression analysis revealed that the risk for PTB before 34 weeks was lower in the Q3, Q4, and Q5 groups than in the Q1 group (Q3: adjusted odds ratio [aOR] 0.78, 95% confidence interval [CI] 0.62-0.997; Q4: aOR 0.74, 95% CI 0.57-0.95; Q5: aOR 0.68, 95% CI 0.50-0.92). However, there was no significant difference between preconception dietary fiber intake and PTB before 37 weeks. In conclusion, higher preconception dietary fiber intake correlated with a reduced the risk for PTB before 34 weeks. Therefore, new recommendations on dietary fiber intake as part of preconception care should be considered.

A disrupted FOXP3 transcriptional signature underpins systemic regulatory T cell insufficiency in early pregnancy failure

Regulatory T (Treg) cell defects are implicated in disorders of embryo implantation and placental development, but the origins of Treg cell dysfunction are unknown. Here, we comprehensively analyzed the phenotypes and transcriptional profile of peripheral blood Treg cells in individuals with early pregnancy failure (EPF). Compared to fertile subjects, EPF subjects had 32% fewer total Treg cells and 54% fewer CD45RA+CCR7+ naive Treg cells among CD4+ T cells, an altered Treg cell phenotype with reduced transcription factor FOXP3 and suppressive marker CTLA4 expression, and lower Treg:Th1 and Treg:Th17 ratios. RNA sequencing demonstrated an aberrant gene expression profile, with upregulation of pro-inflammatory genes including CSF2, IL4, IL17A, IL21, and IFNG in EPF Treg cells. In silico analysis revealed 25% of the Treg cell dysregulated genes are targets of FOXP3. We conclude that EPF is associated with systemic Treg cell defects arising due to disrupted FOXP3 transcriptional control and loss of lineage fidelity.

Obstetric and neonatal outcomes following taxane use during pregnancy: a systematic review

BACKGROUND

The use of taxanes following the first trimester of pregnancy is endorsed by current clinical guidelines. However, evidence regarding their safety in terms of obstetric and neonatal outcomes is limited.

METHODS

A comprehensive literature search was performed using the MEDLINE, CENTRAL and Web of Sciences databases from their inception up to 12/16/2022. Eligibility criteria included gestational taxane use, presentation of original findings, and individual case data presented. A descriptive statistical analysis was undertaken.

RESULTS

A total of 159 patients treated with taxane-containing regimens during pregnancy were identified, resulting in 162 fetuses exposed in utero. The majority of patients had breast cancer (n = 88; 55.3%) or cervical cancer (n = 45; 28.3%). The most commonly employed taxane was paclitaxel (n = 131; 82.4%). A total of 111 (69.8%) patients were also treated with other cytotoxic drugs during pregnancy, including platinum salts (n = 70; 63.0%) and doxorubicin/cyclophosphamide (n = 20; 18.0%). While most patients received taxanes during the second trimester of pregnancy (n = 79; 70.0%), two were exposed to taxanes in the first trimester. Obstetric outcomes were reported in 105 (66.0%) cases, with the most frequent adverse events being preterm contractions or premature rupture of membranes (n = 12; 11.4%), pre-eclampsia/HELLP syndrome (n = 6; 5.7%), and oligohydramnios/anhydramnios (n = 6; 5.7%). All cases with pregnancy outcome available resulted in live births (n = 132). Overall, 72 (54.5%) neonates were delivered preterm, 40 (30.3%) were classified as small for gestational age (SGA), and 2 (1.5%) had an Apgar score of < 7 at 5 min. Perinatal complications included acute respiratory distress syndrome (n = 14; 10.6%), hyperbilirubinemia (n = 5; 3.8%), and hypoglycemia (n = 2; 1.5%). In addition, 7 (5.3%) cases of congenital malformations were reported. At a median follow-up of 16 months, offspring health status was available for 86 (65.2%), of which 13 (15.1%) had a documented complication, including delayed speech development, recurrent otitis media, and acute myeloid leukemia.

CONCLUSIONS

Taxanes appear to be safe following the first trimester of pregnancy, with obstetric and fetal outcomes being similar to those observed in the general obstetric population. Future studies should aim to determine the most effective taxane regimen and dosage for use during gestation, with a specific focus on treatment safety.

Host-microbiome interactions in distinct subsets of preterm labor and birth

Preterm birth, the leading cause of perinatal morbidity, often follows premature labor, a syndrome whose prevention remains a challenge. To better understand the relationship between premature labor and host-microbiome interactions, we conducted a mechanistic investigation using three preterm birth models. We report that intra-amniotic delivery of LPS triggers inflammatory responses in the amniotic cavity and cervico-vaginal microenvironment, causing vaginal microbiome changes and signs of active labor. Intra-amniotic IL-1α delivery causes a moderate inflammatory response in the amniotic cavity but increasing inflammation in the cervico-vaginal space, leading to vaginal microbiome disruption and signs of active labor. Conversely, progesterone action blockade by RU-486 triggers local immune responses accompanying signs of active labor without altering the vaginal microbiome. Preterm labor facilitates ascension of cervico-vaginal bacteria into the amniotic cavity, regardless of stimulus. This study provides compelling mechanistic insights into the dynamic host-microbiome interactions within the cervico-vaginal microenvironment that accompany premature labor and birth.

Memory regulatory T cells in pregnancy

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

Regulatory T cell adoptive transfer alters uterine immune populations, increasing a novel MHC-IIlow macrophage associated with healthy pregnancy

Intrauterine fetal demise (IUFD) - fetal loss after 20 weeks - affects 6 pregnancies per 1,000 live births in the United States, and the majority are of unknown etiology. Maternal systemic regulatory T cell (Treg) deficits have been implicated in fetal loss, but whether mucosal immune cells at the maternal-fetal interface contribute to fetal loss is under-explored. We hypothesized that the immune cell composition and function of the uterine mucosa would contribute to the pathogenesis of IUFD. To investigate local immune mechanisms of IUFD, we used the CBA mouse strain, which naturally has mid-late gestation fetal loss. We performed a Treg adoptive transfer and interrogated both pregnancy outcomes and the impact of systemic maternal Tregs on mucosal immune populations at the maternal-fetal interface. Treg transfer prevented fetal loss and increased an MHC-IIlow population of uterine macrophages. Single-cell RNA-sequencing was utilized to precisely evaluate the impact of systemic Tregs on uterine myeloid populations. A population of C1q+, Trem2+, MHC-IIlow uterine macrophages were increased in Treg-recipient mice. The transcriptional signature of this novel uterine macrophage subtype is enriched in multiple studies of human healthy decidual macrophages, suggesting a conserved role for these macrophages in preventing fetal loss.

Immunosequencing and Profiling of T Cells at the Maternal-Fetal Interface of Women with Preterm Labor and Chronic Chorioamnionitis

T cells are implicated in the pathophysiology of preterm labor and birth, the leading cause of neonatal morbidity and mortality worldwide. Specifically, maternal decidual T cells infiltrate the chorioamniotic membranes in chronic chorioamnionitis (CCA), a placental lesion considered to reflect maternal anti-fetal rejection, leading to preterm labor and birth. However, the phenotype and TCR repertoire of decidual T cells in women with preterm labor and CCA have not been investigated. In this study, we used phenotyping, TCR sequencing, and functional assays to elucidate the molecular characteristics and Ag specificity of T cells infiltrating the chorioamniotic membranes in women with CCA who underwent term or preterm labor. Phenotyping indicated distinct enrichment of human decidual effector memory T cell subsets in cases of preterm labor with CCA without altered regulatory T cell proportions. TCR sequencing revealed that the T cell repertoire of CCA is characterized by increased TCR richness and decreased clonal expansion in women with preterm labor. We identified 15 clones associated with CCA and compared these against established TCR databases, reporting that infiltrating T cells may possess specificity for maternal and fetal Ags, but not common viral Ags. Functional assays demonstrated that choriodecidual T cells can respond to maternal and fetal Ags. Collectively, our findings provide, to our knowledge, novel insight into the complex processes underlying chronic placental inflammation and further support a role for effector T cells in the mechanisms of disease for preterm labor and birth. Moreover, this work further strengthens the contribution of adaptive immunity to the syndromic nature of preterm labor and birth.

Reproductive outcomes after pregnancy-induced displacement of preexisting microchimeric cells

Pregnancy confers partner-specific protection against complications in future pregnancy that parallel persistence of fetal microchimeric cells (FMcs) in mothers after parturition. We show that preexisting FMcs become displaced by new FMcs during pregnancy and that FMc tonic stimulation is essential for expansion of protective fetal-specific forkhead box P3 (FOXP3)-positive regulatory T cells (Treg cells). Maternal microchimeric cells and accumulation of Treg cells with noninherited maternal antigen (NIMA) specificity are similarly overturned in daughters after pregnancy, highlighting a fixed microchimeric cell niche. Whereas NIMA-specific tolerance is functionally erased by pregnancy, partner-specific resiliency against pregnancy complications persists in mothers despite paternity changes in intervening pregnancy. Persistent fetal tolerance reflects FOXP3 expression plasticity, which allows mothers to more durably remember their babies, whereas daughters forget their mothers with new pregnancy-imprinted immunological memories.

A key role for NLRP3 signaling in preterm labor and birth driven by the alarmin S100B

Preterm birth remains the leading cause of neonatal morbidity and mortality worldwide. A substantial number of spontaneous preterm births occur in the context of sterile intra-amniotic inflammation, a condition that has been mechanistically proven to be triggered by alarmins. However, sterile intra-amniotic inflammation still lacks treatment. The NLRP3 inflammasome has been implicated in sterile intra-amniotic inflammation; yet, its underlying mechanisms, as well as the maternal and fetal contributions to this signaling pathway, are unclear. Herein, by utilizing a translational and clinically relevant model of alarmin-induced preterm labor and birth in Nlrp3-/- mice, we investigated the role of NLRP3 signaling by using imaging and molecular biology approaches. Nlrp3 deficiency abrogated preterm birth and the resulting neonatal mortality induced by the alarmin S100B by impeding the premature activation of the common pathway of labor as well as by dampening intra-amniotic and fetal inflammation. Moreover, Nlrp3 deficiency altered leukocyte infiltration and functionality in the uterus and decidua. Last, embryo transfer revealed that maternal and fetal Nlrp3 signaling contribute to alarmin-induced preterm birth and neonatal mortality, further strengthening the concept that both individuals participate in the complex process of preterm parturition. These findings provide novel insights into sterile intra-amniotic inflammation, a common etiology of preterm labor and birth, suggesting that the adverse perinatal outcomes resulting from prematurity can be prevented by targeting NLRP3 signaling.

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

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

An Evaluation of T-Regulatory Cells and Inflammatory Cytokines in Preeclampsia

Background Preeclampsia (PE) is a prenatal hypertension condition with unknown aetiology which is one of the leading causes of maternal morbidity and mortality, premature delivery, and foetal and neonatal mortality. T-regulatory cells (T-regs) are the specific subsets of T-lymphocytes that play a key role in the mechanisms of maternal-foetal tolerance, contributing to an effective immunological role in protecting the allogenic foetus during pregnancy and preventing pregnancy-related complications. This study evaluated the T-regs in PE and correlated the T-regs with inflammatory markers in the pathophysiology and for early diagnosis of PE. Methods After clearance from Institutional Ethics Committee, the participants were recruited from the Department of Obstetrics and Gynaecology. Three study groups were included a) normal reproductive age group women b) normal pregnant women c) PE pregnant women. 5 ml of venous blood was collected from each participant. Biochemical and haematological parameters estimation was done in Hospital's central laboratory. T-regs (CD4, CD25, FOXP3) were assessed using a flow-cytometer, and inflammatory markers (TGF-β1, IL-6, hsCRP) were assessed by ELISA and Beckman Coulter autoanalyzer in the Department of Biochemistry, AIIMS, Bhubaneswar. Results We found that the levels of CD4+CD25+ T-regs were lower in PE than in normal pregnancy, but this difference was not statistically significant (p = 0.349). The levels of CD4+FOXP3+ T-regs in PE were significantly lower compared to both normal pregnant women (p = 0.001) and normal non-pregnant women (p = 0.001). In comparison to women with PE, the levels of TGF-β1 were significantly higher in normal non-pregnant women (p = 0.020) and were higher, although not significantly so, in normal pregnant women (p = 0.994). The levels of IL-6 in women with PE were significantly higher than in normal pregnant women (p = 0.01) and normal non-pregnant women (p = 0.048). The levels of hsCRP in women with PE were significantly higher than in normal pregnant women (p = 0.045) and were higher, but not statistically significant, compared to normal non-pregnant women (p = 0.094). Conclusion The results of the study, showing a decrease in T-regs and an increase in inflammatory markers like TGF-β1, IL-6, and hsCRP levels in PE, have potential implications for the early diagnosis and management of the condition. Incorporating assessments of CD4+FOXP3+ T-regs and inflammatory markers into screening protocols, along with regular prenatal care and monitoring, can aid in the timely detection and implementation of appropriate management strategies. By intervening early, the risks associated with PE can be reduced, optimizing both maternal and fetal health.

Proteogenomic and V(D)J Analysis of Human Decidual T Cells Highlights Unique Transcriptional Programming and Clonal Distribution

Immunological tolerance toward the semiallogeneic fetus is one of many maternal adaptations required for a successful pregnancy. T cells are major players of the adaptive immune system and balance tolerance and protection at the maternal-fetal interface; however, their repertoire and subset programming are still poorly understood. Using emerging single-cell RNA sequencing technologies, we simultaneously obtained transcript, limited protein, and receptor repertoire at the single-cell level, from decidual and matched maternal peripheral human T cells. The decidua maintains a tissue-specific distribution of T cell subsets compared with the periphery. We find that decidual T cells maintain a unique transcriptome programming, characterized by restraint of inflammatory pathways by overexpression of negative regulators (DUSP, TNFAIP3, ZFP36) and expression of PD-1, CTLA-4, TIGIT, and LAG3 in some CD8 clusters. Finally, analyzing TCR clonotypes demonstrated decreased diversity in specific decidual T cell populations. Overall, our data demonstrate the power of multiomics analysis in revealing regulation of fetal-maternal immune coexistence.

The increased cfRNA of TNFSF4 in peripheral blood at late gestation and preterm labor: its implication as a noninvasive biomarker for premature delivery

Introduction

Given the important roles of immune tolerance and inflammation in both preterm and term labor, some inflammation-related genes could be related to the initiation of labor, even preterm labor. Inspection of cell-free RNA (cfRNA) engaged in inflammation in maternal blood may represent the varied gestational age and may have significant implications for the development of noninvasive diagnostics for preterm birth.

Methods

To identify potential biomarkers of preterm birth, we investigated the cfRNA and exosomal miRNA in the peripheral blood of pregnant women at different gestational ages that undergo term labor or preterm labor. 17 inflammatory initiation-related cfRNAs were screened by overlapping with the targets of decreasing miRNAs during gestation and highly expressed cfRNAs at late gestation in maternal blood. To reveal the origins and mechanisms of these screened cfRNAs, the datasets of single-cell RNA sequencing from peripheral blood mononuclear cells of pregnant women, the fetal lung, and the placenta across different gestational ages were analyzed.

Results

During late gestation, TNFSF4 expression increased exclusively in pro-inflammatory macrophages of maternal blood, whereas its receptor, TNFRSF4, increased expression in T cells from the decidua, which suggested the potential cell-cell communication of maternally-originated pro-inflammatory macrophages with the decidual T cells and contributed to the initiation of labor. Additionally, the cfRNA of TNFSF4 was also increased in preterm labor compared to term labor in the validation cohorts. The EIF2AK2 and TLR4 transcripts were increased in pro-inflammatory macrophages from both fetal lung and placenta but not in those from maternal mononuclear cells at late gestation, suggesting these cfRNAs are possibly derived from fetal tissues exclusively. Moreover, EIF2AK2 and TLR4 transcripts were found highly expressed in the pro-inflammatory macrophages from decidua as well, which suggested these specific fetal-origin macrophages may function at the maternal-fetal interface to stimulate uterine contractions, which have been implicated as the trigger of parturition and preterm labor.

Discussion

Taken together, our findings not only revealed the potential of peripheral TNFSF4 as a novel cfRNA biomarker for noninvasive testing of preterm labor but further illustrated how maternal and fetal signals coordinately modulate the inflammatory process at the maternal-fetal interface, causing the initiation of term or preterm labor.

Pregnancy-specific responses to COVID-19 revealed by high-throughput proteomics of human plasma

BACKGROUND

Pregnant women are at greater risk of adverse outcomes, including mortality, as well as obstetrical complications resulting from COVID-19. However, pregnancy-specific changes that underlie such worsened outcomes remain unclear.

METHODS

Plasma samples were collected from pregnant women and non-pregnant individuals (male and female) with (n = 72 pregnant, 52 non-pregnant) and without (n = 29 pregnant, 41 non-pregnant) COVID-19. COVID-19 patients were grouped as asymptomatic, mild, moderate, severe, or critically ill according to NIH classifications. Proteomic profiling of 7,288 analytes corresponding to 6,596 unique protein targets was performed using the SOMAmer platform.

RESULTS

Herein, we profile the plasma proteome of pregnant and non-pregnant COVID-19 patients and controls and show alterations that display a dose-response relationship with disease severity; yet, such proteomic perturbations are dampened during pregnancy. In both pregnant and non-pregnant state, the proteome response induced by COVID-19 shows enrichment of mediators implicated in cytokine storm, endothelial dysfunction, and angiogenesis. Shared and pregnancy-specific proteomic changes are identified: pregnant women display a tailored response that may protect the conceptus from heightened inflammation, while non-pregnant individuals display a stronger response to repel infection. Furthermore, the plasma proteome can accurately identify COVID-19 patients, even when asymptomatic or with mild symptoms.

CONCLUSION

This study represents the most comprehensive characterization of the plasma proteome of pregnant and non-pregnant COVID-19 patients. Our findings emphasize the distinct immune modulation between the non-pregnant and pregnant states, providing insight into the pathogenesis of COVID-19 as well as a potential explanation for the more severe outcomes observed in pregnant women.

Sex-specific differences in T-cell immune dysregulation and aberrant response to inflammatory stimuli in offspring exposed to maternal chronic inflammation

PROBLEMS

Maternal chronic inflammation (MI) can adversely affect offspring's immune development resulting in dysregulation of splenic T cells. Interleukin 1 beta (IL-1β) contributes to mediating inflammation in the placenta to induce fetal toxicity and cause long-term postnatal sequelae. In this study, we investigated how MI affects the T-cell immune development from the fetal to the neonatal period and how offspring responded to postnatal IL-1β challenge when exposed to an adverse intrauterine environment. We also extend these studies to examine the sex-specific differences.

METHODS OF STUDY

Time-pregnant CD1 dams were administrated with four consecutive injections of mouse recombinant Interleukin-1β (rIL-1β) or phosphate-buffered saline (PBS) from embryonic day (E)14 to E17. Pups were treated with rIL-1β or PBS at postnatal day (PND)11 (pre-weaning) or PND24 (post-weaning). Pups' splenic immune cells were isolated and then characterized using flow cytometry.

RESULTS

At PND12, no differences were observed either in Ctrl or MI offspring. At PND25, we observed elevated amount of CD8⁺ T cells, descending CD4⁺ /CD8⁺ and Treg/Teff ratio in MI offspring. Pre-weaning rIL-1β administration did not affect T-cell subpopulation in Ctrl pups while post-weaning rIL-1β administration increased T cells and CD8⁺ T cells and decreased CD4⁺ /CD8⁺ and Treg/Teff ratio in Ctrl offspring. Furthermore, pre-weaning rIL-1β administration decreased the frequency of T cells and Treg/Teff ratio in MI pups while post-weaning rIL-1β administration increased Tregs and Treg/Teff in MI pups. Regarding sex-specific changes, we observed that at PND12, MI females exhibited higher CD4⁺ /CD8⁺ and Treg/Teff ratio than Ctrl females. At PND25, we observed elevated amount of CD8⁺ T cells, descending CD4⁺ /CD8⁺ and Treg/Teff ratio in MI Females, while MI males did not show any changes in T-cell population. Pre-weaning rIL-1β administration decreased T-cell frequency in both MI males and females and decreased Treg/Teff ratio only in MI females. Post-weaning rIL-1β administration increased Tregs and Treg/Teff ratio, and decreased CD4⁺ /CD8⁺ ratio in MI females.

CONCLUSIONS

Prenatal-inflammation-exposed offspring exhibited dysfunctional T-cell immunity and regulatory immune responses to postnatal challenges, showing both sex-specific and age-dependent differences. It could be speculated from our results that experiencing environmental challenges or adverse stimuli during the vulnerable intrauterine period, such as maternal chronic inflammation, stress, preterm birth, and chronic infections, might induce fetal immune reprogramming and potentially cause long-term adverse immune consequences, such as a predisposition to allergic diseases, autoimmune diseases, asthma and pediatric mortality of unknown etiology.

Setting a stage: Inflammation during preeclampsia and postpartum

Preeclampsia (PE) is a leading cause of maternal and fetal mortality worldwide. The immune system plays a critical role in normal pregnancy progression; however, inappropriate inflammatory responses have been consistently linked with PE pathophysiology. This inflammatory phenotype consists of activation of the innate immune system, adaptive immune system, and increased inflammatory mediators in circulation. Moreover, recent studies have shown that the inflammatory profile seen in PE persists into the postpartum period. This manuscript aims to highlight recent advances in research relating to inflammation in PE as well as the inflammation that persists postpartum in women after a PE pregnancy. With the advent of the COVID-19 pandemic, there has been an increase in obstetric disorders associated with COVID-19 infection during pregnancy. This manuscript also aims to shed light on the relationship between COVID-19 infection during pregnancy and the increased incidence of PE in these women.

Dynamics of neuropilin1 (Nrp1)-positive thymus-derived and Nrp1-negative peripherally induced paternal antigen specific regulatory T cells in the uterus and spleen during pregnancy in mice

Paternal antigen-specific regulatory T (PA-Treg) cells suppress the immune response against the fetus. Naturally occurring Treg (nTreg) cells derived from the thymus and peripherally induced Treg (iTreg) cells are functional for sustaining pregnancy. This study aimed to compare the variation in PA-Treg cells between the feto-maternal interface and the spleen and to elucidate the dynamics of nTreg and iTreg cells during the gestational period. PA-Treg cells, defined as Treg cells with paternally derived Mls-1a antigen-specific T cell receptors Vβ6, from allogeneic pregnant mice on days 3.5, 5.5, 11.5, and 18.5 post-coitum (pc) were evaluated by flow cytometry. The percentage of Vβ6⁺ Ki67⁺ PA-Treg cells activated by the paternal antigen increased on day 11.5 pc in the decidua (p < 0.05) compared to non-pregnant mice. On day 18.5 pc, this percentage in the decidua parietalis decreased to the level of the non-pregnant state but was significantly higher (p < 0.05) in the decidua basalis. No changes were observed in the spleens. We used two nTreg cell markers, neuropilin1 (Nrp1) and Helios, to distinguish between nTreg cells and iTreg cells. Nrp1⁺ PA-Treg cell levels decreased in late pregnancy compared to those observed in early pregnancy (day 3.5 pc: 57.14 ± 6.16% vs. day 18.5 pc: 30.43 ± 3.09%; p < 0.05), whereas Helios⁺ cell levels did not change. In conclusion, PA immune tolerance is induced by Nrp1⁺ nTreg cells in early pregnancy and Nrp1-negative Treg cells in late pregnancy.

Association between Pet Ownership and Threatened Abortion in Pregnant Women: The China Birth Cohort Study

Background: The aim of this study was to assess the association between pet ownership and threatened abortion (TA) in pregnant Chinese women. Materials and Methods: We enrolled pregnant women from 18 provinces and autonomous regions across China between November 2017 and December 2020. Participants were grouped based on the presence or absence of pet ownership. Pet owners were further sub-grouped based on the presence or absence of close contact with their pets. Pet species included cats, dogs, and both. Generalised linear mixed models, with province as a random effect, were used to estimate the associations between pet ownership and TA. Results: Pet ownership, whether or not one had close contact with pets, was associated with greater odds of TA (OR: 1.30, 95% CI: 1.21, 1.40). Keeping pet cats (OR: 1.24, 95% CI: 1.11, 1.40), dogs (OR: 1.29, 95% CI: 1.18, 1.41), or both cats and dogs (OR: 1.36, 95% CI: 1.04, 1.68) during pregnancy were all risk factors for TA. We observed significant group differences (p for difference < 0.05) in pre-pregnancy body mass index, education levels, and annual household income. Conclusions: Cat or dog ownership during pregnancy was associated with an increased risk of TA, especially among overweight, less educated, or lower-income participants.

Term and Preterm Birth Initiation Is Associated with the Macrophages Shifting to M1 Polarization in Gestational Tissues in Mice

Inflammation in gestational tissues plays critical role in parturition initiation. We sought to investigate the leukocyte infiltration and cytokine profile in uterine tissues to understand the inflammation during term and preterm labor in the mouse model. Preterm birth was induced by the administration of lipopolysaccharide (LPS) or RU38486. The populations of leukocytes were determined by flow cytometry. Macrophages were the largest population in the myometrium and decidua in late gestation. The macrophage population was significantly changed in the myometrium and decidua from late pregnancy to term labor and significantly changed at LPS- and RU386-induced preterm labor. Neutrophils, T cells, and NKT cells were increased in LPS- and RU38486-induced preterm labor. The above changes were accompanied by the increased expression of cytokines and chemokines. In late gestation, M2 macrophages were the predominant phenotype in gestational tissues. M1 macrophages significantly increased in these tissues at term and preterm labor. IL-6 and NLRP3 expression was significantly increased in macrophages at labor, supporting that macrophages exhibit proinflammatory phenotypes. NLRP3 inflammasome inhibitor MCC950 mainly suppressed macrophage infiltration in the myometrium at term labor and preterm labor. Our data suggest that the M1 polarization of macrophages contributes to inflammation linked to term and preterm labor initiation in gestational tissues.

Pregnancy imparts distinct systemic adaptive immune function

PROBLEM

Pregnancy represents a state of systemic immune activation that is primarily driven by alterations in circulating innate immune cells. Recent studies have suggested that cellular adaptive immune components, T cells and B cells, also undergo changes throughout gestation. However, the phenotypes and functions of such adaptive immune cells are poorly understood. Herein, we utilized high-dimensional flow cytometry and functional assays to characterize T-cell and B-cell responses in pregnant and non-pregnant women.

METHODS

Peripheral blood mononuclear cells from pregnant (n = 20) and non-pregnant (n = 25) women were used for phenotyping of T-cell and B-cell subsets. T-cell proliferation and B-cell activation were assessed by flow cytometry after in vitro stimulation, and lymphocyte cytotoxicity was evaluated by using a cell-based assay. Statistical comparisons were performed with linear mixed-effects models.

RESULTS

Pregnancy was associated with modestly enhanced basal activation of peripheral CD4+ T cells. Both CD4+ and CD8+ T cells from pregnant women showed increased activation-induced proliferation; yet, a reduced proportion of these cells expressed activation markers compared to non-pregnant women. There were no differences in peripheral lymphocyte cytotoxicity between study groups. A greater proportion of B cells from pregnant women displayed memory-like and activated phenotypes, and such cells exhibited higher activation following stimulation.

CONCLUSION

Maternal circulating T cells and B cells display distinct responses during pregnancy. The former may reflect the unique capacity of T cells to respond to potential threats without undergoing aberrant activation, thereby preventing systemic inflammatory responses that can lead to adverse perinatal consequences.

Single-Cell Immunobiology of the Maternal-Fetal Interface

Pregnancy success requires constant dialogue between the mother and developing conceptus. Such crosstalk is facilitated through complex interactions between maternal and fetal cells at distinct tissue sites, collectively termed the "maternal-fetal interface." The emergence of single-cell technologies has enabled a deeper understanding of the unique processes taking place at the maternal-fetal interface as well as the discovery of novel pathways and immune and nonimmune cell types. Single-cell approaches have also been applied to decipher the cellular dynamics throughout pregnancy, in parturition, and in obstetrical syndromes such as recurrent spontaneous abortion, preeclampsia, and preterm labor. Furthermore, single-cell technologies have been used during the recent COVID-19 pandemic to evaluate placental viral cell entry and the impact of SARS-CoV-2 infection on maternal and fetal immunity. In this brief review, we summarize the current knowledge of cellular immunobiology in pregnancy and its complications that has been generated through single-cell investigations of the maternal-fetal interface.

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

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

A randomised, double-blind, placebo-controlled, multicentre clinical trial of AZD1656 in diabetic patients hospitalised with COVID-19: The ARCADIA Trial - implications for therapeutic immune modulation

BACKGROUND

A potential immunotherapeutic role for AZD1656 (a glucokinase activator) in the treatment of COVID-19 was hypothesized. The ARCADIA trial investigated the safety and efficacy of AZD1656 in diabetic patients admitted to hospital with COVID-19.

METHODS

The ARCADIA trial was a Phase II randomised, double-blind, placebo-controlled clinical trial. Adult diabetic patients, admitted with COVID-19, were recruited at 28 hospitals in the UK, Romania and Czech Republic and randomly assigned (1:1) to receive AZD1656 tablets (100mg twice a day), or matched placebo, for up to 21 days, in addition to usual care. All involved were masked to treatment allocation. The primary endpoint was clinical improvement measured at Day 14. The Full Analysis Set (FAS) included all patients who received at least one dose of assigned treatment. ARCADIA is complete and registered with ClinicalTrials.gov (NCT04516759).

FINDINGS

Between 29 September 2020 to 16 April 2021, 170 patients were screened and 156 patients were randomised, three of whom did not commence treatment. Of the remaining 153, 80 were assigned to AZD1656 and 73 were assigned to placebo and included in the Full Analysis Set (FAS). The primary analysis showed no statistically significant difference between groups (AZD1656: 76·3%; Placebo: 69·9%, p=0·19). There was no difference in the number of adverse events between groups (AZD1656: 35·7%; Placebo: 33·3%). Mortality was lower in the AZD1656 group compared to the placebo group (AZD1656: four (5%); Placebo: nine (12·3%), p=0·090)). At Day 7 there were zero deaths in the AZD1656 group compared to six deaths in the placebo group (p=0·011, post hoc). A difference between groups in time to hospital discharge was also seen (p=0·16). Immunophenotyping data suggested that AZD1656-treated patients had a less pro-inflammatory immune response and a better adaptive immune response than those treated with placebo.

INTERPRETATION

Although the trial did not achieve its primary endpoint, AZD1656 was associated with a decrease in deaths and a reduction in the duration of hospitalisation, as compared to Placebo. Immunophenotyping and immunochemistry indicated an immunomodulatory effect of AZD1656. The trial suggests a beneficial therapeutic effect of AZD1656 and identifies a new therapeutic concept: small molecule activation of endogenous homeostatic immune cells which themselves become the therapeutic agent within the body. Phase 2 trials of this size carry the risk of false positive results and confirmation of these results in a larger clinical trial is now required.

FUNDING

UK Research and Innovation (UKRI) 'Innovate UK' programme and Excalibur Medicines Ltd.

Pregnancy-specific responses to COVID-19 are revealed by high-throughput proteomics of human plasma

Pregnant women are at greater risk of adverse outcomes, including mortality, as well as obstetrical complications resulting from COVID-19. However, pregnancy-specific changes that underlie such worsened outcomes remain unclear. Herein, we profiled the plasma proteome of pregnant and non-pregnant COVID-19 patients and controls and showed alterations that display a dose-response relationship with disease severity; yet, such proteomic perturbations are dampened during pregnancy. In both pregnant and non-pregnant state, the proteome response induced by COVID-19 showed enrichment of mediators implicated in cytokine storm, endothelial dysfunction, and angiogenesis. Shared and pregnancy-specific proteomic changes were identified: pregnant women display a tailored response that may protect the conceptus from heightened inflammation, while non-pregnant individuals display a stronger response to repel infection. Furthermore, the plasma proteome can accurately identify COVID-19 patients, even when asymptomatic or with mild symptoms. This study represents the most comprehensive characterization of the plasma proteome of pregnant and non-pregnant COVID-19 patients.

Boosting regulatory T cell function for the treatment of autoimmune diseases – That’s only half the battle!

Regulatory T cells (Treg) represent a subset of specialized T cells that are essential for the regulation of immune responses and maintenance of peripheral tolerance. Once activated, Treg exert powerful immunosuppressive properties, for example by inhibiting T cell-mediated immune responses against self-antigens, thereby protecting our body from autoimmunity. Autoimmune diseases such as multiple sclerosis, rheumatoid arthritis or systemic lupus erythematosus, exhibit an immunological imbalance mainly characterized by a reduced frequency and impaired function of Treg. In addition, there has been increasing evidence that – besides Treg dysfunction – immunoregulatory mechanisms fail to control autoreactive T cells due to a reduced responsiveness of T effector cells (Teff) for the suppressive properties of Treg, a process termed Treg resistance. In order to efficiently treat autoimmune diseases and thus fully induce immunological tolerance, a combined therapy aimed at both enhancing Treg function and restoring Teff responsiveness could most likely be beneficial. This review provides an overview of immunomodulating drugs that are currently used to treat various autoimmune diseases in the clinic and have been shown to increase Treg frequency as well as Teff sensitivity to Treg-mediated suppression. Furthermore, we discuss strategies on how to boost Treg activity and function, and their potential use in the treatment of autoimmunity. Finally, we present a humanized mouse model for the preclinical testing of Treg-activating substances in vivo.

Microbiota of the Pregnant Mouse: Characterization of the Bacterial Communities in the Oral Cavity, Lung, Intestine, and Vagina through Culture and DNA Sequencing

Mice are frequently used as animal models for mechanistic studies of infection and obstetrical disease, yet characterization of the murine microbiota during pregnancy is lacking. The objective of this study was to characterize the microbiotas of distinct body sites of the pregnant mouse—vagina, oral cavity, intestine, and lung—that harbor microorganisms that could potentially invade the murine amniotic cavity, thus leading to adverse pregnancy outcomes. The microbiotas of these body sites were characterized through anoxic, hypoxic, and oxic culture as well as through 16S rRNA gene sequencing. With the exception of the vagina, the cultured microbiotas of each body site varied by atmosphere, with the greatest diversity in the cultured microbiota appearing under anoxic conditions. Only cultures of the vagina were comprehensively representative of the microbiota observed through direct DNA sequencing of body site samples, primarily due to the predominance of two Rodentibacter strains. Identified as Rodentibacter pneumotropicus and Rodentibacter heylii, these isolates exhibited predominance patterns similar to those of Lactobacillus crispatus and Lactobacillus iners in the human vagina. Whole-genome sequencing of these Rodentibacter strains revealed shared genomic features, including the ability to degrade glycogen, an abundant polysaccharide in the vagina. In summary, we report body site-specific microbiotas in the pregnant mouse with potential ecological parallels to those of humans. Importantly, our findings indicate that the vaginal microbiotas of pregnant mice can be readily cultured, suggesting that mock vaginal microbiotas can be tractably generated and maintained for experimental manipulation in future mechanistic studies of host vaginal-microbiome interactions.

IMPORTANCE Mice are widely utilized as animal models of obstetrical complications; however, the characterization of the murine microbiota during pregnancy has been neglected. Microorganisms from the vagina, oral cavity, intestine, and lung have been found in the intra-amniotic space, where their presence threatens the progression of gestation. Here, we characterized the microbiotas of pregnant mice and established the appropriateness of culture in capturing the microbiota at each site. The high relative abundance of Rodentibacter observed in the vagina is similar to that of Lactobacillus in humans, suggesting potential ecological parallels. Importantly, we report that the vaginal microbiota of the pregnant mouse can be readily cultured under hypoxic conditions, demonstrating that mock microbial communities can be utilized to test the potential ecological parallels between microbiotas in human and murine pregnancy and to evaluate the relevance of the structure of these microbiotas for adverse pregnancy outcomes, especially intra-amniotic infection and preterm birth.

Immune Deviation in the Decidua During Term and Preterm Labor

The maternal-fetal immune disorder is considered to be an important factor of preterm birth (PTB); however, the underlying mechanism is still not fully understood. This study was designed to explore the innate and adaptive immune features in the decidua during term and preterm labor. Women delivered at term or preterm were classified into four groups: term not in labor (TNL, N=19), term in labor (TL, N=17), preterm not in labor (PNL, N=10), and preterm in labor (PIL, N=10). Decidua basalis and parietalis were collected and analyzed for macrophage subtypes (M1 and M2) as well as T helper 1 (Th1), Th2, Th17 and regulatory T (Treg) cells by flow cytometry and immunohistochemistry. Our results demonstrated significantly decreased frequencies of M2 cells and elevated M1/M2 ratio in the PIL group compared to that in the PNL group in both decidua basalis and parietalis, whereas no significant differences were found between the above two groups in both sites in terms of the polarization status of Th cells. On the contrary, macrophage subsets were comparable in the TL and TNL groups, whereas elevated Th1 percentages and Th1/Th2 ratio were observed in TL women compared to that in TNL women in the decidua. Interestingly, although the frequencies and ratios of Th17 and Treg were comparable among the four groups, the Th17/Treg ratios of these groups were significantly increased in decidua basalis than that in decidua parietalis. Collectively, the M1/M2 imbalance is associated with the breakdown of maternal-fetal immune tolerance during PTB, whereas the aberrant Th1/Th2 profile plays an important role in immune disorder during term labor. Moreover, Th17/Treg deviation is more remarkable in decidua basalis than in decidua parietalis.

The immunobiology of preterm labor and birth: intra-amniotic inflammation or breakdown of maternal-fetal homeostasis

In brief

The syndrome of preterm labor comprises multiple established and novel etiologies. This review summarizes the distinct immune mechanisms implicated in preterm labor and birth and highlights potential strategies for its prevention.

Abstract

Preterm birth, the leading cause of neonatal morbidity and mortality worldwide, results from preterm labor, a syndrome that includes multiple etiologies. In this review, we have summarized the immune mechanisms implicated in intra-amniotic inflammation, the best-characterized cause of preterm labor and birth, as well as novel etiologies non-associated with intra-amniotic inflammation (i.e. formally known as idiopathic). While the intra-amniotic inflammatory responses driven by microbes (infection) or alarmins (sterile) have some overlap in the participating cellular and molecular processes, the distinct natures of these two conditions necessitate the implementation of specific approaches to prevent adverse pregnancy and neonatal outcomes. Intra-amniotic infection can be treated with the correct antibiotics, whereas sterile intra-amniotic inflammation could potentially be treated by administering a combination of anti-inflammatory drugs (e.g. betamethasone, inflammasome inhibitors, etc.). Recent evidence also supports the role of fetal T-cell activation as a newly described trigger for preterm labor and birth in a subset of cases diagnosed as idiopathic. Moreover, herein we also provide evidence of two maternally-driven immune mechanisms responsible for preterm births formerly considered to be idiopathic. First, the impairment of maternal Tregs can lead to preterm birth, likely due to the loss of immunosuppressive activity resulting in unleashed effector T-cell responses. Secondly, homeostatic macrophages were shown to be essential for maintaining pregnancy and promoting fetal development, and the adoptive transfer of homeostatic M2-polarized macrophages shows great promise for preventing inflammation-induced preterm birth. Collectively, in this review, we discuss the established and novel immune mechanisms responsible for preterm birth and highlight the potential targets for novel strategies aimed at preventing the multi-etiological syndrome of preterm labor leading to preterm birth.

Maternal-fetal conflict averted by progesterone- induced FOXP3+ regulatory T cells

Pregnancy stimulates an intricately coordinated assortment of physiological changes to accommodate growth of the developing fetus, while simultaneously averting rejection of genetically foreign fetal cells and tissues. Despite increasing evidence that expansion of immune-suppressive maternal regulatory T cells enforces fetal tolerance and protects against pregnancy complications, the pregnancy-associated signals driving this essential adaptation remain poorly understood. Here we show that the female reproductive hormone, progesterone, coordinates immune tolerance by stimulating expansion of FOXP3+ regulatory T cells. Conditional loss of the canonical nuclear progesterone receptor in maternal FOXP3+ regulatory T cells blunts their proliferation and accumulation, which is associated with fetal wastage and decidual infiltration of activated CD8+ T cells. Reciprocally, the synthetic progestin 17α-hydroxyprogesterone caproate (17-OHPC) administered to pregnant mice reinforces fetal tolerance and protects against fetal wastage. These immune modulatory effects of progesterone that promote fetal tolerance establish a molecular link between immunological and other physiological adaptions during pregnancy.

TNF-α/anti-TNF-α drugs and its effect on pregnancy outcomes

Pregnancy is a complex biological process. The establishment and maintenance of foetal-maternal interface are pivotal events. Decidual immune cells and inflammatory cytokines play indispensable roles in the foetal-maternal interface. The disfunction of decidual immune cells leads to adverse pregnancy outcome. Tumour necrosis factor (TNF)-α, a common inflammatory cytokine, has critical roles in different stages of normal pregnancy process. However, the relationship between the disorder of TNF-α and adverse pregnancy outcomes, including preeclampsia (PE), intrauterine growth restriction (IUGR), spontaneous abortion (SA), preterm birth and so on, is still indefinite. In this review, we thoroughly reviewed the effect of TNF-α disorder on pathological conditions. Moreover, we summarized the reports about the adverse pregnancy outcomes (PE, IUGR, SA and preterm birth) of using anti-TNF-α drugs (infliximab, etanercept and adalimumab, certolizumab and golimumab) currently in the clinical studies. Overall, IUGR, SA and preterm birth are the most common adverse pregnancy outcomes of anti-TNF-α drugs. Our review may provide insight for the immunological treatment of pregnancy-related complication, and help practitioners make informed decisions based on the current evidences.

The Regulatory-T-Cell Memory Phenotype: What We Know

In immunology, the discovery of regulatory T (Treg) cells was a major breakthrough. Treg cells play a key role in pregnancy maintenance, in the prevention of autoimmune responses, and in the control of all immune responses, including responses to self cells, cancer, infection, and a transplant. It is currently unclear whether Treg cells are capable of long-term memory of an encounter with an antigen. Although the term “immunological memory” usually means an enhanced ability to protect the body from reinfection, the memory of the suppressive activity of Treg cells helps to avoid the state of generalized immunosuppression that may result from the second activation of the immune system. In this review, we would like to discuss the concept of regulatory memory and in which tissues memory Treg cells can perform their functions.

Immunological Changes in Pregnancy and Prospects of Therapeutic Pla-Xosomes in Adverse Pregnancy Outcomes

Stringent balance of the immune system is a key regulatory factor in defining successful implantation, fetal development, and timely parturition. Interference in these primary regulatory mechanisms, either at adolescence or prenatal state led to adverse pregnancy outcomes. Fertility restoration with the help of injectable gonadotrophins/progesterone, ovulation-inducing drugs, immunomodulatory drugs (corticosteroids), and reproductive surgeries provides inadequate responses, which manifest its own side effects. The development of a potential diagnostic biomarker and an effectual treatment for adverse pregnancy outcomes is a prerequisite to maternal and child health. Parent cell originated bi-layered-intraluminal nano-vesicles (30-150 nm) also known as exosomes are detected in all types of bodily fluids like blood, saliva, breast milk, urine, etc. Exosomes being the most biological residual structures with the least cytotoxicity are loaded with cargo in the form of RNAs (miRNAs), proteins (cytokines), hormones (estrogen, progesterone, etc.), cDNAs, and metabolites making them chief molecules of cell-cell communication. Their keen involvement in the regulation of biological processes has portrayed them as the power shots of cues to understand the disease's pathophysiology and progression. Recent studies have demonstrated the role of immunexosomes (immunomodulating exosomes) in maintaining unwavering immune homeostasis between the mother and developing fetus for a healthy pregnancy. Moreover, the concentration and size of the exosomes are extensively studied in adverse pregnancies like preeclampsia, gestational diabetes mellitus (GDM), and preterm premature rupture of membrane (pPROMs) as an early diagnostic marker, thus giving in-depth information about their pathophysiology. Exosomes have also been engineered physically as well as genetically to enhance their encapsulation efficiency and specificity in therapy for cancer and adverse pregnancies. Successful bench to bedside discoveries and interventions in cancer has motivated developmental biologists to investigate the role of immunexosomes and their active components. Our review summarizes the pre-clinical studies for the use of these power-shots as therapeutic agents. We envisage that these studies will pave the path for the use of immunexosomes in clinical settings for reproductive problems that arise due to immune perturbance in homeostasis either at adolescence or prenatal state.

Pregnancy tailors endotoxin-induced monocyte and neutrophil responses in the maternal circulation

Objective

To comprehensively characterize monocyte and neutrophil responses to E. coli and its product [lipopolysaccharide (LPS) or endotoxin] in vitro during pregnancy.

Material or subjects

Peripheral blood was collected from pregnant women during the third trimester (n = 20) and from non-pregnant women (n = 20).

Methods

The number, phagocytic activity, and reactive oxygen species (ROS) production of peripheral monocytes and neutrophils were investigated using flow cytometry. The phenotypes of peripheral monocytes and neutrophils after acute or chronic LPS stimulation were also determined using flow cytometry. Cytokine profiles were quantified for LPS-stimulated peripheral blood mononuclear cells (PBMCs) and a whole blood TruCulture^® system using a multiplex immunoassay.

Results

Increased number, phagocytic activity, and ROS production capacity of monocytes and neutrophils were found in pregnant compared to non-pregnant women. Additionally, specific subsets of pro-inflammatory monocytes (IL-6⁺CD14⁺ or MIP-1α⁺CD14⁺ cells) and neutrophils (IL-1β⁺CD15⁺ or MIP-1β⁺CD15⁺ cells) were increased in pregnant women in response to acute LPS stimulation. Moreover, distinct subsets of intermediate-activated monocytes expressing CD142, IL-6, and IL-1RA were increased in pregnant women upon chronic LPS stimulation. Last, pregnant women displayed a different cytokine profile than non-pregnant women in LPS-stimulated PBMCs and in whole blood.

Conclusions

Pregnancy tailors the immune responses of circulating monocytes and neutrophils to endotoxin, a Gram-negative bacterial product.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00011-022-01569-z.

Distinct Cellular Immune Responses to SARS-CoV-2 in Pregnant Women

Pregnant women are at increased risk of adverse outcomes, including preeclampsia and preterm birth, that may result from severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. Pregnancy imprints specific maternal immune responses that can modulate host susceptibility to microbial infection; therefore, recent studies have focused on the humoral response against SARS-CoV-2 in pregnant women. However, the pregnancy-specific cellular immune responses triggered by SARS-CoV-2 infection are poorly understood. In this study, we undertook an extensive in vitro investigation to determine the cellular immune responses to SARS-CoV-2 particles and proteins/peptides in pregnant women. First, we show that SARS-CoV-2 particles do not alter the pregnancy-specific oxidative burst of neutrophils and monocytes. Yet, SARS-CoV-2 particles/proteins shift monocyte activation from the classical to intermediate states in pregnant, but not in nonpregnant, women. Furthermore, SARS-CoV-2 proteins, but not particles or peptide pools, mildly enhance T cell activation during pregnancy. As expected, B cell phenotypes are heavily modulated by SARS-CoV-2 particles in all women; yet, pregnancy itself further modified such responses in these adaptive immune cells. Lastly, we report that pregnancy itself governs cytokine responses in the maternal circulation, of which IFN-β and IL-8 were diminished upon SARS-CoV-2 challenge. Collectively, these findings highlight the differential in vitro responses to SARS-CoV-2 in pregnant and nonpregnant women and shed light on the immune mechanisms implicated in coronavirus disease 2019 during pregnancy.