Increased human leukocyte antigen-G expression at the maternal-fetal interface is associated with preterm birth

HLA-G Expression/Secretion and T-Cell Cytotoxicity in Missed Abortion in Comparison to Normal Pregnancy

The main role of HLA-G is to protect the semi-allogeneic embryo from immune rejection by proper interaction with its cognate receptors on the maternal immune cells. Spontaneous abortion is the most common adverse pregnancy outcome, with an incidence rate between 10% and 15%, with immunologic dysregulation being thought to play a role in some of the cases. In this study, we aimed to detect the membrane and soluble HLA-G molecule at the maternal-fetal interface (MFI) and in the serum of women experiencing missed abortion (asymptomatic early pregnancy loss) in comparison to the women experiencing normal early pregnancy. In addition, the proportion of T cells and their cytotoxic profile was evaluated. We observed no difference in the spatial expression of HLA-G at the MFI and in its serum levels between the women with missed abortions and those with normal early pregnancy. In addition, comparable numbers of peripheral blood and decidual total T and γδT cells were found. In addition, as novel data we showed that missed abortion is not associated with altered extravilous invasion into uterine blood vessels and increased cytotoxicity of γδT cells. A strong signal for HLA-G on non-migrating extravilous trophoblast in the full-term normal placental bed was detected. In conclusion, HLA-G production at the MFI or in the blood of the women could not be used as a marker for normal pregnancy or missed abortions.

Evaluation of Complete Blood Cell Count Parameters in the Diagnosis of Threatened Preterm Labor and Premature Rupture of Membranes

<b><i>Purpose:</i></b> The purpose of this study was to investigate a possible relationship between systemic inflammatory markers such as neutrophil-lymphocyte ratio (NLR), platelet-lymphocyte ratio (PLR), lymphocyte monocyte ratio (LMR), threatened preterm labor (TPL), and preterm premature rupture of membranes (PPROM), using complete blood cell count (CBC) parameters. <b><i>Method:</i></b> The study was carried out prospectively with patients admitted to our university hospital due to preterm labor and at risk of PPROM. The cases were divided into three groups according to their pregnancy status. Group 1 consisted of 90 patients with PPROM between 24th and 36th gestational weeks; group 2, 115 patients diagnosed with TPL between 24th and 36th gestational weeks; group 3, 101 patients over 36 weeks of gestation (control) who were not in labor. In addition to the demographic data of the patients, CBC parameters (white blood cell (WBC), Hg, Hct, Plt, lymphocyte, monocyte, mean platelet volume, PLR, LMR, and NLR) and C-reactive protein (CRP) values were examined and compared in each of the three groups. <b><i>Results:</i></b> CRP and WBC values of group 1 (PPROM) were higher than group 2 (TPL) and group 3 (control) (<i>p</i> &#x3c; 0.05 for both). Pearson correlation between the gestational age and PLR and NLR values was significant (<i>r</i> and <i>p</i> values for PLR and NLR, respectively, <i>r</i> = −0.18, <i>p</i> &#x3c; 0.001; <i>r</i> = −0.23, <i>p</i> &#x3c; 0.001). However, there was no significant difference between the groups regarding PLR, NLR, LMR, platelet, monocytes, and lymphocyte counts. <b><i>Conclusions:</i></b> Only WBC was a valuable parameter in predicting preterm labor and PPROM. Although there was no significant difference between the groups in PLR and NLR, a negative correlation was found with gestational age at delivery. CRP value is still a helpful parameter in PPROM and TPL prediction.

Fetal inflammatory response at the fetomaternal interface: A requirement for labor at term and preterm

Human parturition at term and preterm is an inflammatory process synchronously executed by both fetomaternal tissues to transition them from a quiescent state t an active state of labor to ensure delivery. The initiators of the inflammatory signaling mechanism can be both maternal and fetal. The placental (fetal)-maternal immune and endocrine mediated homeostatic imbalances and inflammation are well reported. However, the fetal inflammatory response (FIR) theories initiated by the fetal membranes (amniochorion) at the choriodecidual interface are not well established. Although immune cell migration, activation, and production of proparturition cytokines to the fetal membranes are reported, cellular level events that can generate a unique set of inflammation are not well discussed. This review discusses derangements to fetal membrane cells (physiologically and pathologically at term and preterm, respectively) in response to both endogenous and exogenous factors to generate inflammatory signals. In addition, the mechanisms of inflammatory signal propagation (fetal signaling of parturition) and how these signals cause immune imbalances at the choriodecidual interface are discussed. In addition to maternal inflammation, this review projects FIR as an additional mediator of inflammatory overload required to promote parturition.

Histocompatibility Antigen, Class I, G (HLA-G)'s Role during Pregnancy and Parturition: A Systematic Review of the Literature

Introduction: Immune homeostasis of the intrauterine cavity is vital for pregnancy maintenance. At term or preterm, fetal and maternal tissue inflammation contributes to the onset of labor. Though multiple immune-modulating molecules are known, human leukocyte antigen (HLA)-G is unique to gestational tissues and contributes to maternal–fetal immune tolerance. Several reports on HLA-G’s role exist; however, ambiguity exists regarding its functional contributions during pregnancy and parturition. To fill these knowledge gaps, a systematic review (SR) of the literature was conducted to better understand the expression, localization, function, and regulation of HLA-G during pregnancy and parturition. Methods: A SR of the literature on HLA-G expression and function reported in reproductive tissues during pregnancy, published between 1976–2020 in English, using three electronic databases (SCOPE, Medline, and ClinicalTrials.gov) was conducted. The selection of studies, data extraction, and quality assessment were performed in duplicate by two independent reviewers. Manuscripts were separated into three categories: (1) expression and localization of HLA-G, (2) regulators of HLA-G, and (3) the mechanistic roles of HAL-G. Data were extracted, analyzed, and summarized. Results: The literature search yielded 2554 citations, 117 of which were selected for full-text evaluation, and 115 were included for the final review based on our inclusion/exclusion criteria. HLA-G expression and function were mostly studied in placental tissue and/or cells and peripheral blood immune cells, while only 13% of the studies reported data on amniotic fluid/cord blood and fetal membranes. Measurements of soluble and membranous HLA-G were determined mostly by RNA-based methods and protein by immunostaining, Western blot, or flow cytometric analyses. HLA-G was reported to regulate inflammation and inhibit immune-cell-mediated cytotoxicity and trophoblast invasion. Clinically, downregulation of HLA-G is reported to be associated with poor placentation in preeclampsia and immune cell infiltration during ascending infection. Conclusions: This SR identified several reports supporting the hypothesized role of immune regulation in gestational tissues during pregnancy. A lack of rigor and reproducibility in the experimental approaches and models in several reports make it difficult to fully elucidate the mechanisms of action of HLA-G in immune tolerance during pregnancy.

Importance of haemogram parameters for prediction of the time of birth in women diagnosed with threatened preterm labour

Objective

This study aimed to estimate the importance of complete blood count parameters for predicting the timing of birth in threatened preterm labour cases.

Methods

We performed a retrospective study of 92 patients who were diagnosed with threatened preterm labour (24–34 gestational weeks). The patients were divided into two groups according to the time of birth (group 1: delivered within the first week after diagnosis; group 2: delivered later than 1 week). We compared characteristics and complete blood count parameters between these two groups.

Results

There were no significant differences in maternal age, body mass index, gravida, parity, haemoglobin levels, and gestational weeks between the two groups. The mean cervical length was 24.24 ± 3.60 mm in group 1 and 30.70 ± 5.32 mm in group 2. There were significant differences in the neutrophil to lymphocyte ratio, white blood cell count, red cell distribution width (RDW), absolute lymphocyte cell count, and absolute neutrophil cell count between the two groups.

Conclusion

Maternal serum RDW, the neutrophil to lymphocyte ratio, white blood cell count, absolute lymphocyte cell count, and the absolute neutrophil cell count profile could guide clinicians in predicting the time of birth in threatened preterm labour cases.

Role of Human Leukocyte Antigens at the Feto-Maternal Interface in Normal and Pathological Pregnancy: An Update

The successful maternal tolerance of the semi-allogeneic fetus provides an apparent immunologic paradox. Indeed, deep invasion of placental trophoblast cells into maternal uterine tissue and the following growth of the fetus have to be tolerated by a pregnant woman’s immune system. Among the various possible protective mechanisms that may be involved in human pregnancy, the expression of a non-classical pattern of human leukocyte antigen (HLA) class I molecules and the complete lack of expression of HLA class II molecules in placental tissues seem to be the most relevant mechanisms of fetal escape from maternal immune recognition. The importance of HLA molecules in fetal toleration by the maternal immune system is highlighted by pregnancy complications occurring in cases of abnormal HLA molecule expression at the maternal–fetal interface. In this review, we summarize evidences about the role of placental HLA molecules in normal and pathological pregnancies.

Can Inflammatory Hematological Parameters be a Guide to Late-onset Fetal Growth Restriction?

PURPOSE

To compare the rates obtained from hematological parameters in cases of late-onset idiopathic fetal growth restriction (FGR) with healthy pregnancies and to evaluate the effect on neonatal outcomes.

METHODS

The study group consisted of 63 pregnant women with late-onset idiopathic FGR and the control group consisted of 91 healthy pregnant women. The determined rates were calculated from the control hemograms of patients at 28 weeks. Both groups were compared for neutrophil/lymphocyte ratio (NLR), platelet/lymphocyte ratio (PLR), and other parameters.

RESULTS

NLR, leukocyte and neutrophil levels were significantly higher in the FGR group (p<0.05). There was no significant difference in PLR, platelet and lymphocyte levels between the groups (p>0.05). To predict FGR, the best cut-off value of NLR was determined to be 4.11 with 56% sensitivity and 88% specificity values.

CONCLUSION

Neutrophil, lymphocyte and platelet interactions have an important role in FGR development. Inflammation can be involved in the etiopathogenesis in late-onset FGR.

Maternal and fetal T cells in term pregnancy and preterm labor

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

Chronic inflammatory lesions of the placenta are associated with an up-regulation of amniotic fluid CXCR3: A marker of allograft rejection

OBJECTIVE

The objective of this study is to determine whether the amniotic fluid (AF) concentration of soluble CXCR3 and its ligands CXCL9 and CXCL10 changes in patients whose placentas show evidence of chronic chorioamnionitis or other placental lesions consistent with maternal anti-fetal rejection.

METHODS

This retrospective case-control study included 425 women with (1) preterm delivery (n=92); (2) term in labor (n=68); and (3) term not in labor (n=265). Amniotic fluid CXCR3, CXCL9 and CXCL10 concentrations were determined by ELISA.

RESULTS

(1) Amniotic fluid concentrations of CXCR3 and its ligands CXCL9 and CXCL10 are higher in patients with preterm labor and maternal anti-fetal rejection lesions than in those without these lesions [CXCR3: preterm labor and delivery with maternal anti-fetal rejection placental lesions (median, 17.24 ng/mL; IQR, 6.79-26.68) vs. preterm labor and delivery without these placental lesions (median 8.79 ng/mL; IQR, 4.98-14.7; P=0.028)]; (2) patients with preterm labor and chronic chorioamnionitis had higher AF concentrations of CXCL9 and CXCL10, but not CXCR3, than those without this lesion [CXCR3: preterm labor with chronic chorioamnionitis (median, 17.02 ng/mL; IQR, 5.57-26.68) vs. preterm labor without chronic chorioamnionitis (median, 10.37 ng/mL; IQR 5.01-17.81; P=0.283)]; (3) patients with preterm labor had a significantly higher AF concentration of CXCR3 than those in labor at term regardless of the presence or absence of placental lesions.

CONCLUSION

Our findings support a role for maternal anti-fetal rejection in a subset of patients with preterm labor.

Correlations of maternal neutrophil to lymphocyte ratio (NLR) and platelet to lymphocyte ratio (PLR) with birth weight

OBJECTIVE

The aim of this study is to investigate the possible correlation of hemogram parameters including neutrophil to lymphocyte ratio (NLR) and platelet to lymphocyte ratio (PLR) with birth weight and gestational week.

MATERIALS AND METHODS

This prospective study has been conducted with 783 patients. The maternal age, parity, gestational age, type of delivery, values of complete blood count (CBC) variables and the weight of newborn were recorded. We analyzed the statistical differences between the NLR, PLR, hemoglobin (HGB), platelet distribution width (PDW), red cell distribution width (RDW), mean platelet volume (MPV), platelet, neutrophil, lymphocyte and white blood cells (WBC) in terms of the birth weight.

RESULTS

There was no statistically significant difference in the NLR in terms of the birth weight (p = 0.097), whereas there was a statistically significant difference in the PLR (p < 0.001). In correlation analyses, a linear, negative, weak and statistically significant correlation was detected between NLR and PLR with the birth weight of infant and gestational week (p = 0.011 and p < 0.001, respectively).

CONCLUSION

This prospective study is the first in the literature which investigates the correlation of NLR and PLR with the week of birth and birth weight of the infant. Our study suggested that the maternal NLR and PLR are negatively correlated with the week of birth and birth weight of the infant.

ATG16L1 governs placental infection risk and preterm birth in mice and women

The placenta is a barrier against maternal-fetal transmission of pathogens. Placental infections can cause several adverse pregnancy outcomes, including preterm birth (PTB). Yet, we have limited knowledge regarding the mechanisms the placenta uses to control infections. Here, we show that autophagy, a cellular recycling pathway important for host defense against pathogens, and the autophagy gene Atg16L1 play a key role in placental defense and are negatively associated with PTB in pregnant women. First, we demonstrate that placentas from women who delivered preterm exhibit reduced autophagy activity and are associated with higher infection indicators. Second, we identify the cellular location of the autophagy activity as being in syncytial trophoblasts. Third, we demonstrate that higher levels of autophagy and ATG16L1 in human trophoblasts were associated with increased resistance to infection. Accordingly, loss of autophagy or ATG16L1 impaired trophoblast antibacterial defenses. Fourth, we show that Atg16l1-deficient mice gave birth prematurely upon an inflammatory stimulus and their placentas were significantly less able to withstand infection. Finally, global induction of autophagy in both mouse placentas and human trophoblasts increased infection resistance. Our study has significant implications for understanding the etiology of placental infections and prematurity and developing strategies to mitigate placental infection-induced PTB.

Placental Microbiome and Its Role in Preterm Birth

Despite the well-known fact that the placenta has long-term effects on maternal and fetal health, the placenta remains a poorly understood and understudied organ. Not only is the placenta a site of exchange of nutrients and blood and gases between the fetal and maternal systems, but it also performs critical metabolic functions for supporting fetal development and maintaining maternal-fetal tolerance. It is also abundantly clear that impairment of placental function leads to severe pregnancy complications, including preterm birth (PTB), a significant cause of perinatal mortality and morbidity worldwide. Understanding the causes of PTB and other adverse outcomes is clearly essential for the development of effective methods of prevention and treatment. We focus our review of one major known cause of PTB, namely, infection. We also introduce a new and somewhat unexpected factor(s) that may well affect PTB and every aspect of placental biology and function: the placental microbiome. We discuss the implications of the placenta housing a microbial biomass for PTB and the effect of maternal microbiomes at various niches for fetal colonization and health outcomes. We suggest that the placenta is an integral part of the pipeline for microbe-powered driver of fetal destiny.