Placental Trophoblast from Successful Human Pregnancies Expresses the Tolerance Signaling Molecule, CD200 (OX-2)*

A Comparative Review of Pregnancy and Cancer and Their Association with Endoplasmic Reticulum Aminopeptidase 1 and 2

The fundamental basis of pregnancy and cancer is to determine the fate of the survival or the death of humanity. However, the development of fetuses and tumors share many similarities and differences, making them two sides of the same coin. This review presents an overview of the similarities and differences between pregnancy and cancer. In addition, we will also discuss the critical roles that Endoplasmic Reticulum Aminopeptidase (ERAP) 1 and 2 may play in the immune system, cell migration, and angiogenesis, all of which are essential for fetal and tumor development. Even though the comprehensive understanding of ERAP2 lags that of ERAP1 due to the lack of an animal model, recent studies have shown that both enzymes are associated with an increased risk of several diseases, including pregnancy disorder pre-eclampsia (PE), recurrent miscarriages, and cancer. The exact mechanisms in both pregnancy and cancer need to be elucidated. Therefore, a deeper understanding of ERAP's role in diseases can make it a potential therapeutic target for pregnancy complications and cancer and offer greater insight into its impact on the immune system.

GNAI2 Is a Risk Factor for Gastric Cancer: Study of Tumor Microenvironment (TME) and Establishment of Immune Risk Score (IRS)

Purpose

Although the G protein subunit α i2 (GNAI2) is upregulated in multiple cancers, its prognostic value and exact role in the development of gastric cancer (GC) remain largely unknown.

Methods

This study evaluated the effect of GNAI2 on the tumor microenvironment (TME) in GC, constructed an immune risk score (IRS) model based on differentially-expressed immune genes, and systematically correlated GNAI2 and epigenetic factor expression patterns with TME and IRS. Also, RT-qPCR, flow cytometry, Western blotting (WB), and transwell assays were carried out to explore the regulatory mechanism of GNAI2 in GC.

Results

High GNAI2 expression was associated with poor prognosis. Cytokine activation, an increase in tumor-infiltrating immune cells (TIIC), and the accumulation of regulatory T cells in the tumor immune cycle were all promoted by the TME, which was significantly associated with GNAI2 expression. Two different differentially expressed mRNA (DER) modification patterns were determined. These two DERs-clusters had significantly different TME cell infiltrations and were classified as either noninflamed or immune-inflamed phenotypes. The IRS model constructed using differentially expressed genes (DEGs) had great potential in predicting GC prognosis. The IRS model was also used in assessing clinicopathological features, such as microsatellite instability (MSI) status, epithelial-mesenchymal transition (EMT) status, clinical stages, tumor mutational burden (TMB), and tumor immune dysfunction and exclusion (TIDE) scores. Low IRS scores were associated with high immune checkpoint gene expression. Cell and animal studies confirmed that GNAI2 activated PI3K/AKT pathway and promoted the growth and migration of GC cells.

Conclusion

The IRS model can be used for survival prediction and GNAI2 serves as a candidate therapeutic target for GC patients.

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.

Regulatory T Cells in Pregnancy: It Is Not All About FoxP3

In pregnancy, the semi-allogeneic fetus needs to be tolerated by the mother's immune system. Regulatory T cells (Tregs) play a prominent role in this process. Novel technologies allow for in-depth phenotyping of previously unidentified immune cell subsets, which has resulted in the appreciation of a vast heterogeneity of Treg subsets. Similar to other immunological events, there appears to be great diversity within the Treg population during pregnancy, both at the maternal-fetal interface as in the peripheral blood. Different Treg subsets have distinct phenotypes and various ways of functioning. Furthermore, the frequency of individual Treg subsets varies throughout gestation and is altered in aberrant pregnancies. This suggests that distinct Treg subsets play a role at different time points of gestation and that their role in maintaining healthy pregnancy is crucial, as reflected for instance by their reduced frequency in women with recurrent pregnancy loss. Since pregnancy is essential for the existence of mankind, multiple immune regulatory mechanisms and cell types are likely at play to assure successful pregnancy. Therefore, it is important to understand the complete microenvironment of the decidua, preferably in the context of the whole immune cell repertoire of the pregnant woman. So far, most studies have focused on a single mechanism or cell type, which often is the FoxP3 positive regulatory T cell when studying immune regulation. In this review, we instead focus on the contribution of FoxP3 negative Treg subsets to the decidual microenvironment and their possible role in pregnancy complications. Their phenotype, function, and effect in pregnancy are discussed.

γδ T Cells Number, CD200, and Flt3 Expression Is Associated with Higher Progression Free Survival in Patients with Chronic Myeloid Leukemia

BACKGROUND

Tumor immunoedition involves alterations in cells of immune system, which may play an important role in the immunosurveillance of patients with cancer diseases.

AIM OF THE STUDY

To determine the association between the number of immune cells and the expression of surface markers in leukemic cells of patients with de novo CML who achieved molecular response.

METHODS

A longitudinal study was conducted in 31 patients with de novo CML. Peripheral blood samples were obtained at diagnosis for quantification of immune cells and tumor cells expressing CD200, CD135, GpP, and Bcl-2. Results were compared with a group of 60 healthy donors. Lymphocyte subsets were analyzed during a 48 month follow-up period and molecular response to treatment was assessed simultaneously by QT-PCR. The group of patients with deep molecular response was compared with de novo CML patients; the cut-off value of cell count was determined by ROC analysis. Kaplan-Meier and Cox proportional hazard model were used to determine the significant association between the number of cells and progression-free survival.

RESULTS

Differences in number of CD4, CD4Tregs, NK, γδT, monocytes, and pDC's, tumor-cells expressing CD200⁺, CD135⁺, GpP⁺, and Bcl-2⁺ were observed between patients and healthy donors. The number of γδT lymphocytes, CD200⁺, and CD135⁺ cells were associated with longer progression-free survival (p = 0.0112, p = 0.0012 and p = 0.0201 respectively).

CONCLUSION

A γδT lymphocyte count <63 cel/uL, CD200⁺ <997 cel/uL, and CD135⁺ <23 317 cel/uL at diagnosis is associated with the maintenance of deep molecular response at 48 months in patients with de novo CML.

Phase I study of samalizumab in chronic lymphocytic leukemia and multiple myeloma: blockade of the immune checkpoint CD200

PURPOSE

Samalizumab is a novel recombinant humanized monoclonal antibody that targets CD200, an immunoregulatory cell surface member of the immunoglobulin superfamily that dampens excessive immune responses and maintains self-tolerance. This first-in-human study investigated the therapeutic use of samalizumab as a CD200 immune checkpoint inhibitor in chronic lymphocytic leukemia (CLL) and multiple myeloma (MM).

EXPERIMENTAL DESIGN

Twenty-three patients with advanced CLL and 3 patients with MM were enrolled in an open-label phase 1 study (NCT00648739). Patients were assigned sequentially to one of 7 dose level cohorts (50 to 600 mg/m²) in a 3 + 3 study design, receiving a single dose of samalizumab intravenously once every 28 days. Primary endpoints were safety, identification of the maximum tolerated dose (MTD), and pharmacokinetics. Secondary endpoints were samalizumab binding to CD200, pharmacodynamic effects on circulating tumor cells and leukocyte subsets, and clinical responses.

RESULTS

Twenty-one patients received > 1 treatment cycle. Adverse events (AEs) were generally mild to moderate in severity. Samalizumab produced dose-dependent decreases in CD200 expression on CLL cells and decreased frequencies of circulating CD200 + CD4+ T cells that were sustained at higher doses. The MTD was not reached. Decreased tumor burden was observed in 14 CLL patients. One CLL patient achieved a durable partial response and 16 patients had stable disease. All MM patients had disease progression.

CONCLUSIONS

Samalizumab had a good safety profile and treatment was associated with reduced tumor burden in a majority of patients with advanced CLL. These preliminary positive results support further development of samalizumab as an immune checkpoint inhibitor.

TRIAL REGISTRATION

ClinicalTrials.gov, NCT00648739 registered April 1, 2008.

Decreased expression of CD200 and CD200R1 by human decidual tissues in spontaneous early abortion

Objective: To examine the cellular distribution and the expression of CD200 and its receptor 1 (CD200R1) in human deciduas in first-trimester pregnant women with spontaneous early abortion (SEA) and normal pregnancy, and to explore their role in the etiology of SEA.Subjects and methods: Thirty-five women at 6-10-week gestation with SA and 30 women of similar gestational age with a healthy pregnancy were recruited. Expression of CD200 and CD200R1 in the deciduas was determined using immunohistochemistry, confocal laser scanning microscope, Western blot, and real-time PCR (RT-PCR).Results: The decidual stromal cells, glandular epithelial cells, and vessel endothelial cells during the first trimester of pregnancy express both CD200 and CD200R1 proteins. During this period, the expression of CD200 in glandular epithelial cells and vessel endothelial cells is significantly higher in normal pregnancy than that in women with SEA (0.3079 ± 0.0674 versus 0.2735 ± 0.0515; 0.4077 ± 0.1366 versus 0.3249 ± 0.0993); the expression of CD200R1 in stromal cells, decidual stromal cells, glandular epithelial cells is significantly higher during normal pregnancy than SEA (0.2574 ± 0.0588 versus 0.2292 ± 0.0415; 0.3617 ± 0.1046 versus 0.2804 ± 0.0640). Western blot analysis showed an approximately 44% decrease in CD200R1expression in decidua in the SEA versus the controls. Finally, in decidua, the expression of both CD200 protein and CD200R1 transcript are significantly higher in healthy first-trimester pregnancy than in SEA (CD200: 2.2089 ± 1.2754 versus 0.7241 ± 0.2143; CD200R1: 15.7843 ± 10.7085 versus 7.3381 ± 5.8529).Conclusions: Women with SEA have a lower level of CD200 and CD200R1 expression in deciduas compared with normal pregnant women suggesting that under physiological conditions, CD200 and CD200R1 expression by deciduas is important to prevent fetal loss ensure a successful pregnancy.

Interaction of CD200 Overexpression on Tumor Cells with CD200R1 Overexpression on Stromal Cells: An Escape from the Host Immune Response in Rectal Cancer Patients

CD200 imparts an immunoregulatory signal through its receptor, CD200R1, leading to the suppression of tumor specific immunity. The mechanism of CD200:CD200R1 signaling pathway is still uncertain. Our aim was to investigate the expression and localization of CD200 and its receptor CD200R1 and their clinical significance in rectal cancer patients. We examined the immunohistochemical expressions and localizations of CD200 and CD200R1 in 140 rectal cancer patients. Among the patients, 79 underwent the preoperative radiotherapy and the others were untreated prior to the surgery. In addition, 121 matched normal rectal mucosa samples were evaluated. The results of immunohistochemical analysis showed a strikingly high level of CD200 in tumor cells (p=0.001) and CD200R1 expression in normal mucosal epithelium and stromal cells. Importantly, CD200R1 was overexpressed in stromal cells of the metastatic cancer patients compared to patients without metastases (p=0.002). More than that, 87% of metastatic patients had a phenotype of upregulated CD200 in tumor cells accompanied by overexpressed CD200R1 in stromal cells. In addition, low levels of CD200 were correlated with improved overall survival in untreated patients. We showed that tumor-stroma communication through CD200 and its receptor interaction is selected in patients with high risk of relapse. High levels of these molecules support instigation of the far and local metastatic nest that provides solid ground for metastasis. Our current data also disclose a mechanism by which CD200:CD200R1 affects tumor progression and may strengthen the feasibility of targeting CD200 or CD200R1 as anticancer strategy.

Reduced CD200 expression is associated with altered Th1/Th2 cytokine production in placental trophoblasts from preeclampsia

PROBLEM

To determine if altered trophoblast CD200 and CD200R expressions promote inflammatory cytokine production in preeclamptic placentas.

METHODS OF STUDY

Placental tissue CD200 and CD200R expressions were determined by immunostaining. Tissue sections from first-, second-, and third-trimester, normal term, and preeclamptic placentas were used. CD200 and CD200R expressions and cytokine production of TNFα, sTNFR1, INFγ, IL-4, IL-6, IL-8, and IL-10 were determined in trophoblasts from normal and preeclamptic placentas and in normal trophoblasts transfected with CD200 siRNA.

RESULTS

CD200, but not CD200R, expression was significantly reduced in trophoblasts from preeclamptic compared to normal placentas. Trophoblast from preeclamptic placentas and trophoblast transfected with CD200 siRNA produced significantly more TNFα, sTNFR1, IL-6, and IL-8, but significantly less IL-10, than trophoblasts from normal control placentas.

CONCLUSION

Downregulation of CD200 expression resulted in an imbalance of increased Th1 cytokine and decreased Th2 cytokine production in placental trophoblasts in preeclampsia.

Co-Signaling Molecules in Maternal-Fetal Immunity

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

Over-Expression of CD200 Protects Mice from Dextran Sodium Sulfate Induced Colitis

BACKGROUND AND AIM

CD200:CD200 receptor (CD200R) interactions lead to potent immunosuppression and inhibition of autoimmune inflammation. We investigated the effect of "knockout"of CD200 or CD200R, or over-expression of CD200, on susceptibility to dextran sodium sulfate (DSS)-induced colitis, a mouse model of inflammatory bowel disease (IBD).

METHODS

Acute or chronic colitis was induced by administration of dextran sodium sulfate (DSS) in four groups of age-matched C57BL/6 female mice: (1) CD200-transgenic mice (CD200tg); (2) wild-type (WT) mice; (3) CD200 receptor 1-deficient (CD200R1KO) mice; and (4) CD200-deficient (CD200KO) mice. The extent of colitis was determined using a histological scoring system. Colon tissues were collected for quantitative RT-PCR and Immunohistochemical staining. Supernatants from colonic explant cultures and mononuclear cells isolated from colonic tissue were used for ELISA.

RESULTS

CD200KO and CD200R1KO mice showed greater sensitivity to acute colitis than WT mice, with accelerated loss of body weight, significantly higher histological scores, more severe infiltration of macrophages, neutrophils and CD3+ cells, and greater expression of macrophage-derived inflammatory cytokines, whose production was inhibited in vitro (in WT/CD200KO mouse cells) by CD200. In contrast, CD200tg mice showed less sensitivity to DSS compared with WT mice, with attenuation of all of the features seen in other groups. In a chronic colitis model, greater infiltration of Foxp3+ regulatory T (Treg) cells was seen in the colon of CD200tg mice compared to WT mice, and anti-CD25 mAb given to these mice attenuated protection.

CONCLUSIONS

The CD200:CD200R axis plays an immunoregulatory role in control of DSS induced colitis in mice.

Reduced CD200 and CD200R1 expression in human chorionic villi contributes to early spontaneous abortion

OBJECTIVE

To examine the expression of CD200 and its receptor (CD200R) in human chorionic villi during the first trimester of normal pregnancy and early spontaneous abortion (ESA).

DESIGN

Prospective study.

METHODS

Expression of CD200 and CD200R in the chorionic villi was determined using streptavidin-peroxidase immunohistochemistry, confocal laser scanning microscopy and real-time polymerase chain reaction.

POPULATION

Thirty-five women diagnosed with ESA and 30 women experiencing a healthy pregnancy in a medical university hospital in China were enrolled in this study between 2011 and 2013.

MAIN OUTCOME MEASURES

CD200 and CD200R expression.

RESULTS

The expression of CD200 in syncytiotrophoblast cells was significantly higher during normal pregnancy than in ESA (0.51 ± 0.05 vs. 0.35 ± 0.05). In contrast, expression of CD200 in cytotrophoblast cells and CD200R in stromal cells was significantly lower during normal pregnancy when compared with ESA (CD200: 0.16 ± 0.02 vs. 0.32 ± 0.03; CD200R: 0.19 ± 0.03 vs. 0.22 ± 0.02). In villi, the expression of both CD200 protein and CD200R transcripts were significantly higher in healthy first-trimester pregnancy than in ESA (CD200: 156.89 ± 105.65 vs. 37.51 ± 17.62).

CONCLUSIONS

There is an increase in inhibitory properties of human chorionic villi during normal pregnancy. The mechanism underlying ESA might be associated with enhanced expression of CD200 and CD200R in the trophoblast, leading to an upregulation of the immune response during the first trimester of pregnancy.

Human placenta-derived adherent cells induce tolerogenic immune responses

Human placenta-derived adherent cells (PDAC cells) are a culture expanded, undifferentiated mesenchymal-like population derived from full-term placental tissue, with immunomodulatory and anti-inflammatory properties. PDA-001 (cenplacel-L), an intravenous formulation of PDAC cells, is in clinical development for the treatment of autoimmune and inflammatory diseases. To elucidate the mechanisms underlying the immunoregulatory properties of PDAC cells, we investigated their effects on immune cell populations, including T cells and dendritic cells (DC) in vitro and in vivo. PDAC cells suppressed T-cell proliferation in an OT-II T-cell adoptive transfer model, reduced the severity of myelin oligodendrocyte glycoprotein peptide-induced experimental autoimmune encephalomyelitis and ameliorated inflammation in a delayed type hypersensitivity response model. In vitro, PDAC cells suppressed T-cell proliferation and inhibited Th1 and Th17 differentiation. Analysis of tissues derived from PDAC cell-treated animals revealed diminished CD86 expression on splenic DC, suggesting that they can also modulate DC populations. Furthermore, PDAC cells modulate the differentiation and maturation of mouse bone marrow-derived DC. Similarly, human DC differentiated from CD14(+) monocytes in the presence of PDAC cells acquired a tolerogenic phenotype. These tolerogenic DC failed to induce allogeneic T-cell proliferation and differentiation toward Th1, but skewed T-cell differentiation toward Th2. Inhibition of cyclo-oxygenase-2 activity resulted in a significant, but not complete, abrogation of PDAC cells' effects on DC phenotype and function, implying a role for prostaglandin E2 in PDAC-mediated immunomodulation. This study identifies modulation of DC differentiation toward immune tolerance as a key mechanism underlying the immunomodulatory activities of PDAC cells.

Long-term immunomodulatory effect of amniotic stem cells in an Alzheimer's disease model

Amyloid beta (Aβ) plays a major role in Alzheimer's disease (AD), and neuroinflammatory processes mediated by Aβ plaque-induced microglial cells and astrocytes contribute to AD pathogenesis. The present study examined human placenta amniotic membrane-derived mesenchymal stem cells (AMSCs), which have potent immunomodulatory and paracrine effects in a Tg2576 (APPswe) transgenic mouse model of AD. AMSCs secreted high levels of transforming growth factor-β under in vitro inflammatory environment conditions. Six weeks after the intravenous injection of AMSCs, APPswe mice showed evidence of improved spatial learning, which significantly correlated with the observation of fewer Aβ plaques in brain. The number of ED1-positive phagocytic microglial cells associated with Aβ plaques was higher in AMSC-injected mice than in phosphate-buffered saline-injected mice, and the level of Aβ-degrading enzymes (matrix metallopeptidase-9 and insulin-degrading enzyme) was also significantly higher. Furthermore, the level of proinflammatory cytokines, interleukin-1 and tumor necrosis factor-α, was lower and that of anti-inflammatory cytokines, interleukin-10 and transforming growth factor-β, was higher in AMSC-injected mice than phosphate-buffered saline-injected mice. These effects lasted until 12 weeks after AMSC injection. Taken together, these results collectively suggest that injection of AMSCs might show significant long-lasting improvement in AD pathology and memory function via immunomodulatory and paracrine mechanisms.

Amniotic fluid CD200 levels in pregnancies complicated by preterm prelabor rupture of the membranes

OBJECTIVE

To determine the amniotic fluid CD200 levels in uncomplicated pregnancies and in preterm prelabor rupture of the membranes (PPROM) according to microbial invasion of the amniotic cavity and histological chorioamnionitis and its association with neonatal outcomes.

METHODS

One hundred and fifty-nine women with singleton pregnancies were included in this study. Amniotic fluid was collected, and CD200 levels were determined using ELISA.

RESULTS

No difference was found in CD200 levels between women in the second trimester and women at term without labor. Women at term with labor had higher CD200 levels than women in the second trimester and women at term without labor. The presence of funisitis in PPROM pregnancies was associated with higher CD200 levels independent of gestational age (with funisitis: median 197.5 pg/mL versus without funisitis: median 61.0 pg/mL; p = 0.003). The need for tracheal intubation and the development of bronchopulmonary dysplasia were associated with higher CD200 levels.

CONCLUSIONS

Amniotic fluid CD200 levels remained stable in advanced pregnancy and they were increased during parturition. Elevated CD200 levels in the presence of funisitis suggest the involvement of negative regulatory mechanisms of innate immunity. CD200 may play a role in the development of pulmonary aspects of neonatal morbidity.

CD200:CD200R-Mediated Regulation of Immunity

The type 1 membrane glycoprotein CD200, widely expressed on multiple cells/tissues, uses a structurally similar receptor (CD200R1), whose expression is more restricted to cells of the myeloid and lymphoid lineages, to transmit signals affecting responses in multiple physiological systems. Thus CD200 expression is reported to exert effects on cancer growth, autoimmune and allergic disorders, infection, transplantation, bone development and homeostasis, and reproductive biology. It was initially thought, based on the idea that CD200R1 was mostly expressed on cells of myeloid origin, that CD200:CD200R1 interactions were primarily dedicated to controlling myeloid cell function. However additional members of the CD200R family have now also been identified, although their function(s) remain unclear, and CD200R1 itself is now known to be expressed by subsets of T cells and other cells. Together these observations add layers of complexity to our understanding of CD200-related regulation. In common with a number of physiological systems, the mechanism(s) of CD200-induced signaling seem to fit within a similar framework of opposing actions of kinases and phosphatases. This paper highlights the advances in our knowledge of immunoregulation achieved following CD200:CD200R interaction and the potential clinical applicability of that information.

Regulatory T cells and reproduction: how do they do it?

Regulatory T cells (Treg cells) identified by expression of Foxp3 play an important role in successful implantation and gestation. Various mechanisms have been proposed to explain their actions, and the more credible and less credible are set out in this review. Induction of Treg cells is believed to occur in response to paternal antigens in seminal plasma at the time of mating, and these Treg cells home to the uterus prior to implantation. Tolerogenic dendritic cells are proposed to play an important role in the generation of Treg cells in the draining lymph nodes and in maintaining Treg activity in the uterus. Recent data indicate that abortion in the CBAxDBA/2 model may be prevented by seminal plasma antigens from DBA/2 and BALB/c males, but H-2(d) restriction suggests that presentation to Treg cells might occur via a novel mechanism. The relevance of findings in mice to human pregnancy problems is also discussed.

Regulation of pregnancy maintenance and fetal survival in mice by CD27(low) mature NK cells

Uterine natural killer (NK) cells are pivotal for successful mammalian reproduction. However, insights on functionally distinct subpopulations of uterine NK cells are largely elusive. Furthermore, translation of findings from murine into human pregnancy has been overshadowed by the limited number of mutual phenotypic NK cell markers. We here provide evidence that a subset of murine mature NK (mNK) cells present at the feto-maternal interface, identified as CD27(low)DX5(+)CD3(neg), is pivotal in maintaining pregnancy. This mNK subset has low cytotoxic capacity, produces higher amounts of interferon (IFN)-γ, and expresses functional homologs of human NK cell immunoglobulin-like receptors. We further show that bone marrow-derived CD27(low) mNK cells are selectively recruited to the uterus and ameliorate the rate of fetal loss when adoptively transferred into alymphoid RAG2(-/-)/γc(-/-) mice. Additionally, expression of CD27 is down-modulated on mNK cells upon migration to the uterus. Hence, we propose the existence of a regulatory mNK cell subset, which is licensed toward successful pregnancy maintenance at the fetomaternal interface in mice. As CD27(low) NK cells are also present in human decidua, the CD27(low) NK subset may provide a tool to foster translational research in reproduction, aiming to improve pregnancy outcome in humans.

Human Wharton's jelly stem cells have unique transcriptome profiles compared to human embryonic stem cells and other mesenchymal stem cells

The human umbilical cord that originates from the embryo is an extra-embryonic membrane and the Wharton's jelly within it is a rich source of stem cells (hWJSCs). It is not definitely known whether these cells behave as human embryonic stem cells (hESCs), human mesenchymal stem cells (hMSC) or both. They have the unique properties of high proliferation rates, wide multipotency, hypoimmunogenicity, do not induce teratomas and have anticancer properties. These advantages are important considerations for their use in cell based therapies and treatment of cancers. In a search for properties that confer these advantages we compared a detailed transcriptome profiling of hWJSCs using DNA microarrays with that of a panel of known hESCs, hMSCs and stromal cells. hWJSCs expressed low levels of the pluripotent embryonic stem cell markers including POUF1, NANOG, SOX2 and LIN28, thus explaining why they do not produce teratomas. Several cytokines were significantly upregulated in hWJSCs including IL12A which is associated with the induction of apoptosis, thus explaining their anticancer properties. When GO Biological Process analysis was compared between the various stem cell types, hWJSCs showed an increased expression of genes associated with the immune system, chemotaxis and cell death. The ability to modulate immune responses makes hWJSCs an important compatible stem cell source for transplantation therapy in allogeneic settings without immunorejection. The data in the present study which is the first detailed report on hWJSC transcriptomes provide a foundation for future functional studies where the exact mechanisms of these unique properties of hWJSCs can be confirmed.

The effect of human placenta cytotrophoblast cells on the maturation and T cell stimulating ability of dendritic cells in vitro

The success of pregnancy depends upon regulatory mechanisms that allow the fetus to survive and develop to term in the uterus, despite maternal immune cells' awareness of paternal alloantigens. At least some of these specific mechanisms are mediated by the effect of fetal trophoblast cells. In the present study we examine the effect of human placental cytotrophoblast cells (CTCs) on the maturation of dendritic cells (DCs) in vitro. For that purpose, CTCs were isolated from samples of placentae at 5-11 weeks of gestation and co-cultured with peripheral blood monocytes under conditions inducing DC maturation. CTC were shown to alter the morphology, phenotype and functional properties of DCs. As a result, a significant portion of cells acquire fibroblast-like morphology and some of the cells retain the expression of CD14. DCs matured in the presence of CTCs do not differ from usual DCs in terms of CD80, CD83 and CD86 expression, as well as the ability to induce allogenic lymphocytes proliferation. However, CTCs reduce significantly the ability of DCs to stimulate interferon-γ production and the loss of CD62L by T cells. The results obtained indicate that DCs may be involved in pregnancy-associated changes of cytokine production and T cell migration.

Cancer and pregnancy: parallels in growth, invasion, and immune modulation and implications for cancer therapeutic agents

Many proliferative, invasive, and immune tolerance mechanisms that support normal human pregnancy are also exploited by malignancies to establish a nutrient supply and evade or edit the host immune response. In addition to the shared capacity for invading through normal tissues, both cancer cells and cells of the developing placenta create a microenvironment supportive of both immunologic privilege and angiogenesis. Systemic alterations in immunity are also detectable, particularly with respect to a helper T cell type 2 polarization evident in advanced cancers and midtrimester pregnancy. This review summarizes the similarities between growth and immune privilege in cancer and pregnancy and identifies areas for further investigation. Our PubMed search strategy included combinations of terms such as immune tolerance, pregnancy, cancer, cytokines, angiogenesis, and invasion. We did not place any restrictions on publication dates. The knowledge gained from analyzing similarities and differences between the physiologic state of pregnancy and the pathologic state of cancer could lead to identification of new potential targets for cancer therapeutic agents.

Decreased expression of CD200 and CD200 receptor in Alzheimer's disease: a potential mechanism leading to chronic inflammation

Inflammatory activation of microglia in response to neurodegenerative changes in diseases such as Alzheimer's disease (AD) and Parkinson's disease has been extensively described. These observations have suggested that inflammation could be contributing to disease progression. In this paper, the potential role of CD200 and CD200 receptor (CD200R), whose known functions are to activate anti-inflammatory pathways and induce immune tolerance through binding of CD200 to CD200 receptor (CD200R), was studied in AD. Quantitative studies showed a significant decrease in CD200 protein and mRNA in AD hippocampus and inferior temporal gyrus, but not cerebellum. Immunohistochemistry of brain tissue sections of hippocampus, superior frontal gyrus, inferior temporal gyrus and cerebellum from AD and non-demented cases demonstrated a predominant, though heterogeneous, neuronal localization for CD200. Decreased neuronal expression was apparent in brain regions affected by AD pathology. There was also a significant decrease in CD200R mRNA expression in AD hippocampus and inferior temporal gyrus, but not cerebellum. Low expression of CD200R by microglia was confirmed at the mRNA and protein level using cultured human microglia compared to blood-derived macrophages. Treatment of microglia and macrophages with interleukin-4 and interleukin-13 significantly increased expression of CD200R. Expression of these cytokines was not generally detectable in brain. These data indicate that the anti-inflammatory CD200/CD200R system may be deficient in AD brains. Mechanisms aimed at increasing levels of CD200 and CD200R could have therapeutic potential for controlling inflammation in human neurodegenerative diseases.

Human embryo immune escape mechanisms rediscovered by the tumor

Towards the end of the 1990s, the two opposing theories on immunosurveillance and immunostimulation were extensively studied by researchers in an attempt to understand the complex mechanisms that regulate the relation between tumors and the host's immune system. Both theories probably have elements that would help us to comprehend how the host can induce anti-tumor clinical responses through stimulation of the immune system and which could also give us a deeper insight into the mechanisms of tumor immunosuppression. The model that most resembles the behavior of tumor cells in terms of growth, infiltration and suppression of the immune system of the environment in which they live is undoubtedly that of the embryonic cell. The fetus behaves like an allogenic transplant within the mother's body, using every means it has to escape from and defend itself against the mother's immune system. The majority of these mechanisms are the same as those found in tumor cells: antigenic loss, lack of expression of classic HLA-I molecules, production of immunosuppressive cytokines, induction of lack of expression of co-stimulatory molecules in antigen presenting cells, and induction of apoptosis in infiltrating lymphocytes, with activation of a type Th2 regulatory lymphocyte response. A careful and comparative study of key mechanisms capable of triggering tolerance or cytotoxicity in both embryonic and tumor cells could prove immensely valuable in designing new strategies for anti-tumor immunotherapy.

Gene expression profiling of human decidual macrophages: evidence for immunosuppressive phenotype

Background

Although uterine macrophages are thought to play an important regulatory role at the maternal-fetal interface, their global gene expression profile is not known.

Methodology/Principal Findings

Using micro-array comprising approximately 14,000 genes, the gene expression pattern of human first trimester decidual CD14+ monocytes/macrophages was characterized and compared with the expression profile of the corresponding cells in blood. Some of the key findings were confirmed by real time PCR or by secreted protein. A unique gene expression pattern intrinsic of first trimester decidual CD14+ cells was demonstrated. A large number of regulated genes were functionally related to immunomodulation and tissue remodelling, corroborating polarization patterns of differentiated macrophages mainly of the alternatively activated M2 phenotype. These include known M2 markers such as CCL-18, CD209, insulin-like growth factor (IGF)-1, mannose receptor c type (MRC)-1 and fibronectin-1. Further, the selective up-regulation of triggering receptor expressed on myeloid cells (TREM)-2, alpha-2-macroglobulin (A2M) and prostaglandin D2 synthase (PGDS) provides new insights into the regulatory function of decidual macrophages in pregnancy that may have implications in pregnancy complications.

Conclusions/Significance

The molecular characterization of decidual macrophages presents a unique transcriptional profile replete with important components for fetal immunoprotection and provides several clues for further studies of these cells.

Tolerance signaling molecules and pregnancy: IDO, galectins, and the renaissance of regulatory T cells

PROBLEM

Is the concept of maternal tolerance preventing rejection of the semi-allogeneic 'fetal allograft' still valid?

METHOD OF STUDY

Compilation of expert reviews of literature and recent advances in research on indoleamine-2,3 dioxygenase (IDO), regulatory T cells and galectin-1.

RESULTS AND CONCLUSION

A role for IDO in pregnancy success remains speculative, but solid data exist to support a role for Treg cells, and for galectin-1 in induction and action of Treg cells. Just as several signals may need to be simultaneously present to induce Th1 cytokine-triggered abortions, more than 1 signal may need to be simultaneously present to prevent rejection and ensure success. Both complement and coagulation pathways appear necessary for embryo execution.

Dendritic cells: key to fetal tolerance?

Pregnancy is a unique event in which a fetus, despite being genetically and immunologically different from the mother (a hemi-allograft), develops in the uterus. Successful pregnancy implies avoidance of rejection by the maternal immune system. Fetal and maternal immune cells come into direct contact at the decidua, which is a highly specialized mucous membrane that plays a key role in fetal tolerance. Uterine dendritic cells (DC) within the decidua have been implicated in pregnancy maintenance. DC serve as antigen-presenting cells with the unique ability to induce primary immune responses. Just as lymphocytes comprise different subsets, DC subsets have been identified that differentially control lymphocyte function. DC may also act to induce immunologic tolerance and regulation of T cell-mediated immunity. Current understanding of DC immunobiology within the context of mammalian fetal-maternal tolerance is reviewed and discussed herein.

Potential role of toll-like receptor 3 in a murine model of polyinosinic-polycytidylic acid-induced embryo resorption

OBJECTIVE

To investigate the potential role that toll-like receptor 3 (TLR3) may play in a murine model of polyinosinic-polycytidylic acid (polyIC)-induced embryo resorption.

DESIGN

An animal model-based study on induced embryo resorption.

SETTING

University animal laboratory.

ANIMAL(S)

Pathogen-free animals housed under barrier conditions and monitored for health status. Pregnant BALB/c mouse mated by C57BL/6 male was used as a model of allogeneic gestation.

INTERVENTION(S)

The administration of polyIC was performed to establish a murine model of induced embryo resorption, with or without TLR3 blocking by multiple injection of mAb against this receptor.

MAIN OUTCOME MEASURE(S)

Flow cytometric analysis was performed to detect the percentage of CD45(+)DX5+ and DX5(+)CD69+ cell subsets, with the DX5 antigen used as a common natural killer (NK) cell marker, and CD69 as a marker for activated NK cells, respectively.

RESULT(S)

In the allogeneic mating model, BALB/cxC57BL/6, both the CD45(+)DX5+ and DX5(+)CD69+ cell percentages were significantly elevated upon polyIC stimulation at the absence of anti-TLR3 administration but were kept unchanged if the female mice were pretreated with anti-TLR3 monoclonal antibody. Accordingly, the resorption rate of embryos was boosted by polyIC administration, but this effect could be abrogated by pretreatment of anti-TLR3 mAb.

CONCLUSION(S)

The engagement of polyIC with TLR3 may be critical to the activation of NK cells infiltrated at the feto-maternal interface, subsequently resulting in an increase in embryo resorption.

TLR3-involved modulation of pregnancy tolerance in double-stranded RNA-stimulated NOD/SCID mice

This study aims to extend understanding of the relationship between TLR3-involved cell signaling and dsRNA-induced embryo resorption. Upon stimulation of dsRNA, the resorption rate of embryos was boosted dramatically in syngeneic mating BALB/c mice, but not significantly influenced in syngeneic mating NOD/SCID mice. Accordingly, there was an enhanced cell surface expression of TLR3 on placental CD45(+) cells derived from BALB/c mice, concomitant with both increased percentages of CD45(+)CD80(+) cells and CD8alpha(+)CD80(+) cells in flow cytometric analysis. In addition, both increased IL-2 and decreased IL-10 expression could be observed in CD45(+) cell group in the intracellular detection by flow cytometry. In contrast, no such trends were observed in NOD/SCID model, and its resorption rate of embryos was kept at a low level throughout pregnancy. Neutralizing Abs against TLR3 could abrogate the embryo rejection induced by dsRNA in BALB/c mice, and simultaneously could reduce the CD80(+) percentage in the CD45(+) cell group. These results indicate that the interaction between dsRNA and TLR3 may be involved in the mobilization of CD45(+)CD80(+) and CD8alpha(+)CD80(+) cells, followed by the up-regulation of IL-2 and down-regulation of IL-10 expression at the feto-maternal interface, and finally resulting in embryo rejection. The relatively low responsiveness of NOD/SCID mice may be one of the reasons why these mice appeared to be resistant to dsRNA-induced embryo resorption.

Murine CD200+ CK7+ trophoblasts in a poly (I:C)-induced embryo resorption model

Cytokeratin 7 (CK7) is currently regarded as the best marker for trophoblast cells, while CD200 (OX-2), known as 'tolerance signal', plays an important role in normal pregnancy. In this study, the status of CD200 expression was investigated in BALB/c x C57BL/6 and BALB/c x BALB/c mating combinations designed as allogeneic and syngeneic murine models of induced embryo resorption, in which the resorption rate was boosted by an i.p. injection of poly (I:C), a synthetic double-stranded RNA. The percentage of CD200+ cells in the CK7+ cell population (CD200+ CK7+ percentage) and the absolute number of these cells were determined with flow cytometry, using trophoblast cells collected at day 8.5 and day 13.5 of gestation. The potential effect of poly (I:C) on CD200 expression was also evaluated by detecting the CD200+ CK7+ percentage in trophoblast cells incubated in the presence or absence of poly (I:C), in vitro. The distribution pattern of CD200+ cells at the feto-maternal interface was evaluated by immunocytochemical examination. When 10(4) cells were analyzed at day 8.5 of gestation in each case, no significant difference was observed between the poly (I:C)-treated group and the control PBS group either in the CD200+ CK7+ percentage or in the absolute number of these cells. Similar results were observed both in BALB/c x C57BL/6 mice and in BALB/c x BALB/c mice. However, the CD200+ CK7+ percentage was significantly decreased in the poly (I:C)-treated group when evaluated at day 13.5 of gestation. Accordingly, a dramatically elevated rate of embryo resorption was observed at this time point of pregnancy after the administration of poly (I:C). In addition, the CD200+ CK7+ percentage was significantly lower in trophoblast cells incubated with poly (I:C) at a certain concentration, in vitro, while histocytochemical examination showed the CD200+ cells mainly scattered in placental tissue adjacent to the interface of the placenta and uterus. This indicates that sufficient expression of the CD200 molecule on CK7+ cells at the feto-maternal interface may be necessary for the maintenance of embryos during pregnancy in this rodent model, while poly (I:C) administration may increase embryo resorption, at least partially via direct inhibition of CD200 expression on CK7+ cells.

Differential effects of lipopolysaccharide and thrombin on interleukin-8 expression in syncytiotrophoblasts and endothelial cells: implications for fetal survival

Syncytiotrophoblasts (SCTs) are directly bathed by maternal blood and, as such, are in direct contact with proinflammatory stimuli present in the maternal circulation. The extent and nature of cytokine responses induced in SCTs play a central role in the maintenance of pregnancy. Thrombin is a critical mediator of tissue factor-initiated blood coagulation. Thrombin has been more recently demonstrated to induce cytokine expression and inflammation in several cell types. To dissect the patterns of regulation of cytokine production in the placental villus, we compared the effects of thrombin and lipopolysaccharide (LPS) treatments on cytokine expression in SCTs and endothelial cells. For studies, primary cultures of cytotrophoblasts from human term placentas were differentiated to SCTs. We observed that the presence of thrombin only modestly enhanced interleukin-8 (IL-8) levels in SCTs in a manner that was not dose-dependent. Conversely, SCTs were exquisitely sensitive to LPS, the presence of which induced approximately a 10-fold increase in IL-8 levels with an EC(50) approximately 1 ng/mL. Northern blotting and real-time PCR results indicated that LPS (but not thrombin) treatment induced a >4-fold increase in levels of IL-8 mRNA. The addition of the anti-inflammatory steroid, dexamethasone, significantly reduced the LPS-mediated increase in levels of IL-8 in SCTs. Conversely, in human umbilical vein endothelial cells, thrombin and LPS treatments induced 10- and 20-fold increases in IL-8 expression, respectively. These results indicate that LPS, but not thrombin, promotes proinflammatory processes in SCTs, with cell-type specificity. The inability of thrombin in the intervillous space to evoke inflammatory responses in SCTs may constitute an important aspect of fetal survival. Conversely, our results suggest that SCTs do play a key role in infection-associated changes in placental cytokine expression.

Ecology of Danger-dependent Cytokine-boosted Spontaneous Abortion in the CBA × DBA/2 Mouse Model. I. Synergistic Effect of LPS and (TNF-α + IFN-γ) on Pregnancy Loss

PROBLEM

Previous data have shown "danger" signals, such as bacterial lipopolysaccharide (LPS) acting via toll-like (tlr) receptors are required for early pregnancy failure in several murine abortion models. Indeed, the abortion rate increased in the CBA x DBA/2 model after a gestation day (gd) 7.5 injection of tumour necrosis factor (TNF)-alpha + interferon (IFN)-gamma only if the LPS-tlr signalling pathway was intact. High rates of cytokine-boosted abortion >80% loss can be achieved in certain animal colonies, that have a high endogenous (spontaneous) rate of resorption (30-50%). A specific role for LPS has been postulated to determine both the endogenous and cytokine-boosted losses.

METHODS

To test the role of LPS in spontaneous and cytokine-boosted abortions, recombinant TNF-alpha + IFN-gamma, and LPS were injected in different doses and sequences intraperitoneally (i.p.) into CBA x DBA/2 mated mice in the Toronto General Research Institute animal facility where the endogenous abortion rate is <30%. The effects of poly IC, a tlr3 agonist that induces IFN-gamma that can reverse LPS-induced tolerance, and effects of anti-MD-1 on TNF-alpha induction by LPS, poly IC, CPG, or HSP in vitro were also examined.

RESULTS

A high endogenous rate of loss similar to that seen in Clamart could be achieved by increasing exposure to LPS on the morning after mating (gd 0.5). The magnitude by which the abortion rate could be increased by an i.p. injection of 2000 u TNF-alpha + 1000 u IFN-gamma on gd 7.5 was independent of the endogenous rate of loss, and could not be increased by doubling the dose. One microgram of LPS given on day 7.5 achieved a similar rate of loss, and if given with the cytokines, synergistically boosted the rate of loss to near Clamart rates. LPS given 1 day prior to the cytokines abrogated the cytokine effect, whereas LPS given day 0.5 had no significant effect on the response to day 7.5 cytokine injection. Blocking MD-1 inhibited TNF-alpha stimulation by poly IC, LPS, CPG, or HSP in vitro, and reduced abortion rates. Poly IC did not avert LPS-type tolerance effects in vivo.

CONCLUSIONS

High endogenous rates of abortion in the CBA x DBA/2 model may be explained by exposure to LPS at the time of mating. Increased rates of loss triggered by cytokines later in pregnancy may depend on increased absorption of LPS from intestinal flora.

Expression of CD200 on epithelial cells of the murine hair follicle: a role in tissue-specific immune tolerance?

CD200 (OX-2) is a transmembrane glycoprotein that transmits an immunoregulatory signal through the CD200 receptor (CD200R) to attenuate inflammatory reactions and promote immune tolerance. CD200 expression in the skin has not been described previously. We now report that freshly isolated cells of the murine epidermis contain a subpopulation of major histocompatibility complex (MHC) class II-negative, CD3-negative keratinocytes that are CD200-positive. CD200 expression was accentuated in keratinocytes comprising the outer root sheath of the murine hair follicle (HF). When syngeneic skin grafts were exchanged between gender-matched wild-type (WT) and CD200-deficient C57BL/6 mice, significant perifollicular and intrafollicular inflammation was observed, eventually leading to the destruction of virtually all HF (alopecia) without significant loss of the CD200-negative grafts. Minimal and transient inflammation was observed in WT grafts, which persisted long term with hair. There was a 2-fold increase in graft-infiltrating T cells in CD200-deficient skin at 14 d. Alopecia and skin lesions were induced in CD200-deficient hosts by adoptive transfer of splenocytes from WT mice previously grafted with CD200-negative skin, but not from mice grafted with WT skin. Collectively, these results suggest that the expression of CD200 in follicular epithelium attenuates inflammatory reactions and may play a role in maintaining immune tolerance to HF-associated autoantigens.

Murine plasmacytoid dendritic cells initiate the immunosuppressive pathway of tryptophan catabolism in response to CD200 receptor engagement

In this study, using a soluble CD200-Ig fusion protein, we provide evidence that murine dendritic cells (DCs) possess a functional CD200R, whose engagement results in the reinforcement or appearance of immunosuppressive properties in these cells. In particular, the plasmacytoid subset (CD11c+B220+120G8+) of splenic DCs (pDCs) is induced by CD200-Ig to express the enzyme IDO, which initiates the tolerogenic pathway of tryptophan catabolism. As a result, pDCs are capable of suppressing Ag-specific responses in vivo when transferred into recipient hosts after treatment with CD200-Ig. IDO induction in pDCs through CD200R engagement requires type I IFNR signaling. Although the release of IFN-alpha may contribute to the full expression of CD200-Ig activity, autocrine IFN-alpha is unlikely to mediate alone the effects of CD200R engagement. These data prospect novel functions for both pDCs and the CD200-CD200R pair in the mouse. At the same time, these data underscore the possible unifying role of the IDO mechanism in immune tolerance.