Regulation of FasL expression in natural killer cells

Suppression of NK Cell Activation by JAK3 Inhibition: Implication in the Treatment of Autoimmune Diseases

Natural killer (NK) cell is an essential cytotoxic lymphocyte in our innate immunity. Activation of NK cells is of paramount importance in defending against pathogens, suppressing autoantibody production and regulating other immune cells. Common gamma chain (γc) cytokines, including IL-2, IL-15, and IL-21, are defined as essential regulators for NK cell homeostasis and development. However, it is inconclusive whether γc cytokine-driven NK cell activation plays a protective or pathogenic role in the development of autoimmunity. In this study, we investigate and correlate the differential effects of γc cytokines in NK cell expansion and activation. IL-2 and IL-15 are mainly responsible for NK cell activation, while IL-21 preferentially stimulates NK cell proliferation. Blockade of Janus tyrosine kinase/signal transducer and activator of transcription (JAK/STAT) signaling pathway by either JAK inhibitors or antibodies targeting γc receptor subunits reverses the γc cytokine-induced NK cell activation, leading to suppression of its autoimmunity-like phenotype in vitro. These results underline the mechanisms of how γc cytokines trigger autoimmune phenotype in NK cells as a potential target to autoimmune diseases.

Cadmium impairs the development of natural killer cells and bidirectionally modifies their capacity for cytotoxicity

Cadmium (Cd) is a highly toxic heavy metal in the environment. The aim of this study was to investigate the impact of Cd on natural killer (NK) cells. C57BL/6 mice were treated with 10 ppm Cd via drinking water for 3 months, and the development of NK cells in the bone marrow (BM) and the cytotoxicity of mature NK (mNK) cells in the peripheral immune organs were evaluated thereafter; the impact of Cd on the cytotoxicity of mNK cells from human peripheral blood mononuclear cells (PBMC) was also investigated. Whereas Cd treatment impaired the differentiation of NK progenitors in the BM, Cd treatment activated the JAK3/STAT5 signaling to drive the proliferation of mNK cells and thereby lead to a compensation increase of mNK cells in the peripheral immune organs of mice. Additionally, Cd treatment bidirectionally regulated the cytotoxicity of mouse mNK cells to differential tumor cells, dependent on the levels of Fas expression in the tumor cells; mechanically, Cd treatment activated the JAK3/STAT5 signaling to promote the expression of FasL in mNK cells to increase their cytotoxicity, while Cd treatment reduced the expression of granzyme B in mNK cells to impair their cytotoxicity in the peripheral immune organs of mice. Likewise, in vitro assays indicated that Cd treatment also activated the JAK3/STAT5 signaling to increase the expression of FasL, whereas Cd treatment reduced the expression of granzyme B in human mNK cells. Thus Cd treatment impaired the development of NK cells in the BM and bidirectionally regulated the cytotoxicity of mNK cells in the peripheral immune organs, which may extend our current understanding for the immunotoxicity of Cd.

Immunostimulatory effects of a polysaccharide from Pimpinella anisum seeds on RAW264.7 and NK-92 cells

Polysaccharides from Pimpinella anisum were isolated using water at elevated temperature and DEAE Sepharose FF chromatography to examine their chemical structure and activation capacity on immune cells. P. anisum fractions (PAF1, PAF2 and PAF3) were mainly composed of neutral sugars (84.0-98.2%) and uronic acids (2.1-11.8%) with weight average molecular weight (M_w) ranging from 186.6 to 5474.5 × 10³ g/mol. Polysaccharides induced a significant inflammatory response in RAW264.7 murine macrophage cells releasing nitric oxide and expressing TNF-α, IL-1β, IL-6 and IL-10 cytokines. The induction of NK-92 natural killer cells resulted in TNF-α and IFN-γ production and activation of GrB/perforin-, NKG2D- and FasL-mediated cytotoxicity. Polysaccharides triggered the phosphorylation of NF-κB, ERK, JNK and p38 proteins in RAW264.7 and NK-92 cells indicating the involvement of NF-κB and MAPKs signaling pathways. The most active polysaccharide was a galactoarabinan with complex structure.

Enhancement of Neuroblastoma NK-Cell-Mediated Lysis through NF-kB p65 Subunit-Induced Expression of FAS and PVR, the Loss of Which Is Associated with Poor Patient Outcome

Simple Summary

Neuroblastoma (NB) cells adopt several molecular strategies to evade the Natural Killer (NK)-mediated response. Herein, we found that the overexpression of the NF-kB p65 subunit in NB cell lines upregulates the expression of both the death receptor FAS and the activating ligand PVR, thus rendering NB cells more susceptible to NK-cell-mediated apoptosis, recognition, and killing. These data could provide a clue for a novel NK-cell-based immunotherapy of NB. In addition, array CGH analysis performed in our cohort of NB patients showed that loss of both the FAS and PVR genes correlated with low survival, thus revealing a novel biomarker predicting the outcome of NB patients.

Abstract

High-risk neuroblastoma (NB) is a rare childhood cancer whose aggressiveness is due to a variety of chromosomal genetic aberrations, including those conferring immune evasion. Indeed, NB cells adopt several molecular strategies to evade recognition by the immune system, including the downregulation of ligands for NK-cell-activating receptors. To date, while molecular strategies aimed at enhancing the expression of ligands for NKG2D- and DNAM-1-activating receptors have been explored, no evidence has been reported on the immunomodulatory mechanisms acting on the expression of death receptors such as Fas in NB cells. Here, we demonstrated that transient overexpression of the NF-kB p65 subunit upregulates the surface expression of Fas and PVR, the ligand of DNAM-1, thus making NB cell lines significantly more susceptible to NK-cell-mediated apoptosis, recognition, and killing. In contrast, IFNγ and TNFα treatment, although it induced the upregulation of FAS in NB cells and consequently enhanced NK-cell-mediated apoptosis, triggered immune evasion processes, including the strong upregulation of MHC class I and IDO1, both of which are involved in mechanisms leading to the impairment of a proper NK-cell-mediated killing of NB. In addition, high-resolution array CGH analysis performed in our cohort of NB patients revealed that the loss of FAS and/or PVR genes correlated with low survival independently of the disease stage. Our data identify the status of the FAS and PVR genes as prognostic biomarkers of NB that may predict the efficacy of NK-cell-based immunotherapy of NB. Overall, restoration of surface expression of Fas and PVR, through transient upregulation of NF-kB, may be a clue to a novel NK-cell-based immunotherapy of NB.

Novel Insights into the Immunotherapy of Soft Tissue Sarcomas: Do We Need a Change of Perspective?

Soft tissue sarcomas (STSs) are rare mesenchymal tumors. With more than 80 histological subtypes of STSs, data regarding novel biomarkers of strong prognostic and therapeutic value are very limited. To date, the most important prognostic factor is the tumor grade, and approximately 50% of patients that are diagnosed with high-grade STSs die of metastatic disease within five years. Systemic chemotherapy represents the mainstay of metastatic STSs treatment for decades but induces response in only 15–35% of the patients, irrespective of the histological subtype. In the era of immunotherapy, deciphering the immune cell signatures within the STSs tumors may discriminate immunotherapy responders from non-responders and different immunotherapeutic approaches could be combined based on the predominant cell subpopulations infiltrating the STS tumors. Furthermore, understanding the immune diversity of the STS tumor microenvironment (TME) in different histological subtypes may provide a rationale for stratifying patients according to the TME immune parameters. In this review, we introduce the most important immune cell types infiltrating the STSs tumors and discuss different immunotherapies, as well as promising clinical trials, that would target these immune cells to enhance the antitumor immune responses and improve the prognosis of metastatic STSs patients.

Branched I antigen regulated cell susceptibility against natural killer cytotoxicity through its N-linked glycosylation and overall expression

Cell surface glycosylation has been known as an important modification process that can be targeted and manipulated by malignant cells to escape from host immunosurveillance. We previously showed that the blood group branched I antigen on the leukemia cell surface can regulate the cell susceptibility against natural killer (NK) cell-mediated cytotoxicity through interfering target-NK interaction. In this work, we first identified N-linkage as the major glycosylation linkage type for branched I glycan formation on leukemia cells, and this linkage was responsible for cell sensitivity against therapeutic NK-92MI targeting. Secondly, by examining different leukemia cell surface death receptors, we showed death receptor Fas had highest expressions in both Raji and TF-1a cells. Mutations on two Fas extracellular N-linkage sites (118 and 136) for glycosylation impaired activation of Fas-mediated apoptosis during NK-92MI cytotoxicity. Last, we found that the surface I antigen expression levels enable leukemia cells to respond differently against NK-92MI targeting. In low I antigen expressing K-562 cell, reduction of I antigen presence greatly reduced leukemia cell susceptibility against NK-92MI targeting. But in other high I antigen expressing leukemia cells, similar reduction in I antigen expression did not affect cell susceptibility.

Mechanical suppression of breast cancer cell invasion and paracrine signaling to osteoclasts requires nucleo-cytoskeletal connectivity

Exercise benefits the musculoskeletal system and reduces the effects of cancer. The effects of exercise are multifactorial, where metabolic changes and tissue adaptation influence outcomes. Mechanical signals, a principal component of exercise, are anabolic to the musculoskeletal system and restrict cancer progression. We examined the mechanisms through which cancer cells sense and respond to low-magnitude mechanical signals introduced in the form of vibration. Low-magnitude, high-frequency vibration was applied to human breast cancer cells in the form of low-intensity vibration (LIV). LIV decreased matrix invasion and impaired secretion of osteolytic factors PTHLH, IL-11, and RANKL. Furthermore, paracrine signals from mechanically stimulated cancer cells, reduced osteoclast differentiation and resorptive capacity. Disconnecting the nucleus by knockdown of SUN1 and SUN2 impaired LIV-mediated suppression of invasion and osteolytic factor secretion. LIV increased cell stiffness; an effect dependent on the LINC complex. These data show that mechanical vibration reduces the metastatic potential of human breast cancer cells, where the nucleus serves as a mechanosensory apparatus to alter cell structure and intercellular signaling.

An in vitro model of chronic wounding and its implication for age-related macular degeneration

Degeneration of the retinal pigment epithelium (RPE) plays a central role in age-related macular degeneration (AMD). Throughout life, RPE cells are challenged by a variety of cytotoxic stressors, some of which are cumulative with age and may ultimately contribute to drusen and lipofuscin accumulation. Stressors such as these continually damage RPE cells resulting in a state of chronic wounding. Current cell-based platforms that model a state of chronic RPE cell wounding are limited, and the RPE cellular response is not entirely understood. Here, we used the electric cell-substrate impedance sensing (ECIS) system to induce a state of acute or chronic wounding on differentiated human fetal RPE cells to analyze changes in the wound repair response. RPE cells surrounding the lesioned area employ both cell migration and proliferation to repair wounds but fail to reestablish their original cell morphology or density after repetitive wounding. Chronically wounded RPE cells develop phenotypic AMD characteristics such as loss of cuboidal morphology, enlarged size, and multinucleation. Transcriptomic analysis suggests a systemic misregulation of RPE cell functions in bystander cells, which are not directly adjacent to the wound. Genes associated with the major RPE cell functions (LRAT, MITF, RDH11) significantly downregulate after wounding, in addition to differential expression of genes associated with the cell cycle (CDK1, CDC6, CDC20), inflammation (IL-18, CCL2), and apoptosis (FAS). Interestingly, repetitive wounding resulted in prolonged misregulation of genes, including FAS, LRAT, and PEDF. The use of ECIS to induce wounding resulted in an over-representation of AMD-associated genes among those dysregulated genes, particularly genes associated with advanced AMD. This simple system provides a new model for further investigation of RPE cell wound response in AMD pathogenesis.

Novel Application of Radotinib for the Treatment of Solid Tumors via Natural Killer Cell Activation

Radotinib (Supect™) was developed to treat chronic myeloid leukemia (CML) as a BCR-ABL1 tyrosine kinase inhibitor (TKI). Other TKIs, including imatinib and nilotinib, were also developed for treatment of CML, and recent studies were increasing about the therapeutic effects of other TKIs on solid tumors. However, the effect of radotinib on solid tumors has not yet been investigated. In this study, radotinib killed CML cell line K562 directly; however, radotinib did not enhance NK cell cytotoxicity against K562 cells. Because K562 is known as a Fas-negative cell line, we investigated whether radotinib could regulate cell cytotoxicity against various Fas-expressing solid cancer cell lines. Radotinib dramatically increased NK cell cytotoxicity against various Fas-expressing solid cancer cells, including lung, breast, and melanoma cells. Additionally, the efficiency of radotinib-enhanced cytotoxicity was lower in Fas siRNA-transfected cells than in negative controls, suggesting that Fas signaling might be involved in the radotinib-enhanced NK cell cytotoxicity. This study provides the first evidence that radotinib could be used as an effective and strong therapeutic to treat solid tumors via upregulation of NK cell cytotoxicity, suggesting that radotinib has indirect killing mechanisms via upregulation of antitumor innate immune responses as well as direct killing activities for CML cells.

Treatment of advanced hepatocellular carcinoma: immunotherapy from checkpoint blockade to potential of cellular treatment

The absence of potent therapeutic option accounts for the dismal prognosis of advanced hepatocellular carcinoma (HCC) with high mortality and recurrence rate. For a decade, sorafenib is the only approved systemic drug in the first-line setting and warrants as the standard-of-care for HCC in the advanced stage. Given the common failures of chemotherapies and targeted therapies in the field of HCC treatment, promising breakthroughs were eagerly needed and until recently, immunotherapies have opened a new era of anticancer treatment. The liver organ is perceived as "immunotolerant" owing to its functional role, and the hepatic immune balance is found to be deregulated during chronic liver inflammation and HCC tumorigenesis. Restoring a competent immunity by mitigation of immunosuppression signals is a contemporary approach. In this regard, novel immune checkpoint inhibitors have revolutionized cancer pharmacological treatment options with remarkable clinical outcomes in hematologic malignancy and multiple solid tumors including advanced HCC. Nivolumab, an immunotherapeutic agent to block programmed cell death protein 1 (PD-1), showed high efficacy potential for patients progressed with sorafenib and granted accelerated approval by the US Food and Drug Administration (FDA) recently. The development of this class of immunotherapeutic drug is currently based on myriad studies established on the role of T-cell mediated immunosuppression through immune checkpoints. Heterogeneous results have led to further explorations to the profile of oncogenic processes and signaling pathways associated with PD1/PD-L1 axis. Emerging evidence from preclinical studies implicate natural killer (NK) cells as a mediator to the PD-1 checkpoint signaling immunoevasion. The strategy of adopting immunomodulating ability of NK cells by immune checkpoints inhibitors is potential to additive effects in stimulating anticancer immunity. This idea is not entirely newfound but has recently gained prominence because of advances in defining phenotypic heterogeneity of NK cell populations. The physiological significance and synergistic value of NK cells await further investigation in clinical trials. In this review, an overview of the treatment paradigm shift of HCC management is presented. Current knowledge concerning immunological mechanisms of immune checkpoints attributed to T cell is further discussed and relevant ongoing clinical trials are summarized. We proposed that NK cells should be viewed as part of the network of checkpoint immunoevasion and delineate current evidence of translational clinical research in this area. It is conceivable that immune checkpoint inhibitors in combination with NK cell-based therapeutic strategies will be great promise for treatment of advanced HCC.

Hepatocellular carcinoma: Prospects for natural killer cell immunotherapy

Liver disease is a growing cause of death in the United Kingdom and the incidence of hepatocellular carcinoma (HCC) is rising (http://www.cancerresearchuk.org/). The combination of an immunosuppressive environment within the liver and suboptimal host anti-tumour immune responses may account for the poor survival outcome of HCC. Understanding how tumours evade immune recognition coupled with new insights into the unique immunological environment within the liver will be critical to developing liver-specific immunotherapies.

Natural Killer Cell-Based Immunotherapy in Gynecologic Malignancy: A Review

Harnessing the immune system has proven an effective therapy in treating malignancies. Since the discovery of natural killer (NK) cells, strategies aimed to manipulate and augment their effector function against cancer have been the subject of intense research. Recent progress in the immunobiology of NK cells has led to the development of promising therapeutic approaches. In this review, we will focus on the recent advances in NK cell immunobiology and the clinical application of NK cell immunotherapy in ovarian, cervical, and uterine cancer.

Recombinant Antibodies to Arm Cytotoxic Lymphocytes in Cancer Immunotherapy

Immunotherapy has the potential to support and expand the body's own armamentarium of immune effector functions, which have been circumvented during malignant transformation and establishment of cancer and is presently considered to be the most promising treatment option for cancer patients. Recombinant antibody technologies have led to a multitude of novel antibody formats, which are in clinical development and hold great promise for future therapies. Among these formats, bispecific antibodies are extremely versatile due to their high efficacy to recruit and activate anti-tumoral immune effector cells, their excellent safety profile, and the opportunity for use in combination with cellular therapies. This review article summarizes the latest developments in cancer immunotherapy using immuno-engagers for recruiting T cells and NK cells to the tumor site. In addition to antibody formats, malignant cell targets, and immune cell targets, opportunities for combination therapies, including check point inhibitors, cytokines and adoptive transfer of immune cells, will be summarized and discussed.

Black Raspberries Enhance Natural Killer Cell Infiltration into the Colon and Suppress the Progression of Colorectal Cancer

Natural killer (NK) cells are an essential component of innate immunity against cancer development. Many studies have been conducted to evaluate immune-modulating effects using dietary compounds. Our laboratory has been investigating the chemopreventive potential of black raspberries (BRBs) and previously demonstrated their beneficial modulation of genetic and epigenetic biomarkers in patients with colorectal cancer (CRC). The current study investigated their potential on modulating NK cells. To avoid the excessive inflammation caused by the dextran sulfate sodium (DSS) treatment that leads to colitis, we treated the mice with overnight DSS so that it would slightly irritate the colon but still promote colon carcinogenesis with 100% incidence in both the Apc^Min/+ mice and azoxymethane (AOM)-treated mice. A significant decrease of tissue-infiltrating NK cells along the progression of microadenoma-to-adenoma and adenoma-to-adenocarcinoma was observed in the Apc^Min/+ /DSS and AOM/DSS mice, respectively. Depletion of NK cells significantly promoted the development of CRC, suggesting a critical role of NK cells in combating CRC progression. BRBs significantly suppressed the CRC progression and increased the number of tissue-infiltrating NK cells in both mouse models. Moreover, we further determined BRBs' effects on NK cells in the human biopsy specimens collected from our previously completed clinical trial, in which CRC patients consumed BRBs for an average of 4 weeks during a presurgical window. We observed an increased number and an enhanced cytotoxicity of NK cells by BRB intervention. The current study provides evidence that BRBs have the potential to enhance the tumor immunesurveillance of NK cells that can be beneficial in the setting of CRC prevention and treatment.

Cytotoxic lymphocytes and atherosclerosis: significance, mechanisms and therapeutic challenges

Cytotoxic lymphocytes encompass natural killer lymphocytes (cells) and cytotoxic T cells that include CD8+ T cells, natural killer (NK) T cells, γ, δ (γδ)-T cells and human CD4 + CD28- T cells. These cells play critical roles in inflammatory diseases and in controlling cancers and infections. Cytotoxic lymphocytes can be activated via a number of mechanisms that may involve dendritic cells, macrophages, cytokines or surface proteins on stressed cells. Upon activation, they secrete pro-inflammatory cytokines as well as anti-inflammatory cytokines, chemokines and cytotoxins to promote inflammation and the development of atherosclerotic lesions including vulnerable lesions, which are strongly implicated in myocardial infarctions and strokes. Here, we review the mechanisms that activate and regulate cytotoxic lymphocyte activity, including activating and inhibitory receptors, cytokines, chemokine receptors-chemokine systems utilized to home to inflamed lesions and cytotoxins and cytokines through which they affect other cells within lesions. We also examine their roles in human and mouse models of atherosclerosis and the mechanisms by which they exert their pathogenic effects. Finally, we discuss strategies for therapeutically targeting these cells to prevent the development of atherosclerotic lesions and vulnerable plaques and the challenge of developing highly targeted therapies that only minimally affect the body's immune system, avoiding the complications, such as increased susceptibility to infections, which are currently associated with many immunotherapies for autoimmune diseases.

LINKED ARTICLES

This article is part of a themed section on Targeting Inflammation to Reduce Cardiovascular Disease Risk. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v174.22/issuetoc and http://onlinelibrary.wiley.com/doi/10.1111/bcp.v82.4/issuetoc.

NK Cell-Mediated Antibody-Dependent Cellular Cytotoxicity in Cancer Immunotherapy

Natural killer (NK) cells play a major role in cancer immunotherapies that involve tumor-antigen targeting by monoclonal antibodies (mAbs). NK cells express a variety of activating and inhibitory receptors that serve to regulate the function and activity of the cells. In the context of targeting cells, NK cells can be "specifically activated" through certain Fc receptors that are expressed on their cell surface. NK cells can express FcγRIIIA and/or FcγRIIC, which can bind to the Fc portion of immunoglobulins, transmitting activating signals within NK cells. Once activated through Fc receptors by antibodies bound to target cells, NK cells are able to lyse target cells without priming, and secrete cytokines like interferon gamma to recruit adaptive immune cells. This antibody-dependent cell-mediated cytotoxicity (ADCC) of tumor cells is utilized in the treatment of various cancers overexpressing unique antigens, such as neuroblastoma, breast cancer, B cell lymphoma, and others. NK cells also express a family of receptors called killer immunoglobulin-like receptors (KIRs), which regulate the function and response of NK cells toward target cells through their interaction with their cognate ligands that are expressed on tumor cells. Genetic polymorphisms in KIR and KIR-ligands, as well as FcγRs may influence NK cell responsiveness in conjunction with mAb immunotherapies. This review focuses on current therapeutic mAbs, different strategies to augment the anti-tumor efficacy of ADCC, and genotypic factors that may influence patient responses to antibody-dependent immunotherapies.

The impact of ageing on natural killer cell function and potential consequences for health in older adults

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Roles are emerging for natural killer (NK) cells beyond removing transformed cells.

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These include immune regulation and the elimination of senescent cells.

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Human ageing is associated with a decline in NK cell function.

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We propose some aspects of human ageing are due in part to reduced NK cell function.

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These include reduced vaccination efficacy and delayed resolution of inflammation.

Forming the first line of defence against virally infected and malignant cells, natural killer (NK) cells are critical effector cells of the innate immune system. With age, significant impairments have been reported in the two main mechanisms by which NK cells confer host protection: direct cytotoxicity and the secretion of immunoregulatory cytokines and chemokines. In elderly subjects, decreased NK cell activity has been shown to be associated with an increased incidence and severity of viral infection, highlighting the clinical implications that age-associated changes in NK cell biology have on the health of older adults. However, is an increased susceptibility to viral infection the only consequence of these age-related changes in NK cell function? Recently, evidence has emerged that has shown that in addition to eliminating transformed cells, NK cells are involved in many other biological processes such as immune regulation, anti-microbial immune responses and the recognition and elimination of senescent cells, novel functions that involve NK-mediated cytotoxicity and/or cytokine production. Thus, the decrease in NK cell function that accompanies physiological ageing is likely to have wider implications for the health of older adults than originally thought. Here, we give a detailed description of the changes in NK cell biology that accompany human ageing and propose that certain features of the ageing process such as: (i) the increased reactivation rates of latent Mycobacterium tuberculosis, (ii) the slower resolution of inflammatory responses and (iii) the increased incidence of bacterial and fungal infection are attributable in part to an age-associated decline in NK cell function.

Effect of the disintegrin eristostatin on melanoma-natural killer cell interactions

Malignant melanoma is difficult to treat due to its resistance to chemotherapeutic regimens. Discovery of new pharmaceuticals with inhibitory potential can be helpful in the development of novel treatments. The snake venom disintegrin eristostatin, from the viper Eristicophis macmahoni, caused immunodeficient mice to be significantly protected from development of lung colonization when melanoma cells and the disintegrin were co-injected in vivo into the lateral tail vein compared to vehicle controls. Cytotoxicity assays suggested that eristostatin makes the melanoma cells a better target for lysis by human natural killer cells. Direct binding assays using atomic force microscopy showed eristostatin does specifically bind the surface of the six melanoma cell lines tested. Eristostatin binding was partially inhibited by the addition of soluble RGDS peptide, suggesting an integrin as one likely, but not the sole, binding partner. Studies done with melanoma cells on a culture dish and natural killer cells attached to a cantilever tip in atomic force microscopy showed four major populations of interactions which exhibited altered frequency and unbinding strength in the presence of eristostatin.

Human NK cells differ more in their KIR2DL1-dependent thresholds for HLA-Cw6-mediated inhibition than in their maximal killing capacity

In this study we have addressed the question of how activation and inhibition of human NK cells is regulated by the expression level of MHC class I protein on target cells. Using target cell transfectants sorted to stably express different levels of the MHC class I protein HLA-Cw6, we show that induction of degranulation and that of IFN-γ secretion are not correlated. In contrast, the inhibition of these two processes by MHC class-I occurs at the same level of class I MHC protein. Primary human NK cell clones were found to differ in the amount of target MHC class I protein required for their inhibition, rather than in their maximum killing capacity. Importantly, we show that KIR2DL1 expression determines the thresholds (in terms of MHC I protein levels) required for NK cell inhibition, while the expression of other receptors such as LIR1 is less important. Furthermore, using mathematical models to explore the dynamics of target cell killing, we found that the observed delay in target cell killing is exhibited by a model in which NK cells require some activation or priming, such that each cell can lyse a target cell only after being activated by a first encounter with the same or a different target cell, but not by models which lack this feature.

Phenotype of NK cells and cytotoxic/apoptotic mediators expression in ectopic pregnancy

PROBLEM

The expression of cytotoxic/apoptotic mediators and the phenotype characteristics of uterine NK cells (uNK) in tubal ectopic pregnancy (EP) were investigated.

METHOD OF STUDY

Samples of uterine decidua and tubal mucosa as well as peripheral blood (PB) of the same women with EP were used for phenotype characterization of NK cells and detection of cytotoxic/apoptotic mediators and IL-15.

RESULTS

In tubal mucosa, perforin, FasL, granulysin and IL-15 were almost completely absent, but they were present in normal and EP uterine deciduas. TRAIL was present on trophoblast and tubal mucosa, contrary to its lack in normal and EP uterine decidua. CD16⁻ CD56(dim) NK cells, mostly CD94⁻ and NKG2A⁻, predominate in tubal mucosa, whereas CD16⁻ CD56(bright) NK cells, predominantly CD94(+) and NKG2A(+) prevail in EP uterine decidua. NK cells at the EP implantation site express lower percentages of perforin and granulysin, but they express a higher percentage of TRAIL than do EP uterine decidual and PB NK cells. Lower percentage of TNF-α-expressing and IL-4-expressing NK cells were found at the implantation site compared to EP uterine decidua.

CONCLUSIONS

Authentic uNK cell population seems to be insufficient to restrict trophoblast invasion because of low expression of cytotoxic/apoptotic mediators.

Tethered epidermal growth factor provides a survival advantage to mesenchymal stem cells

MSC can act as a pluripotent source of reparative cells during injury and therefore have great potential in regenerative medicine and tissue engineering. However, the response of MSC to many growth factors and cytokines is unknown. Many envisioned applications of MSC, such as treating large defects in bone, involve in vivo implantation of MSC attached to a scaffold, a process that creates an acute inflammatory environment that may be hostile to MSC survival. Here, we investigated cellular responses of MSC on a biomaterial surface covalently modified with epidermal growth factor (EGF). We found that surface-tethered EGF promotes both cell spreading and survival more strongly than saturating concentrations of soluble EGF. By sustaining mitogen-activated protein kinase kinase-extracellular-regulated kinase signaling, tethered EGF increases the contact of MSC with an otherwise moderately adhesive synthetic polymer and confers resistance to cell death induced by the proinflammatory cytokine, Fas ligand. We concluded that tethered EGF may offer a protective advantage to MSC in vivo during acute inflammatory reactions to tissue engineering scaffolds. The tethered EGF-modified polymers described here could be used together with structural materials to construct MSC scaffolds for the treatment of hard-tissue lesions, such as large bony defects. Disclosure of potential conflicts of interest is found at the end of this article.

Early pregnancy decidual lymphocytes beside perforin use Fas ligand (FasL) mediated cytotoxicity

Decidual natural killer (NK) cells are the predominant lymphocytes at the maternal-fetal interface. They are involved in defense against virally infected, parasitized and transformed cells and may contribute to the control of trophoblast invasion. The presence of perforin and other possible cytolytic mediators suggests these functions. Cytolytic mechanisms of unstimulated and Th1 cytokine stimulated decidual lymphocytes (DL), as well as purified decidual CD56(+) cells, were analyzed against NK sensitive and resistant targets. DL were isolated from decidual mononuclear cells (DMC) cultured in the medium only or in the presence of Th1 cytokines: IL-2, IL-12, IL-15, IL-18 and their combinations (IL-12/IL-18 or IL-15/IL-18). Fas ligand (FasL), perforin and granzyme B mRNAs expression and cytotoxicity were analyzed by flow cytometry and/or RT-PCR. DL (containing 72.19+/-7.53% of CD56(+) cells), obtained from 18h-cultured DMC in the medium only, expressed perforin, FasL and granzyme B mRNAs and lysed the NK-sensitive K-562 cell line, and also the NK-resistant P815 and P815-Fas transfected cell lines. Concanamycin A, a blocker of granule exocytosis, decreased significantly K-562 lysis, but not P815 lysis. However, the addition of anti-FasL antibody diminished significantly P815 lysis as well. IL-2 and IL-15, known inducers of perforin and FasL mRNAs and protein expression, could not additionally increase P 815 cell lysis by DL cultured within DMC. These results suggest that DL cultured in DMC for 18h, have the characteristics of lymphokine-activated killer (LAK) cells and are able to use efficiently both the perforin and the FasL cytolytic pathways.