Cytolytic Natural Killer Cells Research Articles

Zoledronic acid negatively affects the expansion of in vitro activated human NK cells and their cytolytic interactions with Ewing sarcoma cells

Disseminated Ewing sarcoma remains a fatal disease despite advanced multimodal treatment regimens. Immunotherapies as well as novel drugs and biologicals are currently being explored to eliminate minimal residual disease after conventional therapy thereby rescuing patients at a high risk for relapse. Insights into the interactions between novel therapies provide the basis for the development of effective combination strategies. We investigated the effects of the aminobisphosphonate zoledronic acid (ZA) on the invitro expansion of human natural killer (NK) cells and their cytolytic activity against Ewing sarcoma cells. ZA significantly impaired the invitro expansion of activated NK cells from both healthy donors and Ewing sarcoma patients in a dose-dependent manner. Expression of differentiation markers and activating receptors was unaffected by the drug. Activated NK cells from both healthy donors and patients had potent degranulation responses to Ewing sarcoma cells. In the presence of ZA at concentrations reflecting pharmaceutical serum levels, the invitro antitumor activity of NK cells from Ewing sarcoma patients was significantly impaired. We conclude that ZA can impede invitro NK cell expansion and cytolytic NK cell responses to Ewing sarcoma. These observations raise caution against the combination of adoptive NK cell transfer with ZA maintenance therapy in Ewing sarcoma. Future studies aim to identify potentiating interactions of novel drugs with cellular therapies.

Immune Cell Dysfunction in Chronic Lymphocytic Leukemia/Small Lymphocytic Lymphoma (CLL/SLL)

AbstractAbstract 3875 Introduction:Immunologic environment influences progression of lymphoid malignancies. Specifically, shifts in subsets of natural killer (NK) and T cells as well as tumor expression of inhibitory ligands may contribute to ability to evade host detection. Immune dysfunction may be particularly important in CLL/SLL, as prevalent circulating tumor cells engage in persistent, widespread interactions with immune cells; commonly-used mAb therapies (e.g. rituximab, alemtuzumab) rely upon ADCC mediated by NK cells and other innate effectors; and disease course is highly variable and not fully accounted for by tumor-intrinsic prognostic factors. Therefore, to better characterize the immune system in CLL/SLL, we prospectively assessed NK and T cell frequency, phenotype, and function in a series of CLL/SLL patients. Methods:Serial blood samples (up to 3 samples each, 3–6 months apart) were collected from 31 untreated CLL/SLL patients (median age 66) and 15 healthy age-matched controls (HC), and peripheral blood lymphocytes (PBL) analyzed directly ex vivo by multiparameter flow cytometry (160 distinct parameters evaluated, primarily on T and NK cells). NK cell-mediated natural and antibody-dependent cytotoxicity were also assessed by CD107a degranulation assay following PBL co-culture with rituximab, 721.221 EBV-transformed lymphoma cells, or both. Differences in parameters between patients and controls, or between progressors and non-progressors [categorized based on updated NCI-WG criteria (Blood 2008;111:5446)] were analyzed by Wilcoxon rank-sum test. All subjects signed IRB approved informed consent forms. Results:CLL/SLL VS. HC: CLL/SLL samples displayed a marked decrease in the ability of the cytolytic CD56dim NK cells to degranulate in response to tumor, both with or without rituximab (Table 1). CD56dim NK cells from CLL/SLL patients also displayed a more immature phenotype (↓CD57, ↓NKG2D, ↑CD27, ↓KIR) than those from HC, suggesting either a block in differentiation or elimination of the most-differentiated cells. NK cell expression of NKp44, CD69, CD62L, CD137, granzyme B, perforin, or PD-1, as well as tumor-induced NK cell production of IFNγ, did not differ. CLL/SLL patients had increased total T cells with a decreased CD4:CD8 ratio, associated with increased total number of CD8 T cells, greater activation of naive CD4 T cells and transition to a memory phenotype. Treg (CD4+CD25+FoxP3+) frequency was significantly higher in CLL/SLL patients (4.5% vs. 1.8% of CD4 T cells, p=0.005), as was PD-1 expression on both CD4 and CD8 T cells, while CD137 and ICOS expression was similar in both groups. PROGRESSORS VS. NON-PROGRESSORS: With median follow-up of 16.5 months (range 1–37), 7 of 31 patients have met criteria for progression. Compared to non-progressors, progressors showed changes in the CD56bright NK cell compartment suggestive of increased activation and accelerated differentiation, with increased expression of CD69, granzyme B, perforin, CD16, and KIR. However, no significant functional differences in NK cells, or consistent differences in T cell subsets, have been observed to date. Conclusions:CLL/SLL patients have a shift toward less mature NK cells, associated with deficits in NK cell degranulation against tumor targets, compared with healthy donors. Those CLL/SLL patients who progressed had greater CD56 bright NK cell phenotypic aberrancies than non-progressors, though these findings require confirmation with a larger cohort. Taken together, our findings support the hypothesis that immune dysfunction in CLL/SLL may be due in part to a block in NK cell differentiation or loss of more mature cells, and current studies are exploring these possibilities and potential mechanisms. Given these findings, along with the immunosuppressive changes observed in the T cell compartment (↑Tregs, ↑PD-1), these data support therapeutic strategies in CLL/SLL aimed at augmenting NK and/or T cell function.Table 1Parameters Differentially Expressed in cytolytic CD56 dimNK cellsParametersCLL/SLL (median)HC (median)P-Value%CD107a+ (PBL + tumor)14.9%37.4%0.001%CD107a+ (PBL + rituximab + tumor)37.5%62%0.0008CD57 MFI493720,6400.03CD27 MFI3681900.04NKG2D MFI418753780.006%KIR2DS4+0.310.20.008%KIR2DS1+8.016.80.02%KIR3DL1+7.919.90.008 Disclosures:No relevant conflicts of interest to declare.

Proteasome inhibitor lactacystin augments natural killer cell cytotoxicity of myeloma via downregulation of HLA class I

Modulation of inhibitory and activating natural killer (NK) receptor ligands on tumor cells represents a promising therapeutic approach against cancer, including multiple myeloma (MM). Human leukocyte antigen (HLA) class I molecules, the NK cell inhibitory killer cell immunoglobulin-like receptor (KIR) ligands, are critical determinants of NK cell activity. Proteasome inhibitors have demonstrated significant anti-myeloma activity in MM patients. In this study, we evaluated the effect of proteasome inhibitors on the surface expression of class I in human MM cells. We found that proteasome inhibitors downregulated surface expression of class I in a dose- and time-dependent manner in MM cell line and patient MM cells. No significant changes in the expression of the MHC class I chain-related molecules (MIC) A/B and the UL16-binding proteins (ULBPs) 1–3 were observed. Downregulation of class I by lactacystin (LAC) significantly enhances NK cell-mediated lysis of MM. Furthermore, the downregulation degree of class I was associated with increased susceptibility of myeloma cells to NK cell killing. HLA blocking antibody produced results that were similar to the findings from proteasome inhibitor. Taken together, our data suggest that proteasome inhibitors, possible targeting inhibitory KIR ligand class I on tumor cells, may contribute to the activation of cytolytic effector NK cells in vitro, enhancing their anti-myeloma activity. Our findings provide a rationale for clinical evaluation of proteasome inhibitor, alone or in combination, as a novel approach to immunotherapy of MM.

Remodelling of Cortical Actin Where Lytic Granules Dock at Natural Killer Cell Immune Synapses Revealed by Super-Resolution Microscopy

Author SummaryNatural Killer (NK) cells are immune cells that can recognise and kill virus-infected and cancerous cells. This killing requires an intercellular contact —termed an immune synapse—between the NK cell and its target cell through which molecules can be delivered to trigger lysis. Reorganisation of the NK cell cytoskeleton is essential for the delivery and release at the synapse of granules containing the cytolytic molecules. Understanding precisely how the cytoskeleton is involved in these cytolytic events has been hampered by our inability to resolve cytoskeletal structure at immune synapses by conventional light microscopy. Very recent advances in imaging technology have now provided the resolving power to see previously undetectable cellular structures. Here, we have used 3D super-resolution imaging to observe the structure of the actin cytoskeleton at the NK immune synapse. We found that a dense mesh of actin underlies the immune synapse and that it is remodelled upon NK cell activation. Domains within the actin meshwork open up specifying where the lytic granules dock and also where the microtubule-organising centre moves towards. Thus, actin remodelling occurs at the immune synapse during secretion and this may be important for the regulation of lytic granule secretion.

Live Cell Linear Dichroism Imaging Reveals Extensive Membrane Ruffling within the Docking Structure of Natural Killer Cell Immune Synapses

We have applied fluorescence imaging of two-photon linear dichroism to measure the subresolution organization of the cell membrane during formation of the activating (cytolytic) natural killer (NK) cell immune synapse (IS). This approach revealed that the NK cell plasma membrane is convoluted into ruffles at the periphery, but not in the center of a mature cytolytic NK cell IS. Time-lapse imaging showed that the membrane ruffles formed at the initial point of contact between NK cells and target cells and then spread radialy across the intercellular contact as the size of the IS increased, becoming absent from the center of the mature synapse. Understanding the role of such extensive membrane ruffling in the assembly of cytolytic synapses is an intriguing new goal.

Elevated CD56dimCD16neg NK Cells on Day 28 after HCT: Role in Immunity Against Viral Infections or Residual Tumor Cells?.

Natural killer (NK) cells represent a lymphocyte subset important in the immune surveillance against virus infected and malignant cells. In humans, two major NK cell subsets have been defined by CD56 and CD16 staining:1.Regulatory NK cells (CD56 high CD16 neg), which are potent cytokine (IFNg) producers; and2.Cytolytic NK cells (CD56 dim CD16 pos) that are involved in target cell lysis.Functions of other NK cell subset are unknown. One of such subset, CD56 dimCD16 neg NK cells have recently been reported to represent cytolytic cells, degranulated after contact with target cells. NK cells are the first lymphocyte subset recovering to normal quantity and function after an allogeneic or autologous HCT, typically by 4 weeks post HCT. In the present investigation, we attempted to determine percentages of following NK cell subsets (Regulatory NK cells, Cytolytic NK cells, CD56dimCD16 neg, CD56 highCD16 pos and CD56neg CD16 high NK cells) at multiple time points (day 28, 56, 84, 180 and 365) after allogeneic (n= 32) and autologous (n= 25) HCT and compared with that of healthy individuals (n=14). Whole blood specimen was incubated with fluorochrome-conjugated monoclonal antibodies (CD3-ECD, CD14-PE, CD56-FITC and CD16-PC5) and analyzed by four color flowcytometry. NK cells were defined as mononuclear cells expressing CD16 or CD56 and not expressing CD3 or CD14. The most striking finding was that of significant increase in percentage of CD56dimCD16−ve cells (among NK cells) on day 28. This was true for both autologous HCT recipient (n=24; median = 1.02% of total NK cells) and allogeneic HCT recipient (n=26; median = 1.1% of total NK cells) in comparison to the healthy individuals (n=14; median = 0.56% of total NK cells). We speculate the rise in CD56dimCD16−ve NK cells at 1 month post HCT may be due to increased degranulation of cytolytic NK cells in response to viral infections or residual malignancy.

Emerging Roles of Antiangiogenic and Angiogenic Proteins in Pathogenesis and Prediction of Preeclampsia

Hypertensive disorders are a major cause of maternal and fetal death, especially in developing nations, with the pregnancy-specific disease preeclampsia-eclampsia responsible for most of this mortality. Preeclampsia, recognized by ancient Greeks, was only sporadically investigated until late last century, current literature still labeling this disorder a “disease of theories.” Thus, not surprisingly, we have started the new millennium unable to predict or prevent preeclampsia, and management strategies remain but supportive, with pregnancy termination still the only definitive “therapy.” This may be about to change, as focused research, mainly in the past decade, has resulted in dramatic progress regarding pathogenesis of disease manifestations and risk assessment, while investigators have begun designing and testing definitive therapy.1 There are still a myriad of uncertainties and unanswered questions to address, but here we summarize the extent of 1 new and exciting chapter in preeclampsia research: the roles of angiogenic and antiangiogenic factors, to which an article in this issue by Rana and colleagues,2 contributes. A landmark report published in 2003 set the stage for all that followed.3 Dr Karumanchi’s laboratory, previously involved in renal cancer research, changed its focus to the kidney in preeclampsia. Using microarray chip technology, they probed gene expression profiles in placentas of women with preeclampsia and those with uncomplicated pregnancies. Of course many differences were noted, but one that caught the investigators’ attention was upregulation of the mRNA for the antiangiogenic protein soluble fms-like tyrosine kinase 1 (abbreviated as sFlt-1 or sVEGFR-1) in placentas from women with preeclampsia. Aware that de novo hypertension and proteinuria were 2 disturbing side effects of certain antiangiogenic compounds tested in cancer patients, these …

Mild Hyperthermia Modulates the Relative Frequency of Lymphocyte Cell Subpopulations: an Increase in a Cytolytic NK Cell Subset and a Decrease in a Regulatory T Cell Subset

Although mild hyperthermia (MHT) cannot directly kill tumor cells, an augmented immunological effect resulting from MHT has been reported to induce injury of malignant tumors. In this study, the impact of regional MHT on lymphocyte subpopulations was investigated. Of particular interest was the effect of MHT on natural killer (NK) cells and T cells, which are important in the innate and adaptive immune systems. Regional MHT treatment was performed using an 8-MHz capacitive heating device, the Thermotron RF8 (Yamamoto Vinita Co., Ltd., Osaka, Japan). An average continuous radio-frequency irradiation of approximately 900 W was applied between two 30-cm electrodes placed on opposite sides of a volunteer's upper abdominal region for 30 min. In healthy volunteers exposed to this thermal treatment, NK cell activity and the percentage of NK cells and cytolytic NK cells (CD3-CD56dim cells) in lymphocyte populations increased significantly at 1 and 7 days after regional MHT treatment compared with pre-treatment numbers. The number of cytolytic NK cells also increased significantly at 1 day after treatment. The percentage of T cells and CD4+ T cells decreased significantly from 1 to 7 days following the heating procedure. However, no significant changes in the percentage and the number of CD8+ T cells was observed. Interestingly, the percentage and the number of CD4+CD25+ T lymphocytes which are recognized as regulatory T lymphocytes (Treg) decreased significantly during the 7 day post-treatment period. These results suggest that regional MHT may activate both, the innate and adaptive immune systems, through activation of NK cells and through a decrease in the number of regulatory T cells.

Function of natural killer cells in immune defence against human leukaemia.

Although progress has been made in the management of acute leukaemias, most patients who fail to respond to front-line therapies with cytostatic agents and stem cell transplantation, or who relapse after an initial response die from progressive disease. Novel treatment modalities exploiting donor-derived natural killer (NK) cells generate an alloreactive graft-versus-leukaemia response and eliminate the residual malignant clones in transplanted patients. NK cells are components of the innate immunity playing an important role in the surveillance of human tumours. Recognition of malignant cells depends on a dynamic balance between antagonistic functions of an array of NK activating and inhibitory receptors. The natural cytotoxicity receptors (NCRs) are NK cell-specific and together with the NKG2D receptor are responsible for NK cell activation and tumour cell killing. The killer immunoglobulin-like receptors (KIRs) recruit phosphatases and can antagonise the activating signals and prevent the cytolytic NK cell programme. Understanding of the integration of these multiple signals at the molecular level is central for exploring the cytolytic function of NK cells. This review describes molecular mechanisms of NK receptor-ligand interactions controlling target cell recognition and addresses the potential of NK cells for the specific elimination of leukaemic clones with the goal of advancing immunotherapy of leukaemia.

Decreased NK cell frequency in chronic hepatitis C does not affect ex vivo cytolytic killing

Prior studies have suggested that natural killer (NK) cell function might be impaired in chronic hepatitis C virus (HCV) infection. Circulating NK cell frequency and cytolytic activity were examined freshly ex vivo in HCV-infected and uninfected subjects. Surprisingly, the intrinsic cytolytic activity of peripheral blood NK-enriched cells was similar between HCV-infected and uninfected groups (P = .91). Although the percentage of circulating CD3- CD16/56+ NK cells was 30% lower in HCV-infected compared with uninfected subjects (P = .02) paralleled by a decrease of CD56(dim) cytolytic NK cells (P = .02), overall K562 cytolysis by unfractionated peripheral blood mononuclear cells was not affected (P = .29). Analysis of the relationships between NK cytolytic activity and other clinical information revealed an inverse association with liver fibrosis stage (P = .035). In conclusion, NK cell cytolytic function does not appear to be impaired in chronic hepatitis C, but higher levels of NK cell cytolysis are associated with less liver fibrosis.

Phenotypic and cytolytic activity ofMacaca nemestrina natural killer cells isolated from blood and expanded in vitro

Natural killer (NK) cells from nonhuman primates have not been completely characterized, and methods for expanding nonhuman primates NK cells in vitro have been described only in rhesus species. The purpose of this report was to characterize NK cells in pigtail macaques (Macaca nemestrina), a species that is frequently used in studies of transplantation biology/immunology, virology, vaccine development, and reproductive biology. NK cells from Macaca nemestrina peripheral blood were best defined by the expression of CD16 and CD8alpha, and the absence of CD3. Subsets of these cells express CD56, NKp30, and NKp46. An enhanced ability to kill K562 cells was not present in fluorescence activated cell sorted (FACS)-purified CD16-/CD3+ and CD16-/CD56+ cells isolated from fresh peripheral blood. However, FACS-purified CD16+/CD3- and CD16+/CD56- cells were highly efficient killers of K562 cells. Macaca nemestrina NK cells can be expanded by in vitro culturing of FACS-purified CD16+/CD2-/CD3-/CD56- cells, or from peripheral blood cells depleted of cells expressing CD3, CD4, and HLA-DR. Cells in these cultures expand 70-fold after 21 days of culturing. After culturing, these cells express high levels of natural cytotoxicity receptors (NCRs) NKp30 and NKp46. NK cell populations obtained from FACS-purified CD16+/CD3-, CD16+/CD56- cells and CD3/CD4/HLA-DR-depleted cells were highly efficient killers of K562 cells. These data suggest that a population of highly enriched cytolytic NK cells can be obtained from purified CD16+/CD3- and CD16+/CD56- cells obtained from peripheral blood, as well as from cells that have been cultured and expanded from peripheral blood that is depleted of CD3/CD4/HLA-DR-expressing cells.

A Human CD34(+) Subset Resides in Lymph Nodes and Differentiates into CD56 brightNatural Killer Cells

In humans, T cells differentiate in thymus and B cells develop in bone marrow (BM), but the natural killer (NK) precursor cell(s) and site(s) of NK development are unclear. The CD56bright NK subset predominates in lymph nodes (LN) and produces abundant cytokines compared to the cytolytic CD56dim NK cell that predominates in blood. Here, we identify a novel CD34dimCD45RA(+) hematopoietic precursor cell (HPC) that is integrin alpha4beta7bright. CD34dimCD45RA(+)beta7bright HPCs constitute <1% of BM CD34(+) HPCs and approximately 6% of blood CD34(+) HPCs, but >95% of LN CD34(+) HPCs. They reside in the parafollicular T cell regions of LN with CD56bright NK cells, and when stimulated by IL-15, IL-2, or activated LN T cells, they become CD56bright NK cells. The data identify a new NK precursor and support a model of human NK development in which BM-derived CD34dimCD45RA(+)beta7bright HPCs reside in LN where endogenous cytokines drive their differentiation to CD56bright NK cells in vivo.

Adenovirus-mediated interleukin-12 gene therapy for prostate cancer: suppression of orthotopic tumor growth and pre-established lung metastases in an orthotopic model.

Interleukin-12 (IL-12) can elicit potent antitumoral effects that involve the recruitment of specific immune effector cells. We investigated the efficacy of a single injection of a recombinant adenovirus expressing murine IL-12 (AdmIL-12) directly into orthotopic mouse prostate carcinomas generated from a poorly immunogenic cell line (RM-9) derived from the mouse prostate reconstitution system. Significant growth suppression (> 50% reduction of tumor weight) and increased mean survival time (23.4 to 28.9 days) were observed compared with controls. Suppression of pre-established lung metastases was also observed following the injection of AdmIL-12 into the orthotopic tumor. Cytolytic natural killer cell activity was markedly enhanced 1-2 days after virus injection. Immunohistochemical analysis showed significantly elevated intratumoral infiltration of CD4+ and CD8+ T cells 7 days after virus injection. However, splenocyte-derived cytotoxic T lymphocytes were not detected during the 14 days following treatment. Increased numbers of nitric oxide synthase-positive macrophages were seen in the AdmIL-12 treated group 7 days following injection. Systemic inhibition of natural killer cells with antiasialo-GM1 serum led to increased numbers of lung metastases in AdmIL-12-treated orthotopic tumors but did not affect local tumor growth. In this model system the antitumor effects of a single injection of adenovirus-mediated IL-12 appears to be based to a large extent on the activation of nitric oxide synthase in macrophages and possibly T cell activities, whereas the relatively early cytolytic activity of natural killer cells are largely but not exclusively responsible for the antimetastatic effects.

Interleukin-12 and its free p40 subunit regulate immune recognition of endometrial cells: potential role in endometriosis.

An alteration of immune recognition and killing of misplaced endometrial cells, refluxed with menstrual debris in ectopic sites, has been claimed to be responsible for the initiation and progression of endometriosis. In particular, current evidence emphasizes the role of natural killer (NK) cells as potential effectors of peritoneal immune surveillance. Interleukin-12 (IL-12), a heterodimeric cytokine composed of p40 and p35 chains, has potent regulatory effects on NK cell growth and function. The purpose of this study was to evaluate whether this cytokine may also have a role in the specific cytolytic NK cell response toward endometrial antigens. To this aim, concentrations of IL-12 and its free p40 subunit were determined in peritoneal fluid of 33 patients with endometriosis and 40 women without laparoscopic evidence of the disease. Similar concentrations of IL-12, but significantly higher levels of free p40, were present in peritoneal fluid of patients with endometriosis compared to those in women without the disease. We also observed that the IL-12 plus free p40/IL-12 ratio increased with the severity of the disease. Moreover, we investigated whether incubation of NK cells with heterodimeric IL-12 and/or p40 has any effect on NK cell-mediated lysis of endometrial cells. NK cells pretreated with heterodimeric IL-12 exhibited an enhanced cytotoxic response toward endometrial targets. This IL-12-induced cytotoxicity could be abrogated by the p40 subunit in a specific and dose-dependent manner. The p40 inhibitory effect was mediated by down-regulation of IL-12 high affinity binding sites on NK cells, as we observed inhibition of surface IL-12 receptor beta1-chain expression, a decrease in IL-12-binding capacity, and inhibition of phosphorylation of STAT4 (signal transducer and activator of transcription) protein. These data suggest that the excess of p40 present in peritoneal fluid of patients with endometriosis may be related to the NK cell defect associated with the disease. Moreover, IL-12 could be a potential specific agent able to correct the p40-induced defect in vivo.

IL-2-dependent generation of natural killer cells from bone marrow: Role of MAC-1 −, NK1-1 − precursors

We have previously shown that interleukin-2 (IL-2) is able to induce the generation of natural killer (NK) activity in bone marrow (BM) cell cultures from mice pretreated with 5-fluorouracil (5-FU). Cell fractionation experiments to analyze the nature of BM precursors indicate that MAC-1 −, NK1-1 − noncytotoxic precursors are induced by IL-2 to proliferate and generate cytolytic NK cells. These data demonstrate that the phenotype and functional characteristics of the IL-2-responsive cells in the FUBM are different from those of mature NK cells in that they are MAC-1 +, NK1.1 +, CD3 − and susceptible to boosting by IFN-α.

Up-regulation of NK cell function against head and neck cancer in response to ss-isRNA requires TLR7

Natural killer (NK) cells play a crucial role in innate immunity as effectors against tumor and pathogen-infected cells. NK-mediated host defense against tumor cells is strongly impaired in patients with head and neck squamous cell carcinoma (HNSCC). Tumor secretion of various immune suppressive mediators contributes to massively compromised immune functions. Herein we demonstrate that NK cell cytotoxicity against tumor cells of HNSCC can be efficiently stimulated by single-stranded immunostimulatory RNA (ss-isRNA). Stimulation with ss-isRNA results in an increased production of interferon-gamma and effector proteins perforin and granzyme B. Our investigations revealed that supernatants of permanent HNSCC cell lines negatively affect the ss-isRNA-triggered stimulation of cytolytic NK cell functions. Stimulation of cytotoxicity requires toll-like receptor 7 (TLR7). Increased expression of NK cell TLR7 was shown in response to ss-isRNA. These results suggest ss-isRNA as a potential immunostimulatory tool of human NK cells against HNSCC.