The thymus is the primary organ able to support T cell ontogeny, abrogated in FOXN1−/− human athymia. Although evidence indicates that in animal models T lymphocytes may differentiate at extrathymic sites, whether this process is really thymus-independent has still to be clarified. In an athymic FOXN1−/− fetus, in which we previously described a total blockage of CD4+ and partial blockage of CD8+ cell development, we investigated whether intestine could play a role as extrathymic site of T-lymphopoiesis in humans. We document the presence of few extrathymically developed T lymphocytes and the presence in the intestine of CD3+ and CD8+, but not of CD4+ cells, a few of them exhibiting a CD45RA+ naïve phenotype. The expression of CD3εεpTα, RAG1 and RAG2 transcripts in the intestine and TCR gene rearrangement was also documented, thus indicating that in humans the partial T cell ontogeny occurring at extrathymic sites is a thymus- and FOXN1-independent process.
Eric Vivier and colleagues discuss recent publications demonstrating that T reg cell restriction of IL-2 availability regulates NK cell function.
In light of their role in the immune response against tumors and viruses, natural killer (NK) cells represent a promising target for immunotherapy. Before this target is reached, the various mechanisms that control NK cell activity must first be identified and understood. In the past decades, studies have identified two critical processes that prevent spontaneous NK cell–mediated autoimmune activation while maximizing the efficiency of these cells during an immune response. First is the education process, whereby NK cells adapt to their environment by sensing ligands for inhibitory and activating receptors. Second is the priming phase of NK cell activation, which arms NK cells with appropriate cytotoxic molecules during inflammation. New studies now indicate that NK cell proliferation, accumulation, and activation are also under the control of regulatory T cells that restrict availability of IL-2 released by activated CD4+ T cells. Together with other recent studies, these data highlight the importance of the adaptive immune system in the regulation of NK cell activity.
Atherosclerosis is a chronic inflammatory disease mediated by immune cells. Th22 cells are CD4+ T cells that secret IL-22 but not IL-17 or IFN-γ and are implicated in the pathogenesis of inflammatory disease. The roles of Th22 cells in the pathophysiologic procedures of acute coronary syndrome (ACS) remain unclear. The purpose of this study is to investigate the profile of Th22, Th17 and Th17/Th1 cells in ACS patients, including unstable angina (UA) and acute myocardial infarction (AMI) patients.
Design and Methods
In this study, 26 AMI patients, 16 UA patients, 16 stable angina (SA) patients and 16 healthy controls were included. The frequencies of Th22, Th17 and Th17/Th1 cells in AMI, UA, SA patients and healthy controls were examined by flow cytometry. Plasma levels of IL-22, IL-17 and IFN-γ were measured by enzyme-linked immunosorbent assay (ELISA).
Th22, Th17 and Th17/Th1 cells were significantly increased in AMI and UA patients compared with SA patients and healthy controls. Moreover, plasma IL-22 level was significantly elevated in AMI and UA patients. In addition, Th22 cells correlated positively with IL-22 as well as Th17 cells in AMI and UA patients.
Our findings showed increased frequencies of both Th22 and Th17 cells in ACS patients, which suggest that Th22 and Th17 cells may play a potential role in plaque destabilization and the development of ACS.
The role of the immune response to oncolytic Herpes Simplex viral (oHSV) therapy for glioblastoma is controversial. Within hours of oHSV infection of human or syngeneic glioblastoma in mice, activated natural killer (NK) cells are recruited to the site of infection. This response significantly diminished the efficacy of glioblastoma virotherapy. oHSV-activated NK cells coordinated macrophage and microglia activation within tumors. In vitro, human NK cells preferentially lysed oHSV-infected human glioblastoma cell lines. This enhanced killing depended on NK cell natural cytotoxicity receptors (NCR) NKp30 and NKp46, whose ligands were up-regulated in oHSV-infected glioblastoma cells. HSV titers and oHSV efficacy were increased in Ncr1−/− mice and in a Ncr1−/− NK cell adoptive transfer model of glioma, respectively. These in vitro and in vivo (mouse) results demonstrate that glioblastoma virotherapy is partly limited by an antiviral NK cell response involving specific NCRs, uncovering novel potential targets to enhance cancer virotherapy.
Herpes simplex virus; gene therapy; oncolytic virus; brain tumor; microglia; macrophages
NK cells are large granular lymphocytes that form a critical component of the innate immune system, whose functions include the killing of cells expressing stress-induced molecules. It is increasingly accepted that despite being considered prototypical effector cells, NK cells require signals to reach their full cytotoxic potential. We previously showed that IL-15 is capable of arming CD8 effector T cells to kill independently of their TCR via NKG2D in a cPLA2-dependent process. As NK cells also express NKG2D, we wanted to investigate whether this pathway functioned in an analogous manner and if resting NK cells could be primed to the effector phase by IL-15. Furthermore, to establish relevance to human disease we studied a possible role for this pathway in the pathogenesis of psoriatic arthritis, since there are aspects of this disease that suggest a potential effector role for the innate immune system. We found that PsA patients had upregulated IL-15 and MIC in their affected synovial tissues, and that this unique inflammatory environment enabled NK cell activation and killing via NKG2D and cPLA2. Moreover, we were able to reproduce the phenotype of joint NK cells from blood NK cells by incubating them with IL-15. Altogether, these findings suggest a destructive role for NK cells when activated by environmental stress signals during the pathogenesis of PsA and demonstrate that IL-15 is capable of priming resting NK cells in tissues to the effector phase.
Natural killer (NK) cells have important functions in immunity. NK recognition in mammals can be mediated through killer cell immunoglobulin-like receptors (KIR) and/or killer cell lectin-like Ly49 receptors. Genes encoding highly variable NK cell receptors (NKR) represent rapidly evolving genomic regions. No single conservative model of NKR genes was observed in mammals. Single-copy low polymorphic NKR genes present in one mammalian species may expand into highly polymorphic multigene families in other species. In contrast to other non-rodent mammals, multiple Ly49-like genes appear to exist in the horse, while no functional KIR genes were observed in this species. In this study, Ly49 and KIR were sought and their evolution was characterized in the entire family Equidae. Genomic sequences retrieved showed the presence of at least five highly conserved polymorphic Ly49 genes in horses, asses and zebras. These findings confirmed that the expansion of Ly49 occurred in the entire family. Several KIR-like sequences were also identified in the genome of Equids. Besides a previously identified non-functional KIR-Immunoglobulin-like transcript fusion gene (KIR-ILTA) and two putative pseudogenes, a KIR3DL-like sequence was analyzed. In contrast to previous observations made in the horse, the KIR3DL sequence, genomic organization and mRNA expression suggest that all Equids might produce a functional KIR receptor protein molecule with a single non-mutated immune tyrosine-based inhibition motif (ITIM) domain. No evidence for positive selection in the KIR3DL gene was found. Phylogenetic analysis including rhinoceros and tapir genomic DNA and deduced amino acid KIR-related sequences showed differences between families and even between species within the order Perissodactyla. The results suggest that the order Perissodactyla and its family Equidae with expanded Ly49 genes and with a potentially functional KIR gene may represent an interesting model for evolutionary biology of NKR genes.
Vγ9Vδ2 cells are cytotoxic T cells that are able to recognize epithelial ovarian carcinoma (EOC) cells. Therefore, Vγ9Vδ2 cell-based adoptive transfer is an attractive therapy for EOC. However, the inefficient ex vivo expansion after specific stimulation of Vγ9Vδ2 cells from some patients and the relationships between Vγ9Vδ2 cells and clinical course of EOC are issues that remain to be clarified. Herein, peripheral blood mononuclear cells (PBMCs) from 60 EOC patients were stimulated with bromohydrin pyrophosphate (BrHPP) or zoledronate, which are specific agonists of Vγ9Vδ2 cells. The compounds differed in their efficacies to induce ex vivo Vγ9Vδ2 PBMC expansion, but 16/60 samples remained inefficiently expanded with both stimuli. Interestingly, the Vγ9Vδ2 cells in these low-responding PBMCs displayed before expansion (ex vivo PBMCs) an altered production of the pro-inflammatory cytokines IFN-γ and TNF-α, a decreased naive fraction and a reduced frequency. No evidence of an involvement of CD4+CD25+Foxp3+ regulatory cells was observed. Importantly, our data also demonstrate that a Vγ9Vδ2 cell frequency of 0.35% or less in EOC PBMCs could be used to predict low responses to both BrHPP and zoledronate. Moreover, our data highlight that such a deficiency is not correlated with advanced EOC stages but is associated with more refractory states to platinum-based chemotherapy and is an independent predictor of shorter disease-free survival after treatment. These results are the first to suggest a potential contribution of Vγ9Vδ2 cells to the anti-tumor effects of chemotherapeutic agents and they strengthen interest in strategies that might increase Vγ9Vδ2 cells in cancer patients.
Although hepatic fibrosis typically follows chronic inflammation, fibrosis will often regress after cessation of liver injury. Here we examined whether liver dendritic cells (DC) play a role in liver fibrosis regression using carbon tetrachloride (CCl4) to induce liver injury. We examined DC dynamics during fibrosis regression and their capacity to modulate liver fibrosis regression upon cessation of injury. We show that conditional DC depletion soon after discontinuation of the liver insult leads to delayed fibrosis regression and reduced clearance of activated hepatic stellate cells, the key fibrogenic cell in liver. Conversely, DC expansion induced either by Flt3L (Fms-like tyrosine kinase-3 ligand) or adoptive transfer of purified DC accelerates liver fibrosis regression. DC modulation of fibrosis was partially dependent on MMP-9, as MMP-9 inhibition abolished Flt3L-mediated effect and the ability of transferred DC to accelerate fibrosis regression. In contrast, transfer of DC from MMP-9 deficient mice failed to improve fibrosis regression.
Altogether, these results suggest that DC increase fibrosis regression, and that the effect is correlated with their production of MMP-9. These results also suggest that Flt3L treatment during fibrosis resolution merits evaluation to accelerate regression of advanced liver fibrosis.
Flt3L; NK cells; MMP-9; collagen; hepatic stellate cells
Cells of the immune system have evolved various molecular mechanisms to sense their environment and react to alterations of self. NK cells are lymphocytes with effector and regulatory functions, which are remarkably adaptable to changes in self. In a study published in this issue of the JCI, Tarek and colleagues report the clinical benefits of manipulating NK cell adaptation to self in an innovative mAb-based therapy against neuroblastoma (NB). This novel therapeutic strategy should stimulate further research on NK cell therapies.
Natural killer cells, as a major source of interferon-γ, contribute to the amplification of the inflammatory response as well as to mortality during severe sepsis in animal models.
We studied the phenotype and functions of circulating NK cells in critically-ill septic patients.
Blood samples were taken <48 hours after admission from 42 ICU patients with severe sepsis (n = 15) or septic shock (n = 14) (Sepsis group), non-septic SIRS (n = 13) (SIRS group), as well as 21 healthy controls. The immuno-phenotype and functions of NK cells were studied by flow cytometry.
The absolute number of peripheral blood CD3–CD56+ NK cells was similarly reduced in all groups of ICU patients, but with a normal percentage of NK cells. When NK cell cytotoxicity was evaluated with degranulation assays (CD107 expression), no difference was observed between Sepsis patients and healthy controls. Under antibody-dependent cell cytotoxicity (ADCC) conditions, SIRS patients exhibited increased CD107 surface expression on NK cells (62.9[61.3–70]%) compared to healthy controls (43.5[32.1–53.1]%) or Sepsis patients (49.2[37.3–62.9]%) (p = 0.002). Compared to healthy (10.2[6.3–13.1]%), reduced interferon-γ production by NK cells (K562 stimulation) was observed in Sepsis group (6.2[2.2–9.9]%, p<0.01), and especially in patients with septic shock. Conversely, SIRS patients exhibited increased interferon-γ production (42.9[30.1–54.7]%) compared to Sepsis patients (18.4[11.7–35.7]%, p<0.01) or healthy controls (26.8[19.3–44.9]%, p = 0.09) in ADCC condition.
Extensive monitoring of the NK-cell phenotype and function in critically-ill septic patients revealed early decreased NK-cell function with impaired interferon-γ production. These results may aid future NK-based immuno-interventions.
Neutropenia in mice and humans results in the generation of NK cells with an immature and hyporesponsive phenotype.
Natural killer (NK) cells are bone marrow (BM)–derived granular lymphocytes involved in immune defense against microbial infections and tumors. In an N-ethyl N-nitrosourea (ENU) mutagenesis strategy, we identified a mouse mutant with impaired NK cell reactivity both in vitro and in vivo. Dissection of this phenotype showed that mature neutrophils were required both in the BM and in the periphery for proper NK cell development. In mice lacking neutrophils, NK cells displayed hyperproliferation and poor survival and were blocked at an immature stage associated with hyporesponsiveness. The role of neutrophils as key regulators of NK cell functions was confirmed in patients with severe congenital neutropenia and autoimmune neutropenia. In addition to their direct antimicrobial activity, mature neutrophils are thus endowed with immunoregulatory functions that are conserved across species. These findings reveal novel types of cooperation between cells of the innate immune system and prompt examination of NK cell functional deficiency in patients suffering from neutropenia-associated diseases.
The risk of influenza infection depends on biological characteristics, individual or collective behaviors and the environmental context. The Cohorts for Pandemic Influenza (CoPanFlu) France study was set up in 2009 after the identification of the novel swine-origin A/H1N1 pandemic influenza virus. This cohort of 601 households (1450 subjects) representative for the general population aims at using an integrative approach to study the risk and characteristics of influenza infection as a complex combination of data collected from questionnaires regarding sociodemographic, medical, behavioral characteristics of subjects and indoor environment, using biological samples or environmental databases.
Households were included between December 2009 and July 2010. The design of this study relies on systematic follow-up visits between influenza seasons and additional visits during influenza seasons, when an influenza-like illness is detected in a household via an active surveillance system. During systematic visits, a nurse collects individual and environmental data on questionnaires and obtains blood samples from all members of the household. When an influenza-like-illness is detected, a nurse visits the household three times during the 12 following days, and collects data on questionnaires regarding exposure and symptoms, and biological samples (including nasal swabs) from all subjects in the household. The end of the follow-up period is expected in fall 2012.
The large amount of data collected throughout the follow-up will permit a multidisciplinary study of influenza infections. Additional data is being collected and analyzed in this ongoing cohort. The longitudinal analysis of these households will permit integrative analyses of complex phenomena such as individual, collective and environmental risk factors of infection, routes of transmission, or determinants of the immune response to infection or vaccination.
Influenza a virus H1N1 subtype; Cohort study; Risk factors; France
Natural killer (NK) cells are circulating cytotoxic lymphocytes that exert potent and nonredundant antiviral activity and antitumoral activity in the mouse; however, their function in host defense in humans remains unclear. Here, we investigated 6 related patients with autosomal recessive growth retardation, adrenal insufficiency, and a selective NK cell deficiency characterized by a lack of the CD56dim NK subset. Using linkage analysis and fine mapping, we identified the disease-causing gene, MCM4, which encodes a component of the MCM2-7 helicase complex required for DNA replication. A splice-site mutation in the patients produced a frameshift, but the mutation was hypomorphic due to the creation of two new translation initiation methionine codons downstream of the premature termination codon. The patients’ fibroblasts exhibited genomic instability, which was rescued by expression of WT MCM4. These data indicate that the patients’ growth retardation and adrenal insufficiency likely reflect the ubiquitous but heterogeneous impact of the MCM4 mutation in various tissues. In addition, the specific loss of the NK CD56dim subset in patients was associated with a lower rate of NK CD56bright cell proliferation, and the maturation of NK CD56bright cells toward an NK CD56dim phenotype was tightly dependent on MCM4-dependent cell division. Thus, partial MCM4 deficiency results in a genetic syndrome of growth retardation with adrenal insufficiency and selective NK deficiency.
Hemophagocytic lymphohistiocytosis (HLH) is a life-threatening condition due to the association of an infectious agent with lymphocyte cytotoxicity defects, either of congenital genetic origin in children or presumably acquired in adults. In HLH patients, an excess of lymphocyte or macrophage cytokines, such as IFN-γ and TNFα is present in serum. In animal models of the disease, IFN-γ and TNF-α have been shown to play a central pathogenic role. In humans, unusually high concentrations of IL-18, an inducer of IFN-γ, and TNF-α have been reported, and are associated with an imbalance between IL-18 and its natural inhibitor IL-18 binding protein (IL-18BP) resulting in an excess of free IL-18. Here we studied whether IL-18BP could reduce disease severity in an animal model of HLH. Mouse cytomegalovirus infection in perforin-1 knock-out mice induced a lethal condition similar to human HLH characterized by cytopenia with marked inflammatory lesions in the liver and spleen as well as the presence of hemophagocytosis in bone marrow. IL-18BP treatment decreased hemophagocytosis and reversed liver as well as spleen damage. IL-18BP treatment also reduced both IFN-γ and TNF-α production by CD8+ T and NK cells, as well as Fas ligand expression on NK cell surface. These data suggest that IL-18BP is beneficial in an animal model of HLH and in combination with anti-infectious therapy may be a promising strategy to treat HLH patients.
IL-18; IL-18 binding protein; natural killer cells; hemophagocytic lymphohistiocytosis; macrophage activation syndrome
Understanding Natural Killer (NK) cell anatomical distribution is key to dissect the role of these unconventional lymphocytes in physiological and disease conditions. In mouse, NK cells have been detected in various lymphoid and non-lymphoid organs, while in humans the current knowledge of NK cell distribution at steady state is mainly restricted to lymphoid tissues. The translation to humans of findings obtained in mice is facilitated by the identification of NK cell markers conserved between these two species. The Natural Cytotoxicity Receptor (NCR) NKp46 is a marker of the NK cell lineage evolutionary conserved in mammals. In mice, NKp46 is also present on rare T cell subsets and on a subset of gut Innate Lymphoid Cells (ILCs) expressing the retinoic acid receptor-related orphan receptor γt (RORγt) transcription factor. Here, we documented the distribution and the phenotype of human NKp46+ cells in lymphoid and non-lymphoid tissues isolated from healthy donors. Human NKp46+ cells were found in splenic red pulp, in lymph nodes, in lungs, and gut lamina propria, thus mirroring mouse NKp46+ cell distribution. We also identified a novel cell subset of CD56dimNKp46low cells that includes RORγt+ ILCs with a lineage−CD94−CD117brightCD127bright phenotype. The use of NKp46 thus contributes to establish the basis for analyzing quantitative and qualitative changes of NK cell and ILC subsets in human diseases.
NKp46; human NK cells; tissue distribution; phenotype; expression profiling
Severe sepsis and septic shock are still deadly conditions urging to develop novel therapies. A better understanding of the complex modifications of the immune system of septic patients is needed for the development of innovative immunointerventions. Natural killer (NK) cells are characterized as CD3−NKp46+CD56+ cells that can be cytotoxic and/or produce high amounts of cytokines such as IFN-γ. NK cells are also engaged in crosstalks with other immune cells, such as dendritic cells, macrophages, and neutrophils. During the early stage of septic shock, NK cells may play a key role in the promotion of the systemic inflammation, as suggested in mice models. Alternatively, at a later stage, NK cells-acquired dysfunction could favor nosocomial infections and mortality. Standardized biological tools defining patients' NK cell status during the different stages of sepsis are mandatory to guide potential immuno-interventions. Herein, we review the potential role of NK cells during severe sepsis and septic shock.
Natural killer (NK) cells were originally defined as effector lymphocytes of innate immunity endowed with constitutive cytolytic functions. More recently, a more nuanced view of NK cells has emerged. NK cells are now recognized to express a repertoire of activating and inhibitory receptors that is calibrated to ensure self-tolerance while allowing efficacy against assaults such as viral infection and tumor development. Moreover, NK cells do not react in an invariant manner but rather adapt to their environment. Finally, recent studies have unveiled that NK cells can also mount a form of antigen-specific immunologic memory. NK cells thus exert sophisticated biological functions that are attributes of both innate and adaptive immunity, blurring the functional borders between these two arms of the immune response.
Allotransplantation of natural killer (NK) cells has been shown to be a key factor in the control and cure of at least some hematologic diseases, such as acute myeloid leukemia or pediatric acute lymphocytic leukemia. These results support the idea that stimulation of NK cells could be an important therapeutic tool in many diseases, and several such approaches are now in clinical trials, sometimes with conflicting results. In parallel, recent advances in the understanding of the molecular mechanisms governing NK-cell maturation and activity show that NK-cell effector functions are controlled by complex mechanisms that must be taken into account for optimal design of therapeutic protocols. We review here innovative protocols based on allotransplantation, use of NK-cell therapies, and use of newly available drug candidates targeting NK-cell receptors, in the light of fundamental new data on NK-cell biology.
Inhibitory receptors that engage self-MHC class I molecules enable NK cells to detect disease-associated loss of MHC class I on surrounding cells. Previous studies showed that some NK cells lack all receptors for self-MHC class I, yet fail to exhibit autoimmunity because they are generally hyporesponsive to stimulation. We asked whether NK cells exist in only two states, responsive and hyporesponsive, corresponding to cells that express or fail to express inhibitory receptors for self-MHC class I. The alternative model is that NK cells vary continuously in their responsiveness, based on variations in the number of different inhibitory and stimulatory receptors they express, which is known to vary. Here we show in the murine system that NK cell responsiveness increases quantitatively with each added self MHC-specific inhibitory receptor. Genetic analysis demonstrated that interactions of each of the receptors with self-MHC class I were necessary to observe augmented responsiveness. These findings suggest that NK cell responsiveness is comparable to a rheostat: it is tuned to an optimal set point depending on the inhibitory and stimulatory interactions encountered in the normal environment, so as to ensure self-tolerance and yet optimize sensitivity to changes in normal cells.
Cancer development is often associated with the lack of specific and efficient recognition of tumor cells by the immune system. Natural killer (NK) cells are lymphocytes of the innate immune system that participate in the elimination of tumors. We report the identification of a tumor cell surface molecule that binds NKp30, a human receptor which triggers antitumor NK cell cytotoxicity and cytokine secretion. This previously unannotated gene belongs to the B7 family and, hence, was designated B7-H6. B7-H6 triggers NKp30-mediated activation of human NK cells. B7-H6 was not detected in normal human tissues but was expressed on human tumor cells, emphasizing that the expression of stress-induced self-molecules associated with cell transformation serves as a mode of cell recognition in innate immunity.
Fc receptor-like 6 (FCRL6), the most recently characterized member of the FCRL family, is a cell surface glycoprotein with tyrosine-based regulatory potential. An extensive survey of human hematopoietic tissues disclosed that FCRL6 expression by NK and T cell subpopulations increases as a function of differentiation and is remarkably restricted to mature lymphocytes with cytotoxic capability. In particular, FCRL6 distinguishes perforin-expressing CD56dim NK cells, Vδ1+ and Vδ2+ γδ T cells, effector and effector memory CD8+ T cells, and rare cytotoxic CD4+ T cells in adult tissues. Analysis of this receptor in B cell chronic lymphocytic leukemia (CLL) was also performed. FCRL6 was found to mark significantly expanded populations of cytotoxic CD8+ T, CD4+ T, and NK cells in patients with CLL. Despite sequence homology with the known Fc receptors for IgG and IgE, FCRL6 did not bind immunoglobulin. Although FCRL6 can be tyrosine-phosphorylated, its antibody-mediated ligation was unable to influence cellular activation. Collectively these results demonstrate that FCRL6 is a distinct indicator of cytotoxic effector lymphocytes that is upregulated in diseases characterized by chronic immune stimulation.
Human NK cells; Human cytotoxic T cells; Fc Receptor-like; Chronic lymphocytic leukemia
Lymphoid tissue-inducer cells are hematopoietic cells essential for the organogenesis of several lymphoid structures during both fetal and adult life, whereas natural killer cells are key effector lymphocytes of the innate immune system. A series of recent reports has identified RORγt+NKp46+ interleukin-22-producing cells in gut and tonsils that share features with both lymphoid tissue-inducer cells and natural killer cells and that may be involved in mucosal immunity and homeostasis.
Multinucleated giant cells, formed by fusion of macrophages, are a hallmark of granulomatous inflammation. With a genetic approach, we show that signaling through the adaptor protein DAP12 (DNAX activating protein of 12 kD), its associated receptor triggering receptor expressed by myeloid cells 2 (TREM-2), and the downstream protein tyrosine kinase Syk is required for the cytokine-induced formation of giant cells and that overexpression of DAP12 potentiates macrophage fusion. We also present evidence that DAP12 is a general macrophage fusion regulator and is involved in modulating the expression of several macrophage-associated genes, including those encoding known mediators of macrophage fusion, such as DC-STAMP and Cadherin 1. Thus, DAP12 is involved in programming of macrophages through the regulation of gene and protein expression to induce a fusion-competent state.