Rhesus rotavirus VP4 sequence-specific activation of mononuclear cells is associated with cholangiopathy in murine biliary atresia

Biliary atresia (BA), a neonatal obstructive cholangiopathy, remains the most common indication for pediatric liver transplantation in the United States. In the murine model of BA, Rhesus rotavirus (RRV) VP4 surface protein determines biliary duct tropism. In this study, we investigated how VP4 governs induction of murine BA. Newborn mice were injected with 16 strains of rotavirus and observed for clinical symptoms of BA and mortality. Cholangiograms were performed to confirm bile duct obstruction. Livers and bile ducts were harvested 7 days postinfection for virus titers and histology. Flow cytometry assessed mononuclear cell activation in harvested cell populations from the liver. Cytotoxic NK cell activity was determined by the ability of NK cells to kill noninfected cholangiocytes. Of the 16 strains investigated, the 6 with the highest homology to the RRV VP4 (>87%) were capable of infecting bile ducts in vivo. Although the strain Ro1845 replicated to a titer similar to RRV in vivo, it caused no symptoms or mortality. A Ro1845 reassortant containing the RRV VP4 induced all BA symptoms, with a mortality rate of 89%. Flow cytometry revealed that NK cell activation was significantly increased in the disease-inducing strains and these NK cells demonstrated a significantly higher percentage of cytotoxicity against noninfected cholangiocytes. Rotavirus strains with >87% homology to RRV's VP4 were capable of infecting murine bile ducts in vivo. Development of murine BA was mediated by RRV VP4-specific activation of mononuclear cells, independent of viral titers.

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Interferon-γ-Mediated Natural Killer Cell Activation by an AqueousPanax ginsengExtract

Evidence-based Complementary and Alternative Medicine ◽

10.1155/2015/603198 ◽

2015 ◽

Vol 2015 ◽

pp. 1-11 ◽

Cited By ~ 6

Author(s):

Kazuyoshi Takeda ◽

Ko Okumura

Keyword(s):

Cytotoxic Activity ◽

Nk Cells ◽

Natural Killer ◽

Aqueous Extract ◽

Cell Activation ◽

Mononuclear Cells ◽

Nk Cell ◽

Killer Cell ◽

Cell Activity

Panax ginsengextracts are used in traditional herbal medicines, particularly in eastern Asia, but their effect on natural killer (NK) cell activity is not completely understood. This study aimed to examine the effects ofP. ginsengextracts on the cytotoxic activity of NK cells. We orally administeredP. ginsengextracts or ginsenosides to wild-type (WT) C57BL/6 (B6) and BALB/c mice and to B6 mice deficient in either recombination activating gene 2 (RAG-2) or interferon-γ(IFN-γ). We then tested the cytotoxic activity of NK cells (of spleen and liver mononuclear cells) against NK-sensitive YAC-1 cells. Oral administration ofP. ginsengaqueous extract augmented the cytotoxicity of NK cells in WT B6 and BALB/c mice and in RAG-2-deficient B6 mice, but not in IFN-γ-deficient B6 mice. This effect was only observed with the aqueous extract ofP. ginseng. Interestingly, the ginsenosides Rb1 and Rg1 did not augment NK cell cytotoxicity. These results demonstrated that the aqueousP. ginsengextract augmented NK cell activationin vivovia an IFN-γ-dependent pathway.

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Optimizing the Procedure to Manufacture Clinical-Grade NK Cells for Adoptive Immunotherapy

Cancers ◽

10.3390/cancers13030577 ◽

2021 ◽

Vol 13 (3) ◽

pp. 577

Author(s):

Adrián Fernández ◽

Alfonso Navarro-Zapata ◽

Adela Escudero ◽

Nerea Matamala ◽

Beatriz Ruz-Caracuel ◽

...

Keyword(s):

Nk Cells ◽

Cell Activation ◽

Mononuclear Cells ◽

Nk Cell ◽

Fold Increase ◽

Clinical Grade ◽

Transcriptome Profile ◽

Expansion Process ◽

Peripheral Blood Mononuclear ◽

Activation Status

Natural killer (NK) cells represent promising tools for cancer immunotherapy. We report the optimization of an NK cell activation–expansion process and its validation on clinical-scale. Methods: RPMI-1640, stem cell growth medium (SCGM), NK MACS and TexMACS were used as culture mediums. Activated and expanded NK cells (NKAE) were obtained by coculturing total peripheral blood mononuclear cells (PBMC) or CD45RA+ cells with irradiated K562mbIL15-41BBL or K562mbIL21-41BBL. Fold increase, NK cell purity, activation status, cytotoxicity and transcriptome profile were analyzed. Clinical-grade NKAE cells were manufactured in CliniMACS Prodigy. Results: NK MACS and TexMACs achieved the highest NK cell purity and lowest T cell contamination. Obtaining NKAE cells from CD45RA+ cells was feasible although PBMC yielded higher total cell numbers and NK cell purity than CD45RA+ cells. The highest fold expansion and NK purity were achieved by using PBMC and K562mbIL21-41BBL cells. However, no differences in activation and cytotoxicity were found when using either NK cell source or activating cell line. Transcriptome profile showed to be different between basal NK cells and NKAE cells expanded with K562mbIL21-41BBL or K562mbIL15-41BBL. Clinical-grade manufactured NKAE cells complied with the specifications from the Spanish Regulatory Agency. Conclusions: GMP-grade NK cells for clinical use can be obtained by using different starting cells and aAPC.

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Umbilical Mesenchymal Stem Cell-Derived Extracellular Vesicle Conditioning Has an Immunosuppressive Effect on NK Cells

Stem Cells and Regenerative Medicine - Biomedical and Health Research ◽

10.3233/bhr210028 ◽

2021 ◽

Author(s):

G. Dostert ◽

V. Jouan-Hureaux ◽

H. Louis ◽

É. Velot

Keyword(s):

Flow Cytometry ◽

Stem Cell ◽

Mesenchymal Stem Cell ◽

Nk Cells ◽

Cell Activation ◽

Nk Cell ◽

Cell Communication ◽

K562 Cells ◽

Cell Cytotoxicity ◽

Nk Cell Cytotoxicity

Background: In peripheral blood, human natural killer (NK) cells are immunological cells that nearly don’t express the ectonucleotidase CD73 on their plasma membrane. When exposed to mesenchymal stem cells (MSCs), NK cells are able to acquire CD73. MSCs are known to be CD73-positive (CD73+) and also to modulate the immune system, e.g. through adenosynergic pathway by ectonucleosidases, such as CD73. Extracellular vesicles (EVs) are involved in cell-to-cell communication. Mesenchymal stem cell-derived extracellular vesicles (MSC-EVs) have emerged as paracrine mediators that are part of MSC immunomodulatory effects including immunosuppressive properties and immune privilege. Objective: The aim of our work was to study if CD73 could be acquired by NK cells through cell-to-cell communication with MSC-EVs as cell culture additives. We also hypothesised that MSC-EVs would act as tolerance inducers to attenuate NK cell cytotoxicity. Methods: Cell isolation was made from human umbilical cords for MSCs and from human peripheral blood for NK cells. MSC-EVs were isolated by ultracentrifugation and filtration, then characterized by nanoparticle tracking assay and flow cytometry (CD9, 63, 81 and 73). MSC-EV interaction with NK cells was monitored by PKH67 staining. NK cell activation was followed by measuring the expression of CD73 and NK-activating receptor natural-killer group 2, member D (NKG2D) by flow cytometry. The cytotoxicity of NK cells or EV-conditioned NK cells was evaluated after co-culture with K562 cells. Results: We showed that MSC-EVs are nanoparticles able to express CD73 and interact with NK cells. MSC-EV conditioned NK cells seem to increase CD73 and decrease NKG2D through an EV-mediated mechanism. MSC-EVs have an immunosuppressive effect on NK cells by preventing NK cell activation and NK cell cytotoxicity towards K562 cells. Conclusions: Our results demonstrate that MSC-EVs could influence NK cell behaviour and act as immunosuppressant cell-based products.

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P03.24 Calreticulin exposure on malignant blasts correlates with improved NK cell-mediated cytotoxicity in AML patients

Journal for ImmunoTherapy of Cancer ◽

10.1136/jitc-2020-itoc7.62 ◽

2020 ◽

Vol 8 (Suppl 2) ◽

pp. A32.1-A32

Author(s):

I Truxova ◽

L Kasikova ◽

C Salek ◽

M Hensler ◽

D Lysak ◽

...

Keyword(s):

Nk Cells ◽

Cell Activation ◽

Nk Cell ◽

Type I ◽

Danger Signals ◽

Hla Dr ◽

Patient Prognosis ◽

Molecular Patterns ◽

Damage Associated Molecular Patterns

In some settings, cancer cells responding to treatment undergo an immunogenic form of cell death that is associated with the abundant emission of danger signals in the form of damage-associated molecular patterns. Accumulating preclinical and clinical evidence indicates that danger signals play a crucial role in the (re-)activation of antitumor immune responses in vivo, thus having a major impact on patient prognosis. We have previously demonstrated that the presence of calreticulin on the surface of malignant blasts is a positive prognostic biomarker for patients with acute myeloid leukemia (AML). Calreticulin exposure not only correlated with enhanced T-cell-dependent antitumor immunity in this setting but also affected the number of circulating natural killer (NK) cells upon restoration of normal hematopoiesis. Here, we report that calreticulin exposure on malignant blasts is associated with enhanced NK cell cytotoxic and secretory functions, both in AML patients and in vivo in mice. The ability of calreticulin to stimulate NK-cells relies on CD11c+CD14high cells that, upon exposure to CRT, express higher levels of IL-15Rα, maturation markers (CD86 and HLA- DR) and CCR7. CRT exposure on malignant blasts also correlates with the upregulation of genes coding for type I interferon. This suggests that CD11c+CD14high cells have increased capacity to migrate to secondary lymphoid organs, where can efficiently deliver stimulatory signals (IL-15Rα/IL- 15) to NK cells. These findings delineate a multipronged, clinically relevant mechanism whereby surface-exposed calreticulin favors NK-cell activation in AML patients.Disclosure InformationI. Truxova: None. L. Kasikova: None. C. Salek: None. M. Hensler: None. D. Lysak: None. P. Holicek: None. P. Bilkova: None. M. Holubova: None. X. Chen: None. R. Mikyskova: None. M. Reinis: None. M. Kovar: None. B. Tomalova: None. J.P. Kline: None. L. Galluzzi: None. R. Spisek: None. J. Fucikova: None.

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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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Natural-killer cells and dendritic cells: “l'union fait la force”

Blood ◽

10.1182/blood-2005-03-1154 ◽

2005 ◽

Vol 106 (7) ◽

pp. 2252-2258 ◽

Cited By ~ 386

Author(s):

Thierry Walzer ◽

Marc Dalod ◽

Scott H. Robbins ◽

Laurence Zitvogel ◽

Eric Vivier

Keyword(s):

Dendritic Cells ◽

Nk Cells ◽

Natural Killer ◽

Cell Activation ◽

Nk Cell ◽

Interleukin 12 ◽

Cell Contact ◽

Ifn Γ

AbstractSeveral recent publications have focused on the newly described interactions between natural-killer (NK) cells and dendritic cells (DCs). Activated NK cells induce DC maturation either directly or in synergy with suboptimal levels of microbial signals. Immature DCs appear susceptible to autologous NK-cell-mediated cytolysis while mature DCs are protected. NK-cell-induced DC activation is dependent on both tumor necrosis factor-α (TNF-α)/interferon-γ (IFN-γ) secretion and a cell-cell contact involving NKp30. In vitro, interleukin-12 (IL-12)/IL-18, IL-15, and IFN-α/β production by activated DCs enhance, in turn, NK-cell IFN-γ production, proliferation, and cytotoxic potential, respectively. In vivo, NK-cell/DC interactions may occur in lymphoid organs as well as in nonlymphoid tissues, and their consequences are multiple. By inducing DC activation, NK-cell activation induced by tumor cells can indirectly promote antitumoral T-cell responses. Reciprocally, DCs activated through Toll-like receptors (TLRs) induce potent NK-cell activation in antiviral responses. Thus, DCs and NK cells are equipped with complementary sets of receptors that allow the recognition of various pathogenic agents, emphasizing the role of NK-cell/DC crosstalk in the coordination of innate and adaptive immune responses.

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Immunostimulatory Properties of the Human Ortholog of the GMCSF/IL2 Fusion Protein for Cell Based Therapy.

Blood ◽

10.1182/blood.v110.11.4894.4894 ◽

2007 ◽

Vol 110 (11) ◽

pp. 4894-4894

Author(s):

Claudia Penafuerte Graduate ◽

Jacques Galipeau

Keyword(s):

Fusion Protein ◽

Nk Cells ◽

Cell Expansion ◽

Cell Activation ◽

Nk Cell ◽

Ex Vivo ◽

Potential Candidate ◽

Activation Markers ◽

Cell Based Therapy

Abstract NK cells constitute a potential candidate for cancer cell therapy because they express a diverse array of inhibitory and activating receptors, which recognize and kill infected or tumor cells without prior immune sensitization. However, autologous NK cell mediated adoptive immunotherapy is restricted due to insufficient cytolytic activity of NK cells from patient with aggressive malignancies. In contrast, the infusion of alloreactive NK cells has shown more successful outcomes in the treatment of cancer, but this approach also presents difficulties such as the high doses of cytokines required to induce NK cell expansion ex vivo, which may also sensitize NK cells to apoptosis. Therefore, a critical issue for NK cell based therapy is the use of appropriate growth factors or cytokines that promote NK cell expansion and activation. We have previously shown that a murine GM-CSF/IL-2 fusion protein (aka GIFT2) displays novel antitumor properties in vivo compared to both cytokines in combination regarding tumor site recruitment of macrophages and significant functional NK cell infiltration [Stagg et al., Cancer Research (December 2004)]. In the present work, we found that human GIFT2 will lead to a substantial two fold proliferation of human blood-derived NK cells which is significantly (p<0.05) superior to either IL2 or GMCSF single cytokine treatment or both cytokines combined at equimolar concentration. In addition, we observed that GIFT2 leads to robust expression of NK-cell activation markers CD69 and CD107a. In conclusion, the human GIFT2 fusokine is a novel and potent tool for ex vivo expansion of activated NK cells which may be of use in cell-based immunotherapy of cancer.

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The JAK1/JAK2 Inhibitor Ruxolitinib Substantially Affects NK Cell Biology

Blood ◽

10.1182/blood.v122.21.16.16 ◽

2013 ◽

Vol 122 (21) ◽

pp. 16-16 ◽

Cited By ~ 5

Author(s):

Kathrin Schönberg ◽

Janna Rudolph ◽

Isabelle Cornez ◽

Peter Brossart ◽

Dominik Wolf

Keyword(s):

Flow Cytometry ◽

Cell Proliferation ◽

Nk Cells ◽

Cell Activation ◽

Nk Cell ◽

Granzyme B ◽

Receptor Activation ◽

Jak2 Inhibitor ◽

Signaling Events ◽

Ifn Γ

Abstract Introduction We recently demonstrated that ruxolitinib (INCB018424), the first approved JAK1/JAK2 inhibitor for treatment of myelofibrosis (MF), exerts potent anti-inflammatory activity. This may at least in part explain higher infection rates observed in ruxolitinib-treated patients. NK cells are critical for cancer-immune surveillance and cytokine-mediated signals are central for proper NK cell activation. We here aimed to characterize in detail the effects of JAK1/2 inhibition on human NK cells. Methods Highly purified CD56+ NK cells were isolated from human peripheral buffy coats by magnetic bead isolation and subsequently exposed to increasing concentrations of ruxolitinib (0.1-10 µM). Cytokine (1000U/ml IL-2, 25ng/ml IL-15)-induced NK cell proliferation was analyzed by CFSE dilution. Phenotypic and functional NK cell activation markers (NKp46, NKG2D, Granzyme B, CD16, and CD69) were analyzed by flow cytometry (including CD107a expression for degranulation). NK cell function was tested by flow-cytometry-based killing assays and quantification of IFN-γ production upon stimulation with either MHC class I-deficient K562 target cells or cytokines (IL-12, IL-18). In addition, phenotypic and functional analyses were also tested during NK receptor activation via plate-bound activating NKp46 antibodies. Signaling events were analyzed by Western Blot analysis to detect phosphorylation of JAK1 and JAK2 as well as by applying phospho-flow technology to evaluate ruxolitinib-mediated changes of cytokine-dependent signalling cascades (pS6, pSTAT1, pSTAT3, pSTAT5, pERK, pAKT, pP38, and pZAP70). Results Our results demonstrate provide first evidence that ruxolitinib profoundly affects cytokine-induced NK cell activation. This includes a significant and dose-dependent reduction of NK cell proliferation, reduced induction of activation-associated surface markers (including NKp46, NKG2D, Granzyme B, CD16, CD69) as well as impaired killing activity against the classical NK target cell line K562. In addition, all main functional activities of NK cells are down-regulated as shown by reduced cytotoxic capacity, impaired degranulation and IFN-γ production. After wash-out, the inhibitory effects of ruxolitinib on NK cells are fully reversible, as shown by proper re-activation by cytokines. In contrast to cytokine-mediated NK cell activation, stimulation via the NK-specific receptor NKp46 are not affected by ruxolitinib. Of note, ruxolitinib does not affect NK cell viability. On a molecular level, phospho-flow analyses revealed that cytokine associated signaling events, such as phosphorylation of STAT5 and S6 were dose-dependently reduced by ruxolitinib in primary human NK cells. Conclusions Ruxolitinib strongly inhibits NK cell activation leading to impaired proliferation and functional activity. Experiments verifying these effects in patients are currently ongoing and will be presented at the meeting. Our findings may have important clinical implications, when considering the application of ruxolitinib as GvHD therapy, because NK cells are critically involved in the GvL effect after allogeneic stem cell transplantation. Disclosures: Wolf: Novartis: Honoraria, Research Funding.

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The IL-15 Super-Agonist ALT-803 Promotes Superior Activation and Cytotoxicity of Ex Vivo Expanded NK Cells Against AML

Blood ◽

10.1182/blood.v126.23.3090.3090 ◽

2015 ◽

Vol 126 (23) ◽

pp. 3090-3090 ◽

Cited By ~ 1

Author(s):

Folashade Otegbeye ◽

Nathan Mackowski ◽

Evelyn Ojo ◽

Marcos De Lima ◽

David N. Wald

Keyword(s):

Bone Marrow ◽

Flow Cytometry ◽

Nk Cells ◽

Myeloid Leukemia ◽

Nk Cell ◽

Ex Vivo ◽

Leukemia Cells ◽

Activating Receptor

Abstract Introduction: A crucial component of the innate immune response system, natural killer (NK) cells are uniquely competent to mediate anti-myeloid leukemia responses. NKG2D is an activating receptor on the surface of NK cells that engages stress ligands MICA and MICB, typically upregulated on myeloid leukemia cells. Adoptive transfer of NK cells is a promising treatment strategy for AML. Strategies to optimize the anti-leukemia effect of NK cell adoptive transfer are an area of active research. These include attempts to enhance NK cell activity and to maintain the activation status and proliferation of the NK cells in vivo. Traditionally, IL-2 has been used to maintain the in vivo proliferation of adoptively transferred NK cells, but it leads to unwanted proliferation of regulatory T cells and suboptimal NK cell proliferation. IL-15 may be superior to IL-2, without the effects on T regulatory cells. The IL-15 superagonist, ALT-803 exhibits >25 fold enhancement in biological activity as compared to IL-15. ALT-803 is a fusion protein of an IL-15 mutant and the IL-15Rα/Fc complex that has recently entered clinical trials as a direct immunomodulatory agent in cancer clinical trials We hypothesized ALT-803 would augment the activity and/or proliferation of adoptively transferred NK cells in vitro and in a mouse model system.. Methods: Human NK cells were isolated from healthy donor peripheral blood and were expanded over a 21-day period in co-culture with irradiated K562 cells genetically modified to express membrane-bound IL-21. (Somanchi et al. 2011 JoVE 48. doi: 10.3791/2540) The NK cells were expanded with IL-2 (50mU/mL) and/or ALT-803 (200ng/mL). On Day 21, NK cells were examined for cytotoxicity against AML cells as well as by flow cytometry for expression of known activating receptors. An NSG murine xenograft model of human AML was developed to test the in vivo function of NK cells expanded above. Briefly, NSG mice (n=5 per group) were non-lethally irradiated and each injected IV with 5 x106 OCI-AML3 leukemic cells. Two days later, each mouse received weekly NK cell infusions for 2 weeks. Mice that received NK cells expanded with IL2 got cytokine support with IL-2 (75kU IP three times a week). Mice infused with ALT-803 expanded cells (alone or in combination with IL2) received ALT-803 (0.2mg/kg IV weekly). One control group received OCI cells but were infused weekly only with 2% FBS vehicle, no NK cells. Leukemic burden in each mouse was assessed by flow cytometry of bone marrow aspirates on day 28 following start of NK cell infusions). This time point was chosen as the control mice appeared moribund. Results: ALT-803 did not have any differential effect on the proliferation of the NK cells ex vivo as compared to IL-2. However, the presence of ALT-803 either alone or in combination with IL-2 resulted in a significant increase (30% increase, p<0.0001) in the cytotoxic activity of the NK cells against leukemia cells as compared with IL-2 alone in vitro (figure 1). In addition, the percentages of NK cells that express the activating receptor NKG2D as well as CD16 were significantly higher (p<0.001 for both) after ALT-803 exposure (figure 1). Finally, in the murine xenograft AML model, ALT-803 expanded NK cells, which were also supported in vivo with ALT-803, resulted in an 8-fold reduction in disease burden in the bone marrow (p<0.0001). Importantly the efficacy of NK cells in the ALT-803 injected mice was significantly higher (3-fold, p= 0.0447) than IL-2 treated mice (figure 2). Discussion: Our results suggest that the presence of ALT-803 during ex-vivo expansion of NK cells results in increased activation and cytotoxicity against AML cells. In addition our results using a murine model of human AML show that the use of ALT-803 in combination with adoptively transferred NK cells provides a significant anti-leukemic benefit as compared to IL-2. Future studies to test larger panels of leukemia cells as well as other cancer cell lines are currently in progress. It is hoped that this work will lead to an improvement in the efficacy of adoptively transferred NK cells for AML patients due to an improvement in survival and activity of the NK cells. Disclosures Wald: Invenio Therapeutics: Equity Ownership.

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Continuous engagement of a self-specific activation receptor induces NK cell tolerance

Journal of Experimental Medicine ◽

10.1084/jem.20072446 ◽

2008 ◽

Vol 205 (8) ◽

pp. 1829-1841 ◽

Cited By ~ 119

Author(s):

Sandeep K. Tripathy ◽

Peter A. Keyel ◽

Liping Yang ◽

Jeanette T. Pingel ◽

Tammy P. Cheng ◽

...

Keyword(s):

Nk Cells ◽

Cell Activation ◽

Nk Cell ◽

Murine Cytomegalovirus ◽

Cell Tolerance ◽

Major Histocompatability Complex ◽

Inhibitory Receptors ◽

Mcmv Infection ◽

Functional Defects

Natural killer (NK) cell tolerance mechanisms are incompletely understood. One possibility is that they possess self-specific activation receptors that result in hyporesponsiveness unless modulated by self–major histocompatability complex (MHC)–specific inhibitory receptors. As putative self-specific activation receptors have not been well characterized, we studied a transgenic C57BL/6 mouse that ubiquitously expresses m157 (m157-Tg), which is the murine cytomegalovirus (MCMV)–encoded ligand for the Ly49H NK cell activation receptor. The transgenic mice were more susceptible to MCMV infection and were unable to reject m157-Tg bone marrow, suggesting defects in Ly49H+ NK cells. There was a reversible hyporesponsiveness of Ly49H+ NK cells that extended to Ly49H-independent stimuli. Continuous Ly49H–m157 interaction was necessary for the functional defects. Interestingly, functional defects occurred when mature wild-type NK cells were adoptively transferred to m157-Tg mice, suggesting that mature NK cells may acquire hyporesponsiveness. Importantly, NK cell tolerance caused by Ly49H–m157 interaction was similar in NK cells regardless of expression of Ly49C, an inhibitory receptor specific for a self-MHC allele in C57BL/6 mice. Thus, engagement of self-specific activation receptors in vivo induces an NK cell tolerance effect that is not affected by self-MHC–specific inhibitory receptors.

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