When killers become helpers

Decreased CD56+CD16-CD94+uNK cells in the mid-luteal phase in women with recurrent implantation failure are associated with IL-15 deficiency

PROBLEM

Whether the abnormal development of uterine natural killer (uNK) cells contributes to women with recurrent implantation failure (RIF) remains unclear.

METHOD OF STUDY

We characterized the development of uNK cells and peripheral blood NK cells (pbNK) in the mid-luteal phase in women with RIF (n = 31) and controls (n = 14) by flow cytometry. Endometrial IL-15 mRNA expression was studied by quantitative reverse transcription-PCR. The GSE58144 dataset was used to validate the correlation results.

RESULTS

We found decreased proportions of stage 4 CD56+CD16-CD94+ uNK cells (median: 9.56% vs. 17.78%, P .014) and increased proportions of stage 6 CD56+CD16+CD57+ uNK cells (median: 1.54% vs. 0.74%, P = .020) in the mid-luteal endometrium of women with RIF compared to fertile women. We also found that there was no quantitative correlation between uNK cells and the corresponding pbNK cell subpopulations (P > .05). In addition, IL-15 mRNA levels in the mid-luteal endometrium were positively correlated with the proportion of CD56+ uNK cells (r = .392, P = .008), especially with stage 4 uNK cell populations (r = .408, P = .005).

CONCLUSIONS

We showed that the proportion of stage 4 uNK cells decreased in the RIF group compared to controls, and the decrease in stage 4 uNK cells correlated positively with low IL-15 mRNA expression. We suggest that the reduced stage 4 uNK cells in women with RIF are associated with IL-15 deficiency.

Immature natural killer cells promote progression of triple-negative breast cancer

Natural killer (NK) cells are cytotoxic lymphocytes that accumulate within the tumor microenvironment and are generally considered to be antitumorigenic. Using single-cell RNA sequencing and functional analysis of multiple triple-negative breast cancer (TNBC) and basal tumor samples, we observed a unique subcluster of Socs3highCD11b-CD27- immature NK cells that were present only in TNBC samples. These tumor-infiltrating NK cells expressed a reduced cytotoxic granzyme signature and, in mice, were responsible for activating cancer stem cells through Wnt signaling. NK cell-mediated activation of these cancer stem cells subsequently enhanced tumor progression in mice, whereas depletion of NK cells or Wnt ligand secretion from NK cells by LGK-974 decreased tumor progression. In addition, NK cell depletion or inhibition of their function improved anti-programmed cell death ligand 1 (PD-L1) antibody or chemotherapy response in mice with TNBC. Furthermore, tumor samples from patients with TNBC and non-TNBC revealed that increased numbers of CD56bright NK cells were present in TNBC tumors and were correlated to poor overall survival in patients with TNBC. Together, our findings identify a population of protumorigenic NK cells that may be exploited for both diagnostic and therapeutic strategies to improve outcomes for patients with TNBC.

Endometrial microbial alterations disrupt endometrial immune homeostasis by overactivation of Eicosapentaenoic acid biosynthesis leading to altered endometrial receptivity

Embryo implantation is a key step in human reproduction, and the endometrium plays a key role in this process. Changes in the receptive state of the endometrium are one of the main reasons for embryo implantation failure. However, the mechanism underlying the altered endometrial receptivity remains unclear. In this study, we recruited 140 women undergoing assisted reproductive technology and divided them into a shifting group and a normal group based on their embryo implantation window results. Endometrial transcriptome data suggested that changes in the remodeling process of decidual spiral arterioles and changes in the immune environment might be important mechanisms of implantation window shift. The functional enrichment analysis results also suggested that the changes in microbiota had an important role in the changes in endometrial status. The endometrial functionally active microbial profiles were obtained based on previously validated metatranscriptomic analysis pipelines. Combining host gene expression information, immune cell abundance information and functionally active microbial abundance and activity information, we found that Treponema succinifaciens, Fusobacterium sp. oral taxon 203 and other potentially harmful species may over-activate Eicosapentaenoic acid (EPA) biosynthesis Thus, the balance of the immune environment of the endometrium is disrupted, resulting in the shift of the implantation window and the failure of embryo implantation.

Potential Therapeutic Effects of Human Amniotic Epithelial Cells on Gynecological Disorders Leading to Infertility or Abortion

The induction of feto-maternal tolerance, fetal non-immunogenicity, and the regulation of mother's immune system are essential variables in a successful pregnancy. Fetal membranes have been used as a source of stem cells and biological components in recent decades. Human amniotic epithelial cells (hAEC) have stem/progenitor characteristics like those found in the amniotic membrane. Based on their immunomodulatory capabilities, recent studies have focused on the experimental and therapeutic applications of hAECs in allograft transplantation, autoimmune disorders, and gynecological problems such as recurrent spontaneous abortion (RSA), recurrent implantation failure (RIF), and premature ovarian failure (POF). This review discusses some of the immunomodulatory features and therapeutic potential of hAECs in preventing infertility, miscarriage, and implantation failure by controlling the maternal immune system.

Functional prominence of natural killer cells and natural killer T cells in pregnancy and infertility: A comprehensive review and update

During pregnancy, complicated connections are formed between a mother and a fetus. In a successful pregnancy, the maternal-fetal interface is affected by dynamic changes, and the fetus is protected against the mother's immune system. Natural killer (NK) cells are one of the immune system cells in the female reproductive system that play an essential role in the physiology of pregnancy. NK cells not only exist in peripheral blood (PB) but also can exist in the decidua. Studies have suggested multiple roles for these cells, including decidualization, control of trophoblast growth and invasion, embryo acceptance and maintenance by the mother, and facilitation of placental development during pregnancy. Natural killer T (NKT) cells are another group of NK cells that play a crucial role in the maintenance of pregnancy and regulation of the immune system during pregnancy. Studies show that NK and NKT cells are not only effective in maintaining pregnancy but also can be involved in infertility-related diseases. This review focuses on NK and NKT cells biology and provides a detailed description of the functions of these cells in implantation, placentation, and immune tolerance during pregnancy and their role in pregnancy complications.

Immunity at maternal-fetal interface: KIR/HLA (Allo)recognition

Both KIR and HLA are the most variable gene families in the human genome. The recognition of the semi-allogeneic embryo-derived trophoblasts by maternal decidual NK (dNK) cells is essential for the establishment of the functional placenta. This recognition is based on the KIR-HLA interactions and trophoblast expresses a specific HLA profile that constitutes classical polymorphic HLA-C and non-classical oligomorphic HLA-E, HLA-F, and HLA-G molecules. This review highlights some features of the KIR/HLA-C (allo)recognition by decidual NK (dNK) cells as a main immune cell population specifically enriched at maternal-fetal interface during human early pregnancy. How KIR/HLA-C axis operates in pregnancy disorders and in the context of transplacental infections is discussed as well. We summarized old and new data on dNK-cell functional plasticity, their selective expression of KIR and fetal maternal/paternal HLA-C haplotypes present. Results showed that KIR-HLA-C combinations and the corresponding axis operate differently in each pregnancy, determined by the variability of both maternal KIR haplotypes and fetus' maternal/paternal HLA-C allotype combinations. Moreover, the maturation of NK cells strongly depends on if or not HLA allotypes for certain KIR are present. We suggest that the unique KIR/HLA combinations reached in each pregnancy (normal and pathological) should be studied according to well-defined guidelines and unified methodologies to have comparable results ease to interpret and use in clinics.

Interaction Between Chronic Endometritis Caused Endometrial Microbiota Disorder and Endometrial Immune Environment Change in Recurrent Implantation Failure

Objective

To investigate the Interaction between chronic endometritis (CE) caused endometrial microbiota disorder and endometrial immune environment change in recurrent implantation failure (RIF).

Method

Transcriptome sequencing analysis of the endometrial of 112 patients was preform by using High-Throughput Sequencing. The endometrial microbiota of 43 patients was analyzed by using 16s rRNA sequencing technology.

Result

In host endometrium, CD4 T cell and macrophage exhibited significant differences abundance between CE and non-CE patients. The enrichment analysis indicated differentially expressed genes mainly enriched in immune-related functional terms. Phyllobacterium and Sphingomonas were significantly high infiltration in CE patients, and active in pathways related to carbohydrate metabolism and/or fat metabolism. The increased synthesis of lipopolysaccharide, an important immunomodulator, was the result of microbial disorders in the endometrium.

Conclusion

The composition of endometrial microorganisms in CE and non-CE patients were significantly different. Phyllobacterium and Sphingomonas mainly regulated immune cells by interfering with the process of carbohydrate metabolism and/or fat metabolism in the endometrium. CE endometrial microorganisms might regulate Th17 response and the ratio of Th1 to Th17 through lipopolysaccharide (LPS).

Angiogenic Properties of NK Cells in Cancer and Other Angiogenesis-Dependent Diseases

The pathogenesis of many serious diseases, including cancer, is closely related to disturbances in the angiogenesis process. Angiogenesis is essential for the progression of tumor growth and metastasis. The tumor microenvironment (TME) has immunosuppressive properties, which contribute to tumor expansion and angiogenesis. Similarly, the uterine microenvironment (UME) exerts a tolerogenic (immunosuppressive) and proangiogenic effect on its cells, promoting implantation and development of the embryo and placenta. In the TME and UME natural killer (NK) cells, which otherwise are capable of killing target cells autonomously, enter a state of reduced cytotoxicity or anergy. Both TME and UME are rich with factors (e.g., TGF-β, glycodelin, hypoxia), which support a conversion of NK cells to the low/non-cytotoxic, proangiogenic CD56^brightCD16^low phenotype. It is plausible that the phenomenon of acquiring proangiogenic and low cytotoxic features by NK cells is not only limited to cancer but is a common feature of different angiogenesis-dependent diseases (ADDs). In this review, we will discuss the role of NK cells in angiogenesis disturbances associated with cancer and other selected ADDs. Expanding the knowledge of the mechanisms responsible for angiogenesis and its disorders contributes to a better understanding of ADDs and may have therapeutic implications.

Paradigms for investigating invasive trophoblast cell development and contributions to uterine spiral artery remodeling

Uterine spiral arteries are extensively remodeled during placentation to ensure sufficient delivery of maternal blood to the developing fetus. Uterine spiral arterial remodeling is complex, as cells originating from both mother and developing conceptus interact at the maternal interface to regulate the extracellular matrix remodeling and vasculature restructuring necessary for successful placentation. Despite this complexity, one mechanism critical to spiral artery remodeling is trophoblast cell invasion into the maternal compartment. Invasive trophoblast cells include both interstitial and endovascular populations that exhibit spatiotemporal differences in uterine invasion, including proximity to uterine spiral arteries. Interstitial trophoblast cells invade the uterine parenchyma where they are interspersed among stromal cells. Endovascular trophoblast cells infiltrate uterine spiral arteries, replace endothelial cells, adopt a pseudo-endothelial cell phenotype, and engineer vessel remodeling. Impaired trophoblast cell invasion and, consequently, insufficient uterine spiral arterial remodeling can lead to the development of pregnancy disorders, such as preeclampsia, intrauterine growth restriction, and premature birth. This review provides insights into invasive trophoblast cells and their function during normal placentation as well as in settings of disease.

Variation in the HLA-F gene locus with functional impact is associated with pregnancy success and time-to-pregnancy after fertility treatment

STUDY QUESTION

The aim of this study was to investigate a possible influence of three single nucleotide polymorphisms (SNPs) in the HLA-F gene locus on time-to-pregnancy and pregnancy success after fertility treatment.

SUMMARY ANSWER

HLA-F SNP genotypes and HLA-F diplotypes are associated with the number of fertility treatment cycles needed to achieve pregnancy and live birth.

WHAT IS KNOWN ALREADY

HLA class Ib molecules, including HLA-F, which are known to be expressed by extra-villous trophoblast cells have immunomodulatory properties and play a role at the feto-maternal interface. However, a few recent studies suggest that HLA-F expressed in the mid-luteal endometrium may play a part in the establishment of pregnancy as well. Three genetic polymorphisms in the HLA-F gene locus influence the expression of HLA-F in the mid-luteal endometrium and are associated with time-to-pregnancy in healthy women.

STUDY DESIGN, SIZE, DURATION

The current study included 102 female patients and 91 male patients attending for ART treatment and recruited between 2009 and 2014 at fertility clinics in a University Hospital setting, and 78 fertile female controls recruited in 2017 and 2018 at a department of Obstetrics and Gynaecology in a University Hospital. All women in the control group conceived naturally, and no other clinical data for the controls were retrieved.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Genotyping of genomic DNA from blood samples was performed with Sanger sequencing for the three SNPs of interest in the HLA-F gene locus: rs1362126 (G/A), rs2523405 (T/G) and rs2523393 (A/G). Furthermore, clinical data were collected for the couples in fertility treatment.

MAIN RESULTS AND THE ROLE OF CHANCE

There were no significant differences in the distributions of the three HLA-F SNP genotypes and alleles between the female fertile control group and the female infertility group. We considered if the number of treatment cycles was related to the HLA-F SNP genotypes and HLA-F diplotypes in a discrete time to event analyses. A significant association with longer time-to-pregnancy, measured as number of fertility treatment cycles, was observed for women in the ART group who carried the HLA-F genotypes that are associated with a lower amount of HLA-F mRNA expressed in mid-luteal endometrium. For the rs1362126 AA genotype relative to the GG genotype, the odds ratio (OR) was 0.30 (95% CI = 0.10-0.87, P = 0.02); for the rs2523405 GG genotype relative to the TT genotype, the OR was 0.40 (95% CI = 0.15-1.04, P = 0.06); and for the rs2523393 GG genotype relative to the AA genotype, the OR was 0.27 (95% CI = 0.09-0.78, P = 0.01). In addition to comparing the HLA-F genotypes by a standard likelihood-ratio test, a trend test based on the number of G or A alleles were also performed. The HLA-F genotypes associated with longer time-to-pregnancy in these tests were as follows: number of A alleles at rs1362126 (P = 0.01), the OR was 0.56 per A allele (95% CI = 0.35-0.89); number of G alleles at rs2523405 (P = 0.05), OR was 0.65 per G allele (95% CI = 0.42-1.00); and number of G alleles at rs2523393 (P = 0.01), OR was 0.56 per G allele (95% CI = 0.36-0.86). On average, for the rs1362126 SNP, 2.1 more treatment cycles for a woman who carried the AA genotype were needed to achieve pregnancy within the first eight treatment cycles compared with a woman who carried the GG genotype. Likewise, for the rs2523405 SNP, 1.8 more cycles for the GG genotype compared with the TT genotype were needed, and for the rs2523393 SNP, 2.2 more treatment cycles for a woman who carried the GG genotype compared with a woman who carried the AA genotype were needed. Adjustments for the covariates BMI, female age, IVF (yes/no for each cycle), ICSI (yes/no for each cycle), female factor (yes/no) and male factor (yes/no), were also performed modeling the cycle-specific probabilities and the genotypes remained significant and almost unchanged.

LIMITATIONS, REASONS FOR CAUTION

Specific types of ART will be chosen from the start of treatment, which means that the chances of achieving pregnancy could differ between the women solely due to their first line of treatment. However, multivariate analyses are performed to adjust for type of ART treatment.

WIDER IMPLICATIONS OF THE FINDINGS

To our knowledge, this is the first study that shows associations between, and implications of, HLA-F gene locus variation and time-to-pregnancy and pregnancy success in a clinical setting for fertility treatment/ART.

STUDY FUNDING/COMPETING INTEREST(S)

Supported by the Region Zealand Health Sciences Research foundation and by Zealand University Hospital through the ReproHealth Research Consortium ZUH. The authors declare no conflict of interest.

Natural killer cells in cancer biology and therapy

The tumor microenvironment is highly complex, and immune escape is currently considered an important hallmark of cancer, largely contributing to tumor progression and metastasis. Named for their capability of killing target cells autonomously, natural killer (NK) cells serve as the main effector cells toward cancer in innate immunity and are highly heterogeneous in the microenvironment. Most current treatment options harnessing the tumor microenvironment focus on T cell-immunity, either by promoting activating signals or suppressing inhibitory ones. The limited success achieved by T cell immunotherapy highlights the importance of developing new-generation immunotherapeutics, for example utilizing previously ignored NK cells. Although tumors also evolve to resist NK cell-induced cytotoxicity, cytokine supplement, blockade of suppressive molecules and genetic engineering of NK cells may overcome such resistance with great promise in both solid and hematological malignancies. In this review, we summarized the fundamental characteristics and recent advances of NK cells within tumor immunometabolic microenvironment, and discussed potential application and limitations of emerging NK cell-based therapeutic strategies in the era of presicion medicine.

Mesenchymal Stromal Cells from Fetal and Maternal Placenta Possess Key Similarities and Differences: Potential Implications for Their Applications in Regenerative Medicine

Placenta-derived mesenchymal stromal cells (MSC) have attracted more attention for their immune modulatory properties and poor immunogenicity, which makes them suitable for allogeneic transplantation. Although MSC isolated from different areas of the placenta share several features, they also present significant biological differences, which might point to distinct clinical applications. Hence, we compared cells from full term placenta distinguishing them on the basis of their origin, either maternal or fetal. We used cells developed by Pluristem LTD: PLacenta expanded mesenchymal-like adherent stromal cells (PLX), maternal-derived cells (PLX-PAD), fetal-derived cells (PLX-R18), and amniotic membrane-derived MSC (hAMSC). We compared immune modulatory properties evaluating effects on T-lymphocyte proliferation, expression of cytotoxicity markers, T-helper and T-regulatory cell polarization, and monocyte differentiation toward antigen presenting cells (APC). Furthermore, we investigated cell immunogenicity. We show that MSCs and MSC-like cells from both fetal and maternal sources present immune modulatory properties versus lymphoid (T cells) and myeloid (APC) cells, whereby fetal-derived cells (PLX-R18 and hAMSC) have a stronger capacity to modulate immune cell proliferation and differentiation. Our results emphasize the importance of understanding the cell origin and characteristics in order to obtain a desired result, such as modulation of the inflammatory response that is critical in fostering regenerative processes.

Hemochorial placentation: development, function, and adaptations

Placentation is a reproductive adaptation that permits fetal growth and development within the protected confines of the female reproductive tract. Through this important role, the placenta also determines postnatal health and susceptibility to disease. The hemochorial placenta is a prominent feature in primate and rodent development. This manuscript provides an overview of the basics of hemochorial placental development and function, provides perspectives on major discoveries that have shaped placental research, and thoughts on strategies for future investigation.

Expression of the Pseudorabies Virus gB Glycoprotein Triggers NK Cell Cytotoxicity and Increases Binding of the Activating NK Cell Receptor PILRβ

Natural killer (NK) cells are components of the innate immunity and are key players in the defense against virus-infected and malignant cells. NK cells are particularly important in the innate defense against herpesviruses, including alphaherpesviruses. Aggravated and life-threatening alphaherpesvirus-induced disease has been reported in patients with NK cell deficiencies. NK cells are regulated by a diversity of activating and inhibitory cell surface receptors that recognize specific ligands on the plasma membrane of virus-infected or malignant target cells. Although alphaherpesviruses have developed several evasion strategies against NK cell-mediated attack, alphaherpesvirus-infected cells are still readily recognized and killed by NK cells. However, the (viral) factors that trigger NK cell activation against alphaherpesvirus-infected cells are largely unknown. In this study, we show that expression of the gB glycoprotein of the alphaherpesvirus pseudorabies virus (PRV) triggers NK cell-mediated cytotoxicity, both in PRV-infected and in gB-transfected cells. In addition, we report that, like their human and murine counterpart, porcine NK cells express the activating receptor paired immunoglobulin-like type 2 receptor beta (PILRβ), and we show that gB expression triggers increased binding of recombinant porcine PILRβ to the surfaces of PRV-infected cells and gB-transfected cells.IMPORTANCE Natural killer (NK) cells display a prominent cytolytic activity against virus-infected cells and are indispensable in the innate antiviral response, particularly against herpesviruses. Despite their importance in the control of alphaherpesvirus infections, relatively little is known about the mechanisms that trigger NK cell cytotoxicity against alphaherpesvirus-infected cells. Here, using the porcine alphaherpesvirus pseudorabies virus (PRV), we found that the conserved alphaherpesvirus glycoprotein gB triggers NK cell-mediated cytotoxicity, both in virus-infected and in gB-transfected cells. In addition, we report that gB expression results in increased cell surface binding of porcine paired immunoglobulin-like type 2 receptor beta (PILRβ), an activating NK cell receptor. The interaction between PILRβ and viral gB may have consequences that stretch beyond the interaction with NK cells, including virus entry into host cells. The identification of gB as an NK cell-activating viral protein may be of importance in the construction of future vaccines and therapeutics requiring optimized interactions of alphaherpesviruses with NK cells.

Heterogeneity of NK Cells and Other Innate Lymphoid Cells in Human and Murine Decidua

Innate lymphoid cells (ILCs) represent a heterogeneous group of cells lacking genetically rearranged antigen receptors that derive from common lymphoid progenitors. Five major groups of ILCs have been defined based on their cytokine production pattern and developmental transcription factor requirements: namely, natural killer (NK) cells, ILC1s, ILC2s, ILC3s, and lymphoid tissue-inducer (LTi) cells. ILC1s, ILC2s, and ILC3s mirror the corresponding T helper subsets (Th1, Th2, and Th17, respectively) and produce cytokines involved in defense against pathogens, lymphoid organogenesis, and tissue remodeling. During the first trimester of pregnancy, decidual tissues contain high proportion of decidual NK (dNK) cells, representing up to 50% of decidual lymphocytes, and ILC3s. They release peculiar cytokines and chemokines that contribute to successful pregnancy. Recent studies revealed that ILCs display a high degree of plasticity allowing their prompt adaptation to environmental changes. Decidual NK cells may derive from peripheral blood NK cells migrated when pregnancy establishes or from in situ differentiation of hematopoietic precursors. Previous studies showed that human and murine decidua contain dNK cells, tissue resident NK cells, and ILC3s, all characterized by unique phenotypic and functional properties, most likely induced by decidual microenvironment to favor the establishment and the maintenance of pregnancy. Thus, during the early phase of pregnancy, the simultaneous presence of different ILC subsets further underscores the complexity of the cellular components of decidual tissues as well as the role of decidual microenvironment in shaping the plasticity and the function of ILCs.

How uterine microbiota might be responsible for a receptive, fertile endometrium

BACKGROUND

Fertility depends on a receptive state of the endometrium, influenced by hormonal and anatomical adaptations, as well as the immune system. Local and systemic immunity is greatly influenced by microbiota. Recent discoveries of 16S rRNA in the endometrium and the ability to detect low-biomass microbiota fueled the notion that the uterus may be indeed a non-sterile compartment. To date, the concept of the 'sterile womb' focuses on in utero effects of microbiota on offspring and neonatal immunity. However, little awareness has been raised regarding the importance of uterine microbiota for endometrial physiology in reproductive health; manifested in fertility and placentation.

OBJECTIVE AND RATIONALE

Commensal colonization of the uterus has been widely discussed in the literature. The objective of this review is to outline the possible importance of this uterine colonization for a healthy, fertile uterus. We present the available evidence regarding uterine microbiota, focusing on recent findings based on 16S rRNA, and depict the possible importance of uterine colonization for a receptive endometrium. We highlight a possible role of uterine microbiota for host immunity and tissue adaptation, as well as conferring protection against pathogens. Based on knowledge of the interaction of the mucosal immune cells of the gut with the local microbiome, we want to investigate the potential implications of commensal colonization for uterine health.

SEARCH METHODS

PubMed and Google Scholar were searched for articles in English indexed from 1 January 2008 to 1 March 2018 for '16S rRNA', 'uterus' and related search terms to assess available evidence on uterine microbiome analysis. A manual search of the references within the resulting articles was performed. To investigate possible functional contributions of uterine microbiota to health, studies on microbiota of other body sites were additionally assessed.

OUTCOMES

Challenging the view of a sterile uterus is in its infancy and, to date, no conclusions on a 'core uterine microbiome' can be drawn. Nevertheless, evidence for certain microbiota and/or associated compounds in the uterus accumulates. The presence of microbiota or their constituent molecules, such as polysaccharide A of the Bacteroides fragilis capsule, go together with healthy physiological function. Lessons learned from the gut microbiome suggest that the microbiota of the uterus may potentially modulate immune cell subsets needed for implantation and have implications for tissue morphology. Microbiota can also be crucial in protection against uterine infections by defending their niche and competing with pathogens. Our review highlights the need for well-designed studies on a 'baseline' microbial state of the uterus representing the optimal starting point for implantation and subsequent placenta formation.

WIDER IMPLICATIONS

The complex interplay of processes and cells involved in healthy pregnancy is still poorly understood. The correct receptive endometrial state, including the local immune environment, is crucial not only for fertility but also placenta formation since initiation of placentation highly depends on interaction with immune cells. Implantation failure, recurrent pregnancy loss, and other pathologies of endometrium and placenta, such as pre-eclampsia, represent an increasing societal burden. More robust studies are needed to investigate uterine colonization. Based on current data, future research needs to include the uterine microbiome as a relevant factor in order to understand the players needed for healthy pregnancy.

Porcine NK Cells Stimulate Proliferation of Pseudorabies Virus-Experienced CD8+ and CD4+CD8+ T Cells

Natural killer (NK) cells belong to the innate immune system and play a central role in the defense against viral infections and cancer development, but also contribute to shaping adaptive immune responses. NK cells are particularly important in the first line defense against herpesviruses, including alphaherpesviruses. In addition to their ability to kill target cells and produce interferon-γ, porcine and human NK cell subsets have been reported to display features associated with professional antigen presenting cells (APC), although it is currently unclear whether NK cells may internalize debris of virus-infected cells and whether this APC-like activity of NK cells may stimulate proliferation of antiviral T cells. Here, using the porcine alphaherpesvirus pseudorabies virus (PRV), we show that vaccination of pigs with a live attenuated PRV vaccine strain triggers expression of MHC class II on porcine NK cells, that porcine NK cells can internalize debris from PRV-infected target cells, and that NK cells can stimulate proliferation of CD8⁺ and CD4⁺CD8⁺ PRV-experienced T cells. These results highlight the potential of targeting these NK cell features in future vaccination strategies.

Regulation of Placental Extravillous Trophoblasts by the Maternal Uterine Environment

During placentation invasive extravillous trophoblasts (EVTs) migrate into the maternal uterus and modify its vessels. In particular, remodeling of the spiral arteries by EVTs is critical for adapting blood flow and nutrient transport to the developing fetus. Failures in this process have been noticed in different pregnancy complications such as preeclampsia, intrauterine growth restriction, stillbirth, or recurrent abortion. Upon invasion into the decidua, the endometrium of pregnancy, EVTs encounter different maternal cell types such as decidual macrophages, uterine NK (uNK) cells and stromal cells expressing a plethora of growth factors and cytokines. Here, we will summarize development of the EVT lineage, a process occurring independently of the uterine environment, and formation of its different subtypes. Further, we will discuss interactions of EVTs with arteries, veins and lymphatics and illustrate how the decidua and its different immune cells regulate EVT differentiation, invasion and survival. The present literature suggests that the decidual environment and its soluble factors critically modulate EVT function and reproductive success.

Molecular Mechanisms Directing Migration and Retention of Natural Killer Cells in Human Tissues

A large body of data shows that Natural Killer (NK) cells are immune effectors exerting a potent cytolytic activity against tumors and virus infected cells. The discovery and characterization of several inhibitory and activating receptors unveiled most of the mechanisms allowing NK cells to spare healthy cells while selectively attacking abnormal tissues. Nevertheless, the mechanisms ruling NK cell subset recirculation among the different compartments of human body have only lately started to be investigated. This is particularly true for pathological settings such as tumors or infected tissues but also for para-physiological condition like pregnant human uterine mucosa. It is becoming evident that the microenvironment associated to a particular clinical condition can deeply influence the migratory capabilities of NK cells. In this review we describe the main mechanisms and stimuli known to regulate the expression of chemokine receptors and other molecules involved in NK cell homing to either normal or pathological/inflamed tissues, including tumors or organs such as lung and liver. We will also discuss the role played by the chemokine/chemokine receptor axes in the orchestration of physiological events such as NK cell differentiation, lymphoid organ retention/egress and recruitment to decidua during pregnancy.

Cross talk between natural killer cells and mast cells in tumor angiogenesis

Natural killer (NK) cells are large granular lymphocytes of the innate immune system, responsible for direct targeting and killing of both virally infected and transformed cells. Under pathological conditions and during inflammation, NK cells extravasate into the lymph nodes and accumulate at inflammatory or tumor sites. The activation of NK cells depends on an intricate balance between activating and inhibitory signals that determines if a target will be susceptible to NK-mediated lysis. Many experimental evidences indicate that NK cells are also involved in several immunoregulatory processes and have the ability to modulate the adaptive immune responses. Many other important aspects about NK cell biology are emerging in these last years. The aim of this review is to elucidate the role of NK cells in tumor angiogenesis and their interaction with mast cells. In fact, it has been observed that NK cells produce pro-angiogenic factors and participate alone or in cooperation with mast cells to the regulation of angiogenesis in both physiological and pathological conditions including tumors.

Disruption in the Regulation of Immune Responses in the Placental Subtype of Preeclampsia

Preeclampsia is a pregnancy-specific disorder, of which one of its major subtypes, the placental subtype is considered a response to an ischemic placental environment, impacting fetal growth and pregnancy outcome. Inflammatory immune responses have been linked to metabolic and inflammatory disorders as well as reproductive failures. In healthy pregnancy, immune regulatory mechanisms prevent excessive systemic inflammation. However, in preeclampsia, the regulation of immune responses is disrupted as a result of aberrant activation of innate immune cells and imbalanced differentiation of T-helper cell subsets creating a cytotoxic environment in utero. Recognition events that facilitate immune interaction between maternal decidual T cells, NK cells, and cytotrophoblasts are considered an indirect cause of the incomplete remodeling of spiral arteries in preeclampsia. The mechanisms involved include the activation of immune cells and the subsequent secretion of cytokines and placental growth factors affecting trophoblast invasion, angiogenesis, and eventually placentation. In this review, we focus on the role of excessive systemic inflammation as the result of a dysregulated immune system in the development of preeclampsia. These include insufficient control of inflammation, failure of tolerance toward paternal antigens at the fetal-maternal interface, and subsequent over- or insufficient activation of immune mediators. It is also possible that external stimuli, such as bacterial endotoxin, may contribute to the excessive systemic inflammation in preeclampsia by stimulating the release of pro-inflammatory cytokines. In conclusion, a disrupted immune system might be a predisposing factor or result of placental oxidative stress or excessive inflammation in preeclampsia. Preeclampsia can thus be considered a hyperinflammatory state associated with defective regulation of the immune system proposed as a key element in the pathological events of the placental subtype of this disorder.

Incorporating placental tissue in cord blood banking for stem cell transplantation

INTRODUCTION

Human term placenta is comprised of various tissues from which different cells can be obtained, including hematopoietic stem cells and mesenchymal stem/stromal cells (MSCs). Areas covered: This review will discuss the possibility to incorporate placental tissue cells in cord blood banking. It will discuss general features of human placenta, with a brief review of the immune cells at the fetal-maternal interface and the different cell populations isolated from placenta, with a particular focus on MSCs. It will address the question as to why placenta-derived MSCs should be banked with their hematopoietic counterparts. It will discuss clinical trials which are studying safety and efficacy of placenta tissue-derived MSCs in selected diseases, and preclinical studies which have proven their therapeutic properties in other diseases. It will discuss banking of umbilical cord blood and raise several issues for improvement, and the applications of cord blood cells in non-malignant disorders. Expert commentary: Umbilical cord blood banking saves lives worldwide. The concomitant banking of non-hematopoietic cells from placenta, which could be applied therapeutically in the future, alone or in combination to their hematopoietic counterparts, could exploit current banking processes while laying the foundation for clinical trials exploring placenta-derived cell therapies in regenerative medicine.

Angiogenin and the MMP9-TIMP2 axis are up-regulated in proangiogenic, decidual NK-like cells from patients with colorectal cancer

NK cells are effector lymphocytes involved in tumor immunosurveillance; however, in patients with solid malignancies, NK cells have compromised functions. We have previously reported that lung tumor-associated NK cells (TANKs; peripheral blood) and tumor-infiltrating NK cells (TINKs) show proangiogenic, decidual NK-like (dNK) phenotype. In this study, we functionally and molecularly investigated TINKs and TANKs from blood and tissue samples of patients with colorectal cancer (CRC), a neoplasm in which inflammation and angiogenesis have clinical relevance, and compared them to NK cells from controls and patients with nononcologic inflammatory bowel disease. CRC TINKs/TANKs showed decreased expression for the activatory marker NKG2D, impaired degranulation activity, a decidual-like NK polarization toward the CD56^brightCD16^dim/-CD9⁺CD49⁺ subset. TINKs and TANKs secreted cytokines with proangiogenic activities, and induce endothelial cell proliferation, migration, adhesion, and the formation of capillary-like structures in vitro. dNK cells release specific proangiogenic factors; among which, angiogenin and invasion-associated enzymes related to the MMP9-TIMP1/2 axis. Here, we describe, for the first time, to our knowledge, the expression of angiogenin, MMP2/9, and TIMP by TANKs in patients with CRC. This phenotype could be relevant to the invasive capabilities and proangiogenic functions of CRC-NK cells and become a novel biomarker. STAT3/STAT5 activation was observed in CRC-TANKs, and treatment with pimozide, a STAT5 inhibitor, reduced endothelial cell capability to form capillary-like networks, inhibiting VEGF and angiogenin production without affecting the levels of TIMP1, TIMP2, and MMP9, indicating that STAT5 is involved in cytokine modulation but not invasion-associated molecules. Combination of Stat5 or MMP inhibitors with immunotherapy could help repolarize CRC TINKs and TANKs to anti-tumor antimetastatic ones.-Bruno, A., Bassani, B., D'Urso, D. G., Pitaku, I., Cassinotti, E., Pelosi, G., Boni, L., Dominioni, L., Noonan, D. M., Mortara, L., Albini, A. Angiogenin and the MMP9-TIMP2 axis are up-regulated in proangiogenic, decidual NK-like cells from patients with colorectal cancer.

Contribution to Tumor Angiogenesis From Innate Immune Cells Within the Tumor Microenvironment: Implications for Immunotherapy

The critical role of angiogenesis in promoting tumor growth and metastasis is strongly established. However, tumors show considerable variation in angiogenic characteristics and in their sensitivity to antiangiogenic therapy. Tumor angiogenesis involves not only cancer cells but also various tumor-associated leukocytes (TALs) and stromal cells. TALs produce chemokines, cytokines, proteases, structural proteins, and microvescicles. Vascular endothelial growth factor (VEGF) and inflammatory chemokines are not only major proangiogenic factors but are also immune modulators, which increase angiogenesis and lead to immune suppression. In our review, we discuss the regulation of angiogenesis by innate immune cells in the tumor microenvironment, specific features, and roles of major players: macrophages, neutrophils, myeloid-derived suppressor and dendritic cells, mast cells, γδT cells, innate lymphoid cells, and natural killer cells. Anti-VEGF or anti-inflammatory drugs could balance an immunosuppressive microenvironment to an immune permissive one. Anti-VEGF as well as anti-inflammatory drugs could therefore represent partners for combinations with immune checkpoint inhibitors, enhancing the effects of immune therapy.

The role of HLA-G in parasitic diseases

Little attention has been devoted to the role of HLA-G gene and molecule on parasitic disorders, and the available studies have focused on malaria, African and American trypanosomiasis, leishmaniosis, toxoplasmosis and echinococcosis. After reporting a brief description regarding the role of the cells of innate and adaptive immune system against parasites, we reviewed the major features of the HLA-G gene and molecule and the role of HLA-G on the major cells of immune system. Increased levels of soluble HLA-G (sHLA-G) have been observed in patients presenting toxoplasmosis and in the active phase of echinococcosis. In addition, increased sHLA-G has also been associated with increased susceptibility to malaria and increased susceptibility to develop human African trypanosomiasis (HAT). In contrast, decreased membrane-bound HLA-G has been reported in placenta of patients infected with Plasmodium falciparum and in heart and colon of patients presenting Chagas disease. The 3' untranslated region of the HLA-G gene has been the main focus of studies on malaria, HAT and Chagas disease, exhibiting distinct patterns of associations. Considering that HLA-G is an immune checkpoint molecule, inhibiting the activity of several cells of the immune system, the excessive neoexpression and the increased sHLA-G levels together with the decreased constitutive tissue expression of membrane-bound HLA-G may be detrimental to the host infected with parasite agents.

Evaluation of endometrial natural killer cell expression of CD4, CD103, and CD16 cells in women with unexplained infertility

OBJECTIVE

To determine whether natural killer cell (NK) concentrations in the mid-secretory endometrial tissue of women with unexplained infertility differ from those in the mid-secretory endometrial tissue of fertile women.

METHODS

This study was conducted with 22 patients with unexplained infertility caused by unsuccessful ovulation induced with gonadotrophins and 12 healthy fertile women, who formed a control group. Mid-secretory endometrial tissue samples were obtained with a Pipelle catheter, and the endometrial NK cell phenotypes were determined by flow cytometry.

RESULTS

The median number of CD4+ cells in the endometrium was significantly lower in women with unexplained infertility compared with in the fertile controls (3.31 vs. 5.81; p=0.02). The CD4(+)/CD8(+) cell ratio in the unexplained-infertility group was significantly lower than that in the control group (0.42 vs. 0.76, p=0.01). The median number of CD103(+) cells in the endometrium of the infertile group was significantly lower than that in the endometrium of the control group (4.40 vs. 6.73, p=0.02). The median number of CD16(+) cells was significantly higher in infertile women than in control women (0.12 vs. 0.001, p=0.01).

CONCLUSIONS

Significant reductions in the numbers of CD4(+) and CD103(+) cells as well as in the CD4(+)/CD8(+) ratio but an increased number of CD16(+) cells in the endometrium of infertile women suggest that disordered NK cell activity may be a contributor to the etiology of unexplained infertility.

Survival in acute myeloid leukemia is associated with NKp44 splice variants

NKp44 is a receptor encoded by the NCR2 gene, which is expressed by cytokine-activated natural killer (NK) cells that are involved in anti-AML immunity. NKp44 has three splice variants corresponding to NKp44ITIM+ (NKp44-1) and NKp44ITIM- (NKp44-2, and NKp44-3) isoforms. RNAseq data of AML patients revealed similar survival of NKp46+NKp44+ and NKp46+NKp44- patients. However, if grouped according to the NKp44 splice variant profile, NKp44-1 expression was significantly associated with poor survival of AML patients. Moreover, activation of PBMC from healthy controls showed co-dominant expression of NKp44-1 and NKp44-3, while primary NK clones show more diverse NKp44 splice variant profiles. Cultured primary NK cells resulted in NKp44-1 dominance and impaired function associated with PCNA over-expression by target cells. This impaired functional phenotype could be rescued by blocking of NKp44 receptor. Human NK cell lines revealed co-dominant expression of NKp44-1 and NKp44-3 and showed a functional phenotype that was not inhibited by PCNA over-expression. Furthermore, transfection-based overexpression of NKp44-1, but not NKp44-2/NKp44-3, reversed the endogenous resistance of NK-92 cells to PCNA-mediated inhibition, and resulted in poor formation of stable lytic immune synapses. This research contributes to the understanding of AML prognosis by shedding new light on the functional implications of differential splicing of NKp44.

The Uterine Immune Profile May Help Women With Repeated Unexplained Embryo Implantation Failure After In Vitro Fertilization

LABELED PROBLEM

Embryo implantation remains the main limiting factor in assisted reproductive medicine (20% success rate).

METHODS OF STUDY

An endometrial immune profiling was performed among 394 women with the previous history of repeated embryo implantation failures (RIF). The endometrial immune profile documented the ratio of IL-15/Fn-14 mRNA as a biomarker of uNK cell activation/maturation (together with the uNK cell count) and the IL-18/TWEAK mRNA ratio as a biomarker of both angiogenesis and the Th1/Th2 balance. According to their profile, we recommended personalized care to counteract the documented dysregulation and assessed its effects by the live birth rate (LBR) for the next embryo transfer.

RESULTS

Endometrial immune profiles appeared to be dysregulated in 81.7% of the RIF patients compared to control. Overactivation was diagnosed in 56.6% and low activation in 25%. The LBR among these dysregulated/treated patients at the first subsequent embryo transfer was 39.8%.

CONCLUSION

Endometrial immune profiling may improve our understanding of RIF and subsequent LBR if treated.

To serve and to protect: the role of decidual innate immune cells on human pregnancy

The maternal-fetal interface undergoes dynamic changes that promote successful development of the embryo/fetal allograft during pregnancy. This immune privilege of the conceptus is mediated through local and systemic cellular responses. In species in which endometrial decidualization accompanies pregnancy, unique immune cell niches are found. Many studies have addressed the enigmatic roles of uterine (u)NK cells as killers and helpers because they are frequently found in the uterine lining and decidua of normal and pathological pregnancies. Accumulating evidence indicates that uNK cells are induced and transformed by sensing signals within their microenvironment to both protect the mother from the fetal allograft and support the fetus during its development. Here, we review the mechanisms that modulate these functions of uNK cells during pregnancy. We suggest that uNK cells must be tightly regulated in order to serve these two roles and support a healthy pregnancy.

sHLA-G involved in the apoptosis of decidual natural killer cells following Toxoplasma gondii infection

This study aims to assess whether soluble HLA-G (sHLA-G) is involved in apoptosis of decidual natural killer (dNK) cells following Toxoplasma gondii infection. dNK cells or NK-92 cells were infected with T. gondii and co-cultured with trophoblast cells or BeWo cells. Infected co-cultured cells were treated without or with sHLA-G neutralizing antibody. Uninfected co-cultured cells were used as controls. Apoptosis of dNK cells were analyzed by flow cytometry and confocal microscope. Real-time PCR and Western blot were used to determine caspase 3 and caspase 8 expression. sHLA-G in supernatant were measured by enzyme-linked immunosorbent assay (ELISA). In infection groups, sHLA-G was increased, while dNK apoptosis proteins caspase 3 and caspase 8 were up-regulated, but significantly decreased in the presence of sHLA-G neutralizing antibody compared to controls. Under the situation of T. gondii-infected dNK cells co-cultured with trophoblast cells, the up-regulation of sHLA-G could induce dNK cells apoptosis which ultimately may contribute to the abnormal pregnancy outcomes with T. gondii infection.

Identification of diverse innate lymphoid cells in human decidua

Innate lymphoid cells (ILCs) are developmentally related cells that play an important role in innate defenses and tissue remodeling. So far, only natural killer (NK) cells have been identified and functionally characterized in human decidua where they contribute to induction of immune suppression, neo-angiogenesis, and tissue building/remodeling. The presence of other ILC subsets in human decidua has not been yet characterized. Here we identify in human decidua, during early pregnancy, two subsets of decidual group 3 ILC (ILC3), including lymphoid tissue inducer (LTi)-like cells and natural cytotoxicity receptors (NCRs)(+)ILC3 and interferon-(IFN)γ-producing ILC1, different from NK cells. Decidual LTi-like cells produced interleukin -17 (IL-17) and tumor necrosis factor (TNF), while NCR(+)ILC3 released IL-22 and IL-8. Importantly, NCR(+)ILC3 and LTi-like cells established functional interactions with stromal cells. Decidual LTi-like cells differentiated into NCR(+)ILC3, whereas they marginally contributed to NK cell generation. Our data suggest that decidual ILC3 may play a role in innate defenses and in vessel and tissue building, thus contributing to maintenance of pregnancy.

Immunotoxicity of zinc oxide nanoparticles with different size and electrostatic charge

While zinc oxide (ZnO) nanoparticles (NPs) have been recognized to have promising applications in biomedicine, their immunotoxicity has been inconsistent and even contradictory. To address this issue, we investigated whether ZnO NPs with different size (20 or 100 nm) and electrostatic charge (positive or negative) would cause immunotoxicity in vitro and in vivo, and explored their underlying molecular mechanism. Using Raw 264.7 cell line, we examined the immunotoxicity mechanism of ZnO NPs as cell viability. We found that in a cell viability assay, ZnO NPs with different size and charge could induce differential cytotoxicity to Raw 264.7 cells. Specifically, the positively charged ZnO NPs exerted higher cytotoxicity than the negatively charged ones. Next, to gauge systemic immunotoxicity, we assessed immune responses of C57BL/6 mice after oral administration of 750 mg/kg/day dose of ZnO NPs for 2 weeks. In parallel, ZnO NPs did not alter the cell-mediated immune response in mice but suppressed innate immunity such as natural killer cell activity. The CD4(+)/CD8(+) ratio, a marker for matured T-cells was slightly reduced, which implies the alteration of immune status induced by ZnO NPs. Accordingly, nitric oxide production from splenocyte culture supernatant in ZnO NP-fed mice was lower than control. Consistently, serum levels of pro/anti-inflammatory (interleukin [IL]-1β, tumor necrosis factor-α, and IL-10) and T helper-1 cytokines (interferon-γ and IL-12p70) in ZnO NP-fed mice were significantly suppressed. Collectively, our results indicate that different sized and charged ZnO NPs would cause in vitro and in vivo immunotoxicity, of which nature is an immunosuppression.

Interferon gamma is involved in apoptosis of trophoblast cells at the maternal-fetal interface following Toxoplasma gondii infection

OBJECTIVE

To assess whether interferon gamma (IFN-γ) secreted by decidual natural killer (dNK) cells at the maternal-fetal interface is involved in the apoptosis of trophoblast cells (trophoblasts) following Toxoplasma gondii infection.

METHODS

Human dNK cells were infected with T. gondii and then co-cultured with trophoblasts. The infected co-cultured cells were treated with or without IFN-γ neutralizing antibodies. Uninfected co-cultured cells were used as controls. The level of IFN-γ in the supernatant of co-culture was measured by ELISA and the apoptosis of trophoblasts was analyzed by flow cytometry. The expression of caspase 3 and caspase 8 of trophoblasts cells was determined by Western blotting and real-time RT-PCR.

RESULTS

The levels of IFN-γ were increased at <24h following T. gondii infection and were maintained thereafter. Caspase 3, caspase 8, and the apoptosis of trophoblasts co-cultured with dNK cells were increased compared with the control. Meanwhile, IFN-γ, caspase 3, caspase 8, and trophoblast apoptosis were up-regulated upon increased ratios of dNK cells to trophoblasts. Compared to the infected group, the levels of IFN-γ, caspase 3, caspase 8, and trophoblast apoptosis were significantly decreased upon treatment with the IFN-γ neutralizing antibody. IFN-γ levels were correlated positively with the apoptosis of trophoblasts (r=0.7163, p < 0.01).

CONCLUSIONS

The levels of IFN-γ secreted by dNK cells at the maternal-fetal interface were closely correlated with the apoptosis of trophoblasts upon T. gondii infection. The apoptosis of trophoblasts induced by the increase in IFN-γ depended on the caspase pathway, which may contribute to the abnormal pregnancy outcomes that occur with T. gondii infection.

Models of vertical cytomegalovirus (CMV) transmission and pathogenesis

Despite the considerable clinical impact of congenital human cytomegalovirus (HCMV) infection, the mechanisms of maternal-fetal transmission and the resultant placental and fetal damage are largely unknown. Here, we discuss animal models for the evaluation of CMV vaccines and virus-induced pathology and particularly explore surrogate human models for HCMV transmission and pathogenesis in the maternal-fetal interface. Studies in floating and anchoring placental villi and more recently, ex vivo modeling of HCMV infection in integral human decidual tissues, provide unique insights into patterns of viral tropism, spread, and injury, defining the outcome of congenital infection, and the effect of potential antiviral interventions.

The up side of decidual natural killer cells: new developments in immunology of pregnancy

Early phases of human pregnancy are associated with the accumulation of a unique subset of natural killer (NK) cells in the maternal decidua. Decidual NK (dNK) cells that are devoid of cytotoxicity play a pivotal role in successful pregnancy. By secreting large amounts of cytokines/chemokines and angiogenic factors, dNK cells participate in all steps of placentation including trophoblast invasion into the maternal endometrium and vascular remodelling. In this review, we summarize some of dNK cell features and discuss more recent exciting data that challenge the conventional view of these cells. Our new data demonstrate that dNK cells undergo fine tuning or even subvert their classical inhibitory machinery and turn into a real defence force in order to prevent the spread of viruses to fetal tissue. Today it is not clear how these phenotypic and functional adaptations impact cellular cross-talk at the fetal-maternal interface and tissue homeostasis. Ultimately, precise understanding of the molecular mechanisms that govern dNK cell plasticity during congenital human cytomegalovirus infection should lead to the design of more robust strategies to reverse immune escape during viral infection and cancer.

The role of sex hormones and the tissue environment in immune protection against HIV in the female reproductive tract

Despite extensive studies of the mucosal immune system in the female reproductive tract (FRT) and its regulation by sex hormones, relatively little attention has been paid to the tissue environment in the FRT that regulates immune cell function. Consisting of secretions from epithelial cells (EC), stromal fibroblasts, and immune cells in tissues from the upper (Fallopian tubes, uterus, and endocervix) and lower (ectocervix and vagina) tracts, each tissue compartment is unique and precisely regulates immune cells to optimize conditions for successful pregnancy and protection against sexually transmitted diseases including HIV. Our goal in this review is to focus on the mucosal (tissue) environment in the upper and lower FRT. Specifically, this review will identify the contributions of EC and fibroblasts to the tissue environment and examine the impact of this environment on HIV-target cells. Much remains to be learned about the complex interactions with the tissue environment at different sites in the FRT and the ways in which they are regulated by sex hormones and chemical contraceptives. Awareness of the involvement of the tissue environment in determining immune cell function and HIV acquisition is crucial for understanding the mechanisms that lead to HIV prevention, acquisition, and the development of new therapeutic modalities of immune protection.

Decidual cell regulation of natural killer cell-recruiting chemokines: implications for the pathogenesis and prediction of preeclampsia

First trimester human decidua is composed of decidual cells, CD56(bright)CD16(-) decidual natural killer (dNK) cells, and macrophages. Decidual cells incubated with NK cell-derived IFN-γ and either macrophage-derived TNF-α or IL-1β synergistically enhanced mRNA and protein expression of IP-10 and I-TAC. Both chemokines recruit CXCR3-expressing NK cells. This synergy required IFN-γ receptor 1 and 2 mediation via JAK/STAT and NFκB signaling pathways. However, synergy was not observed on neutrophil, monocyte, and NK cell-recruiting chemokines. Immunostaining of first trimester decidua localized IP-10, I-TAC, IFN-γR1, and -R2 to vimentin-positive decidual cells versus cytokeratin-positive interstitial trophoblasts. Flow cytometry identified high CXCR3 levels on dNK cells and minority peripheral CD56(bright)CD16(-) pNK cells and intermediate CXCR3 levels on the majority of CD56(dim)CD16(+) pNK cells. Incubation of pNK cells with either IP-10 or I-TAC elicited concentration-dependent enhanced CXCR3 levels and migration of both pNK cell subsets that peaked at 10 ng/mL, whereas each chemokine at a concentration of 50 ng/mL inhibited CXCR3 expression and pNK cell migration. Deciduae from women with preeclampsia, a leading cause of maternal and fetal morbidity and mortality, displayed significantly lower dNK cell numbers and higher IP-10 and I-TAC levels versus gestational age-matched controls. Significantly elevated IP-10 levels in first trimester sera from women eventually developing preeclampsia compared with controls, identifying IP-10 as a novel, robust early predictor of preeclampsia.

Stromal cells from human decidua exert a strong inhibitory effect on NK cell function and dendritic cell differentiation

Stromal cells (SC) are an important component of decidual tissues where they are in strict proximity with both NK and CD14⁺ myelomonocytic cells that play a role in the maintenance of pregnancy. In this study we analyzed whether decidual SC (DSC) could exert a regulatory role on NK and CD14⁺ cells that migrate from peripheral blood (PB) to decidua during pregnancy. We show that DSCs inhibit the IL15-mediated up-regulation of major activating NK receptors in PB-derived NK cells. In addition, the IL15-induced NK cell proliferation, cytolytic activity and IFN-γ production were severely impaired. DSCs sharply inhibited dendritic cells differentiation and their ability to induce allogeneic T cell proliferation. Indoleamine 2,3-dioxygenase (IDO) and prostaglandin E2 (PGE2) mediated the inhibitory effect of DSCs. Our results strongly suggest an important role of DSCs in preventing potentially dangerous immune response, thus contributing to maintenance of pregnancy.

Novel cooperation between CX3CL1 and CCL26 inducing NK cell chemotaxis via CX3CR1: a possible mechanism for NK cell infiltration of the allergic nasal tissue

BACKGROUND

Recent data indicated that natural killer (NK) cells and chemokines could play a pivotal role in nasal inflammation. CX3CR1, the only receptor for fractalkine/CX3CL1, is abundantly expressed by NK cells, and was recently shown to also be a receptor for eotaxin-3/CCL26. However, no reports explored the NK cells-CX3CL1-CCL26 axis via CX3CR1 in allergy.

OBJECTIVE

Our goals were first to determine specifically NK cell recruitment pattern in nasal tissue of allergic chronic rhinosinusitis (ACRS) and non-allergic chronic rhinosinusitis (NACRS) patients in comparison with healthy controls, and secondly, to investigate the function of CX3CR1 in NK cell migration.

METHODS

Immunohistochemistry, microchemotaxis chambers, flow cytometry and confocal microscopy were used in this study.

RESULTS

Herein, we showed that NK cells infiltrated the epithelial layers of nasal tissue only in ACRS patients and not in NACRS patients or controls. NK cells were also more numerous in the stroma of the nasal tissue from ACRS patients compared with NACRS patients or controls. This migration could be mediated by both CX3CL1 and CCL26, as these two chemokines induced NK cell migration. Moreover, both molecules also stimulated cytoskeleton changes and F-actin reorganisation in NK cells. Chemotaxis and cytoskeleton changes were sensitive to genistein, a tyrosine kinase inhibitor. By flow cytometry, we demonstrated that a single antigen nasal provocation challenge increased the expression of CX3CR1 on NK cells in allergic rhinitis (AR) patients. The function of this receptor was associated with a significant augmentation of NK cell chemotaxis against the optimal doses of CX3CL1 and CCL26.

CONCLUSIONS AND CLINICAL RELEVANCE

Our results highlight a novel role for CX3CR1 in NK cell migration that may contribute to the NK cell trafficking to the allergic upper airway. This could be mediated largely by CX3CL1 and CCL26 stimulation of the tyrosine kinase pathway.

NK cells in immunotolerant organs

Organs such as the liver, uterus and lung possess hallmark immunotolerant features, making these organs important for sustaining self-homeostasis. These organs contain a relatively large amount of negative regulatory immune cells, which are believed to take part in the regulation of immune responses. Because natural killer cells constitute a large proportion of all lymphocytes in these organs, increasing attention has been given to the roles that these cells play in maintaining immunotolerance. Here, we review the distribution, differentiation, phenotypic features and functional features of natural killer cells in these immunotolerant organs, in addition to the influence of local microenvironments on these cells and how these factors contribute to organ-specific diseases.

HSV-2 specifically down regulates HLA-C expression to render HSV-2-infected DCs susceptible to NK cell killing

Both NK cells and CTLs kill virus-infected and tumor cells. However, the ways by which these killer cells recognize the infected or the tumorigenic cells are different, in fact almost opposite. CTLs are activated through the interaction of the TCR with MHC class I proteins. In contrast, NK cells are inhibited by MHC class I molecules. The inhibitory NK receptors recognize mainly MHC class I proteins and in this regard practically all of the HLA-C proteins are recognized by inhibitory NK cell receptors, while only certain HLA-A and HLA-B proteins interact with these receptors. Sophisticated viruses developed mechanisms to avoid the attack of both NK cells and CTLs through, for example, down regulation of HLA-A and HLA-B molecules to avoid CTL recognition, leaving HLA-C proteins on the cell surface to inhibit NK cell response. Here we provide the first example of a virus that through specific down regulation of HLA-C, harness the NK cells for its own benefit. We initially demonstrated that none of the tested HSV-2 derived microRNAs affect NK cell activity. Then we show that surprisingly upon HSV-2 infection, HLA-C proteins are specifically down regulated, rendering the infected cells susceptible to NK cell attack. We identified a motif in the tail of HLA-C that is responsible for the HSV-2-meduiated HLA-C down regulation and we show that the HLA-C down regulation is mediated by the viral protein ICP47. Finally we show that HLA-C proteins are down regulated from the surface of HSV-2 infected dendritic cells (DCs) and that this leads to the killing of DC by NK cells. Thus, we propose that HSV-2 had developed this unique and surprising NK cell-mediated killing strategy of infected DC to prevent the activation of the adaptive immunity.

Approximately 20% of all humans are latently and asymptomatically infected with HSV-2. This suggests that the virus developed mechanisms to avoid immune cell detection; many of which are still unknown. Infected cells are killed mainly by two lymphocyte populations; NK cells and CTLs that belong to the innate and the adaptive immunity, respectively. While the killing machinery of these two cell types is similar, almost identical, the ways by which they discriminate between infected and uninfected cells is different. CTLs are activated, primarily by DCs, to become effector cells. They then recognize virus-derived peptides in the groove of MHC class I molecules and eliminate the virally infected cells. In contrast, NK cells recognize infected cells through several NK cell activating receptors, while the recognition of MHC class I proteins by NK cells leads to inhibition of NK cell killing. Viruses, such as HIV, developed mechanisms to interfere with the function of both NK cells and CTLs via targeting of specific MHC class I proteins. Here we show that HSV-2 developed a MHC class I-dependent mechanism in which the virus, through specific targeting of HLA-C by the viral protein ICP47, harness the NK cells for its own benefit, probably to avoid the activation of adaptive immune response.