Influence of Btk Inhibitors on Antitumor Activity of Natural Killer Cells

Abstract Small molecule Bruton's tyrosine kinase (Btk) inhibitors are extensively studied in preclinical investigations and clinical trials in the treatment of hematological malignancies derived from B-cells. Ibrutinib, due to its safety and efficiency, has been recently approved for the treatment of patients with Chronic Lymphocytic Leukemia (CLL) who received at least one prior therapy. Moreover, another Btk inhibitor AVL-292 is currently tested in clinical trials in patients with B Cell Non-Hodgkin's Lymphomas, CLL and Waldenstrom Macroglobulinemia. Despite a huge therapeutic potential of Btk inhibitors we have recently demonstrated that both natural killer (NK) cells cytotoxicity and degranulation are significantly impaired upon ibrutinib treatment (Bojarczuk et al., Leukemia 2014). Since NK cells are effectors of innate immune system capable to kill tumor cells directly and in the mechanism of antibody dependent cell-mediated cytotoxicity (ADCC), which constitutes one of the major mechanism of monoclonal antibodies widely used in hematooncology, in our ongoing studies we are focused to determine in details the influence of various Btk inhibitors on NK cells cytotoxicity, degranulation, cytokine secretion and expression of activatory/inhibitory receptors. All experiments were performed fully in vitro using human primary NK cells isolated from PBMC of healthy donors as well as NK92 and NK92.CD16 cell lines. To determine cytolytic activity of NK cells CFSE/PI flow cytometry assay was used. Cytokine secretion and NK cells degranulation, evaluated as the expression of CD107a on the surface of NK cells, were determined with flow cytometry upon incubation with target cells for 4 h. Phenotype of NK cells pre-incubated with tested compounds was determined with flow cytometry using antibodies conjugated with fluorochromes. The initial results of our studies show that various Btk inhibitors differentially regulate NK cells antitumor activity. Ibrutinib and AVL-292 which covalently bind to cysteines at the position 481 significantly inhibit NK cells cytotoxicity. Interestingly, we have observed that pre-incubation of NK cells with ibrutinib as well as AVL-292 results in down-regulation of CD25 and CD69. This effect was not observed upon treatment of NK cells with CGI-1746, a reversible Btk inhibitor which blocks phosphorylation of BTK in Y551 and Y223. Expression of NK cells activatory receptors such as NKp30, NK44, NKp46, NKG2D, DNAM-1 and CD16 remained unchanged. Figure 1 Figure 1. Disclosures No relevant conflicts of interest to declare.

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The Anti-Leukemia Effect of Natural Killer-Derived Exosomes

Blood ◽

10.1182/blood-2019-129986 ◽

2019 ◽

Vol 134 (Supplement_1) ◽

pp. 4652-4652

Author(s):

Michael Anbar ◽

Galit Granot ◽

Pia Raanani ◽

Uri Rozovski

Keyword(s):

Flow Cytometry ◽

Clinical Trials ◽

Nk Cells ◽

Cell Line ◽

Cytotoxic Effect ◽

Leukemia Cells ◽

Target Cells ◽

Cell Of Origin ◽

Proteomics Analysis ◽

Hek 293

Circulating NK cells are the effector arm of the innate immune system. As such, they recognize transformed cells as "non-self" and kill them. Numerous ex vivo studies have demonstrated the ability of NK cells to kill allogeneic leukemia cells. Based on these in vitro studies, several past and ongoing clinical trials have shown allogenic NK cells have a strong anti-leukemia effect. However, the use of NK cells as an "off the shelf" product is limited since they, like most cellular products, induce an allo-reactive immunogenic response which limits efficacy and increases toxicity. Exosomes are nano scaled extracellular vesicles that are released by various types of cells including NK cells. Since the exosomal cargo reflects, in part, the molecular makeup of its cell of origin, we hypothesized that NK-derived exosomes maintain the anti-leukemia effect of their cell of origin. To test this hypothesis, we exposed leukemia cells to NK-derived exosomes and tested their ability to eliminate them. As a source for NK-derived exosomes we used the NK-92MI cell line. This is a genetically altered cell line which constitutively expresses IL-2 that augments the cytotoxic activity of the cells and is routinely used in clinical trials. We cultured these cells in exosome free medium for 48 hours and extracted the exosomes by ultracentrifugation. Nanoparticle analyzing system showed that the pellet was enriched with the typical ~100nm sized vesicles and these particles were visualized by electron microscopy. Western immunoblotting confirmed that these particles express CD63, a known exosomal biomarker. Subsequently, we subjected CML K562, ALL Jurkat and AML HL-60 to NK-92MI-Exo stained with PKH-26 and showed by flow cytometry that these cells uptake the exosomes in a dose- and time- dependent manner. As controls, we used exosomes derived from the human embryonic kidney 293 (HEK-293) cell line. LDH release assay showed a marked increase in LDH activity in NK-92MI-Exo exposed leukemia cells but not in HEK-293-Exo exposed leukemia cells across all cell lines tested. Similarly, flow cytometry of leukemia cells double stained for annexin/PI showed that the rate of apoptosis was markedly increased in NK-92MI-Exo exposed leukemia cells but not in HEK-293-Exo exposed leukemia cells. Together, these assays indicate that NK-92MI-Exo are cytotoxic to various leukemia cell lines and that this effect is specific to NK-derived exosomes. Encouraged by our preliminary results, we harvested leukemia cells from 4 patients with acute myeloid leukemia (AML), 4 patients with acute lymphoblastic leukemia (ALL), 4 patients with chronic lymphocytic leukemia (CLL) and normal B-cells from healthy volunteers and exposed them to NK-92MI-Exo. Similar to the cell line results, we found a marked cytotoxic effect to NK-92MI-Exo on these leukemia cells but not on normal B-cells from healthy individuals whereas HEK-293-Exo had only a minimal or no effect on primary leukemia cells. Clonal assay on peripheral blood sample from 2 CML patients showed that the number of colony forming unit -granulocyte, erythrocyte, megakaryocyte monocyte (CFU-GEMM) is significantly reduced following exposure to NK-92MI-Exo, suggesting that these exosomes target leukemia progenitor cells. Proteomics analysis of NK-92MI-Exo revealed that similar to NK cytotoxic granules, the exosomal cargo include granozymes known to induce apoptosis of target cells but unlike NK cytotoxic granules the exosomal cargo does not include perphorines, known to perforate target cell membrane. Taken together our data suggests that NK-derived exosomes have a potent cytotoxic effect across a wide range of leukemia cells. This effect is specific to NK-exosomes. Furthermore, NK-derived exosomes preferentially kill leukemia cells but not normal cells. We also show that these exosomes are toxic to leukemia progenitor cells. Proteomics analysis suggested that NK-cytotoxic granules and exosomes use different strategies to enter target-cells. Whether NK-derived exosomes may become a-cellular therapeutic strategy to combat leukemia remains to be determined. Figure Disclosures No relevant conflicts of interest to declare.

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C/Ebpg (CCAAT/Enhancer Binding Protein Gamma) Balances Cytotoxic and Secretory Potential of Natural Killer Cells

Blood ◽

10.1182/blood-2018-99-119389 ◽

2018 ◽

Vol 132 (Supplement 1) ◽

pp. 3721-3721

Author(s):

Izabela Aparecida Lopes ◽

Miroslava Kardosova ◽

Thiago Mantello Bianco ◽

Adriana Queiroz Arantes ◽

Cleide Araújo Silva ◽

...

Keyword(s):

Flow Cytometry ◽

Nk Cells ◽

Natural Killer ◽

Cellular Proliferation ◽

Nk Cell ◽

Conflicts Of Interest ◽

Secretory Cells ◽

Target Cells ◽

Functional Assay ◽

Cell Functions

Abstract C/EBPs (CCAAT/enhance-binding proteins) are a family of transcription factors involved in a variety of hematopoietic processes, regulating both terminal differentiation and cellular proliferation. Among these, it was previously reported that C/EBP gamma (C/EBPg) has a role in the development of Natural Killer (NK) cells. However, the mechanisms of such regulation are unknown. NK cells are lymphocytes with effector functions of cytotoxicity and production of cytokines, both dependent on a dynamic equilibrium between the expression of activating and inhibitory receptors as well as cytokine receptors. The two functions (cytotoxic and secretory) make NK cells important components of hematopoiesis, able to eliminate susceptible targets as well as recruit other cells to amplify inflammatory responses. With the aim of studying the regulation of NK cells by C/EBPg, we isolated NK cells from transgenic Cebpg knockout (KO) mice and controls to analyze their function. To characterize NK cells, we analyzed their frequency (Lineage-/CD3-/NK1.1+ cells) and the expression of the receptors NKG2D, Ly49D and NKG2A by flow cytometry of splenocytes. Both analyses showed no difference between control or Cebpg KO NK cells. Although the numbers of NK cells and their receptors were similar between Cebpg WT and KO animals, a functional assay that measured NK cell degranulation by CD107a expression after co-incubation with YAC-1 target cells showed that the expression of this marker was 5-times lower in Cebpg KO splenocytes than in controls (CT = 12.44 ± 2.50%; KO = 2.255 ± 0.67%, p=0.007), suggesting that Cebpg deficient NK cells are not fully activated after target cell recognition. In addition, a cytotoxicity assay by flow cytometry was performed using a fluorescent probe (Cell Tracker Orange) that was incorporated to YAC-1 cells upon exposure to sorted and IL-2 activated NK cells in culture. In the 10:1 NK:target cells ratio, Cebpg KO cells were significantly less cytotoxic than NK control cells (CT = 23.36 ± 8.67%; KO = 10.60 ± 1.66%, p=0.038). The other NK:target cells ratios of 5:1 and 1:1 showed the same tendency. In addition, the functional subtypes of these cells were characterized according to the expression of CD27 and CD11b, which allowed the identification of NK subpopulations as immature secretory, mature secretory, cytotoxic or tolerant. The KO animals showed higher percentages of secretory cells (CT = 10.77 ± 5.38%; KO = 12.98 ± 13.63%, p=0.0002) and a reduction of cytotoxic cells in comparison to the NK control cells (CT = 12.22 ± 11.08%; KO = 10.65 ± 3.82% p=0.013). Cytokine levels of IL-2, IL-4, IL-6, IL-10, IL-17α, TNFα and IFNγ, obtained from NK culture supernatants, were measured by flow cytometry, after IL-2 activation. Among these cytokines, the production of IFNγ by Cebpg-deficient NK cells was reduced (CT = 37.68 ± 0.51 pg/mL; KO = 22.34 ± 0.14 pg/mL, p=0.023). Together, these experiments indicate that C/EBPg regulates NK cell cytotoxicity. This may be explained, at least in part, by the reduced frequency of the mature cytotoxic NK subpopulation as compared to the secretory subtypes. Moreover, IFNγ may be an important target for the regulation of NK cell function. Finally, C/EBPg seems to be critical to mediate NK cell functions and not only for their development from the ontogenetic point of view. Disclosures No relevant conflicts of interest to declare.

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Cryopreservation impairs cytotoxicity and migration of NK cells in 3-D tissue: Implications for cancer immunotherapy

10.1101/812172 ◽

2019 ◽

Cited By ~ 1

Author(s):

Christoph Mark ◽

Tina Czerwinski ◽

Susanne Roessner ◽

Astrid Mainka ◽

Franziska Hörsch ◽

...

Keyword(s):

Clinical Trials ◽

Cell Therapy ◽

Nk Cells ◽

Natural Killer ◽

Solid Tumors ◽

Cell Function ◽

Nk Cell ◽

Target Cells ◽

Collagen Gels ◽

Nk Cell Therapy

AbstractNatural killer (NK) cells are important effector cells in the immune response to cancer. Clinical trials on adoptively transferred NK cells in patients with solid tumors, however, have thus far been unsuccessful. As NK cells need to pass stringent safety evaluation for clinical use, the cells are cryopreserved to bridge the necessary evaluation time. While a degranulation assay confirms the ability of cryopreserved NK cells to kill target cells, we find a significant decrease of cytotoxicity after cryopreservation in a chromium release assay. We complement these standard assays with measurements of NK cell motility and cytotoxicity in 3-dimensional (3-D) collagen gels that serve as a substitute for connective tissue. We find a 5.6 fold decrease of cytotoxicity after cryopreservation and establish that this is mainly caused by a 6-fold decrease in the fraction of motile NK cells. These findings may explain the persistent failure of NK cell therapy in patients with solid tumors and highlight the crucial role of a 3-D environment for testing NK cell function.SynopsisCryopreservation of natural killer (NK) cells dramatically impairs their motility and cytotoxicity in tissue. This finding may explain the persistent failure of clinical trials in which NK cell therapy is used for treating solid tumors.

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NKG2D Natural Killer Cell Receptor—A Short Description and Potential Clinical Applications

Cells ◽

10.3390/cells10061420 ◽

2021 ◽

Vol 10 (6) ◽

pp. 1420

Author(s):

Jagoda Siemaszko ◽

Aleksandra Marzec-Przyszlak ◽

Katarzyna Bogunia-Kubik

Keyword(s):

Nk Cells ◽

Natural Killer ◽

Bacterial Infections ◽

Killer Cell ◽

Cell Receptor ◽

Target Cells ◽

Effector Cells ◽

Stressed Cells ◽

The Right ◽

Nkg2d Receptor

Natural Killer (NK) cells are natural cytotoxic, effector cells of the innate immune system. They can recognize transformed or infected cells. NK cells are armed with a set of activating and inhibitory receptors which are able to bind to their ligands on target cells. The right balance between expression and activation of those receptors is fundamental for the proper functionality of NK cells. One of the best known activating receptors is NKG2D, a member of the CD94/NKG2 family. Due to a specific NKG2D binding with its eight different ligands, which are overexpressed in transformed, infected and stressed cells, NK cells are able to recognize and attack their targets. The NKG2D receptor has an enormous significance in various, autoimmune diseases, viral and bacterial infections as well as for transplantation outcomes and complications. This review focuses on the NKG2D receptor, the mechanism of its action, clinical relevance of its gene polymorphisms and a potential application in various clinical settings.

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542 Expansion of cytotoxic NK Cells from PBMCs using individualized cytokine combination

Journal for ImmunoTherapy of Cancer ◽

10.1136/jitc-2020-sitc2020.0542 ◽

2020 ◽

Vol 8 (Suppl 3) ◽

pp. A578-A578

Author(s):

Andreia Maia ◽

Joana Lerias ◽

Markus Maeurer ◽

Mireia Castillo-Martin

Keyword(s):

Flow Cytometry ◽

Nk Cells ◽

Natural Killer ◽

Peripheral Blood ◽

Blood Donors ◽

Nk Cell ◽

Tumour Cells ◽

List Type ◽

Mhc I ◽

Cytokine Combination

BackgroundAdoptive immunotherapy relies on the use of T-cells to target tumour cells, through Major Histocompatibility Complex (MHC) Class I recognition(1). However, many tumours display alterations in the MHC-I pathway, a well-described immune evasion mechanism(2). Natural Killer (NK) cells recognize transformed cells independently from the presence of MHC-I and may be a reliable therapeutic option for patients with altered tumour MHC-I expression. The source of NK cells may be autologous or allogeneic and NK cells are also clinically relevant recipients of transgenic receptors (TCRs or antibodies) targeting tumour cells. NK cells have been categorized according to their CD56 and CD16 surface expression into different subpopulations: cytotoxic (CD56+CD16+) and regulatory (CD56brightCD16-)(3). Expanding cytotoxic NK cells is challenging, since the frequency of NK cells is low in peripheral blood(4) and there is also – at this point – not an optimal expansion protocol available.The goal of this project is to determine the best cytokine combination that facilitates expansion of cytotoxic NK cells that either target tumor cells directly or serve as recipients for transgenic receptors.MethodsPeripheral Blood Mononuclear Cells (PBMCs) were extracted using Ficoll methodology from blood donors and cultured in T25 flasks with Cell Genix Medium supplemented with 10% human serum and antibiotics. NK cells were expanded supplemented with feeder cells (ratio 1:1) and different cytokine combinations (1000 U/mL of IL-2, 10 U/ml of IL-12, 180 U/mL of IL-15 and/or 1 U/mL of IL-21) during 20 days. The immunophenotype of expanded NK cells was analyzed at days 0, 5, 10, 15 and 20 by flow cytometry. The cytotoxicity of NK cells was measured by a CD107a Assay or by a Total Cytotoxicity and Apoptosis Assay at days 10 and 20. Thirteen different cytokine combinations were tested.Results4/13 cytokine combinations produced a statistically significant increase of the absolute number of NK cells with a higher percentage of cytotoxic NK cells (figure 1). However, induction of cytotoxicity was not associated with a strong NK cell expansion. The regulatory NK cells subset (CD56brightCD16-) showed the highest percentage of CD107a-expressing cells, more than the CD56+CD16+, the most cytotoxic subpopulation of NK cells.Abstract 542 Figure 1Representative percentage of NK cells in total lymphocytes (A), CD56+CD16+ subpopulation in total NK cells (B), and CD56brightCD16- subpopulation amongst total NK cells (C) at different time points (5, 10, 15 and 20 days) expanded from PBMCs* p-value < 0.05ConclusionsThis work shows that we are able to grow and efficiently expand NK cells from PBMCs with different cytokine combinations leading to clinically relevant NK cell numbers as well as cytotoxic functions. This enables to produce NK cell products for therapy and as recipients for transgenic tumor antigen-specific receptors.AcknowledgementsThe authors would like to thank the Champalimaud Foundation Biobank, the Vivarium Facility and the Flow Cytometry Platform of the Champalimaud Centre for the Unknown.Ethics ApprovalThis study was approved by the Champalimaud Foundation Ethics Committee and by the Ethics Research Committee of NOVA Medical School of NOVA University of Lisbon.ConsentWritten informed consent was obtained from the blood donors to use their samples for research purposes.ReferencesRosenberg SA, Restifo NP, Yang JC, Morgan RA, Mark E. Adoptive cell transfer: a clinical path to effective cancer immunotherapy. Nat Rev Cancer 2008;8(4):299–308.Aptsiauri N, Ruiz-Cabello F, Garrido F. The transition from HLA-I positive to HLA-I negative primary tumors: the road to escape from T-cell responses. Curr Opin Immunol 2018;51:123–32.Di Vito C, Mikulak J, Mavilio D. On the way to become a natural killer cell. Front Immunol. 2019;10(August):1–15.Zotto G Del, Antonini F, Pesce S, Moretta F, Moretta L. Comprehensive phenotyping of human PB NK Cells by Flow Cytometry. 2020;1–9.

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Immunosenescence of Natural Killer Cells, Inflammation, and Alzheimer’s Disease

International Journal of Alzheimer s Disease ◽

10.1155/2018/3128758 ◽

2018 ◽

Vol 2018 ◽

pp. 1-9 ◽

Cited By ~ 8

Author(s):

Corona Solana ◽

Raquel Tarazona ◽

Rafael Solana

Keyword(s):

Alzheimer’S Disease ◽

Alzheimer's Disease ◽

Nk Cells ◽

Natural Killer ◽

Nk Cell ◽

Neurodegenerative Disorder ◽

The Elderly ◽

Lymphoid Cells ◽

Target Cells ◽

The Brain

Alzheimer’s disease (AD) represents the most common cause of dementia in the elderly. AD is a neurodegenerative disorder characterized by progressive memory loss and cognitive decline. Although the aetiology of AD is not clear, both environmental factors and heritable predisposition may contribute to disease occurrence. In addition, inflammation and immune system alterations have been linked to AD. The prevailing hypothesis as cause of AD is the deposition in the brain of amyloid beta peptides (Aβ). Although Aβ have a role in defending the brain against infections, their accumulation promotes an inflammatory response mediated by microglia and astrocytes. The production of proinflammatory cytokines and other inflammatory mediators such as prostaglandins and complement factors favours the recruitment of peripheral immune cells further promoting neuroinflammation. Age-related inflammation and chronic infection with herpes virus such as cytomegalovirus may also contribute to inflammation in AD patients. Natural killer (NK) cells are innate lymphoid cells involved in host defence against viral infections and tumours. Once activated NK cells secrete cytokines such as IFN-γ and TNF-α and chemokines and exert cytotoxic activity against target cells. In the elderly, changes in NK cell compartment have been described which may contribute to the lower capacity of elderly individuals to respond to pathogens and tumours. Recently, the role of NK cells in the immunopathogenesis of AD is discussed. Although in AD patients the frequency of NK cells is not affected, a high NK cell response to cytokines has been described together with NK cell dysregulation of signalling pathways which is in part involved in this altered behaviour.

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Ultrastructural analysis of human natural killer cell activation

Blood ◽

10.1182/blood.v69.6.1725.bloodjournal6961725 ◽

1987 ◽

Vol 69 (6) ◽

pp. 1725-1736 ◽

Cited By ~ 1

Author(s):

D Zarcone ◽

EF Prasthofer ◽

F Malavasi ◽

V Pistoia ◽

AF LoBuglio ◽

...

Keyword(s):

Golgi Apparatus ◽

Nk Cells ◽

Natural Killer ◽

Killer Cell ◽

Interleukin 2 ◽

Ultrastructural Changes ◽

Target Cells ◽

Resting Cells ◽

Human Natural Killer Cell ◽

Dense Granules

In this study we describe characteristic ultrastructural changes of CD3- large granular lymphocytes (LGL), ie, natural killer (NK) cells, following stimulation with recombinant (r) interleukin 2 (IL 2) or r- gamma interferon (r-gamma IFN) and after interaction with K562 target cells (TC) or Sepharose-bound anti-Fc gamma receptor (FcR) monoclonal antibody (MoAb). When compared to resting cells the cytolytic activity of r-IL 2- and r-gamma IFN-stimulated cells against K562 TC was enhanced. The r-IL 2-stimulated LGL were larger and consistently displayed the shape and cytoskeletal rearrangement characteristic of activated cells. The Golgi apparatus was expanded, and the number of electron-dense granules and vesicles was increased. The ultrastructural changes in r-gamma IFN-stimulated LGL were markedly different from those observed following r-IL 2 activation. Cells did not exhibit changes in size, shape, cytoskeletal organization, or in the structure of the Golgi apparatus. However, r-gamma IFN-stimulated cells exhibited distinctive changes in the structure and content of electron-dense granules with deaggregation of the matrix and parallel tubular arrays (PTAs). Within organelles apparently derived from the electron-dense granules, vesicular and tubular structures were noted that may be the morphological equivalent of cytotoxic factors produced by cytolytic effector cells. These ultrastructural observations indicate that r-IL 2 and r-gamma IFN enhance the lytic ability of NK cells by acting on distinct cell machineries. The cytolytic ability was decreased when LGL were pretreated with K562 TC or immobilized anti-FcR antibody. In both experimental conditions cells displayed ultrastructural features indicating activation as well as loss of cytoplasmic granules and other Golgi-derived organelles. Stimulation of r-gamma IFN- or r-IL 2- activated LGL with K562 TC or Sepharose-bound anti-FcR antibody decreased their cytolytic ability, with cells depleted of granules at the ultrastructural level. Intracytoplasmic fusion of granules and a massive release of the granule content were found in r-IL 2-stimulated cells, reminiscent of the mechanism of basophil degranulation. These observations suggest that multiple activation signals involving distinct surface membrane molecules induce release of cytolytic factors by both resting and activated NK cells.

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Natural killer-mediated lysis of normal and malignant target cells, and its regulation by monocytes.

Journal of Experimental Medicine ◽

10.1084/jem.162.2.472 ◽

1985 ◽

Vol 162 (2) ◽

pp. 472-486 ◽

Cited By ~ 27

Author(s):

K Oshimi ◽

Y Oshimi ◽

M Satake ◽

H Mizoguchi

Keyword(s):

Nk Cells ◽

Natural Killer ◽

B Lymphocytes ◽

Leukemia Cells ◽

Target Cells ◽

Large Granular Lymphocytes ◽

Percoll Density Gradient ◽

Granular Lymphocytes ◽

Density Gradient Sedimentation

After depletion of monocytes, natural killer (NK) cells were partially purified from peripheral blood by Percoll density gradient sedimentation. The NK cells were then cultured for 1 d and assayed for their cytotoxicity against various types of normal and malignant target cells. All types of target cells tested were found to be susceptible to NK cells. The susceptible targets were autologous T and B lymphocytes, mitogen-induced T and B blasts, monocytes, large granular lymphocytes, autologous or allogeneic lymphoma and leukemia cells isolated from patients, and cultured cell lines, including those resistant to interferon-activated lymphocytes. Such a broad spectrum of cytotoxicity was demonstrated in 1 d of culture, and freshly prepared NK cells were not cytotoxic, or, if anything, were less cytotoxic. Monocytes and their supernatants, added throughout the course of culture, markedly inhibited the development of their cytotoxicity. These results may suggest that, although NK cells having ability to lyse autologous normal and malignant target cells are present in vivo, their lytic activity is regulated by coexisting monocytes.

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Recognition of virus-infected cells by natural killer cell clones is controlled by polymorphic target cell elements.

Journal of Experimental Medicine ◽

10.1084/jem.178.3.961 ◽

1993 ◽

Vol 178 (3) ◽

pp. 961-969 ◽

Cited By ~ 57

Author(s):

M S Malnati ◽

P Lusso ◽

E Ciccone ◽

A Moretta ◽

L Moretta ◽

...

Keyword(s):

T Cells ◽

Nk Cells ◽

Natural Killer ◽

Target Cell ◽

Nk Cell ◽

Class I ◽

Target Cells ◽

Cell Recognition ◽

Infected Cells ◽

Nk Cell Recognition

Natural killer (NK) cells provide a first line of defense against viral infections. The mechanisms by which NK cells recognize and eliminate infected cells are still largely unknown. To test whether target cell elements contribute to NK cell recognition of virus-infected cells, human NK cells were cloned from two unrelated donors and assayed for their ability to kill normal autologous or allogeneic cells before and after infection by human herpesvirus 6 (HHV-6), a T-lymphotropic herpesvirus. Of 132 NK clones isolated from donor 1, all displayed strong cytolytic activity against the NK-sensitive cell line K562, none killed uninfected autologous T cells, and 65 (49%) killed autologous T cells infected with HHV-6. A panel of representative NK clones from donors 1 and 2 was tested on targets obtained from four donors. A wide heterogeneity was observed in the specificity of lysis of infected target cells among the NK clones. Some clones killed none, some killed only one, and others killed more than one of the different HHV-6-infected target cells. Killing of infected targets was not due to complete absence of class I molecules because class I surface levels were only partially affected by HHV-6 infection. Thus, target cell recognition is not controlled by the effector NK cell alone, but also by polymorphic elements on the target cell that restrict NK cell recognition. Furthermore, NK clones from different donors display a variable range of specificities in their recognition of infected target cells.

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