Cytotoxic Potential Of Natural Killer Cells Research Articles

Abstract 83: NK cell ADCC assays: Leveraging flow cytometry and reporter cell lines for enhanced biological relevance and throughput

Abstract Amid the growing arsenal of cancer treatments, antibody-dependent cellular cytotoxicity (ADCC) assays have emerged as a significant contributor to the quest for more effective therapies. The ADCC-based antibody therapy often exploits Natural Killer (NK) cells as effectors. This immunotherapeutic approach harnesses the innate cytotoxic potential of NK cells, offering a promising solution for the precision targeting of malignant cells. In this study, we employed two methods that can be used to measure ADCC potency and specificity during preclinical drug discovery. The first was a flow cytometry-based approach that focused on enhancing biological relevance by utilizing primary human peripheral blood mononuclear cells (PBMCs) as a source for NK effector cells. To this end, target cells were fluorescently labeled with CFSE and cultured with freshly isolated PBMCs at 3 effector to target (E:T) ratios, in the presence of ADCC antibody. After 16h incubation, a viability dye was added, and percent cytotoxicity was measured in CFSE+ targets cells by flow cytometry. The second method offered a high-throughput plate reader-based approach (ADCC Reporter Bioassay; Promega), that utilized an ADCC reporter effector cell line harboring a luciferase cassette driven by an NFAT promoter, which is activated when effector and targets cells are bridged by a therapeutic antibody. Cytotoxicity was read out by measuring light output on a Cytation 3 plate imaging reader (Agilent Technologies) after a 6h cell culture incubation using the recommended 6:1 E:T ratio. Preclinical application for both assays was demonstrated using an anti-HER2 therapeutic antibody (trastuzumab) against BT-474, which is a HER2 positive cell line. To demonstrate specificity, an anti-VEGF antibody (bevacizumab) and Hs 578T cells (HER2 low) were used as controls. Our results revealed trastuzumab induced a strong dose-dependent increase in cytotoxicity in the BT-474 cells but not the Hs 578T cell line (range: 40-70%) while bevacizumab failed to induce any cytotoxicity above background levels at any concentration. Furthermore, the flow cytometry and plate reader methodologies produced similar trends. In summary, both applications can be used to produce reliable ADCC drug screening assessments. Additional considerations include investigational needs surrounding high throughput capability versus biological relevance. Unlike traditional models using immortalized cell lines, primary human PBMCs more faithfully recapitulate the physiological interactions between effector cells and target cells. On the other hand, the more streamlined reporter cell line approach not only accelerates assay throughput but also ensures consistent and reliable results in an attractive option for large-scale screening and drug development efforts. Citation Format: David William Draper, Yewei Xing, Scott Wise. NK cell ADCC assays: Leveraging flow cytometry and reporter cell lines for enhanced biological relevance and throughput [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 83.

T-cell help in the tumor microenvironment enhances rituximab-mediated NK-cell ADCC

AbstractRituximab (RTX) and other monoclonal antibodies (mAbs) that bind directly to malignant cells are of great clinical value but are not effective for all patients. A major mechanism of action of RTX is antibody-dependent cellular cytotoxicity (ADCC) mediated by natural killer (NK) cells. Prior in vitro studies in our laboratory demonstrated that T cells contribute to maintaining the viability and cytotoxic potential of NK cells activated by anti-CD20–coated target B cells. Here, we conducted studies using a novel mouse model and clinical correlative analysis to assess whether T-cell help contribute to RTX-mediated NK-cell ADCC in the tumor microenvironment (TME) in vivo. A humanized mouse model was developed using Raji lymphoma cells and normal donor peripheral blood mononuclear cells that allows for control of T-cell numbers in the lymphoma TME. In this model, NK-cell viability and CD16 and CD25 expression dropped after RTX in the absence of T cells but increased in the presence of T cells. RTX therapy was more effective when T cells were present and was ineffective when NK cells were depleted. In patients with indolent lymphoma, fine needle aspirates were obtained before and ∼1 week after treatment with a RTX-containing regimen. There was a strong correlation between CD4+ T cells as well as total T cells in the pretherapy TME and an increase in NK-cell CD16 and CD25 expression after RTX. We conclude that T-cell help in the TME enhances RTX-mediated NK-cell viability and ADCC.

Impact of antibody architecture and paratope valency on effector functions of bispecific NKp30 x EGFR natural killer cell engagers.

Natural killer (NK) cells emerged as a promising effector population that can be harnessed for anti-tumor therapy. In this work, we constructed NK cell engagers (NKCEs) based on NKp30-targeting single domain antibodies (sdAbs) that redirect the cytotoxic potential of NK cells toward epidermal growth factor receptor (EGFR)-expressing tumor cells. We investigated the impact of crucial parameters such as sdAb location, binding valencies, the targeted epitope on NKp30, and the overall antibody architecture on the redirection capacity. Our study exploited two NKp30-specific sdAbs, one of which binds a similar epitope on NKp30 as its natural ligand B7-H6, while the other sdAb addresses a non-competing epitope. For EGFR-positive tumor targeting, humanized antigen-binding domains of therapeutic antibody cetuximab were used. We demonstrate that NKCEs bivalently targeting EGFR and bivalently engaging NKp30 are superior to monovalent NKCEs in promoting NK cell-mediated tumor cell lysis and that the architecture of the NKCE can substantially influence killing capacities depending on the NKp30-targeting sdAb utilized. While having a pronounced impact on NK cell killing efficacy, the capabilities of triggering antibody-dependent cellular phagocytosis or complement-dependent cytotoxicity were not significantly affected comparing the bivalent IgG-like NKCEs with cetuximab. However, the fusion of sdAbs can have a slight impact on the NK cell release of immunomodulatory cytokines, as well as on the pharmacokinetic profile of the NKCE due to unfavorable spatial orientation within the molecule architecture. Ultimately, our findings reveal novel insights for the engineering of potent NKCEs triggering the NKp30 axis.

­Association of Macrophage Activation Syndrome, Natural Killer (NK) Cell Function and Genetic Polymorphisms With Dengue Disease Severity

Background: Severe dengue is characterized by shock, organ dysfunction, and coagulopathy, driven by an excessive host inflammatory response. We investigated the role of hyperinflammation/macrophage activation syndrome (MAS) in dengue pathogenesis including MAS biomarkers, Natural Killer (NK) cell function and genetic polymorphisms. Methods: Samples were included from patients recruited into an observational study in Vietnam and divided into three severity grades (plasma leak severity grades 0,1 and 2). MAS biomarkers, were measured at 4 time-points. The frequencies, activation status and cytotoxic potential of NK cells were analysed by flow cytometry. RNA was extracted from sorted CD56+ NK cells and libraries prepared using SMART-Seq Stranded Kit and sequenced using HiSeq3000 (Illumina). Results: 70 hospitalized dengue patients were included. Patients with severe plasma leakage (grade 2 leakage) had higher MAS biomarkers than patients without plasma leakage, including a higher proportion had ferritin levels of >2000 ng/ml (83.3% vs 45.2%) and H scores (148.5 vs.105.5). Activated CD69+ total NK and CD56 dim cells were decreased in patients with severe leakage compared to grade 1. Perforin expression was reduced in NK CD56 dim and CD56 bright cells in grade 2 patients compared to grade 1, and granzyme B MFI levels were reduced in total NK cells and CD56 dim NK cells. RNA sequencing analysis revealed three previously unreported SNPs in the genes involved in NK cell function to be associated with more severe disease; two in the NK cell lectin-like receptor K1 gene (KLRK1) and one in the PRF1 gene, encoding perforin 1. Conclusions: Features of MAS/hyperinflammation are associated with dengue disease severity, including higher MAS biomarkers, impaired NK cell activation/cytotoxicity and specific SNPs in genes involved in NK cell cytolytic function (KLRK1 and PRF-1). Clinical trials of targeted therapeutic immunomodulation for patients with dengue-associated MAS are warranted. Funding Information: Young Investigator Research Grant: NMRC/ OFYIRG17may066 awarded to S Yacoub; Open Fund - Individual Research Grant, National Medical Research Council, Singapore NMRC/OFIRG/0049/2017 awarded to L.Rivino. OM Sessions was supported by the Singapore Ministry of Education (https://www.moe.gov.sg) with a Startup grant. Declaration of Interests: The authors report no COI. Ethics Approval Statement: Ethical approval was obtained from the Oxford Tropical Research Ethics Committee and the Ethics review Committee at NHTD. Written informed consent was obtained from all participants. Experimental work on PBMCs was performed at Duke-NUS Medical School after approval by the Singapore-NUS Institutional Review Board.

Vogt–Koyanagi–Harada patients show higher frequencies of circulating NKG2Dpos NK and NK T cells

Vogt-Koyanagi-Harada (VKH) is an autoimmune disease characterized by inflammation in tissues that contain melanocytes. We aimed to increase the knowledge regarding immunological pathways deregulated in VKH disease. We compared the percentages of circulating natural killer (NK), NK T and T cells expressing the activatory markers: CD16, CD69, NK group 2D (NKG2D), natural cytotoxicity triggering receptor 3 (Nkp30), natural cytotoxicity triggering receptor 1 (Nkp46) and the inhibitory marker: NK group 2 member A (NKG2A) in 10 active VKH patients, 20 control subjects (CTR) and seven patients with Behçet disease (BD) by flow cytometry. Cytotoxic potential of NK cells was determined through the degranulation marker CD107a expression after contact with K562 cells by flow cytometry. Moreover, plasmatic levels of 27 cytokines were determined with a multiplex bead-based assay. VKH patients showed higher percentages of NKG2Dpos NK and NK T cells versus CTR. The cytotoxic potential of NK cells induced by K562 cells was comparable between VKH patients and CTR. Finally, higher concentrations of interleukin (IL)-4, IL-5, IL-7, IL-17 and platelet-derived growth factor-subunits B (PDGF-bb) were detected in plasma of VKH patients versus CTR. The immune profile of VKH patients was similar to that of BD patients.

Innate-like Chemokine Receptor Profile and Migratory Behaviour By Terminally Differentiated and Educated NK Cells

Natural Killer (NK) cells play an essential role in cancer surveillance and have a unique capability of spontaneous cytotoxicity against cancer cells. The human NK cell repertoire is functionally diversified through a tightly regulated differentiation process characterized by an early transition from CD56bright to CD56dim NK cells, followed by coordinated changes in expression of inhibitory receptors, including NKG2A and killer cell immunoglobulin-like receptors (KIR). The acquisition of self HLA class I binding KIRs during NK cell differentiation tunes the cytotoxic potential of NK cells in a process termed education, characterized by increased loading of granzyme B in dense core granules. Although NK cell differentiation and education are critical determinants of the functional potential of the cell, little is known about how these events shape the migratory behavior of NK cells. To mediate appropriate and directed immune response against cancer, NK cells must be capable of migration to the tumor site. This process is mediated by chemokines, which guide cell migration by binding to their specific receptors. For example, in multiple myeloma, CXCR3 and CCR5 ligands (MIG, IP-10, and MIP-1a) are significantly upregulated in the bone marrow compared to healthy controls, affecting the composition of immune cells in the tumor microenvironment. In order to delineate the homing patterns of distinct NK cell subsets, we used high-dimensional flow cytometry combined with functional assays to map the NK cell chemokine receptor expression and migratory behavior. We screened resting and cytokine/feeder cell stimulated peripheral blood NK cells for the expression of a panel of 20 chemokine receptors (A). Based on CD56, CD57, NKG2A, and KIR expression, NK cells were divided into 6 phenotypically and functionally distinct subsets that were ordered according to their differentiation status (B). We found that the expression of CX3CR1, CXCR1, CXCR2, and CMKLR1 gradually increased during differentiation, whereas the expression of CXCR3, CCR7, and CCR5 was lower in more differentiated NK cells. CXCR4, CCR4, and CCR2 expression was relatively uniform across all subsets. Interestingly, CCR1 and CXCR6 were expressed mainly on less differentiated NKG2A+ CD56dim NK cells (B). Next, we stratified the chemokine receptor expression on mature KIR+ NK cells based on the expression of self (educated) or non-self KIR (uneducated). Educated NK cells expressed CXCR1, CX3CR1, CCR5, and CMKLR1 at higher levels than the uneducated NK cells. Conversely, CXCR3 was expressed at lower levels on educated NK cells (C). No difference was observed for CXCR2 expression. To determine whether the observed differences in chemokine receptor expression translate into altered chemokine responsiveness between the subsets, we combined the transwell system with multicolor flow cytometry. We found that the chemokine-induced migration capability of NK cells correlated closely with the expression level of corresponding chemokine receptor, leading to subset specific responses to various chemokine gradients (D). The present results show that peripheral blood NK cell chemokine receptor profile changes in a coordinated fashion during NK cell differentiation and is further influenced by the expression of self-specific KIR. Interestingly, receptors which expression declines during NK cell differentiation (CCR5, CCR7, and CXCR3) are commonly associated with adaptive T cell responses to viruses, whereas receptors that are upregulated along the differentiation axis (CXCR1, CXCR2, CX3CR1, CMKLR1) are typical for neutrophils and macrophages as a part of the innate immune response. Thus, our results suggest that NK cell differentiation and education processes together shape the NK cell migratory capabilities to promote homing of the most functional NK cell subsets to the site of inflammation and serve as the first line of defense in the immune response to pathogens and tumors. Figure Disclosures Malmberg: Fate Therapeutics: Consultancy, Patents & Royalties; Vycellix: Membership on an entity's Board of Directors or advisory committees.

Interferon Alpha Enhances NK Cell Function and the Suppressive Capacity of HIV-Specific CD8+ T Cells.

Current shock-and-kill strategies for the eradication of the HIV-1 reservoir have resulted in blips of viremia but not in a decrease in the size of the latent reservoir in patients on suppressive antiretroviral therapy (ART). This discrepancy could potentially be explained by an inability of the immune system to kill HIV-1-infected cells following the reversal of latency. Furthermore, some studies have suggested that certain latency-reversing agents (LRAs) may inhibit CD8+ T cell and natural killer (NK) cell responses. In this study, we tested the hypothesis that alpha interferon (IFN-α) could improve the function of NK cells from chronic progressors (CP) on ART. We show here that IFN-α treatment enhanced cytokine secretion, polyfunctionality, degranulation, and the cytotoxic potential of NK cells from healthy donors (HD) and CP. We also show that this cytokine enhanced the viral suppressive capacity of NK cells from HD and elite controllers or suppressors. Furthermore, IFN-α enhanced global CP CD8+ T cell cytokine responses and the suppressive capacity of ES CD8+ T cells. Our data suggest that IFN-α treatment may potentially be used as an immunomodulatory agent in HIV-1 cure strategies.IMPORTANCE Data suggest that HIV+ individuals unable to control infection fail to do so due to impaired cytokine production and/cytotoxic effector cell function. Consequently, the success of cure agendas such as the shock-and-kill strategy will probably depend on enhancing patient effector cell function. In this regard, NK cells are of particular interest since they complement the function of CD8+ T cells. Here, we demonstrate the ability of short-course alpha interferon (IFN-α) treatments to effectively enhance such effector functions in chronic progressor NK cells without inhibiting their general CD8+ T cell function. These results point to the possibility of exploring such short-course IFN-α treatments for the enhancement of effector cell function in HIV+ patients in future cure strategies.

The multi-functionality of N-809, a novel fusion protein encompassing anti-PD-L1 and the IL-15 superagonist fusion complex

ABSTRACTHere we describe a novel bifunctional fusion protein, designated N-809. This molecule comprises the IL-15/IL15Rα superagonist complex containing the Fc-domain of IgG1 (N-803, formerly designated as ALT-803) fused to two single chain anti-PD-L1 domains. The fully human IgG1 portion of the N-809 molecule was designed to potentially mediate antibody dependent cellular cytotoxicity (ADCC). The studies reported here show that N-809 has the same ability to bind PD-L1 as an anti-PD-L1 monoclonal antibody. RNAseq studies show the ability of N-809 to alter the expression of an array of genes of both CD4+ and CD8+ human T cells, and to enhance their proliferation; CD8+ T cells exposed to N-809 also have enhanced ability to lyse human tumor cells. An array of genes was differentially expressed in human natural killer (NK) cells following N-809 treatment, and there was increased expression of several surface activating receptors; there was, however, no increase in the expression of inhibitory receptors known to be upregulated in exhausted NK cells. N-809 also increased the cytotoxic potential of NK cells, as shown by increased expression of granzyme B and perforin. The lysis of several tumor cell types was increased when either NK cells or tumor cells were exposed to N-809. Similarly, the highest level of ADCC was seen when both NK cells (from donors or cancer patients) and tumor cells were exposed to N-809. These studies thus demonstrate the multi-functionality of this novel agent.

Higher Frequencies of Lymphocytes Expressing the Natural Killer Group 2D Receptor in Patients With Behçet Disease.

Behçet disease (BD) is an inflammatory systemic disease with a fluctuating course, which can affect the skin, eyes, central nervous system, musculoskeletal, gastrointestinal, and vascular systems. No laboratory tests are currently available for the diagnosis of BD and monitoring disease activity. Moreover there is a lack of knowledge on BD pathogenesis. This study focused on circulating Natural Killer (NK), NKT and T cells evaluated as CD3neg CD56pos, CD3pos CD56pos, and CD3pos CD56neg. Peripheral blood mononuclear cells (PBMCs) were collected from 38 BD patients and 20 healthy controls (HC). The frequencies of NK, NKT, and T cells expressing CD16, CD69, NKG2D, Nkp30, Nkp46, and NKG2A were assessed by flow cytometry. Cytotoxic potential of NK cells was evaluated by flow cytometry as the percentage of cells expressing the degranulation marker CD107a after incubation with K562 cells. The levels of 27 cytokines were determined in plasma with a multiplex bead-based assay. Higher percentages of NK, NKT, and T cells expressing NKG2D were detected in PBMCs of BD patients than HC. ROC curve analysis showed that the evaluation of NKG2Dpos NK, NKT, and T cell percentages discriminated between BD patients and HC. Moreover, there was a positive correlation between the BD Current Activity Form (BDCAF) scores and the frequencies of NKG2Dpos NK and NKT cells. A higher frequency of NK cells expressing CD107a was induced in PBMCs from BD patients than HC after incubation with K562 cells. Concentrations of IL-5, IL-6, IL-10, IL-13, IP-10, and MIP-1β were higher in plasma of BD patients than HC. Monitoring the frequencies of NKG2Dpos lymphocytes could help the clinicians in BD patients management. In addition, the increased expression of NKG2D in BD patients is likely involved in disease pathogenesis.

The Smac Mimetic BV6 Improves NK Cell-Mediated Killing of Rhabdomyosarcoma Cells by Simultaneously Targeting Tumor and Effector Cells.

Rhabdomyosarcoma (RMS), the most common cancer of connective tissues in pediatrics, is often resistant to conventional therapies. One underlying mechanism of this resistance is the overexpression of Inhibitor of Apoptosis (IAP) proteins, leading to a dysfunctional cell death program within tumor cells. Smac mimetics (SM) are small molecules that can reactivate the cell death program by antagonizing IAP proteins and thereby compensating their overexpression. Here, we report that SM sensitize two RMS cell lines (RD and RH30) toward natural killer (NK) cell-mediated killing on the one hand, and increase the cytotoxic potential of NK cells on the other. The SM-induced sensitization of RH30 cells toward NK cell-mediated killing is significantly reduced through blocking tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) on NK cells prior to coculture. In addition, the presence of zVAD.fmk, a pancaspase inhibitor, rescues tumor cells from the increase in killing, indicating an apoptosis-dependent cell death. On the NK cell side, the presence of SM in addition to IL-2 during the ex vivo expansion leads to an increase in their cytotoxic activity against RH30 cells. This effect is mainly TNFα-dependent and partially mediated by NK cell activation, which is associated with transcriptional upregulation of NF-κB target genes such as IκBα and RelB. Taken together, our findings implicate that SM represent a novel double-hit strategy, sensitizing tumor and activating NK cells with one single drug.

Targeting AML Using an Fc-Engineered BST1/CD157 Monoclonal Antibody

Antibody-based immunotherapy represents a promising strategy to target and eliminate acute myeloid leukemia (AML) tumor cells. We evaluated BST1/CD157, a novel, slow internalizing surface antigen, for its suitability as immunotherapeutic target in AML. An Fc-optimized antibody against BST1/CD157 was developed (MEN1112/OBT357NF), which binds to the Fc-receptor on natural killer (NK) cells with enhanced affinity. The target antigen expression profile of BST1/CD157 on AML bulk cells as well as on leukemic stem cells (LSC) was analyzed with flow cytometry using a commercially available antibody. BST1/CD157 expression was detected in > 97% of AML patients at primary diagnosis (n=81) and at time of relapse (n=20) using specific fluorescence intensity (SFI, positivity: SFI > 1. 5). Importantly, BST1/CD157 was also expressed on CD34+/CD38-cells (n=20), the compartment with a high percentage of LSCs.Functional titration experiments of MEN1112/OBT357NF showed antibody-mediated lysis of U937 cells in the low picomolar range (EC50 = 30–140 pM) and demonstrated superior ADCC activity compared to its non Fc-engineered parental analogue. To evaluate the additive effect of the complement cascade, healthy donor (HD) monocytes were co-incubated with autologous NK cells and MEN1112/OBT357NF in the presence or absence of 5% donor serum. After 20 hours of incubation, a significantly enhanced lysis efficacy by MEN1112/OBT357NF through the addition of serum compared to control cultures without serum (p=0.02) was demonstrated.For further functional characterization of MEN1112/OBT357NF standard chromium release assays using AML cell lines and NK cells from HDs were performed. In this setting, efficient target cell lysis (30–50%) at various effector cell:target (E:T) ratios (50:1–6:1) was observed. Compared to Rituximab-mediated lysis of RAJI cells, MEN1112/OBT357NF triggered more efficient target cell lysis at much lower effector cell concentrations (33% lysis of OCI-AML3 cells vs. 11% lysis of RAJI cells at E:T 6:1).Furthermore, the cytotoxic potential of NK cells from AML patients after intense double induction chemotherapy on AML cell lines was tested. The results were highly variable with efficient lysis in about one third of samples tested (n=10). As a positive control NK cells from HDs were used which showed superior lysis as compared to patient-derived NK cells. In an autologous set-up using NK cells from either primary diagnosis or at time of remission, we could show efficient lysis of primary AML cells in one of two patient samples (patient in complete remission) in the presence of MEN1112/OBT357NF.In summary, our analysis demonstrates that BST1/CD157 is a promising target antigen for antibody-based therapy in AML. The effective in-vitro ADCC activity supports further development of MEN1112/OBT35NF as an immunotherapy for patients with AML. DisclosuresKrupka:Oxford BioTherapeutics Ltd: Research Funding. Jansen:Oxford BioTherapeutics Ltd: Research Funding. Aud:Oxford BioTherapeutics Ltd: Employment. Dusek:Oxford BioTherapeutics Ltd: Employment. Bisht:Oxford BioTherapeutics Ltd: Employment. Pombo-Villar:Oxford BioTherapeutics Ltd: Employment, Equity Ownership. Rohlff:Oxford BioTherapeutics Ltd: Employment. Subklewe:Oxford BioTherapeutics Ltd: Research Funding.

FRI0020 Blocking the inhibitory CD94/NKG2A NK cell receptor with a novel ANTI-NKG2A MAB enhances the susceptibility of rheumatoid arthritis fibroblast-like synoviocytes (FLS) to NK cell-mediated cytotoxicity

BackgroundRheumatoid arthritis (RA) is an autoimmune disease characterized by chronic inflammation and synovial hyperplasia leading to progressive bone erosion and cartilage degradation [1]. Fibroblast-like synoviocytes (FLS) present in the inflamed...

Enhanced cytotoxic function of natural killer and natural killer T‐like cells associated with decreased CD94 (Kp43) in the chronic obstructive pulmonary disease airway

Natural killer (NK) and natural killer T (NKT)-like cells represent a small but important proportion of effector lymphocytes that we have previously shown to be major sources of pro-inflammatory cytokines and granzymes. We hypothesized that these cells would be increased in the airway in chronic obstructive pulmonary disease (COPD), accompanied by reduced expression of the inhibitory receptor CD94 (Kp43) and increased expression of cytotoxic mediators granzyme B and perforin. We measured NK and NKT-like cells and their expression of CD94 in the blood of COPD patients (n = 71; 30 current and 41 ex-smokers), smokers (16) and healthy controls (25), and bronchoalveolar lavage fluid (BALF) from a cohort of subjects (19 controls, 12 smokers, 33 COPD). Activation was assessed by measuring CD69 in blood and the cytotoxic potential of NK cells by measuring granzymes A and B, and using a cytotoxicity assay in blood and BALF. In blood in COPD, there were no significant changes in the proportion of NK or NKT-like cells or expression of granzyme A or NK cytotoxic potential versus controls. There was, however, increased expression of granzyme B and decreased expression of CD94 by both cell types versus controls. The proportion of NK and NKT-like cells were increased in BALF in COPD, associated with increased NK cytotoxicity, increased expression of granzyme B and decreased expression of the inhibitory receptor CD94 by both cell types. Treatment strategies that target NK and NKT-like cells, their cytotoxicity and production of inflammatory mediators in the airway may improve COPD morbidity.

Activation of natural killer cells by hepatitis C virus particles in vitro

Little is known about the ability of hepatitis C virus (HCV) to alter early innate immune responses in infected patients. Previous studies have shown that natural killer (NK) cells are functionally impaired after interaction of recombinant HCV glycoprotein E2 with the co-stimulatory CD81 molecule in vitro; however, the functional consequences of a prolonged contact of NK cells with HCV particles have remained unclear. We have examined the phenotypes of purified, interleukin-2-activated NK cells from healthy donors and HCV genotype 1b patients after culture for 5 days with HCV pseudoparticles (HCVpp) and serum samples containing HCV genotype 1b. NK cells from healthy donors and chronic HCV patients were found to up-regulate receptors associated with activation (NKp46, NKp44, NKp30, NKG2D), while NK receptors from the killer cell immunoglobulin-like receptor family (KIR/CD158), predominantly having an inhibitory function, were significantly down-modulated after culture in the presence of HCV particles compared with control cultures of NK cells. HCV-infected sera and HCVpp elicited significantly higher secretion of the NK effector lymphokines interferon-γ and tumour necrosis factor-α. Furthermore, HCV stimulated the cytotoxic potential of NK cells from normal donors and patients. The enhanced activation of NK cells after prolonged culture with HCVpp or HCV-containing sera for 5 days suggests that these innate effector cells may play an important role in viral control during early phases of HCV infection.

Activation of Natural Killer Cells by Hepatitis C Virus particles in vitro

Little is known about the ability of hepatitis C virus (HCV) to alter early innate immune responses in infected patients. Previous studies have shown that natural killer (NK) cells are functionally impaired after interaction of recombinant HCV glycoprotein E2 with the co-stimulatory CD81 molecule in vitro; however, the functional consequences of a prolonged contact of NK cells with HCV particles have remained unclear. We have examined the phenotypes of purified, interleukin-2-activated NK cells from healthy donors and HCV genotype 1b patients after culture for 5 days with HCV pseudoparticles (HCVpp) and serum samples containing HCV genotype 1b. NK cells from healthy donors and chronic HCV patients were found to up-regulate receptors associated with activation (NKp46, NKp44, NKp30, NKG2D), while NK receptors from the killer cell immunoglobulin-like receptor family (KIR/CD158), predominantly having an inhibitory function, were significantly down-modulated after culture in the presence of HCV particles compared with control cultures of NK cells. HCV-infected sera and HCVpp elicited significantly higher secretion of the NK effector lymphokines interferon-γ and tumour necrosis factor-α. Furthermore, HCV stimulated the cytotoxic potential of NK cells from normal donors and patients. The enhanced activation of NK cells after prolonged culture with HCVpp or HCV-containing sera for 5 days suggests that these innate effector cells may play an important role in viral control during early phases of HCV infection.

Lenalidomide down regulates the production of interferon-γ and the expression of inhibitory cytotoxic receptors of human Natural Killer cells

Lenalidomide, a daughter molecule of Thalidomide, and IMIDs® are immunomodulatory drugs that have been described as having immunomodulatory properties and anti-tumor activity. The effect of Lenalidomide towards Peripheral Blood Mononuclear Cells (PBMC) has been studied and direct effects towards T cells have been described, such as an increase of interferon-γ (IFN-γ) and interleukin (IL)-2 production. As a consequence, it has been also described that IL-2 subsequently activates Natural Killer (NK) cells. Nevertheless, direct effects of Lenalidomide on NK cells from healthy volunteers have never been described, if searched. Here we show that Lenalidomide can inhibit the production of IFN-γ by NK cells from healthy donors. It also modifies the phenotype of NK cells through a decrease of the expression of Killer cell Immunoglobulin-like Receptors (KIRs) and NKp46. However, we did not detect consequence of these phenotype modifications on the cytotoxic potential of NK cells.

Relevance of target cell-induced apoptosis as mechanism of resistance against natural killer cells

Natural killer (NK) cells contribute to the graft-versus-leukemia effect after allogeneic stem cell transplantation. However, the efficacy of NK cell-mediated tumor cell lysis is limited due to target cell resistance, and target cell-induced apoptosis (TiA) was proposed to contribute to differences in susceptibility to NK cells. Here we analyzed the effects of target cells on the apoptosis of cytokine-activated NK cells in vitro. We found no association of target cell susceptibility and TiA of NK cells in an array of human and murine target-effector cell combinations. Incubation of NK cells with caspase inhibitors blocked TiA incompletely, indicating that TiA is partly based on caspase-independent mechanisms. Modulating NK cell susceptibility against TiA by caspase inhibition did not influence cytotoxic efficacy. Furthermore, we found cytotoxic potential of NK cells to be markedly decreased following first target cell contact. Exhaustion of NK cell activity by first target cell contact was, however, not mediated by TiA. In addition, we found no relevant TiA by lymphoma cell lines against activated murine NK cells. We conclude that TiA represents only a minor factor of target cell resistance against NK cell-mediated cytolysis.

Inhibition of term decidual NK cell cytotoxicity by soluble HLA‐G1

Soluble (s)HLA-G1 is produced by trophoblast cells. Aim was to analyze the capacities and mechanisms of sHLA-G1 to regulate interleukin (IL)-2-induced cytotoxicity of natural killer (NK) cells from human deciduas. Natural killer cells were isolated from decidual layers of term placentae, stimulated or not with IL-2 and supplemented with various concentrations of recombinant soluble HLA-G1 (sHLA-G1). For NK cell cytotoxicity assays, K562 cells were used as targets. Expression of signal transducer and activator of transcription 3 (STAT3) and perforin was analyzed by Western blotting. Apoptosis was examined by assessment of poly(ADP-ribose) polymerase cleavage. NK cells were analyzed by flow cytometry for IL-2receptor-alpha (IL-2R alpha; CD25) and transferrin receptor CD71 expression. Interleukin-2 increases CD71, STAT3, perforin expression and cytotoxic potential of NK cells. Expression of CD71, STAT3 and perforin decreased simultaneously with cytotoxicity and dose-dependently when sHLA-G1 (1.6 micro g/mL-1.6 ng/mL) was added to IL-2 stimulated cultures. sHLA-G1 did not induce apoptosis and CD25 expression was not affected. Interleukin-2R alpha expression is not controlled by sHLA-G1, but its signal transducer STAT3 as well as several downstream effects, such as perforin expression, proliferation and cytotoxicity. The control of STAT3 bioavailability through sHLA-G1 may be a key regulator of the mentioned effects.