Peroxisome proliferator-activated receptor-γ and its ligands attenuate biologic functions of human natural killer cells

Abstract Interferon-γ (IFN-γ) production and cytolytic activity are 2 major biologic functions of natural killer (NK) cells that are important for innate immunity. We demonstrate here that these functions are compromised in human NK cells treated with peroxisome proliferator-activated-γ (PPAR-γ) ligands via both PPAR-γ-dependent and -independent pathways due to variation in PPAR-γ expression. In PPAR-γ-null NK cells, 15-deoxy-Δ12,14 prostaglandin J2 (15d-PGJ2), a natural PPAR-γ ligand, reduces IFN-γ production that can be reversed by MG132 and/or chloroquine, and it inhibits cytolytic activity of NK cells through reduction of both conjugate formation and CD69 expression. In PPARγ-positive NK cells, PPAR-γ activation by 15d-PGJ2 and ciglitazone (a synthetic ligand) leads to reduction in both mRNA and protein levels of IFN-γ. Overexpression of PPAR-γ in PPAR-γ-null NK cells reduces IFN-γ gene expression. However, PPAR-γ expression and activation has no effect on NK cell cytolytic activity. In addition, 15d-PGJ2 but not ciglitazone reduces expression of CD69 in human NK cells, whereas CD44 expression is not affected. These results reveal novel pathways regulating NK cell biologic functions and provide a basis for the design of therapeutic agents that can regulate the function of NK cells within the innate immune response. (Blood. 2004;104:3276-3284)

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In Vitro and In Vivo Evidence That the PP2A Inhibitor SET Regulates IFN-γ Production in Monokine-Stimulated Natural Killer Cells.

Blood ◽

10.1182/blood.v108.11.928.928 ◽

2006 ◽

Vol 108 (11) ◽

pp. 928-928 ◽

Cited By ~ 1

Author(s):

Rossana Trotta ◽

Jessica Dal Col ◽

Jeffrey Allard ◽

Paolo Neviani ◽

Ramasamy Santhanam ◽

...

Keyword(s):

Nk Cells ◽

Natural Killer ◽

Interferon Γ ◽

Oligonucleotide Array ◽

Pp2a Activity ◽

Protein Levels ◽

Ifn Γ ◽

Protein Phosphatase Type

Abstract Monokines (i.e. IL-12, IL-18 and IL-15) induce natural killer (NK) cells to produce interferon-γ (IFN-γ), which is critical for monocyte clearance of infectious pathogens and tumor surveillance. To identify new regulators of IFN-γ production we performed oligonucleotide array analysis of unstimulated and IL-12- and IL-18-stimulated NK92 cells. Among the subset of mRNAs differentially regulated in monokine-stimulated cells, we found SET, a potent inhibitor of the protein phosphatase type 2A (PP2A). SET mRNA and/or protein levels were upregulated in IL-12/IL-18- and IL-12/IL-15-stimulated primary human NK cells. Interestingly, the SET protein is also selectively increased in the resting CD56bright NK subset, which is a potent producer of IFN-γ relative to the CD56dim NK subset. To determine whether SET positively regulates IFN-γ production by inhibiting PP2A activity, we employed RNAi and interfered with SET expression in NK92 cells. SET downregulation inhibited IFN-γ secretion by IL-12/IL-18, IL-12/IL-15- or IL-15/IL-18-stimulated NK92 cells. By contrast, ectopic SET expression increased IFN-γ production in monokine-stimulated NK92 and primary human NK cells. Because downregulation of SET augmented PP2A activity in NK92 cells, we sought to investigate whether pharmacologic activation of PP2A inhibits the ability of NK cells to produce IFN-γ. Indeed, suppression of IFN-γ expression and secretion was also observed upon treatment of NK92 and primary NK cells with 1,9-dideoxy-forskolin, a known inducer of PP2A activity. Accordingly, NK cells from mice treated with 1.9-dideoxy-forskolin produced less IFN-γ in response to in vivo monokine stimulation than did NK cells from vehicle-treated mice. Mechanistically, activation of PP2A by SET knock-down or 1,9-dideoxy-forskolin treatment leads to inhibition of ERK1/2, p65RelA and STAT5 activity in monokine-stimulated NK cells. Because these signaling molecules are important for IFN-γ production by monokine-stimulated NK cells, our results strongly suggest that monokine induction of SET expression in NK cells is essential for limiting PP2A activity that, otherwise, would negatively impact the ability of NK cells to produce and release optimal levels of IFN-γ.

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Human Dendritic Cells Activate Resting Natural Killer (NK) Cells and Are Recognized via the NKp30 Receptor by Activated NK Cells

Journal of Experimental Medicine ◽

10.1084/jem.20011149 ◽

2002 ◽

Vol 195 (3) ◽

pp. 343-351 ◽

Cited By ~ 706

Author(s):

Guido Ferlazzo ◽

Ming L. Tsang ◽

Lorenzo Moretta ◽

Giovanni Melioli ◽

Ralph M. Steinman ◽

...

Keyword(s):

Dendritic Cells ◽

Nk Cells ◽

Natural Killer ◽

Nk Cell ◽

Cytolytic Activity ◽

Innate And Adaptive Immunity ◽

Leukocyte Antigen ◽

Histocompatibility Complex ◽

Ifn Γ ◽

Human Dendritic Cells

During the innate response to many inflammatory and infectious stimuli, dendritic cells (DCs) undergo a differentiation process termed maturation. Mature DCs activate antigen-specific naive T cells. Here we show that both immature and mature DCs activate resting human natural killer (NK) cells. Within 1 wk the NK cells increase two– to fourfold in numbers, start secreting interferon (IFN)-γ, and acquire cytolytic activity against the classical NK target LCL721.221. The DC-activated NK cells then kill immature DCs efficiently, even though the latter express substantial levels of major histocompatibility complex (MHC) class I. Similar results are seen with interleukin (IL)-2–activated NK cell lines and clones, i.e., these NK cells kill and secrete IFN-γ in response to immature DCs. Mature DCs are protected from activated NK lysis, but lysis takes place if the NK inhibitory signal is blocked by a human histocompatibility leukocyte antigen (HLA)-A,B,C–specific antibody. The NK activating signal mainly involves the NKp30 natural cytotoxicity receptor, and not the NKp46 or NKp44 receptor. However, both immature and mature DCs seem to use a NKp30 independent mechanism to act as potent stimulators for resting NK cells. We suggest that DCs are able to control directly the expansion of NK cells and that the lysis of immature DCs can regulate the afferent limb of innate and adaptive immunity.

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Hlx homeobox transcription factor negatively regulates interferon-γ production in monokine-activated natural killer cells

Blood ◽

10.1182/blood-2006-10-050096 ◽

2006 ◽

Vol 109 (6) ◽

pp. 2481-2487 ◽

Cited By ~ 16

Author(s):

Brian Becknell ◽

Tiffany L. Hughes ◽

Aharon G. Freud ◽

Bradley W. Blaser ◽

Jianhua Yu ◽

...

Keyword(s):

Transcription Factor ◽

Nk Cells ◽

Natural Killer ◽

Molecular Mechanisms ◽

Interferon Γ ◽

Tumor Surveillance ◽

Protein Levels ◽

Homeobox Transcription Factor ◽

Ifn Γ

Abstract Natural killer (NK) cells contribute to host immunity, including tumor surveillance, through the production of interferon gamma (IFN-γ). Although there is some knowledge about molecular mechanisms that induce IFN-γ in NK cells, considerably less is known about the mechanisms that reduce its expression. Here, we investigate the role of the Hlx transcription factor in IFN-γ production by NK cells. Hlx expression is induced in monokine-activated NK cells, but with delayed kinetics compared to IFN-γ. Ectopic Hlx expression decreases IFN-γ synthesis in primary human NK cells and IFN-γ promoter activity in an NK-like cell line. Hlx protein levels inversely correlate with those of STAT4, a requisite factor for optimal IFN-γ transcription. Mechanistically, we provide evidence indicating that Hlx overexpression accelerates dephosphorylation and proteasome-dependent degradation of the active Y693-phosphorylated form of STAT4. Thus, Hlx expression in activated NK cells temporally controls and limits the monokine-induced production of IFN-γ, in part through the targeted depletion of STAT4.

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Ozone exposed epithelial cells modify cocultured natural killer cells

AJP Lung Cellular and Molecular Physiology ◽

10.1152/ajplung.00256.2012 ◽

2013 ◽

Vol 304 (5) ◽

pp. L332-L341 ◽

Cited By ~ 16

Author(s):

Loretta Müller ◽

Luisa E. Brighton ◽

Ilona Jaspers

Keyword(s):

Epithelial Cells ◽

Nk Cells ◽

Natural Killer ◽

Nk Cell ◽

Recent Observation ◽

Cell Activity ◽

Interferon Γ ◽

Direct Cell ◽

Ifn Γ ◽

Cell Cell

Ozone (O3) causes significant adverse health effects worldwide. Nasal epithelial cells (NECs) are among the first sites within the respiratory system to be exposed to inhaled air pollutants. They recruit, activate, and interact with immune cells via soluble mediators and direct cell-cell contacts. Based on our recent observation demonstrating the presence of natural killer (NK) cells in nasal lavages, the goal of this study was to establish a coculture model of NECs and NK cells and examine how exposure to O3 modifies this interaction. Flow cytometry analysis was used to assess immunophenotypes of NK cells cocultured with either air- or O3-exposed NECs. Our data show that coculturing NK cells with O3-exposed NECs decreased intracellular interferon-γ (IFN-γ), enhanced, albeit not statistically significant, IL-4, and increased CD16 expression on NK cells compared with air controls. Additionally, the cytotoxicity potential of NK cells was reduced after coculturing with O3-exposed NECs. To determine whether soluble mediators released by O3-exposed NECs caused this shift, apical and basolateral supernatants of air- and O3-exposed NECs were used to stimulate NK cells. While the conditioned media of O3-exposed NECs alone did not reduce intracellular IFN-γ, O3 enhanced the expression of NK cell ligands ULBP3 and MICA/B on NECs. Blocking ULBP3 and MICA/B reversed the effects of O3-exposed NECs on IFN-γ production in NK cells. Taken together, these data showed that interactions between NECs and NK cells in the context of O3 exposure changes NK cell activity via direct cell-cell interactions and is dependent on ULBP3/MICA/B expressed on NECs.

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The PP2A inhibitor SET regulates natural killer cell IFN-γ production

Journal of Experimental Medicine ◽

10.1084/jem.20070419 ◽

2007 ◽

Vol 204 (10) ◽

pp. 2397-2405 ◽

Cited By ~ 37

Author(s):

Rossana Trotta ◽

David Ciarlariello ◽

Jessica Dal Col ◽

Jeffrey Allard ◽

Paolo Neviani ◽

...

Keyword(s):

Gene Expression ◽

Nk Cells ◽

Natural Killer ◽

Nk Cell ◽

Killer Cell ◽

Immune Surveillance ◽

Critical Factor ◽

Interferon Γ ◽

Pp2a Activity ◽

Ifn Γ

Monokines (i.e., interleukin [IL]-12, -18, and -15) induce natural killer (NK) cells to produce interferon-γ (IFN-γ), which is a critical factor for immune surveillance of cancer and monocyte clearance of infection. We show that SET, which is a potent inhibitor of protein phosphatase type 2A (PP2A) activity, is highly expressed in human CD56bright NK cells, which produce more IFN-γ than CD56dim NK cells. SET was up-regulated upon monokine stimulation of primary human NK cells. Furthermore, ectopic overexpression of SET significantly enhanced IFN-γ gene expression in monokine-stimulated NK cells. In contrast, RNAi-mediated suppression of SET expression renders NK cells inefficient in producing high levels of IFN-γ in response to monokine costimulation. Mechanistically, suppression of PP2A activity by SET is important for IFN-γ gene expression in NK cells. In fact, treatment of primary human NK cells with the PP2A activator 1,9-dideoxy-forskolin, as well as administration of the drug to C57BL/6 mice, significantly reduced NK-dependent IFN-γ production in response to monokine treatment. Further, SET knockdown or pharmacologic activation of PP2A diminished extracellular signal-regulated kinase 1/2, p65RelA, signal transducer and activator of transduction 4 (STAT4), and STAT5 activity in monokine-stimulated NK cells, potentially contributing to the reduction in IFN-γ gene expression. Thus, SET expression is essential for suppressing PP2A phosphatase activity that would otherwise limit NK cell antitumoral and/or antiinflammatory functions by impairing NK cell production of IFN-γ.

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Human natural killer cells: a unique innate immunoregulatory role for the CD56bright subset

Blood ◽

10.1182/blood.v97.10.3146 ◽

2001 ◽

Vol 97 (10) ◽

pp. 3146-3151 ◽

Cited By ~ 852

Author(s):

Megan A. Cooper ◽

Todd A. Fehniger ◽

Sarah C. Turner ◽

Kenneth S. Chen ◽

Bobak A. Ghaheri ◽

...

Keyword(s):

Immune Response ◽

Nk Cells ◽

Natural Killer ◽

Innate Immune Response ◽

Nk Cell ◽

Primary Source ◽

Interferon Γ ◽

Innate Immune ◽

Immunoregulatory Cytokines ◽

Human Natural Killer Cells

Abstract During the innate immune response to infection, monocyte-derived cytokines (monokines), stimulate natural killer (NK) cells to produce immunoregulatory cytokines that are important to the host's early defense. Human NK cell subsets can be distinguished by CD56 surface density expression (ie, CD56bright and CD56dim). In this report, it is shown that CD56bright NK cells produce significantly greater levels of interferon-γ, tumor necrosis factor-β, granulocyte macrophage–colony-stimulating factor, IL-10, and IL-13 protein in response to monokine stimulation than do CD56dim NK cells, which produce negligible amounts of these cytokines. Further, qualitative differences in CD56bright NK-derived cytokines are shown to be dependent on the specific monokines present. For example, the monokine IL-15 appears to be required for type 2 cytokine production by CD56bright NK cells. It is proposed that human CD56bright NK cells have a unique functional role in the innate immune response as the primary source of NK cell–derived immunoregulatory cytokines, regulated in part by differential monokine production.

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Human NK cells prime inflammatory DC precursors to induce Tc17 differentiation

Blood Advances ◽

10.1182/bloodadvances.2020002084 ◽

2020 ◽

Vol 4 (16) ◽

pp. 3990-4006

Author(s):

Maria A. Clavijo-Salomon ◽

Rosalba Salcedo ◽

Soumen Roy ◽

Rodrigo X. das Neves ◽

Amiran Dzutsev ◽

...

Keyword(s):

Nk Cells ◽

Nk Cell ◽

Interferon Γ ◽

T Cell Subsets ◽

Cell Mediated Immunity ◽

Limited Information ◽

Interleukin 17A ◽

Healthy Donors ◽

Ifn Γ ◽

Inflammatory Dendritic Cells

Abstract Adaptive immune responses are acknowledged to evolve from innate immunity. However, limited information exists regarding whether encounters between innate cells direct the generation of specialized T-cell subsets. We aim to understand how natural killer (NK) cells modulate cell-mediated immunity in humans. We found that human CD14+CD16− monocytes that differentiate into inflammatory dendritic cells (DCs) are shaped at the early stages of differentiation by cell-to-cell interactions with NK cells. Although a fraction of monocytes is eliminated by NK-cell–mediated cytotoxicity, the polarization of interferon-γ (IFN-γ) at the NKp30-stabilized synapses triggers a stable IFN-γ signature in surviving monocytes that persists after their differentiation into DCs. Notably, NK-cell–instructed DCs drive the priming of type 17 CD8+ T cells (Tc17) with the capacity to produce IFN-γ and interleukin-17A. Compared with healthy donors, this cellular network is impaired in patients with classical NK-cell deficiency driven by mutations in the GATA2 gene. Our findings reveal a previously unrecognized connection by which Tc17-mediated immunity might be regulated by NK-cell–mediated tuning of antigen-presenting cells.

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Aberrant anti-viral response of natural killer cells in severe asthma

European Respiratory Journal ◽

10.1183/13993003.02422-2018 ◽

2020 ◽

Vol 55 (5) ◽

pp. 1802422

Author(s):

Justine Devulder ◽

Cécile Chenivesse ◽

Valérie Ledroit ◽

Stéphanie Fry ◽

Pierre-Emmanuel Lobert ◽

...

Keyword(s):

Nk Cells ◽

Natural Killer ◽

Severe Asthma ◽

Cell Activation ◽

Mononuclear Cells ◽

Nk Cell ◽

Peripheral Blood Mononuclear ◽

Healthy Donors ◽

Asthma Patients ◽

Ifn Γ

Rhinovirus infections are the main cause of asthma exacerbations. As natural killer (NK) cells are important actors of the antiviral innate response, we aimed at evaluating the functions of NK cells from severe asthma patients in response to rhinovirus-like molecules or rhinoviruses.Peripheral blood mononuclear cells from patients with severe asthma and healthy donors were stimulated with pathogen-like molecules or with the rhinoviruses (RV)-A9 and RV-2. NK cell activation, degranulation and interferon (IFN)-γ expression were analysed.NK cells from severe asthma patients were less cytotoxic than those from healthy donors in response to toll-like receptor (TLR)3, TLR7/8 or RV-A9 but not in response to RV-2 stimulation. Furthermore, when cultured with interleukin (IL)-12+IL-15, cytokines which are produced during viral infections, NK cells from patients with severe asthma were less cytotoxic and expressed less IFN-γ than NK cells from healthy donors. NK cells from severe asthmatics exhibited an exhausted phenotype, with an increased expression of the checkpoint molecule Tim-3.Together, our findings indicate that the activation of NK cells from patients with severe asthma may be insufficient during some but not all respiratory infections. The exhausted phenotype may participate in NK cell impairment and aggravation of viral-induced asthma exacerbation in these patients.

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Rapid development of exhaustion and down-regulation of eomesodermin limit the antitumor activity of adoptively transferred murine natural killer cells

Blood ◽

10.1182/blood-2012-03-415364 ◽

2012 ◽

Vol 119 (24) ◽

pp. 5758-5768 ◽

Cited By ~ 86

Author(s):

Saar Gill ◽

Adrianne E. Vasey ◽

Alysha De Souza ◽

Jeanette Baker ◽

Aaron T. Smith ◽

...

Keyword(s):

Nk Cells ◽

Natural Killer ◽

Nk Cell ◽

Rapid Development ◽

Receptor Expression ◽

Down Regulation ◽

First Response ◽

Control Tumor Growth ◽

Control Tumor ◽

Ifn Γ

Abstract Natural killer (NK) cells are potent anti-viral and antitumor “first responders” endowed with natural cytotoxicity and cytokine production capabilities. To date, attempts to translate these promising biologic functions through the adoptive transfer of NK cells for the treatment of cancer have been of limited benefit. Here we trace the fate of adoptively transferred murine NK cells and make the surprising observation that NK cells traffic to tumor sites yet fail to control tumor growth or improve survival. This dysfunction is related to a rapid down-regulation of activating receptor expression and loss of important effector functions. Loss of interferon (IFN)γ production occurs early after transfer, whereas loss of cytotoxicity progresses with homeostatic proliferation and tumor exposure. The dysfunctional phenotype is accompanied by down-regulation of the transcription factors Eomesodermin and T-bet, and can be partially reversed by the forced overexpression of Eomesodermin. These results provide the first demonstration of NK-cell exhaustion and suggest that the NK-cell first-response capability is intrinsically limited. Further, novel approaches may be required to circumvent the described dysfunctional phenotype.

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