Granulysin produced by uterine natural killer cells induces apoptosis of extravillous trophoblasts in spontaneous abortion

The regulated cell death at the maternal-fetal interface: beneficial or detrimental?

Regulated cell death (RCD) plays a fundamental role in placental development and tissue homeostasis. Placental development relies upon effective implantation and invasion of the maternal decidua by the trophoblast and an immune tolerant environment maintained by various cells at the maternal-fetal interface. Although cell death in the placenta can affect fetal development and even cause pregnancy-related diseases, accumulating evidence has revealed that several regulated cell death were found at the maternal-fetal interface under physiological or pathological conditions, the exact types of cell death and the precise molecular mechanisms remain elusive. In this review, we summarized the apoptosis, necroptosis and autophagy play both promoting and inhibiting roles in the differentiation, invasion of trophoblast, remodeling of the uterine spiral artery and decidualization, whereas ferroptosis and pyroptosis have adverse effects. RCD serves as a mode of communication between different cells to better maintain the maternal-fetal interface microenvironment. Maintaining the balance of RCD at the maternal-fetal interface is of utmost importance for the development of the placenta, establishment of an immune microenvironment, and prevention of pregnancy disorders. In addition, we also revealed an association between abnormal expression of key molecules in different types of RCD and pregnancy-related diseases, which may yield significant insights into the pathogenesis and treatment of pregnancy-related complications.

Ghrelin misbalance affects mice embryo implantation and pregnancy success by uterine immune dysregulation and nitrosative stress

Introduction

In a previous study we found that ghrelin (Ghrl) misbalance during the peri-implantation period significantly impaired fetus development. In this study we aimed to evaluate the putative mechanisms underlying these effects, including embryo implantation success, uterine nitric oxide synthase (NOS) activity, nitric oxide synthesis and the inflammatory/immune uterine profile.

Methods

Ghrelin misbalance was induced by injecting 4nmol/animal/day of Ghrl (hyperghrelinemia) or 6nmol/animal/day of a Ghrl antagonist (Ant: (D-Lys3)GHRP-6) from day 3 to 8 of pregnancy. Control animals (C) were injected with de vehicle. Females were euthanized at pregnancy day 8 and their uteri excised in order to evaluate: the percentage of reabsorbed embryos (microscopically), eNOS, iNOS and nytrotirosine expression (by immunohistochemistry), nitrite synthesis (by Griess technique), VEGF, IL-10, IL-17, IL-6, MMP9 and GM-CSF expression (by qPCR) and leukocyte infiltration by flow cytometry (evaluating T cells, NK cells, granulocytes, dendritic cells and macrophages).

Results

Ant-treatment significantly increased the percentage of reabsorbed embryos and the uterine expression of eNOS, iNOS and nytrotirosine. (D-Lys3)GHRP-6-treatment increased also the expression of the inflammatory cytokines IL-6, IL-17 and MMP9, and decreased that of IL-10 (anti-inflammatory). Moreover, Ant-treatment increased also the NK cells population and that of CD11b+ dendritic cells; and decreased T cells percentages. Similarly, hyperghrelinemia showed a significant increase vs. C on eNOS, iNOS and nytrotirosineuterine expression and a decrease in T cells percentages.

Conclusion

Ghrl misbalance during the peri-implantation period induces pro-inflammatory changes and nitrosative stress in the gravid uterus, impairing significantly embryo implantation and/or development.

NK and T Cell Subtypes in the Endometrium of Patients with Recurrent Pregnancy Loss and Recurrent Implantation Failure: Implications for Pregnancy Success

BACKGROUND

RPL and RIF are challenges in reproductive medicine. The immune system plays a pivotal role in endometrial receptivity, successful implantation, and pregnancy complications. Immunological changes have been associated with RPL and RIF. Understanding immune dysregulation especially in NK and T cell subtypes may lead to better diagnostic concepts and treatments. From July 2019 to August 2020 patients with RPL and RIF underwent a standardized diagnostic procedure including endometrial biopsies. Immune cell analysis was performed using flow cytometry. Patients were contacted in March 2023 and interviewed concerning their pregnancy outcomes following diagnostics.

RESULTS

Out of 68 patients undergoing endometrial biopsies, 49 patients were finally included. Live birth rates were high with 72% in RPL and 86% in RIF. Immune cell analysis revealed that patients with RPL had more cytotoxic CD56dimCD16high cells, while RIF patients had more CD56+ uNK cells. RPL patients with pregnancy complications showed increased NKT cell percentages.

CONCLUSION

Our findings suggest specific immune changes in RPL and RIF patients, offering potential therapeutic targets. Tailored immunotherapy based on endometrial immunophenotyping might be an option, but further research is needed.

Autoimmune thyroid disease disrupts immune homeostasis in the endometrium of unexplained infertility women-a single-cell RNA transcriptome study during the implantation window

Objective

Autoimmune thyroid disease (AITD) is known to be associated with unexplained infertility in women. Although the presence of antithyroid antibodies have been speculated to be a marker of an immune imbalance that might lead to implantation failure, its underlying mechanism influencing the endometrial receptivity remains to be elucidated. In this study, we used single-cell RNA sequencing (scRNA-seq) to dissect immune microenvironment in endometrium of AITD patients during window of implantation (WOI).

Methods

We collected CD45⁺ immune cell populations of endometrium samples of unexplained infertile women with AITD (n=3), as well as samples of AITD^- controls (n=3). The cells were then processed with 10X Genomics Chromium for further analysis.

Results

We characterized 28 distinct immune cell subtypes totally, and uncovered differences in the composition and gene expression patterns between AITD patients and controls. The proportions of T CD4⁺, cNK, ILC3, T CD8⁺ GZMK⁺, T CD8⁺ Cytotoxic and ILC3 CD3E ^- cells were increased, and CD366⁺ uNK1 was decreased in AITD⁺ patients. And the abnormal expression of GNLY and chemokines was observed in AITD patients. In addition, uNK and T CD8⁺ Cytotoxic cells showed lower cytotoxicity but activation of immune response. Genes enriched in cell adhesion of ILC3 and Tregs were downregulated, while the number of ILC3 and Tregs were increased.

Conclusion

Immune imbalance exists in endometrium during WOI, which may impact embryo implantation.

B2 cells contribute to hypertension and natural killer cell activation possibly via AT1-AA in response to placental ischemia

Preeclampsia, new onset hypertension during pregnancy, is associated with activated T helper cells (Th) and B cells secreting agonistic autoantibodies against the angiotensin II type 1 receptor (AT1-AA). The reduced uterine perfusion pressure (RUPP) model of placental ischemia recapitulates these characteristics. We have shown that Th-B cell communication contributes to AT1-AA and symptoms of preeclampsia in the RUPP rat. B2 cells are classical B cells that communicate with Th cells and are then transformed into memory B cells. We hypothesize that B2 cells cause hypertension, natural killer (NK) cell activation, and complement activation during pregnancy through the production of AT1-AA. To test this hypothesis, total splenic B cells and B2 cells were isolated from normal pregnant (NP) or RUPP rats on gestational day (GD)19 and adoptively transferred into GD12 NP rats. A group of recipient rats was treated with a specific inhibitor peptide of AT1-AA. On GD19, mean arterial pressure was measured, tissues were collected, activated NK cells were measured by flow cytometry, and AT1-AA was measured by cardiomyocyte assay. NP recipients of RUPP B cells or RUPP B2 cells had increased mean arterial pressure, AT1-AA, and circulating activated NK cells compared with recipients of NP B cells. Hypertension in NP recipients of RUPP B cells or RUPP B2 was attenuated with AT1-AA blockade. This study demonstrates that B cells and B2 cells from RUPP rats cause hypertension and increased AT1-AA and NK cell activation in response to placental ischemia during pregnancy.NEW & NOTEWORTHY This study demonstrates that placental ischemia-stimulated B2 cells induce hypertension and circulating natural killer cell activation and angiotensin II type 1 receptor production in normal pregnant rats.

Human Decidual CD1a+ Dendritic Cells Undergo Functional Maturation Program Mediated by Gp96

Heat shock proteins (hsps), in certain circumstances, could shape unique features of decidual dendritic cells (DCs) that play a key role in inducing immunity as well as maintaining tolerance. The aim of the study was to assess the binding of gp96 to Toll-like receptor (TLR) 4 and CD91 receptors on decidual CD1a⁺ DCs present at the maternal-fetal interface in vitro as well as the influence of CD1a⁺ DCs maturation status. Immunohistology and immunofluorescence of paraffin-embedded first-trimester decidua tissue sections of normal and pathological (missed abortion MA and blighted ovum BO) pregnancies were performed together with flow cytometry detection of antigens in CD1a⁺ DCs after gp96 stimulation of decidual mononuclear cells. Gp96 efficiently bound CD91 and TLR4 receptors on decidual CD1a⁺ DCs in a dose-dependent manner and increased the expression of CD83 and HLA-DR. The highest concentration of gp96 (1000 ng/mL) increased the percentage of Interferon-γ (INF-γ) and IL-15 expressing gp96⁺ cells. Gp96 binds CD91 and TLR4 on decidual CD1a⁺ DCs, which causes their maturation and significantly increases INF-γ and IL-15 in the context of Th1 cytokine/chemokine domination, which could support immune response harmful for ongoing pregnancy.

Human decidual gamma/delta T cells possess unique effector and TCR repertoire profiles during pregnancy

Human γδ T cells are enriched at the maternal-fetal interface (MFI, decidua basalis) showing a highly differentiated phenotype. However, their functional potential is not well-known and it is not clear whether this decidua-enrichment is associated with specific γδ T cell receptors (TCR) as is observed in mice. Here we addressed these open questions by investigating decidual γδ T cells during early and late gestation, in comparison with paired blood samples, with flow cytometry (cytotoxic mediators, cytokines) and TCR high-throughput sequencing. While decidual γδ T cells expressed less perforin than their counterparts in the blood, they expressed significant more granulysin during early pregnancy. Strikingly, this high granulysin expression was limited to early pregnancy, as it was reduced at term pregnancy. In contrast to this granulysin expression pattern, decidual γδ T cells produced reduced levels of IFNγ and TNFα (compared to paired blood) in early pregnancy that then increased by term pregnancy. TCR repertoire analysis indicated that human decidual γδ T cells are not generated early in life as in the mouse. Despite this, a specific enrichment of the Vγ2 chain in the decidua in early pregnancy was observed that disappeared later onwards, reflecting dynamic changes in the decidual γδ TCR repertoire during human gestation. In conclusion, our data indicate that decidual γδ T cells express a specific and dynamic pattern of cytotoxic mediators, Th1 cytokines and TCR repertoire suggesting an important role for these unconventional T cells in assuring a healthy pregnancy in human.

Porphyromonas gingivalis-mediated disruption in spiral artery remodeling is associated with altered uterine NK cell populations and dysregulated IL-18 and Htra1

Impaired spiral artery remodeling (IRSA) underpins the great obstetrical syndromes. We previously demonstrated that intrauterine infection with the periodontal pathogen, Porphyromonas gingivalis, induces IRSA in rats. Since our previous studies only examined the end stage of arterial remodeling, the aim of this study was to identify the impact of P. gingivalis infection on the earlier stages of remodeling. Gestation day (GD) 11 specimens, a transition point between trophoblast-independent remodeling and the start of extravillous trophoblast invasion, were compared to late stage GD18 tissues. P. gingivalis was found in decidual stroma of GD11 specimens that already had reduced spiral artery remodeling defined as smaller arterial lumen size, increased retention of vascular smooth muscle, and decreased invasion by extravillous trophoblasts. At GD11, P. gingivalis-induced IRSA coincided with altered uterine natural killer (uNK) cell populations, decreased placental bed expression of interleukin-18 (IL-18) with increased production of temperature requirement A1 (Htra1), a marker of oxidative stress. By GD18, placental bed IL-18 and Htra1 levels, and uNK cell numbers were equivalent in control and infected groups. However, infected GD18 placental bed specimens had decreased TNF + T cells. These results suggest disturbances in placental bed decidual stroma and uNK cells are involved in P. gingivalis-mediated IRSA.

The uterine natural killer cell, cytotoxic T lymphocyte, and granulysin levels are elevated in the endometrium of women with nonstructural abnormal uterine bleeding

OBJECTIVE

To examine the expression of uterine natural killer (uNK) cells and cytotoxic T lymphocytes (CTLs) in endometrial biopsies from reproductive-age women with and without nonstructural abnormal uterine bleeding (AUB) and evaluate the expression of granulysin within these cell populations and potential modulation of matrix metalloproteinase (MMP) expression.

DESIGN

Experimental study, retrospective design.

SETTING

Academic research laboratory.

PATIENT(S)

Patients with nonstructural AUB with no other gynecological pathologies and control patients without AUB.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Immunohistochemical analysis of granulysin, CD56 (uNK cell marker), and CD8 (CTL marker) expression as well as granulysin messenger ribonucleic acid (mRNA) expression levels in endometrial biopsy samples. Assessment of granulysin regulation of human endometrial stromal cell MMP-1 and MMP-3 mRNA expression.

RESULT(S)

The numbers of uNK cells and CTLs were significantly greater in endometrial biopsy tissue from women with AUB than those from controls. In accord with the increased expression of uNK cells and CTLs, granulysin expression was significantly greater in endometrial biopsies from patients with AUB than in from controls and colocalized to both cell types but not endometrial stromal or epithelial cells. The increased granulysin protein expression was associated with the increased granulysin mRNA expression in adjacent serial sections from these same samples. The treatment of the human endometrial stromal cell line t-HESC with granulysin resulted in a significant increase in MMP-1 and MMP-3 mRNA expression.

CONCLUSION(S)

In the current study, immunohistochemistry showed an increased expression of uNK cells, CTLs, and granulysin among subjects with AUB compared with that of subjects without AUB, leading to conclusions that disturbances in the balance of immune cells and an increase in granulysin expression may have implications in the pathophysiology of AUB and include enhanced MMP-1 and MMP-3 expression.

Upregulated serum granulysin levels in women with antiphospholipid antibody‐associated recurrent miscarriage are downregulated by heparin treatment

Purpose

Granulysin is a cytotoxic protein that simultaneously activates innate and cellular immunity. The authors aimed to evaluate whether granulysin is associated with the antiphospholipid antibody syndrome and whether heparin changes the granulysin levels.

Methods

A cohort study was performed with women with antiphospholipid antibody‐positive recurrent pregnancy loss (RPL). The authors examined granulysin levels under RPL and evaluated the changes in serum granulysin levels before and 1 week after the commencement of heparin treatment.

Results

Serum granulysin levels before heparin treatment were significantly higher in women who tested positive for one or more types of antiphospholipid antibodies (2.75 ± 1.03 vs. 2.44 ± 0.69, p = 0.0341 by Welch's t test), particularly anti‐phosphatidylethanolamine antibodies (IgG: 2.98 ± 1.09 vs. 2.51 ± 0.86, p = 0.0013; IgM: 2.85 ± 1.09 vs. 2.47 ± 0.77, p = 0.0024 by Welch's t test). After heparin treatment for 1 week, serum granulysin levels were significantly reduced (p = 0.0017 by the paired t test). The miscarriage rate was significantly higher in women whose serum granulysin levels were not reduced by heparin treatment (p = 0.0086 by Fisher's exact probability test).

Conclusion

The results suggest that heparin may reduce the incidence of miscarriage by suppressing serum granulysin levels.

We examined granulysin levels under recurrent pregnancy loss and evaluated the changes in serum granulysin with heparin treatment. The miscarriage rate was significantly higher in women whose serum granulysin levels were not reduced by heparin treatment. The results suggest that heparin may reduce the incidence of miscarriage by suppressing serum granulysin levels.

Innate Immune Response to Viral Infections at the Maternal-Fetal Interface in Human Pregnancy

The placenta, the first and largest organ to develop after conception, not only nurtures and promotes the development of the conceptus, but, it also functions as a barrier against invading pathogens. Early phases of pregnancy are associated with expansion of specific subsets of Natural Killer cells (dNK) and macrophages (dMφ) at the maternal uterine mucosa, the basal decidua. In concert with cells of fetal origin, dNK cells, and dMφ orchestrate all steps of placenta and fetus development, and provide the first line of defense to limit vertical transmission. However, some pathogens that infect the mother can overcome this protective barrier and jeopardize the fetus health. In this review, we will discuss how members of the classical TORCH family (Toxoplasma, Other, Rubella, Cytomegalovirus, and Herpes simplex virus) and some emerging viruses (Hepatitis E virus, Zika virus, and SARS-CoV2) can afford access to the placental fortress. We will also discuss how changes in the intrauterine environment as a consequence of maternal immune cell activation contribute to placental diseases and devastating pregnancy outcomes.

Adoptive transfer of placental ischemia-stimulated natural killer cells causes a preeclampsia-like phenotype in pregnant rats

PROBLEM

The Reduced Uterine Perfusion Pressure (RUPP) rat model of placental ischemia recapitulates many characteristics of preeclampsia including maternal hypertension, intrauterine growth restriction (IUGR), and increased cytolytic natural killer cells (cNKs). While we have previously shown a 5-fold higher cytotoxicity of RUPP NKs versus normal pregnant NKs, their role in RUPP pathophysiology remains unclear. In this study, we tested the hypotheses that (1) adoptive transfer of RUPP-stimulated NKs will induce maternal hypertension and IUGR in normal pregnant control (Sham) rats and (2) adoptive transfer of Sham NKs will attenuate maternal hypertension and IUGR in RUPP rats.

METHOD OF STUDY

On gestation day (GD)14, vehicle or 5 × 106 RUPP NKs were infused i.v. into a subset of Sham rats (Sham+RUPP NK), and vehicle or 5 × 106 Sham NKs were infused i.v. into a subset of RUPP rats (RUPP+Sham NK; n = 12/group). On GD18, Uterine Artery Resistance Index (UARI) was measured. On GD19, mean arterial pressure (MAP) was measured, animals were sacrificed, and blood and tissues were collected for analysis.

RESULTS

Adoptive transfer of RUPP NKs into Sham rats resulted in elevated NK activation, UARI, placental oxidative stress, and preproendothelin expression as well as reduced circulating nitrate/nitrite. This led to maternal hypertension and IUGR. RUPP recipients of Sham NKs demonstrated normalized NK activation, sFlt-1, circulating and placental VEGF, and UARI, which led to improved maternal blood pressure and normal fetal growth.

CONCLUSION

These data suggest a direct role for cNKs in causing preeclampsia pathophysiology and a role for normal NKs to improve maternal outcomes and IUGR during late gestation.

Molecular and immunological developments in placentas

Cytotrophoblasts differentiate in two directions during early placentation: syncytiotrophoblasts (STBs) and extravillous trophoblasts (EVTs). STBs face maternal immune cells in placentas, and EVTs, which invade the decidua and uterine myometrium, face the cells in the uterus. This situation, in which trophoblasts come into contact with maternal immune cells, is known as the maternal-fetal interface. Despite fetuses and fetus-derived trophoblast cells being of the semi-allogeneic conceptus, fetuses and placentas are not rejected by the maternal immune system because of maternal-fetal tolerance. The acquired tolerance develops during normal placentation, resulting in normal fetal development in humans. In this review, we introduce placental development from the viewpoint of molecular biology. In addition, we discuss how the disruption of placental development could lead to complications in pregnancy, such as hypertensive disorder of pregnancy, fetal growth restriction, or miscarriage.

Do endometrial natural killer and regulatory T cells differ in infertile and clinical pregnancy patients? An analysis in patients undergoing frozen embryo transfer cycles

PROBLEM

Clinical significance of endometrial and peripheral blood natural killer (NK) and regulatory T cells (Tregs) during frozen embryo transfer (FET) cycles has not been well characterized.

DESIGN

Retrospective cohort study.

METHOD OF STUDY

Endometrial tissue was collected from infertility patients prior to a frozen embryo transfer cycle as part of an endometrial receptivity analysis (ERA^® ) biopsy or endometrial scratch test. Uterine NK (uNK) and Treg cell density was compared based on pregnancy status in the subsequent frozen embryo transfer cycle. Peripheral blood was also collected from a separate cohort of patients undergoing frozen embryo transfer. Treg cell density was compared by the presence or the absence of a clinical pregnancy in each phase of the cycle.

RESULTS

In the 33 luteal phase biopsies there were more endometrial Tregs, similar uNK and a trend toward lower CD16⁺ uNK cells in women with a future ongoing clinical pregnancy compared to non-pregnant women. There were no differences in uNK and Treg density in natural scratch cycles vs programmed cycles or in non-receptive vs receptive endometrium (ERA^® cycles). In the peripheral blood analysis, the pregnant group had higher peripheral blood Tregs on the day of serum β-hCG time point when compared to the non-pregnant group.

CONCLUSION

Higher levels of endometrial Tregs and lower levels of CD16⁺ uNK cells are positive prognostic factors for infertile women prior to frozen embryo transfer. Our work on phenotypic and proportional analyses of endometrial immune cells may complement the ERA^® in predicting improved pregnancy rates in patients with implantation failure.

Granzyme B-expressing γδ-T and NK cells as a predictor of clinical pregnancy failure in patients with unexplained repeated implantation failure

The limited cytotoxicity of immune cells facilitates a successful establishment of pregnancy. However, the association between cytotoxic granules and unexplained repeated implantation failure (uRIF) remains unkown. Twenty-one fertile controls and 54 patients with uRIF were included in this study. The pregnancy outcomes were monitored at different gestational periods. The peripheral blood lymphocytes were detected using specific monoclonal antibodies by flow cytometry. The percentage of perforin⁺ (Pfr⁺), granzyme B⁺ (GrB⁺), or granulysin⁺ (Gnly⁺) lymphocytes was not significantly different among fertile controls, uRIF patients with successful pregnancy outcomes, and uRIF patients with pregnancy failure. The percentage of GrB⁺ γδ-T cells in lymphocytes was markedly higher in uRIF patients with implantation failure and clinical pregnancy failure than that in uRIF patients with a corresponding successful pregnancy outcome. A four-tier risk model showed that the risk of suffering clinical pregnancy failure in uRIF patients among high risk tier (83.3 %), normal risk tier (65.0 %) and low risk tier (39.1 %) was elevated by 2-4 fold compared with uRIF patients among lowest risk tier (20.0 %). In addition, the percentage of GrB⁺ NK cells in lymphocytes tended to decrease in uRIF patients with pregnancy failure. The AUC of the combined indicator with GrB⁺ γδ-T cells and GrB⁺ NK cells was increased than that of GrB⁺ γδ-T cells and GrB⁺ NK cells for predicting clinical pregnancy failure. In conclusion, the frequency of GrB-expressing γδ-T and NK cells in peripheral blood could serve as a predictor of clinical pregnancy failure in patients with uRIF.

Role of Caspases in the Cytotoxicity of NK-92 Cells in Various Models of Coculturing with Trophoblasts

Studies of interactions between natural killer (NK) cells and trophoblasts and identification of conditions for the NK cells to perform their cytotoxic function are of fundamental and practical importance for understanding their role in the development of pathological processes and complications during pregnancy. In this study, we examined changes in the content of caspases and studied activation of these enzymes in Jeg-3 trophoblasts in various models of their coculturing with NK-92 cells and demonstrated the necessity of direct contact between these cell populations for the activation of caspase-8 and caspase-3 in the trophoblasts. Contact coculturing of the two cell lines resulted in the appearance of the cytotoxic protein granzyme B in Jeg-3 cells that was accompanied by a decrease in the content of this enzyme in NK-92 cells. Distant coculturing of NK-92 and Jeg-3 cells did not trigger initiator and effector caspases characteristic for the apoptosis development in Jeg-3 cells. The observed decrease in the content of procaspases in the trophoblasts may be associated with alternative non-apoptotic functions of these enzymes.

Trophoblast-derived CXCL12 promotes CD56bright CD82- CD29+ NK cell enrichment in the decidua

PROBLEM

Decidual natural killer (dNK) cells play key roles in maternal-fetal immune regulation, trophoblast invasion, and vascular remodeling, and most dNK cell populations are CD56^bright CD16^- NK cells. However, the enrichment and redistribution of dNK cells in the local decidua have not been clarified yet.

METHOD OF STUDY

A total of 45 women with normal pregnancies and 8 unexplained recurrent spontaneous abortion (RSA) patients were included. We isolated primary human dNK (n = 53) and peripheral blood NK (pNK) cells (n = 5) from specimen and analyzed CD56, CD82, and CD29 by flow cytometry (FCM). We assessed their adhesion ability by cell counts of NK cells adhered to decidual stromal cells (DSCs) in a co-culture system.

RESULTS

We found that RSA patients had more CD56^dim dNK cells with lower CD82 and higher CD29 than women with normal pregnancies. There were negative correlations of CD82 to CD29 on CD56^dim and CD56⁺ dNK cells. In normal pregnancies, dNK cells had lower CD82 and higher CD29 expression with a stronger adhesion ability than pNK cells. Blocking CD82 on dNK cells increased the adhesive ability and CD29 expression, while blocking CD29 decreased the adhesive ability. Co-culturing dNK cells with trophoblast cells decreased CD82 expression and increased the adhesive ability of dNK cells and the percentage of CD56^bright NK cells, while blocking trophoblast-derived CXCL12 increased CD82 expression, decreased CD29 expression, and impaired the adhesive ability of NK cells.

CONCLUSION

Trophoblast cells enhance the adhesive ability of NK cells to DSCs via the CXCL12/CD82/CD29 signaling pathway and contribute to CD56^bright NK cell enrichment in the uterus.

Endoplasmic reticulum stress disrupts lysosomal homeostasis and induces blockade of autophagic flux in human trophoblasts

Pregnancy is a stress factor culminating into mild endoplasmic reticulum (ER) stress, which is necessary for placental development. However, excessive or chronic ER stress in pre-eclamptic placentas leads to placental dysfunction. The precise mechanisms through which excessive ER stress impacts trophoblasts are not well understood. Here, we showed that ER stress reduces the number of lysosomes, resulting in inhibition of autophagic flux in trophoblast cells. ER stress also disrupted the translocation of lysosomes to the surface of trophoblast cells, and inhibited lysosomal exocytosis, whereby the secretion of lysosomal-associated membrane protein 1 (LAMP1) into culture media was significantly attenuated. In addition, we found that serum LAMP1 and beta-galactosidase levels were significantly decreased in pre-eclampsia patients compared to normal pregnant women, potentially indicating lysosomal dysfunction through ER stress in pre-eclamptic placentas. Thus, we demonstrated that excessive ER stress essentially disrupts homeostasis in trophoblasts in conjunction with autophagy inhibition by lysosomal impairment.

Uterine natural killer cells: Time for a re-appraisal?

The presence of unusual natural killer cells in human endometrium has been recognized for 30 years, but despite considerable research effort, the in vivo role of uterine natural killer (uNK) cells in both normal and pathological pregnancy remains uncertain. uNK cells may differentiate from precursors present in endometrium, but migration from peripheral blood in response to chemokine stimuli with in situ modification to a uNK cell phenotype is also possible. uNK cells produce a wide range of secretory products with diverse effects on trophoblast and spiral arteries which may play an important role in implantation and early placentation. Interactions with other decidual cell populations are also becoming clear. Recent evidence has demonstrated subpopulations of uNK cells and the presence of other innate lymphoid cell populations in decidua which may refine future approaches to investigation of the role of uNK cells in human pregnancy.

The State of Peripheral Blood Natural Killer Cells and Cytotoxicity in Women with Recurrent Pregnancy Loss and Unexplained Infertility

Background

The prognostic value of peripheral natural killer (pNK) cells, as a screening test in women with recur- rent pregnancy loss (RPL) and unexplained infertility, is still a matter for discussion. The purpose of this study was to compare the percentage of circulating CD56⁺NK cells, CD69 and perforin markers between women with unexplained infertility and RPL with the healthy control group.

Materials and Methods

In this case-control study, the percentage of CD56⁺NK cells and activation markers (CD69 and perforin levels) in the peripheral blood were measured in 25 women with unexplained infertility, 24 women with idiopathic RPL and 26 women from the healthy control group, using specific monoclonal antibodies by flow cytometry.

Results

The percentage of CD56⁺NK cells was significantly higher in patients with infertility in comparison with the healthy control group (P=0.007). There were not significant differences either in the total number of CD56⁺cells between the RPL group and the control group (P=0.2) or between the RPL group and the infertile group (P=0.36). The percentage of CD69⁺lymphocytes in RPL group was significantly higher than in the infertility group (P=0.004). There was a statistically significant difference in Perforin levels between RLP and control (P=0.001) as well as RPL and infertile (P=0.002) groups.

Conclusion

An increased percentage of CD56⁺NK cells in patients with unexplained infertility, an elevated expression of CD69 on NK cells in patients with RPL and infertility and a high level of perforin on CD56⁺cells in the RPL group might be considered as immunological risk factors in these women.

Trophoblast-Specific Conditional Atg7 Knockout Mice Develop Gestational Hypertension

Hypertensive disorder of pregnancy (HDP) is a serious pregnancy complication that is life threatening to both the mother and fetus. Understanding HDP pathophysiology is important for developing medical treatments. This study demonstrates the involvement of autophagy deficiency in adverse maternal and fetal outcomes using trophoblast-specific autophagy related (Atg)7, an autophagy-related protein, knockout mice. Atg7 conditional knockout (cKO) placentas were significantly smaller than controls in the spongiotrophoblast layer but not the labyrinth layer, which significantly elevated blood pressure in dams. A marker of autophagy deficiency, sequestosome 1/p62, was accumulated in giant trophoblast cells and in the spongiotrophoblast layer, accompanying increased apoptosis. However, neither proteinuria in dams nor fetal growth restriction was observed. Regarding trophoblast function, the number of trophoblasts migrating into the maternal decidua was significantly reduced, and the wall/lumen ratio of the spiral arteries was significantly increased in cKO placentas, suggesting shallow trophoblast invasion and inadequate vascular remodeling. The relative expression of placental growth factor mRNA was significantly decreased in cKO placentas compared with the control, likely causing poor placentation; however, other factors were unchanged in cKO placentas. This is the first report of autophagy deficiency leading to impaired placentation complicated by maternal HDP attributable to trophoblast dysfunction, and it suggests that placental autophagy is required for normal placentation.

Methylated oligonucleotide (MON)-induced promoter hypermethylation is associated with repression of CDH1 expression and contributes to the migration and invasion of human trophoblast cell lines

DNA cytosine-5 methylation plays a vital role in regulating the expression of E-cadherin, which is encoded by the CDH1 gene. In this study, we characterised the DNA methylation and expression pattern of CDH1 in an extravillous trophoblast cell line (HTR-8/SVneo) and two trophoblast cell lines -- JEG-3 and JAR. Promoter hypermethylation with reduced E-cadherin expression in HTR-8/SVneo cells and promoter hypomethylation with increased E-cadherin expression in JEG-3 and JAR cells were observed. Demethylation treatment significantly restored E-cadherin expression, contributing to decreases in the motility and invasiveness of HTR-8/SVneo cells. Sense-methylated oligonucleotides (MONs) labelled with Cy5 and complementary to a region of the human CDH1 promoter were designed, with the cytosines in 5'-cytosine-phosphate-guanine-3' (CpG) dinucleotides being replaced by methylated cytosines. Following MON transfection into JEG-3 cells, the level of CDH1 promoter DNA methylation as well as cell motility and invasiveness were increased and gene expression was significantly repressed. Our results indicate that MON-mediated DNA methylation of the CDH1 promoter and subsequent alterations in gene expression may contribute to trophoblast motility and invasion, suggesting a potential method for controlling the biological function of trophoblasts in vitro through epigenetic modification.

Assessment of seminal granulysin in infertile men with varicocele

Varicocele has a common association with male infertility, but its exact role is still debated. Apoptosis has been suggested as one of the mechanisms of varicocele-associated infertility. Granulysin is a molecule that plays a role in apoptosis with no previous study about its role in male infertility. This case-controlled study aimed to assess seminal plasma granulysin level in infertile patients with varicocele. This study involved 90 men that were allocated into fertile normozoospermic men (n = 20), infertile men without varicocele (n = 30) and infertile men with varicocele (n = 40). These men were subjected to history taking, clinical examination, semen analysis and estimation of seminal granulysin. In general, seminal granulysin level was significantly elevated in infertile men compared with fertile men. Infertile men with varicocele showed significantly higher seminal granulysin compared with infertile men without varicocele, in bilateral varicocele cases and in grade III varicocele. Seminal granulysin level was negatively correlated with sperm concentration, sperm motility, sperm normal forms percentage and testicular volumes. It is concluded that increased seminal granulysin has a negative impact on spermatogenesis in infertile men in general and in infertile men associated with varicocele in particular.

Granulysin-mediated apoptosis of trophoblasts in blighted ovum and missed abortion

PROBLEM

Granulysin (GNLY) is a cytotoxic molecule mostly present in decidual natural killer (NK) cells. Blighted ovum (BO) and missed abortion (MA) represent the early pathological pregnancies with hindered development of the embryoblast or a dead embryo. We investigated the GNLY-mediated apoptotic mechanism potentially responsible for delayed termination of pregnancy.

METHOD OF STUDY

We performed immunohistological and immunofluorescence labeling of decidual tissues (GNLY, Apaf-1, NF-κB). NKG2A expression was analyzed by flow cytometry and GNLY mRNA by RT-qPCR.

RESULTS

The GNLY labeling intensity (H score) was lower in the nuclei of trophoblast cells in BO and MA. GNLY gene levels were inversely detected in BO and MA. A decreased decidual NK cell percentage was found in MA. NK cells from pathological pregnancies expressed lower NKG2A levels. The highest frequency of Apaf-1 was found in trophoblast cells of MA. NF-kB was highly expressed in decidual cells of BO.

CONCLUSION

The reduced activation of GNLY-mediated killing might be implicated in the slower rejection of trophoblast cells in BO and MA. A decreased authentic decidual NK cell number could be responsible for low cytotoxicity against trophoblast cells in MA. In BO, trophoblast cells have a higher survival potential due to increased NF-kB expression.

Lymphocytes in Placental Tissues: Immune Regulation and Translational Possibilities for Immunotherapy

Immune modulation at the fetomaternal interface is crucial to ensure that the fetal allograft is not rejected. In the present review, the focus is to describe basic functions of lymphocyte populations and how they may contribute to fetomaternal immune regulation, as well as determining what proportions and effector functions of these cells are reported to be present in placental tissues in humans. Also explored is the possibility that unique cell populations at the fetomaternal interface may be targets for adoptive cell therapy. Increasing the understanding of immune modulation during pregnancy can give valuable insight into other established fields such as allogeneic hematopoietic stem cell transplantation and solid organ transplantation. In these settings, lymphocytes are key components that contribute to inflammation and rejection of either patient or donor tissues following transplantation. In contrast, an allogeneic fetus eludes rejection by the maternal immune system.

Activated NK cells cause placental dysfunction and miscarriages in fetal alloimmune thrombocytopenia

Miscarriage and intrauterine growth restriction (IUGR) are devastating complications in fetal/neonatal alloimmune thrombocytopenia (FNAIT). We previously reported the mechanisms for bleeding diatheses, but it is unknown whether placental, decidual immune cells or other abnormalities at the maternal-fetal interface contribute to FNAIT. Here we show that maternal immune responses to fetal platelet antigens cause miscarriage and IUGR that are associated with vascular and immune pathologies in murine FNAIT models. Uterine natural killer (uNK) cell recruitment and survival beyond mid-gestation lead to elevated NKp46 and CD107 expression, perforin release and trophoblast apoptosis. Depletion of NK cells restores normal spiral artery remodeling and placental function, prevents miscarriage, and rescues hemorrhage in neonates. Blockade of NK activation receptors (NKp46, FcɣRIIIa) also rescues pregnancy loss. These findings shed light on uNK antibody-dependent cell-mediated cytotoxicity of invasive trophoblasts as a pathological mechanism in FNAIT, and suggest that anti-NK cell therapies may prevent immune-mediated pregnancy loss and ameliorate FNAIT.Fetal/neonatal alloimmune thrombocytopenia (FNAIT) is a gestational disease caused by maternal immune responses against fetal platelets. Using a FNAIT mouse model and human trophoblast cell lines, here the authors show that uterine natural killer cell-mediated trophoblast apoptosis contributes to FNAIT pathogenesis.

Cytotoxic potential of decidual NK cells and CD8+ T cells awakened by infections

To establish a healthy pregnancy the maternal immune system must tolerate fetal allo-antigens, yet remain competent to respond to infections. The ability of decidual NK cells (dNK) to promote migration of fetal extravillous trophoblasts (EVT) and placental growth as well as the capacity of EVT to promote immune tolerance are topics of high interest and extensive research. However, the problem of how dNK and decidual CD8+ T cells (CD8+ dT) provide immunity to infections of the placenta and the mechanisms that regulate their cytolytic function has thus far largely been ignored. Fetal EVT are the most invasive cells of the placenta and directly interact with maternal decidual immune cells at this maternal-fetal interface. Besides the expression of non-polymorphic HLA-E and HLA-G molecules that are associated with immune tolerance, EVT also express highly polymorphic HLA-C molecules that can serve as targets for maternal dNK and CD8+ dT responses. HLA-C expression by EVT has a dual role as the main molecule to which immune tolerance needs to be established and as the only molecule that can present pathogen-derived peptides and provide protective immunity when EVT are infected. The focus of this review is to address the regulation of cytotoxicity of dNK and CD8+ dT, which is essential for maternal-fetal immune tolerance as well as recent evidence that both cell types can provide immunity to infections at the maternal-fetal interface. A particular emphasis is given to the role of HLA-C expressed by EVT and its capacity to elicit dNK and CD8+ dT responses.

Potential role of heat-shock protein 70 and interleukin-15 in the pathogenesis of threatened spontaneous abortions

PROBLEM

The role of HSP70 and both its constitutive (Hsc) and inducible (Hsp) forms in the pathogenesis of threatened spontaneous abortions was investigated.

METHOD OF STUDY

Immunohistology and/or immunofluorescence was used to analyze paraffin-embedded tissue sections, and reverse transcriptase-quantitative polymerase chain reaction and flow cytometry were used for analyses of decidual mononuclear cells (DMCs) and confocal microscopy for the detection of perforin, granulysin, and lysosome-associated membrane protein-1 (LAMP-1) in decidual lymphocytes (DLs).

RESULTS

The percentage of single Hsp70(+) , Hsc70(+) , and IL-15(+) cells and mRNA levels of HSP70, CD91, and TLR4 were lower in the decidua basalis in cases of threatened miscarriages compared to that in cases of normal pregnancy. In a suspension of normal DMCs, IL-15 significantly decreased the HSP70 members and TLR4 in dendritic cells, T cells, and NK cells while increasing CD91 in NK cells alone.

CONCLUSION

Downregulation of Hsc70, Hsp70, and IL-15 expression at gene and/or protein levels might support the retention of fertilization products in cases of missed abortion and blighted ovum.

Evidence for Differential Glycosylation of Trophoblast Cell Types

Human placental villi are surfaced by the syncytiotrophoblast (STB), with a layer of cytotrophoblasts (CTB) positioned just beneath the STB. STB in normal term pregnancies is exposed to maternal immune cells in the placental intervillous space. Extravillous cytotrophoblasts (EVT) invade the decidua and spiral arteries, where they act in conjunction with natural killer (NK) cells to convert the spiral arteries into flaccid conduits for maternal blood that support a 3-4 fold increase in the rate of maternal blood flow into the placental intervillous space. The functional roles of these distinct trophoblast subtypes during pregnancy suggested that they could be differentially glycosylated. Glycomic analysis of these trophoblasts has revealed the expression of elevated levels of biantennary N-glycans in STB and CTB, with the majority of them bearing a bisecting GlcNAc. N-glycans terminated with polylactosamine extensions were also detected at low levels. A subset of the N-glycans linked to these trophoblasts were sialylated, primarily with terminal NeuAcα2-3Gal sequences. EVT were decorated with the same N-glycans as STB and CTB, except in different proportions. The level of bisecting type N-glycans was reduced, but the level of N-glycans decorated with polylactosamine sequences were substantially elevated compared with the other types of trophoblasts. The level of triantennary and tetraantennary N-glycans was also elevated in EVT. The sialylated N-glycans derived from EVT were completely susceptible to an α2-3 specific neuraminidase (sialidase S). The possibility exists that the N-glycans associated with these different trophoblast subpopulations could act as functional groups. These potential relationships will be considered.

Possible role of granulysin in pathogenesis of osteoarthritis

Increased presence of immune mediator and cytotoxic/apoptotic molecule granulysin was noticed in different tissues during pathological processes with the domination of Th1 over Th2 mediated immunity. Beside granulysin expression in T and NKT cells, activated NK cells are thought to be the major source of chemotactic 15 kDa and cytotoxic 9 kDa granulysin in vivo. As NK cells are the principal joint's tissue-infiltrating lymphocyte subset, we hypothesized that granulysin mediated human cell death (apoptosis) could be responsible for the relatively silent damage of the joint's tissue without clinically notable signs of systemic inflammation in the patients with osteoarthritis (OA). The analyzes of the presence and frequency of granulysin expressing lymphocytes at protein and gene levels in peripheral blood and synovial samples and/or the samples of joint's tissue after the joint replacement therapy in patients with OA could give the initial insight to evaluate our hypothesis. It would be of the particular interest to differentiate the expression of 9 kDa and 15 kDa granulysin forms in the effector cells, since only the shorter form exhibits cytotoxic properties. The measurement of granulysin mediated early apoptosis in human NK sensitive K562 cells could be suitable in vitro model for evaluating granulysin activity. Furthermore, disturbed balance of pro-inflammatory and anti-inflammatory cytokines in OA patients, could influence the level of the granulysin expression. Having in mind that the granulysin and its regulation is still unknown in the pathogenesis of OA, it could be worth to explore this important pro-inflammatory, cytotoxic/apoptotic mediator.

Granulysin Expression in Lymphocytes that Populate the Peripheral Blood and the Myocardium after an Acute Coronary Event

We aimed to analyse granulysin (GNLY)-mediated cytotoxicity in the peripheral blood of patients with non-ST-segment elevation myocardial infarction (NSTEMI) treated with anti-ischaemic drug therapy. Thirty-nine NSTEMI patients with a median age of 70 years and 28 age-matched healthy subjects were enrolled in this study. On day 7 after MI, the number of GNLY(+) lymphocytes in the peripheral blood increased approximately six-fold of that in the healthy subjects, measured by flow cytometry. On day 14, the number of GNLY(+) cells significantly decreased in T, NKT, and both CD56(+dim) and CD56(+bright) NK subsets. GNLY(+) CD3(+) and GNLY(+) CD56(+) cells infiltrated central zone of myocardial infarction (MI). In persons who died in the first week after MI, GNLY(+) cells were found within accumulation of apoptotic leucocytes and reached the apoptotic cardiomyocytes in border MI zones probably due to the influence of interleukin-15 in peri-necrotic cardiomyocytes, as it is was shown by immunohistology. By day 28, the percentage of GNLY(+) lymphocytes in peripheral blood returned to the levels similar to that of the healthy subjects. Anti-GNLY mAb decreased apoptosis of K562 targets using peripheral blood NK cells from days 7 and 28 after MI, while in assays using cells from days 1 and 21, both anti-GNLY and anti-perforin mAbs were required to significantly decrease apoptosis. Using NK cells from day 14, K562 apoptosis was nearly absent. In conclusion, it seems that GNLY(+) lymphocytes, probably attracted by IL-15, not only participate partially in myocardial cell apoptosis, but also hasten resolution of cardiac leucocyte infiltration in patients with NSTEMI.

The Role of Uterine NK Cells in Normal Reproduction and Reproductive Disorders

The human endometrium contains a substantial population of leucocytes which vary in distribution during the menstrual cycle and pregnancy. An unusual population of natural killer (NK) cells, termed uterine NK (uNK) cells, are the most abundant of these cells in early pregnancy. The increase in number of uNK cells in the mid-secretory phase of the cycle with further increases in early pregnancy has focused attention on the role of uNK cells in early pregnancy. Despite many studies, the in vivo role of these cells is uncertain. This chapter reviews current information regarding the role of uNK cells in healthy human pregnancy and evidence indicating their importance in various reproductive and pregnancy problems. Studies in humans are limited by the availability of suitable tissues and the limitations of extrapolation from animal models.

Iron overload in Plasmodium berghei-infected placenta as a pathogenesis mechanism of fetal death

Plasmodium infection during gestation may lead to severe clinical manifestations including abortion, stillbirth, intrauterine growth retardation, and low birth weight. Mechanisms underlying such poor pregnancy outcomes are still unclear. In the animal model of severe placental malaria (PM), in utero fetal death frequently occurs and mothers often succumb to infection before or immediately after delivery. Plasmodium berghei-infected erythrocytes (IEs) continuously accumulate in the placenta, where they are then phagocytosed by fetal-derived placental cells, namely trophoblasts. Inside the phagosomes, disruption of IEs leads to the release of non-hemoglobin bound heme, which is subsequently catabolized by heme oxygenase-1 into carbon monoxide, biliverdin, and labile iron. Fine-tuned regulatory mechanisms operate to maintain iron homeostasis, preventing the deleterious effect of iron-induced oxidative stress. Our preliminary results demonstrate that iron overload in trophoblasts of P. berghei-infected placenta is associated with fetal death. Placentas which supported normally developing embryos showed no iron accumulation within the trophoblasts. Placentas from dead fetuses showed massive iron accumulation, which was associated with parasitic burden. Here we present preliminary data suggesting that disruption of iron homeostasis in trophoblasts during the course of PM is a consequence of heme accumulation after intense IE engulfment. We propose that iron overload in placenta is a pathogenic component of PM, contributing to fetal death. The mechanism through which it operates still needs to be elucidated.

Expression profiles of perforin, granzyme B and granulysin genes during the estrous cycle and gestation in the bovine endometrium

The conceptus is susceptible to destruction by maternal cytotoxic lymphocytes, which have cytotoxic potential. Therefore, it is expected that mechanisms for regulating cytotoxic lymphocytes exist, but little is known about the expression of cytotoxic genes in the endometrium. In the present study, we examined the spatial and temporal expression patterns of the cytotoxic genes perforin, granzyme B, and granulysin during the estrous cycle and gestation in the bovine endometrium. Endometrial tissues were collected from cows during the estrous cycle and gestation. The gene expression patterns of the three cytotoxic genes were examined using quantitative polymerase chain reaction and in situ hybridization, and cytotoxic lymphocyte subsets were characterized using immunohistochemistry. During mid- to late gestation in the intercaruncular (ICAR), granulysin expression was significantly increased, and a large number of granulysin-expressing cells were localized in the luminal epithelium. Perforin and granzyme B displayed similar expression profiles and were highly expressed in the peri-implantation endometrium, but few cells expressing these genes were found in the endometrial stroma. In conclusion, these findings suggest that in the ICAR epithelium granulysin may play important roles in the establishment and maintenance of gestation during normal pregnancy.

Natural killer cells and regulatory T cells in early pregnancy loss

Survival of the allogeneic embryo in the uterus depends on the maintenance of immune tolerance at the maternal-fetal interface. The pregnant uterus is replete with activated maternal immune cells. How this immune tolerance is acquired and maintained has been a topic of intense investigation. The key immune cells that predominantly populate the pregnant uterus are natural killer (NK) cells. In normal pregnancy, these cells are not killers, but rather provide a microenvironment that is pregnancy compatible and supports healthy placentation. In placental mammals, an array of highly orchestrated immune elements to support successful pregnancy outcome has been incorporated. This includes active cooperation between maternal immune cells, particularly NK cells, and trophoblast cells. This intricate process is required for placentation, immune regulation and to remodel the blood supply to the fetus. During the past decade, various types of maternal immune cells have been thought to be involved in cross-talk with trophoblasts and in programming immune tolerance. Regulatory T cells (Tregs) have attracted a great deal of attention in promoting implantation and immune tolerance beyond implantation. However, what has not been fully addressed is how this immune-trophoblast axis breaks down during adverse pregnancy outcomes, particularly early pregnancy loss, and in response to unscheduled inflammation. Intense research efforts have begun to shed light on the roles of NK cells and Tregs in early pregnancy loss, although much remains to be unraveled in order to fully characterize the mechanisms underlying their detrimental activity. An increased understanding of host-environment interactions that lead to the cytotoxic phenotype of these otherwise pregnancy compatible maternal immune cells is important for prediction, prevention and treatment of pregnancy maladies, particularly recurrent pregnancy loss. In this review, we discuss relevant information from experimental and human models that may explain the pregnancy disrupting roles of these pivotal sentinel cells at the maternal-fetal interface.

Natural killer cells in human pregnancy

While conventional NK cells play an important role in early defenses against pathogens thanks to their cytolytic activity and production of pro-inflammatory chemokines and cytokines, those present in decidua (dNK cells), during early pregnancy, are primarily involved in tissue building and remodeling and in the formation of new blood vessels. This occurs mainly via the release of IL-8, VEGF, SDF-1 and IP-10. In addition, we show that by interacting with particular myelomonocytic cells (dCD14(+)) they contribute to the induction of regulatory T cells (Tregs). In turn, Tregs are thought to play a pivotal role in immunosuppression and induction of tolerance toward the fetal allograft. We recently demonstrated that CD34(+) hematopoietic precursors (dCD34(+)) are present in decidual tissues, thus suggesting that dNK cells might derive from such precursors. Indeed, this was confined by in vitro experiments in which dCD34(+) cells differentiated into dNK cells upon culture with appropriate cytokine combinations or even in co-culture with decidua-derived stromal cells (dSC). It is possible to speculate that inappropriate cellular interactions in the decidual microenvironment or defects of dNK (or dCD14(+)) cell generation might negatively influence pregnancy success.

Mucins help to avoid alloreactivity at the maternal fetal interface

During gestation, many different mechanisms act to render the maternal immune system tolerant to semi-allogeneic trophoblast cells of foetal origin, including those mediated via mucins that are expressed during the peri-implantation period in the uterus. Tumour- associated glycoprotein-72 (TAG-72) enhances the already established tolerogenic features of decidual dendritic cells with the inability to progress towards Th1 immune orientation due to lowered interferon (IFN)-γ and interleukin (IL)-15 expression. Mucine 1 (Muc 1) supports alternative activation of decidual macrophages, restricts the proliferation of decidual regulatory CD56⁺ bright natural killer (NK) cells, and downregulates their cytotoxic potential, including cytotoxic mediator protein expression. Removing TAG-72 and Muc 1 from the eutopic implantation site likely contributes to better control of trophoblast invasion by T cells and NK cells and appears to have important immunologic advantages for successful implantation, in addition to mechanical advantages. However, these processes may lead to uncontrolled trophoblast growth after implantation, inefficient defence against infection or tumours, and elimination of unwanted immunocompetent cells at the maternal-foetal interface. The use of mucins by tumour cells to affect the local microenvironment in order to avoid the host immune response and to promote local tumour growth, invasion, and metastasis confirms this postulation.

Maternal decidual macrophages inhibit NK cell killing of invasive cytotrophoblasts during human pregnancy

Human pregnancy is an immunological paradox. Semiallogeneic (fetal) placental cells (extravillous cytotrophoblasts [CTBs]) invade the uterine lining (decidua), which contains a unique decidual natural killer (dNK) cell population, identified by the cell surface phenotype CD56(bright) CD16(-) CD3(-) and CD14(+) CD206(+) macrophages (dMac). Previous reports suggested that human dNK cells are not a threat to the fetoplacental unit because they are anergic. In contrast, here we showed that purified and exogenously stimulated dNK cells are capable killers of cellular targets, including semiallogeneic CTBs. However, dMacs in the decidual leukocyte (DL) population restrained dNK killing through a transforming growth factor beta1 (TGF-beta1)-dependent mechanism. Our findings support a new model whereby dNK cells, capable of killing CTBs, are prevented from doing so by neighboring macrophages, thus protecting the fetal cells from NK cell attack. We speculate that this mechanism would inhibit dNK cell-mediated killing, even under conditions where high levels of cytokines may stimulate dNK cells, which could pose a threat to the developing placenta.

Granulysin expression and the interplay of granulysin and perforin at the maternal-fetal interface

Granulysin (GNLY) is a cytolytic/apoptotic molecule highly expressed in immune cells, particularly NK cells, at the maternal-fetal interface. The primary function of GNLY is to carry out lysis or apoptosis induction in target cells, tumor cells or cells infected by intracellular pathogens. To exert some of its functions GNLY needs to collaborate with perforin. The purpose of this study was to determine: (a) the expression of GNLY at the gene and protein levels at the maternal-fetal interface, (b) the relationship(s) between GNLY and perforin, and (c) GNLY secretion by NK cells stimulated by the NK-sensitive K562 cell line and its HLA-C and HLA-G transfectants. GNLY and perforin genes were found to be highly activated at the interface. GNLY mRNA was present at significantly higher levels compared with other cytolytic/apoptotic molecules. Confocal microscopy analysis showed that most first trimester pregnancy decidual lymphocytes simultaneously contained both GNLY and perforin protein in their cytoplasm, with a punctuate pattern consistent with granule localization. In contrast to peripheral blood, in unstimulated decidual lymphocytes GNLY and perforin rarely co-localized (10% of GNLY-positive cells and 20% of perforin-positive cells were positive for both proteins). Contact between decidual lymphocytes and K562 cells caused GNLY and perforin to be expressed in the same granules (approximately 50% co-localization), i.e., to attain the pattern seen in peripheral blood lymphocytes. The abundant GNLY secretion by decidual NK cells compared with peripheral blood NK cells after 2h of contact with the NK-sensitive K562 cells and K562 transfectants was striking.

Granzyme B-dependent and perforin-independent DNA fragmentation in intestinal epithelial cells induced by anti-CD3 mAb-activated intra-epithelial lymphocytes

We previously found that an i.p. injection of anti-CD3 monoclonal antibody (mAb) into mice caused DNA fragmentation in the intestinal villous epithelial cells (IVECs) of the duodenum and the jejunum. In this study, in order to elucidate the mechanism of DNA fragmentation in IVECs, we searched for the inducer(s) of DNA fragmentation by using immunohistochemistry. The release of cytoplasmic granules from intraepithelial lymphocytes (IELs) and the formation of large gaps between IELs and IVECs were observed electron microscopically after antibody administration. The presence and distribution pattern of Granzyme B (GrB), a serine protease in cytolytic granules present in cytotoxic T lymphocytes and natural killer cells and considered to be the responsible molecule for DNA fragmentation in target cells, was examined in detail in intestinal villi by immunohistology. GrB was detected in cytoplasmic granules in nearly all IELs. The time-kinetics of granule release from IELs after mAb injection coincided not only with that of the extracellular diffusion of GrB, but also with that of DNA fragmentation in IVECs. On the other hand, perforin (Pfn), assumed to cooperate with GrB in DNA fragmentation, could not be detected in IELs, and its release was not confirmed after the anti-CD3 mAb injection. Anti-CD3 mAb injection also induced DNA fragmentation in IVECs in Pfn-knockout mice. These results support the notion that DNA fragmentation in IVECs by the stimulated IELs in the present study is induced by a mechanism involving GrB, but independent of Pfn.

Impaired autophagy by soluble endoglin, under physiological hypoxia in early pregnant period, is involved in poor placentation in preeclampsia

In early pregnancy, trophoblasts and the fetus experience hypoxic and low-nutrient conditions; nevertheless, trophoblasts invade the uterine myometrium up to one third of its depth and migrate along the lumina of spiral arterioles, replacing the maternal endothelial lining. Here, we showed that autophagy, an intracellular bulk degradation system, occurred in extravillous trophoblast (EVT) cells under hypoxia in vitro and in vivo. An enhancement of autophagy was observed in EVTs in early placental tissues, which suffer from physiological hypoxia. The invasion and vascular remodeling under hypoxia were significantly reduced in autophagy-deficient EVT cells compared with wild-type EVT cells. Interestingly, soluble endoglin (sENG), which increased in sera in preeclamptic cases, suppressed EVT invasion by inhibiting autophagy. The sENG-inhibited EVT invasion was recovered by TGFB1 treatment in a dose-dependent manner. A high dose of sENG inhibited the vascular construction by EVT cells and human umbilical vein endothelial cells (HUVECs), meanwhile a low dose of sENG inhibited the replacement of HUVECs by EVT cells. A protein selectively degraded by autophagy, SQSTM1, accumulated in EVT cells in preeclamptic placental biopsy samples showing impaired autophagy. This is the first report showing that impaired autophagy in EVT contributes to the pathophysiology of preeclampsia.

Specific decidual CD14(+) cells hamper cognate NK cell proliferation and cytolytic mediator expression after mucin 1 treatment in vitro

Mucin 1 (MUC1) forms a glycocalyx on the surface of decidual epithelial cells that needs to be removed for successful embryo attachment. We investigated whether MUC1 affects human early pregnancy decidual CD14(+) cells and their interactions with cognate decidual natural killer (NK) cells. FITC-dextran internalisation, surface and intracellular antigen levels, and proliferation of CD14(+) and/or CD56(+) cells were analysed by flow cytometry. Magnetic separation was used to purify CD56(+) and CD14(+) cells. Uncultured CD14(+) cells expressed a negligible percentage of CD1a and CD83 molecules. They expressed lower levels of CD16, and higher levels of endocytic mannose receptors (MR), dendritic cell-specific intercellular adhesion molecule grabbing non-integrin (DC-SIGN), proinflammatory chemokine CC receptor 5 (CCR5), and CD163 receptor, than their peripheral blood counterparts. Lipopolysaccharide stimulation did not affect FITC-dextran internalisation in CD14(+) cells. MUC1 bound and internalised, in a dose-dependent manner, the carbohydrate recognition domain of MR, increasing the decoy IL-1 receptor type II and decreasing IL-15 expression in CD14(+) cells. In the presence of MUC1-treated macrophages, the expression levels of the proliferation and cytotoxic mediators (perforin, Fas ligand and TNF-related activation-induced ligand or TRAIL) was attenuated, while that of the anti-inflammatory chemokine CCL17 was increased, in NK cells compared with untreated macrophages. In conclusion, MUC1 supports the alternative activation of tissue-specific CD14(+) cells, and may restrict proliferation of NK cells and regulate their content of cytotoxic mediators. Based on the experiments with first-trimester decidual cells in vitro, we conclude that removing MUC1 from decidual tissue might help control trophoblast invasion by NK cells.