Evolution of non-cytotoxic uterine natural killer cells

Characterization of the fetal blood transcriptome and proteome in maternal anti-fetal rejection: evidence of a distinct and novel type of human fetal systemic inflammatory response

BACKGROUND

The human fetus is able to mount a systemic inflammatory response when exposed to microorganisms. This stereotypic response has been termed the 'fetal inflammatory response syndrome' (FIRS), defined as an elevation of fetal plasma interleukin-6 (IL-6). FIRS is frequently observed in patients whose preterm deliveries are associated with intra-amniotic infection, acute inflammatory lesions of the placenta, and a high rate of neonatal morbidity. Recently, a novel form of fetal systemic inflammation, characterized by an elevation of fetal plasma CXCL10, has been identified in patients with placental lesions consistent with 'maternal anti-fetal rejection'. These lesions include chronic chorioamnionitis, plasma cell deciduitis, and villitis of unknown etiology. In addition, positivity for human leukocyte antigen (HLA) panel-reactive antibodies (PRA) in maternal sera can also be used to increase the index of suspicion for maternal anti-fetal rejection. The purpose of this study was to determine (i) the frequency of pathologic lesions consistent with maternal anti-fetal rejection in term and spontaneous preterm births; (ii) the fetal serum concentration of CXCL10 in patients with and without evidence of maternal anti-fetal rejection; and (iii) the fetal blood transcriptome and proteome in cases with a fetal inflammatory response associated with maternal anti-fetal rejection.

METHOD OF STUDY

Maternal and fetal sera were obtained from normal term (n = 150) and spontaneous preterm births (n = 150). A fetal inflammatory response associated with maternal anti-fetal rejection was diagnosed when the patients met two or more of the following criteria: (i) presence of chronic placental inflammation; (ii) ≥80% of maternal HLA class I PRA positivity; and (iii) fetal serum CXCL10 concentration >75th percentile. Maternal HLA PRA was analyzed by flow cytometry. The concentrations of fetal CXCL10 and IL-6 were determined by ELISA. Transcriptome analysis was undertaken after the extraction of total RNA from white blood cells with a whole-genome DASL assay. Proteomic analysis of fetal serum was conducted by two-dimensional difference gel electrophoresis. Differential gene expression was considered significant when there was a P < 0.01 and a fold-change >1.5.

RESULTS

(i) The frequency of placental lesions consistent with maternal anti-fetal rejection was higher in patients with preterm deliveries than in those with term deliveries (56% versus 32%; P < 0.001); (ii) patients with spontaneous preterm births had a higher rate of maternal HLA PRA class I positivity than those who delivered at term (50% versus 32%; P = 0.002); (iii) fetuses born to mothers with positive maternal HLA PRA results had a higher median serum CXCL10 concentration than those with negative HLA PRA results (P < 0.001); (iv) the median serum CXCL10 concentration (but not IL-6) was higher in fetuses with placental lesions associated with maternal anti-fetal rejection than those without such lesions (P < 0.001); (v) a whole-genome DASL assay of fetal blood RNA demonstrated differential expression of 128 genes between fetuses with and without lesions associated with maternal anti-fetal rejection; and (vi) comparison of the fetal serum proteome demonstrated 20 proteins whose abundance differed between fetuses with and without lesions associated with maternal anti-fetal rejection.

CONCLUSION

We describe a systemic inflammatory response in human fetuses born to mothers with evidence of maternal anti-fetal rejection. The transcriptome and proteome of this novel type of fetal inflammatory response were different from that of FIRS type I (which is associated with acute infection/inflammation).

Natural killer cells in asthma

The worldwide prevalence, morbidity, and mortality of asthma have dramatically increased over the last few decades and there is a clear need to identify new effective therapeutic and prophylactic strategies. Despite high numbers of NK cells in the lung and their ability to generate a variety of immunomodulatory mediators, the potential of NK cells as therapeutic targets in allergic airway disease has been largely overlooked. The fact that IgE, acting through FcγRIII, can activate NK cells resulting in cytokine/chemokine production implies that NK cells may contribute to IgE-mediated allergic responses. Indeed, current evidence suggests that NK cells can promote allergic airway responses during sensitization and ongoing inflammation. In animal models, increased NK cells are observed in the lung following antigen challenge and depletion of the cells before immunization inhibits allergic airway inflammation. Moreover, in asthmatics, NK cell phenotype is altered and may contribute to the promotion of a pro-inflammatory Th2-type environment. Conversely, driving NK cells toward an IFN-γ-secreting phenotype can reduce features of the allergic airway response in animal models. However, we have limited knowledge of the signals that drive the development of distinct subsets and functional phenotypes of NK cells in the lung and thus the role and therapeutic potential of NK cells in the allergic airway remains unclear. Here we review the potentially diverse role of NK cells in allergic airway disease, identify gaps in current knowledge, and discuss the potential of modulating NK cell function as a treatment strategy in asthma.

NKG2D blockade inhibits poly(I:C)-triggered fetal loss in wild type but not in IL-10-/- mice

Infection and inflammation can disturb immune tolerance at the maternal-fetal interface, resulting in adverse pregnancy outcomes. However, the underlying mechanisms for detrimental immune responses remain ill defined. In this study, we provide evidence for immune programming of fetal loss in response to polyinosinic:polycytidylic acid (polyI:C), a viral mimic and an inducer of inflammatory milieu. IL-10 and uterine NK (uNK) cells expressing the activating receptor NKG2D play a critical role in poly(I:C)-induced fetal demise. In wild type (WT) mice, poly(I:C) treatment induced expansion of NKG2D(+) uNK cells and expression of Rae-1 (an NKG2D ligand) on uterine macrophages and led to fetal resorption. In IL-10(-/-) mice, NKG2D(-) T cells instead became the source of fetal resorption during the same gestation period. Interestingly, both uterine NK and T cells produced TNF-α as the key cytotoxic factor contributing to fetal loss. Treatment of WT mice with poly(I:C) resulted in excessive trophoblast migration into the decidua and increased TUNEL-positive signal. IL-10(-/-) mice supplemented with recombinant IL-10 induced fetal loss through NKG2D(+) uNK cells, similar to the response in WT mice. Blockade of NKG2D in poly(I:C)-treated WT mice led to normal pregnancy outcome. Thus, we demonstrate that pregnancy-disrupting inflammatory events mimicked by poly(I:C) are regulated by IL-10 and depend on the effector function of uterine NKG2D(+) NK cells in WT mice and NKG2D(-) T cells in IL-10 null mice.

Differential effects of the CpG-Toll-like receptor 9 axis on pregnancy outcome in nonobese diabetic mice and wild-type controls

OBJECTIVE

To elucidate the relationship between CpG-induced activation of innate immunity and pregnancy outcome.

DESIGN

An animal model-based study.

SETTING

Academic.

ANIMAL(S)

Pregnant nonobese diabetic (NOD) mice were compared with nonimmunodeficient mice.

INTERVENTION(S)

We mimic toll-like receptor 9 (TLR9) activation using CpG ODN administration in pregnant wild-type (WT) and natural killer (NK) cell-deficient NOD mice.

MAIN OUTCOME MEASURE(S)

Evaluation of fetal resorption and preterm birth in pregnant mice; flow-cytometric analysis and ELISA detection.

RESULT(S)

CpG-induced fetal resorption or preterm birth was observed steadily only in NOD mice but not in WT mice. Concurrently, CpG treatment triggered amplification of uterine macrophages and neutrophils. Moreover, CpG induced a substantial increase of serum mouse keratinocyte-derived cytokine (mKC) and tumor necrosis factor-α (TNF-α) that were produced by uterine CD11b(+)F4/80(+) cells but not by NK or CD11b(+)Gr-1(+) cells. In addition, depletion of F4/80(+) cells abrogated a CpG-induced increase in TNF-α production and improved pregnancy outcomes in NOD mice treated with CpG.

CONCLUSION(S)

These results provide evidence that CpG-driven innate immune activation may lead to activation and amplification of macrophages followed by their migration to fetomaternal microenvironment, up-regulated TNF-α production, and consequent adverse pregnancy outcomes.

Depletion of invariant NKT cells reduces inflammation-induced preterm delivery in mice

This study sought to determine whether invariant NKT (iNKT) cells play an essential role in inflammation-induced preterm delivery. Preterm delivery and fetal death rates were determined in wild-type (WT) C57BL/6 mice and iNKT cell-deficient Jα18(-/-) mice injected i.p. with LPS. The percentages of decidual immune cells, including activated subsets, and costimulatory molecule expression were analyzed by flow cytometry. Th1 and Th2 cytokine production in the culture supernatants of decidual mononuclear cells was measured by ELISA. To some extent, Jα18(-/-) mice were resistant to LPS-induced preterm delivery. The proportions of decidual CD3(+) and CD49b(+) cells were slightly lower in Jα18(-/-) mice than in WT Jα18(+/+) mice, whereas almost no CD3(+)CD49b(+) cells could be found in Jα18-null mice. The percentages of activated decidual DCs, T cells, and NK cells were significantly lower in LPS-treated Jα18(-/-) mice than in WT mice. The CD40, CD80, and CD86 expression levels on decidual CD11c(+) cells from Jα18(-/-) mice were also significantly lower than in WT mice. Mean concentrations of Th1 cytokines IFN-γ and IL-12p70 in the culture supernatants of decidual mononuclear cells from LPS-treated Jα18(-/-) mice were apparently lower than those of LPS-induced WT mice. Additionally, the proportions of activated CD11c(+) cells, CD3(+) cells, and CD49b(+) cells in LPS-induced preterm delivery mice were strikingly higher in both WT and null mice when compared with the control PBS group and LPS-injected but normally delivered mice. Our results suggest that iNKT cells may play an essential role in inflammation-induced preterm birth.

Glucocorticoid receptor mediates the effect of progesterone on uterine natural killer cells

PROBLEM

Uterine natural killer cells (uNK) do not express progesterone receptor, but express glucocorticoid receptor (GR). So, we speculate that progesterone may regulate uNK cells through a GR-mediated process.

METHOD OF STUDY

After mouse NK cells were stimulated with CpG with or without IL-12 in the presence or absence pre-treatment of progesterone, the effects of progesterone on NK via GR were investigated by using RU486 (progesterone receptor and GR antagonist) and CDB-2914 (progesterone receptor antagonist). The expressions of CD69 and IFN-γ were determined by flow cytometry and qPCR. Phosphorylation of IκB and STAT4 was determined by Western blot. Furthermore, we purified uNK cells from human decidual tissues using anti-CD56 microbeads to verify the effect of progesterone on uNK via GR.

RESULTS

Progesterone suppressed CD69 and IFN-γ expression of mouse spleen NK cells and human uNK cells induced by CpG combined with IL-12. CDB-2914 had no effect on IFN-γ expression suppressed by progesterone, while RU486 could abolish the inhibitory effect of progesterone. In addition, progesterone could decrease the phosphorylation of both STAT4 and IκB.

CONCLUSIONS

In the present study, we first prove that progesterone can regulate NK cells via GR. It is valuable for further understanding the role of uNK in progesterone regulated gestation process.

Molecular evidence for natural killer-like cells in equine endometrial cups

OBJECTIVES

To identify equine orthologs of major NK cell marker genes and utilize them to determine whether NK cells are present among the dense infiltration of lymphocytes that surround the endometrial cup structures of the horse placenta during early pregnancy.

STUDY DESIGN

PCR primers were developed to detect the equine orthologs of NKP46, CD16, CD56, and CD94; gene expression was detected in RNA isolated from lymphocytes using standard 2-step reverse transcriptase (RT) PCR and products were cloned and sequenced. Absolute real-time RT-PCR was used to quantitate gene expression in total, CD3+, and CD3- peripheral lymphocytes, and invasive trophoblast. Lymphocytes surrounding the endometrial cups (ECL) of five mares in early pregnancy were isolated and NK marker gene expression levels were assayed by quantitative RT-PCR.

MAIN OUTCOME MEASURES

Absolute mRNA transcript numbers were determined by performing quantitative RT-PCR and comparing values to plasmid standards of known quantities.

RESULTS

NKP46 gene expression in peripheral CD3- lymphocytes was higher than in CD3+ lymphocytes, CD16 levels were higher in the CD3+ population, and no significant differences were detected for CD56 and CD94 between the two groups. Expression of all four NK cell markers was significantly higher in lymphocytes isolated from the endometrial cups of pregnant mares compared to PBMC isolated from the same animal on the same day (NKP46, 14-fold higher; CD94, 8-fold higher; CD16, 20-fold higher; CD56, 44-fold higher).

CONCLUSIONS

These data provide the first evidence for the expression of major NK cell markers by horse cells and an enrichment of NK-like cells in the equine endometrium during pregnancy.

Assessment of endometrial receptivity

OBJECTIVE

To provide a focused review of the scientific literature pertaining to endometrial receptivity.

DESIGN

Review of the literature and appraisal of relevant articles.

SETTING

Academic teaching hospital.

PATIENT(S)

Women with infertility.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Critical review of the literature.

RESULT(S)

Although a consensus has been achieved regarding the existence of a temporally defined period during which embryo attachment and invasion can occur (called the "window of implantation"), reliable methods to assess "receptivity" have not been established or adequately validated. In women with certain gynecologic disorders, including endometriosis, tubal disease, and polycystic ovary syndrome, endometrial receptivity seems to be compromised, leading to infertility and pregnancy loss. The establishment of reliable biomarkers for the detection of defects in endometrial receptivity has been a long-sought goal that remains an elusive target. The validation of endometrial biomarkers will require properly designed and implemented studies based on the recognition that endometrial receptivity defects are not equally distributed in women with endometriosis or these other conditions.

CONCLUSION(S)

Rapidly advancing technologies are bringing new biomarkers to the clinical arena that promise to further reveal the complexities of the implantation process.

Proliferating cell nuclear antigen is a novel inhibitory ligand for the natural cytotoxicity receptor NKp44

NK cells play an important role in the early immune response to cancer. The NKp44 activating receptor is the only natural cytotoxicity receptor that is expressed exclusively by primate NK cells, yet its cellular ligands remain largely unknown. Proliferating cell nuclear Ag (PCNA) is overexpressed in cancer cells. In this study, we show that the NKp44 receptor recognizes PCNA. Their interaction inhibits NK cell function through NKp44/ITIM. The physical interaction of NKp44 and PCNA is enabled by recruitment of target cell PCNA to the NK immunological synapse. We demonstrate that PCNA promotes cancer survival by immune evasion through inhibition of NKp44-mediated NK cell attack.

Primary uterine NK-cell lymphoma, nasal-type: a unique malignancy of a prominent cell type of the endometrium

Natural killer (NK) cells host in the human endometrium with dedicated role in reproductive physiology. Interestingly, malignant transformation of these specialized cells has not been presented thus far. Here we report a primary endometrial NK-cell lymphoma of a 48 year-old patient presenting with irregular bleeding. The endometrial curetting showed a dense lymphomatous infiltrate demonstrating highly infiltrative aggressive features with characteristic angiocentric, partially angiodestructive growth pattern and accompanying focal necroses. The lymphoma cells displayed a CD3ε/CD56/TIA-1/granzyme-B-positive and CD5/CD4/CD8/TCRγδ-negative immunophenotype, proved to be positive for Epstein-Barr virus by EBER in situ hybridization, and revealed no clonal T-cell receptor gene rearrangement. The diagnosis of uterine extranodal NK-cell lymphoma, nasal-type was made. Clinically, the disease was limited to the uterus at diagnosis, but progressed rapidly, and the patient died within 5 months due disseminated lymphoma, irrespective of intensive chemotherapy. Genuine NK-cell lymphomas occurring in the uterus as primary site seem to be rare making the therapeutic decisions extremely complicated.

Effect of human endometrial stromal cell-derived conditioned medium on uterine natural killer (uNK) cells' proliferation and cytotoxicity

PROBLEM

Human endometrial stromal cells are involved in the regulation of immune cell proliferation, apoptosis, differentiation, and function. In the endometrium, uNK cells are in close contact with stromal cells. The aim of the study was to investigate the effects of human endometrial stromal cells on uNK-cell proliferation and uNK-cell cytotoxicity.

METHOD OF STUDY

The conditioned medium was derived from the endometrial stromal cells in the proliferative phase, secretory phase, and early pregnancy. The effects of stromal cell-derived conditioned medium on uNK-cell proliferation and cytotoxicity were detected by mitochondrial lactate dehydrogenase-based MTS staining and flow cytometry.

RESULTS

The stromal cell-derived conditioned medium in both secretory phase and early pregnancy significantly promoted uNK-cell proliferation. Compared with the control group, the uNK-cell cytotoxicity were significantly reduced by conditioned medium in the proliferative, secretory, and decidua groups, but there were no significant differences among these different physiological stages in the inhibiting ability.

CONCLUSION

Human endometrial stromal cells may be involved in the regulation of uNK-cell functions through influencing proliferation and cytolytic activity.

Decidualization and angiogenesis in early pregnancy: unravelling the functions of DC and NK cells

Differentiation of endometrial stromal cells and formation of new maternal blood vessels at the time of embryo implantation are critical for the establishment and maintenance of gestation. The regulatory functions of decidual leukocytes during early pregnancy, particularly dendritic cells (DC) and NK cells, may be important not only for the generation of maternal immunological tolerance but also in the regulation of stromal cell differentiation and the vascular responses associated with the implantation process. However, the specific contributions of DC and NK cells during implantation are still difficult to dissect mainly due to reciprocal regulatory interactions established between them within the decidualizing microenvironment. The present review article discusses current evidence on the regulatory pathways driving decidualization in mice, suggesting that NK cells promote uterine vascular modifications that assist decidual growth but DC directly control stromal cell proliferation, angiogenesis and the homing and maturation of NK cell precursors in the pregnant uterus. Thus, successful implantation appears to result from an interplay between cellular components of the decidualizing endometrium involving immunoregulatory and pro-angiogenic functions of DC and NK cells.

HLA-C C1C2 heterozygosity may protect women bearing the killer immunoglobulin-like receptor AA genotype from spontaneous abortion

Spontaneous abortion is the most common complication of human pregnancy. Natural killer (NK) cells expressing killer immunoglobulin-like receptors (KIRs), which may recognize HLA-C (i.e. its C1 or C2 groups) on trophoblast cells, constitute a large leukocyte population in the endometrium. This study investigated whether genetic polymorphisms in the KIR and HLA-C genes are risk factors for spontaneous abortion. One hundred and twenty-five couples with at least two spontaneous abortions, including eighty-five couples with idiopathic recurrent abortion (RSA; three or more abortions), and 117 control couples (with two or more healthy-born children) were tested. The frequencies of the individual KIR genes in the patients were similar to those in the controls. In the group of KIR AA women with HLA-C C2C2 partners, the HLA-C C1C2 heterozygotes were present in the controls but not in the patients (p=0.015 for all patients and p=0.0048 for RSA, but both comparisons lost significance after Bonferroni correction), whereas both homozygotes, C1C1 and C2C2, were absent in the control women but present among the aborting ones. Therefore, our results suggest that among KIR AA women who have HLA-C C2C2 partners, HLA-C heterozygous females show a trend towards an increased chance of successful pregnancy.

Sera from preeclampsia patients elicit symptoms of human disease in mice and provide a basis for an in vitro predictive assay

Early diagnosis and treatment of preeclampsia would significantly reduce maternal and fetal morbidity and mortality. However, its etiology and prediction have remained elusive. Based on the hypothesis that sera from patients with preeclampsia could function as a "blueprint" of causative factors, we describe a serum-based pregnancy-specific mouse model that closely mirrors the human condition as well as an in vitro predictive assay. We show that a single administration of human preeclampsia serum in pregnant IL-10-/- mice induced the full spectrum of preeclampsia-like symptoms, caused hypoxic injury in uteroplacental tissues, and elevated soluble fms-like tyrosine kinase 1 and soluble endoglin, markers thought to be related to the disease. The same serum sample(s) induced a partial preeclampsia phenotype in wild-type mice. Importantly, preeclampsia serum disrupted cross talk between trophoblasts and endothelial cells in an in vitro model of endovascular activity. Disruption of endovascular activity could be documented in serum samples as early as 12 to 14 weeks of gestation from patients who subsequently developed preeclampsia. These results indicate that preeclampsia patient sera can be used to understand the pregnancy-specific disease pathology in mice and can predict the disorder.

Uterine natural killer cells in peri-implantation endometrium from women with repeated implantation failure after IVF

Several studies have suggested that endometrial uNK (CD56+) cells may play a role in implantation. The aim of this study was to investigate the number of CD56+, CD16+ and CD69+ cells in the unstimulated endometrium of women with recurrent implantation failure after IVF. The percentage of stromal cells positive for CD56, CD16 and CD69 was identified by immunocytochemistry in endometrial biopsies from 15 normal control women and 40 women with recurrent implantation failure. All biopsies were obtained on days LH+7 to LH+9. The density of CD56+ cells in endometrium from women with repeated implantation failure after IVF [median (range) CD56+ cell density=14.5% (1.5-71.4%)] was significantly higher (P=0.005) than in endometrium from control women [5% (2.1-19.2%)]. There was no significant difference in the densities of CD16+ and CD69+ cells in the endometrium from women in the two groups. The increased density of CD56+ cells in the endometrium of women with recurrent implantation failure suggests that these cells are directly involved in the implantation process; alternatively this may indicate a general endometrial defect in these women, which leads to the inability of the embryo to implant.

Contribution of interferon-gamma receptor 1 gene polymorphisms to pre-eclampsia in China

PROBLEM

As gene polymorphisms of cytokines receptors have been found to significantly influence cell responses to cytokines, the aim of this study was to test the hypothesis that IFN-gamma receptor 1 (IFNGR1) gene polymorphisms may contribute to the pathogenesis of pre-eclampsia.

METHOD OF STUDY

One hundred and sixty-four pre-eclamptic patients (121 patients with mild pre-eclampsia and 43 patients with severe pre-eclampsia) and 171 controls were included. Polymorphisms of the IFNGR1 gene at positions -611, -270, +56 and +95 were genotyped with the matrix-assisted laser desorption/ionization time of flight mass spectrometry.

RESULTS

This study showed a positive association between -56C/C genotype (OR = 1.7; 95% CI = 1.1-2.7) and pre-eclampsia. Although the genotype frequencies (except for -56C/C) of the two polymorphisms were comparable between cases and controls, higher frequency of the -611A/-56C haplotype (OR = 1.450; 95% CI = 1.070-1.966) was noticed in patients versus controls. All patients and controls were homozygous for the -270T/T and +95T/T genotypes. Specifically, the frequency of the -56C allele (OR = 1.838; 95% CI = 1.127-2.995) was higher among patients with severe pre-eclampsia.

CONCLUSION

The IFNGR1 gene polymorphisms may contribute to the pathogenesis of pre-eclampsia in our population.

Interleukin-10: a multi-faceted agent of pregnancy

It is widely accepted that pregnancy constitutes a unique developmental event. Unprecedented intrauterine actions of angiogenesis, immunity, and neuroendocrine regulation are juxtaposed to mechanisms of senescence that enable fetal growth and protection. The suppressive and regulatory factors that facilitate healthy pregnancy are under investigation. In non-pregnant systems of infection and inflammation, the cytokine interleukin-10 (IL-10) has been widely investigated because of its potential as a key immunosuppressant in response to a multitude of inflammatory events. In the context of pregnancy, IL-10 levels increase markedly in women during early pregnancy and remain elevated well into the third trimester immediately prior to onset of labor. The role of IL-10 during pregnancy as a suppressor of active maternal immunity to allow acceptance of the fetal allograft has been a point of study. Moreover, secretion of IL-10 by a diverse set of maternal and fetal cells has proven to aid in the orchestration of normal processes of pregnancy. Interestingly, some of the more profound findings regarding the actions of IL-10 during pregnancy have manifested from research that focuses on aberrant pregnancy outcomes as a result of inflammation, hormonal imbalances, or gene-environment interactions. This review focuses on the role of IL-10 as a facilitator of successful pregnancy both as an immune suppressive agent and a mediator of cross talk between the placenta and the decidua. Importantly, we discuss investigations on adverse pregnancy conditions to further elucidate the multifarious role of IL-10 at the maternal-fetal interface.

Novel approaches for mechanistic understanding and predicting preeclampsia

Despite intense investigation, preeclampsia (PE) remains largely enigmatic. Relatively late onset of diagnostic signs and heterogeneous nature of the disease further contribute to poor understanding of its etiology and clinical management. There exist no concrete animal models that can provide mechanistic underpinnings for evaluating targeted therapeutic intervention. Poor cross-sectional findings with potential biochemical markers reported so far have proved counterintuitive and suggest a need for novel approaches to predict the early onset of disease. Because of the co-onset of local placental anomalies and systemic manifestation of symptoms, it is highly likely that serum from PE patients can provide a "blueprint" of causative factors. Proteomic and/or functional analysis of maternal serum are expected to predict the onset of disease ahead of manifestation of clinical symptoms. A serum-based predictive assay should overcome complexities resulting from the heterogeneous etiology of PE. This review attempts to address some of these issues and discuss the signature biochemical serum factors and propose new and better ways to predict PE.

TLR9 activation coupled to IL-10 deficiency induces adverse pregnancy outcomes

Pregnancy outcome is severely compromised by intrauterine infections and inflammation. Although the pregnant uterine microenvironment is replete with innate immune cells and TLR expression, the mechanisms that facilitate adverse effects of their activation are largely unknown. In this study, we mimic the activation of TLR9 with its pathogenic ligand hypomethylated CpG and demonstrate that IL-10 proficiency protects against CpG-induced pregnancy complications. We show that fetal resorption and preterm birth are rapidly induced in IL-10(-/-) mice by low doses of CpG (approximately 25 microg/mouse) when injected i.p. on gestational day 6 or gestational day 14, respectively. In contrast, wild-type mice failed to experience such effects at comparable doses, but pups born at term displayed craniofacial/limb defects in response to higher doses (approximately 400 microg/mouse). Pregnancy complications in IL-10(-/-) mice were associated with unexpected and robust TLR9-triggered activation and amplification of uterine neutrophil and macrophage subpopulations followed by their migration to the placental zone. Furthermore, a dramatic increase in serum levels of mouse KC and TNF-alpha production by uterine F4/80(+) cells, but not uterine NK or Gr-1(+)CD11b(+) cells, was observed. Depletion of F4/80(+) macrophages or neutralization of TNF-alpha rescued pregnancy to term. Our results have important implications for IL-10-mediated "uterine tolerance" against CpG-driven innate immune activation.

Proliferation of uterine natural killer cells is induced by human chorionic gonadotropin and mediated via the mannose receptor

The endometrial lining of the human uterus contains a population of phenotypically distinct (CD56(bright), CD16(dim)), tissue-specific, natural killer [uterine natural killer (uNK)] cells that play a key role in the establishment of a successful pregnancy. An increase in the number of endometrial uNK cells occurs when the conceptus implants, and there is a further increase during the early stages of placentation. Here, we describe studies that have identified human chorionic gonadotrophin (hCG), a glycoprotein synthesized by the preimplantation conceptus, as a novel regulator of uNK cell proliferation. The impact of hCG on uNK cells was mediated via the mannose receptor (CD206) rather than by the classical hCG/LH receptor that was not expressed. The mannose receptor and hCG were colocalized on the surface of uNK cells, and proliferation did not occur if cells were incubated with deglycosylated hCG or intact hCG in the presence of excess d-Mannose. These novel observations provide new insight into the endocrine-immune dialogue that exists between the conceptus and immune cells within the receptive endometrium, and have implications for the role of uNK cell-trophoblast interactions and pregnancy outcome.

Vascular endothelial growth factor C facilitates immune tolerance and endovascular activity of human uterine NK cells at the maternal-fetal interface

Although replete with cytotoxic machinery, uterine NK (uNK) cells remain tolerant at the maternal-fetal interface. The mechanisms that facilitate the uNK cell tolerance are largely unknown. In this study, we demonstrate that vascular endothelial growth factor (VEGF) C, a proangiogenic factor produced by uNK cells, is responsible for their noncytotoxic activity. VEGF C-producing uNK cells support endovascular processes as demonstrated in a three-dimensional coculture model of capillary tube formation on Matrigel. Peripheral blood NK cells fail to produce VEGF C and remain cytotoxic. This response can be reversed by exogenous VEGF C. We show that cytoprotection by VEGF C can be related to induction of the TAP-1 expression and MHC class I assembly in target cells. Small interfering RNA-mediated silencing of TAP-1 expression abolished the VEGF C-imparted protection. Overall, these results demonstrate that empowerment of uNK cells with angiogenic factors keeps them noncytotoxic. This phenotype is critical to their pregnancy-compatible immunovascular role during placentation and fetal development.

Dermatan sulfate proteoglycan biglycan as a potential selectin L/CD44 ligand involved in selective recruitment of peripheral blood CD16(-) natural killer cells into human endometrium

Unique CD16(-) NK cells acutely increase in the human uterine endometrium after ovulation. The origin of these NK cells remains unknown, but they may be recruited selectively from the circulation. Proteoglycans and their glycosaminoglycan side-chains expressed on endometrial microvascular endothelial cells play a key role in lymphocyte tethering/rolling, the initial step of lymphocyte extravasation. In this study, we sought for the potential proteoglycans involved in tethering/rolling of peripheral blood CD16(-) NK cells on endometrial microvascular endothelial cells. As compared with CD16(+) NK cells and non-NK cells, enriched peripheral blood CD16(-) NK cells bound preferably to immobilized glycosaminoglycans except for keratan sulfate. CD16(-) NK cells bound maximally to dermatan sulfate (DS), which was diminished by enzymatic pretreatment with dermatanase and chondroitinase ABC, but not with chondroitinase ACII. The binding capacity of CD16(-) NK cells to DS was attenuated by blocking antibodies against selectin L and CD44 or pretreatment of CD16(-) NK cells with IL-15. Of three known DS proteoglycans, biglycan and decorin but not epiphycan were expressed in the human cycling endometrium. In the endometrial microvessels, the immunoreactivity for biglycan was greater in the secretory phase than in the proliferative phase, and there was little, if any, immunoreactivity for decorin throughout the menstrual cycle. The ovarian steroid progesterone enhanced biglycan expression in cultured human uterine microvascular endothelial cells. These findings demonstrated that DS proteoglycan biglycan is a potential selectin L/CD44 ligand involved in tethering/rolling of peripheral blood CD16(-) NK cells on endometrial microvascular endothelial cells.

Uterine natural killer cells are immunogenic in syngeneic male mice

Uterine natural killer (uNK) cells expand rapidly during endometrial decidualization and account for 70% of leukocytes in early gestational uteri of humans and rodents. These cells make unique contributions to pregnancy, contributing to the success of embryo implantation and maintenance of decidual tissue that supports placental and fetal development. We postulated that uNK cells express molecules that are not shared by circulating NK (cNK) cells or other leukocytes and, therefore, would be immunogenic for male mice. We isolated viable uNK cells from gestation day 9 pregnant mice and inoculated them into syngeneic males. This induced antibodies reactive with mouse uNK cells but not with cNK cells or other lymphocytes. The antibodies reacted identically with uNK cells in tissue sections from five different mice strains from gestational day 7-12 and in pregnant rat uterus, suggesting that the recognized antigen should be a specific marker of uNK cell. Spleen cells from inoculated males were used subsequently to produce a monoclonal antibody reactive to a uNK cell surface antigen. These experiments confirm that uNK cells are a pregnancy-specific subset of NK cells expressing distinct surface antigen from those found in other tissues.