Shared and distinct transcriptional programs underlie the hybrid nature of iNKT cells.

Invariant natural killer T cells (iNKT cells) are innate-like T lymphocytes that act as critical regulators of the immune response. To better characterize this population, we profiled gene expression in iNKT cells during ontogeny and in peripheral subsets as part of the Immunological Genome Project. High-resolution comparative transcriptional analyses defined developmental and subset-specific programs of gene expression by iNKT cells. In addition, we found that iNKT cells shared an extensive transcriptional program with NK cells, similar in magnitude to that shared with major histocompatibility complex (MHC)-restricted T cells. Notably, the program shared by NK cells and iNKT cells also operated constitutively in γδ T cells and in adaptive T cells after activation. Together our findings highlight a core effector program regulated distinctly in innate and adaptive lymphocytes.

The transcriptional landscape of αß T cell differentiation.

The differentiation of αßT cells from thymic precursors is a complex process essential for adaptive immunity. Here we exploited the breadth of expression data sets from the Immunological Genome Project to analyze how the differentiation of thymic precursors gives rise to mature T cell transcriptomes. We found that early T cell commitment was driven by unexpectedly gradual changes. In contrast, transit through the CD4(+)CD8(+) stage involved a global shutdown of housekeeping genes that is rare among cells of the immune system and correlated tightly with expression of the transcription factor c-Myc. Selection driven by major histocompatibility complex (MHC) molecules promoted a large-scale transcriptional reactivation. We identified distinct signatures that marked cells destined for positive selection versus apoptotic deletion. Differences in the expression of unexpectedly few genes accompanied commitment to the CD4(+) or CD8(+) lineage, a similarity that carried through to peripheral T cells and their activation, demonstrated by mass cytometry phosphoproteomics. The transcripts newly identified as encoding candidate mediators of key transitions help define the 'known unknowns' of thymocyte differentiation.

Identification of transcriptional regulators in the mouse immune system.

The differentiation of hematopoietic stem cells into cells of the immune system has been studied extensively in mammals, but the transcriptional circuitry that controls it is still only partially understood. Here, the Immunological Genome Project gene-expression profiles across mouse immune lineages allowed us to systematically analyze these circuits. To analyze this data set we developed Ontogenet, an algorithm for reconstructing lineage-specific regulation from gene-expression profiles across lineages. Using Ontogenet, we found differentiation stage-specific regulators of mouse hematopoiesis and identified many known hematopoietic regulators and 175 previously unknown candidate regulators, as well as their target genes and the cell types in which they act. Among the previously unknown regulators, we emphasize the role of ETV5 in the differentiation of γδ T cells. As the transcriptional programs of human and mouse cells are highly conserved, it is likely that many lessons learned from the mouse model apply to humans.

Intrathymic programming of effector fates in three molecularly distinct γδ T cell subtypes.

Innate γδ T cells function in the early phase of immune responses. Although innate γδ T cells have often been studied as one homogenous population, they can be functionally classified into effector subsets on the basis of the production of signature cytokines, analogous to adaptive helper T cell subsets. However, unlike the function of adaptive T cells, γδ effector T cell function correlates with genomically encoded T cell antigen receptor (TCR) chains, which suggests that clonal TCR selection is not the main determinant of the differentiation of γδ effector cells. A high-resolution transcriptome analysis of all emergent γδ thymocyte subsets segregated on the basis of use of the TCR γ-chain or δ-chain indicated the existence of three separate subtypes of γδ effector cells in the thymus. The immature γδ subsets were distinguished by unique transcription-factor modules that program effector function.

The transcriptional programs of iNKT cells.

Invariant natural killer T (iNKT) cells are innate T cells that express a semi-invariant T cell receptor (TCR) and recognize lipid antigens presented by CD1d molecules. As part of innate immunity, iNKT cells rapidly produce large amounts of cytokines after activation and regulate the function of innate and adaptive immune cells in antimicrobial immunity, tumor rejection and inflammatory diseases. Global transcriptional profiling has advanced our understanding of all aspects of iNKT cell biology. In this review, we discuss transcriptional analyses of iNKT cell development, functional subsets of iNKT cells, and global comparisons of iNKT cells to other innate and adaptive immune cells. Global transcriptional analysis revealed that iNKT cells have a transcriptional profile distinct from NK cells and MHC-restricted T cells, both during thymic development and in the periphery. The transcription factors EGR2 and PLZF (and microRNA like miR-150) are key regulators of the iNKT cell transcriptome during development. PLZF is one of several factors that control the homing and maintenance of organ-specific iNKT cell populations. As in MHC-restricted T cells, specific transcription factors are characteristic of functional subsets of iNKT cells, such as the transcription factor T-bet in the NKT1 subset. Exciting future directions for global transcriptional analyses include iNKT cells in disease models, diverse NKT cells and human studies.

[Caregivers and residents, raising awareness of the influenza vaccine]. / Soignants et résidents, sensibilisation à la vaccination antigrippale.

Influenza epidemics in nursing homes can lead to serious complications with a high level of lethality. It has been shown that an active policy of awareness campaigns with obligatory information materials and easy access to influenza immunisation increases the rate of vaccination coverage.

[Internal and external assessment of nursing home residents' satisfaction]. / Évaluation interne et externe de la satisfaction des résidents en Ehpad.

Quality improvement procedures and measuring the satisfaction of nursing home residents is a major priority. A study assessed the differences between the results of a survey conducted by internal staff and of one carried out by an external service provider to evaluate the satisfaction of the residents of a nursing home.

Antigen Presentation by CD1 Lipids, T Cells, and NKT Cells in Microbial Immunity.

The discovery of molecules capable of presenting lipid antigens, the CD1 family, and of the T cells that recognize them, has opened a new dimensionin our understanding of cell-mediated immunity against infection. Like MHC Class I molecules, CD1 isoforms (CD1a, b, c and d) are assembled in the ER and sent to the cell surface. However, in contrast to MHC molecules, CD1 complexes are then re-internalized into specific endocytic compartments where they can bind lipid antigens. These include a broad scope of both self and foreign molecules that range from simple fatty acids or phospholipids, to more complex glycolipids, isoprenoids, mycolates and lipopeptides. Lipid-loaded CD1 molecules are then delivered to the cell surface and can be surveyed by CD1-restricted T cells expressing alphabeta or gammadelta T Cell Receptors (TCR). It has become clear that T cell-mediated lipid antigen recognition plays an important role in detection and clearance of pathogens. CD1a, b and c-restricted T cells have been found to recognize a number of lipid antigens from M. tuberculosis. CD1d-restricted T cells are the only CD1-restricted T cell subset present in mice, which lack the genes encoding CD1a, b and c. Evidence from experiments in CD1d-restricted T cell-deficient mice indicates that these cells play an important role in the immune response against awide range of pathogens including several bacteria, viruses and parasites. One subset of CD1d-restricted T cells in particular, invariant Natural Killer T (iNKT) cells, has been extensively studied. iNKT cells are characterized by the expression of a semi-invariant TCR composed of a strictly conserved alpha chain paired with a limited repertoire of beta chains. During infection, iNKT cells are rapidly elicited. Activated iNKT cells can produce a vast array of cytokines that profoundly affect both the innate and the adaptive arms of the immune response. In this review, we describe the pathways and mechanisms of lipid antigen binding and presentation by CD1 in detail, as well as the diverse roles played by CD1-restricted T cells in the context of microbial infection.

NK T cells provide lipid antigen-specific cognate help for B cells.

The mechanisms of T cell help for production of antilipid antibodies are largely unknown. This study shows that invariant NK T cells (iNK T cells) and B cells cooperate in a model of antilipid antigen-specific antibody responses. We use a model haptenated lipid molecule, 4-hydroxy-3-nitrophenyl-alphaGalactosylCeramide (NP-alphaGalCer), to demonstrate that iNK T cells provide cognate help to lipid-antigen-presenting B cells. B cells proliferate and IgG anti-NP is produced from in vivo-immunized mice and in vitro cocultures of B and NK T cells after exposure to NP-alphaGalCer, but not closely related control glycolipids. This B cell response is absent in CD1d(-/-) and Jalpha18(-/-) mice but not CD4(-/-) mice. The antibody response to NP-alphaGalCer is dominated by the IgM, IgG3, and IgG2c isotypes, and marginal zone B cells stimulate better in vitro lipid antigen-driven proliferation than follicular B cells, suggesting an important role for this B cell subset. iNK T cell help for B cells is shown to involve cognate help from CD1d-instructed lipid-specific iNK T cells, with help provided via CD40L, B7-1/B7-2, and IFN-gamma, but not IL-4. This model provides evidence of iNK T cell help for antilipid antibody production, an important aspect of infections, autoimmune diseases, and vaccine development. Our findings also now allow prediction of those microbial antigens that would be expected to elicit cognate iNKT cell help for antibody production, namely those that can stimulate iNKT cells and at the same time have a polar moiety that can be recognized by antibodies.

Evasion of peptide, but not lipid antigen presentation, through pathogen-induced dendritic cell maturation.

Dendritic cells (DC) present lipid and peptide antigens to T cells on CD1 and MHC Class II (MHCII), respectively. The relative contribution of these systems during the initiation of adaptive immunity after microbial infection is not characterized. MHCII molecules normally acquire antigen and rapidly traffic from phagolysosomes to the plasma membrane as part of DC maturation, whereas CD1 molecules instead continually recycle between these sites before, during, and after DC maturation. We find that in Mycobacterium tuberculosis (Mtb)-infected DCs, CD1 presents antigens quickly. Surprisingly, rapid DC maturation results in early failure and delay in MHCII presentation. Whereas both CD1b and MHCII localize to bacterial phagosomes early after phagocytosis, MHCII traffics from the phagosome to the plasma membrane with a rapid kinetic that can precede antigen availability and loading. Thus, rather than facilitating antigen presentation, a lack of coordination in timing may allow organisms to use DC maturation as a mechanism of immune evasion. In contrast, CD1 antigen presentation occurs in the face of Mtb infection and rapid DC maturation because a pool of CD1 molecules remains available on the phagolysosome membrane that is able to acquire lipid antigens and deliver them to the plasma membrane.

The CARB-X Portfolio of Nontraditional Antibacterial Products.

The growing prevalence of antibiotic-resistant bacterial pathogens and the lack of new medicines to treat the infections they cause remain a significant global threat. In recent years, this ongoing unmet need has encouraged more research groups to focus on the discovery and development of nontraditional antibacterial agents, ranging from anti-virulence strategies to bacteriophage and ways to modulate the microbiome. The Combating Antibiotic-Resistant Bacteria Biopharmaceutical Accelerator (CARB-X) is a global nonprofit public-private partnership dedicated to accelerating antibacterial-related research. Importantly, the CARB-X portfolio supports a wide variety of novel and innovative nontraditional programs to help the global antibacterial research ecosystem understand the potential that these modalities can play in the management or prevention of serious infections. We describe here the breadth of the CARB-X pipeline of novel nontraditional products.

Rapid and reliable generation of invariant natural killer T-cell lines in vitro.

Several tools have proved useful in the study of invariant natural killer T (iNKT) cells, including CD1d-deficient mice, J alpha281-deficient mice, synthetic lipid antigens and antigen-loaded CD1d tetramers. However, the generation and examination of long-term primary murine iNKT cell lines in vitro has been challenging. Here, we show the rapid generation of iNKT cell lines from splenic iNKT cells of V alpha14 T-cell receptor (TCR) transgenic (Tg) mice. These purified iNKT cells were stimulated by bone marrow-derived dendritic cells (BMDCs) loaded with alpha-galactosylceramide (alphaGalCer) and cultured with interleukin (IL)-2 and IL-7. iNKT cells proliferated dramatically, and the cell number exhibited a 100-fold increase within 2 weeks and a 10(5)-fold increase in 8 weeks after repeated stimulation with alphaGalCer. The iNKT cell lines consisted of iNKT cells expressing V beta chains including V beta8.1/8.2, V beta14, V beta10, V beta6 and V beta7, and responded to stimulation with alphaGalCer presented both by BMDCs and by plate-bound CD1d. In addition, the iNKT cell lines produced interferon (IFN)-gamma when activated by lipopolysaccharide (LPS) or CpG oligodeoxynucleotide (ODN)-stimulated BMDCs. Further, we show that iNKT cell lines produced cytokines in response to microbial antigens. In summary, high-yield iNKT cell lines were generated very rapidly and robustly expanded, and these iNKT cells responded to both TCR and cytokine stimulation in vitro. Given the desire to study primary iNKT cells for many purposes, these iNKT cell lines should provide an important tool for the study of iNKT cell subsets, antigen and TCR specificity, activation, inactivation and effector functions.

Impact of hip fracture, heart failure and weight loss on the risk of institutionalization of community-dwelling patients with dementia.

OBJECTIVES: This study sought to identify the influence of medical symptoms and diseases on the risk of nursing home placement in a prospective cohort of newly diagnosed community-dwelling patients with dementia. STUDY DESIGN AND SETTING: This study included 348 patients with dementia, consecutively diagnosed, recruited and followed at a geriatric outpatient center (mean age: 81 years, 65.5% with Alzheimer's disease, mean baseline MMSE score: 20.5, mean follow-up: 20.5 months). RESULTS: After adjustment for factors commonly associated with institutionalization in this population, hip fracture in the 3 years preceding diagnosis, acute congestive heart failure during follow-up and weight loss of more than 5% in any year during follow-up were independently associated with nursing home placement. CONCLUSION: This study confirms the independent contribution of specific medical symptoms and diseases to earlier institutionalization of patients with dementia. These results stress the importance of better knowledge of the specific characteristics of hip fracture, weight loss and congestive heart failure in the context of dementia, to make more effective prevention possible in this patient population.

Impact of a multicomponent hand hygiene-related intervention on the infectious risk in nursing homes: A cluster randomized trial.

BACKGROUND: The aim of this study was to assess the impact of a multifaceted hand hygiene (HH) program on the infectious risk in nursing homes (NHs). METHODS: This was a 2-arm cluster randomized trial; French NHs were allocated randomly to the intervention (13 NHs) or control (13 NHs) groups. The intervention consisted of implementing a bundle of HH-related measures over 1 year, including increased availability of alcohol-based handrub, HH promotion, staff education, and local work groups. The primary end point was the incidence rate of acute respiratory infections and gastroenteritis reported in the context of clustered cases episodes. Secondary end points were mortality, hospitalization, and antibiotic prescription rates. RESULTS: Baseline characteristics did not differ between groups. The overall handrub consumption was higher in the intervention group over the 1-year intervention period. Because of underreporting, data on the primary end points were of insufficient quality for analysis. Hospitalizations did not differ between the 2 groups. However, the intervention group showed significantly lower mortality (2.10 vs 2.65 per 100 residents per month, respectively; P = .003) and antibiotic prescriptions (5.0 vs 5.8 defined daily doses per 100 resident days, respectively; P < .001). These results were confirmed by the longitudinal multivariate analysis adjusted for NH and resident characteristics and for seasonality (mortality rate ratio, 0.76). CONCLUSIONS: A multifaceted HH intervention may have a short-term impact on mortality in NHs. Nevertheless, other strategies may remain necessary to reduce morbidity.

A role for the bacterial GATC methylome in antibiotic stress survival.

Antibiotic resistance is an increasingly serious public health threat. Understanding pathways allowing bacteria to survive antibiotic stress may unveil new therapeutic targets. We explore the role of the bacterial epigenome in antibiotic stress survival using classical genetic tools and single-molecule real-time sequencing to characterize genomic methylation kinetics. We find that Escherichia coli survival under antibiotic pressure is severely compromised without adenine methylation at GATC sites. Although the adenine methylome remains stable during drug stress, without GATC methylation, methyl-dependent mismatch repair (MMR) is deleterious and, fueled by the drug-induced error-prone polymerase Pol IV, overwhelms cells with toxic DNA breaks. In multiple E. coli strains, including pathogenic and drug-resistant clinical isolates, DNA adenine methyltransferase deficiency potentiates antibiotics from the ß-lactam and quinolone classes. This work indicates that the GATC methylome provides structural support for bacterial survival during antibiotic stress and suggests targeting bacterial DNA methylation as a viable approach to enhancing antibiotic activity.

Bactericidal Antibiotics Induce Toxic Metabolic Perturbations that Lead to Cellular Damage.

Understanding how antibiotics impact bacterial metabolism may provide insight into their mechanisms of action and could lead to enhanced therapeutic methodologies. Here, we profiled the metabolome of Escherichia coli after treatment with three different classes of bactericidal antibiotics (?-lactams, aminoglycosides, quinolones). These treatments induced a similar set of metabolic changes after 30 min that then diverged into more distinct profiles at later time points. The most striking changes corresponded to elevated concentrations of central carbon metabolites, active breakdown of the nucleotide pool, reduced lipid levels, and evidence of an elevated redox state. We examined potential end-target consequences of these metabolic perturbations and found that antibiotic-treated cells exhibited cytotoxic changes indicative of oxidative stress, including higher levels of protein carbonylation, malondialdehyde adducts, nucleotide oxidation, and double-strand DNA breaks. This work shows that bactericidal antibiotics induce a complex set of metabolic changes that are correlated with the buildup of toxic metabolic by-products.

Microbial persistence and the road to drug resistance.

Microbial drug persistence is a widespread phenomenon in which a subpopulation of microorganisms is able to survive antimicrobial treatment without acquiring resistance-conferring genetic changes. Microbial persisters can cause recurrent or intractable infections, and, like resistant mutants, they carry an increasing clinical burden. In contrast to heritable drug resistance, however, the biology of persistence is only beginning to be unraveled. Persisters have traditionally been thought of as metabolically dormant, nondividing cells. As discussed in this review, increasing evidence suggests that persistence is in fact an actively maintained state, triggered and enabled by a network of intracellular stress responses that can accelerate processes of adaptive evolution. Beyond shedding light on the basis of persistence, these findings raise the possibility that persisters behave as an evolutionary reservoir from which resistant organisms can emerge. As persistence and its consequences come into clearer focus, so too does the need for clinically useful persister-eradication strategies.

Innate recognition of cell wall ß-glucans drives invariant natural killer T cell responses against fungi.

iNKT cells are innate T lymphocytes recognizing endogenous and foreign lipid antigens presented in the MHC-like molecule CD1d. The semi-invariant iNKT cell TCR can detect certain bacterial and parasitic lipids and drive iNKT cell responses. How iNKT cells respond to fungi, however, is unknown. We found that CD1d-deficient mice, which lack iNKT cells, poorly control infection with the fungal pathogen Aspergillus fumigatus. Furthermore, A. fumigatus rapidly activates iNKT cells in vivo and in vitro in the presence of APCs. Surprisingly, despite a requirement for CD1d recognition, the antifungal iNKT cell response does not require fungal lipids. Instead, Dectin-1- and MyD88-mediated responses to ß-1,3 glucans, major fungal cell-wall polysaccharides, trigger IL-12 production by APCs that drives self-reactive iNKT cells to secrete IFN-γ. Innate recognition of ß-1,3 glucans also drives iNKT cell responses against Candida, Histoplasma, and Alternaria, suggesting that this mechanism may broadly define the basis for antifungal iNKT cell responses.

Innate and cytokine-driven signals, rather than microbial antigens, dominate in natural killer T cell activation during microbial infection.

Invariant natural killer T cells (iNKT cells) are critical for host defense against a variety of microbial pathogens. However, the central question of how iNKT cells are activated by microbes has not been fully explained. The example of adaptive MHC-restricted T cells, studies using synthetic pharmacological α-galactosylceramides, and the recent discovery of microbial iNKT cell ligands have all suggested that recognition of foreign lipid antigens is the main driver for iNKT cell activation during infection. However, when we compared the role of microbial antigens versus innate cytokine-driven mechanisms, we found that iNKT cell interferon-γ production after in vitro stimulation or infection with diverse bacteria overwhelmingly depended on toll-like receptor-driven IL-12. Importantly, activation of iNKT cells in vivo during infection with Sphingomonas yanoikuyae or Streptococcus pneumoniae, pathogens which are known to express iNKT cell antigens and which require iNKT cells for effective protection, also predominantly depended on IL-12. Constitutive expression of high levels of IL-12 receptor by iNKT cells enabled instant IL-12-induced STAT4 activation, demonstrating that among T cells, iNKT cells are uniquely equipped for immediate, cytokine-driven activation. These findings reveal that innate and cytokine-driven signals, rather than cognate microbial antigen, dominate in iNKT cell activation during microbial infections.

Increased surveillance of cells in mitosis by human NK cells suggests a novel strategy for limiting tumor growth and viral replication.

The threat from cancer cells is inherently linked to cell-cycle progression, and viral genomes commonly replicate, for example, within episomes or proviruses, during mitosis. We report here that human natural killer (NK) cells bound cells in mitosis and attacked pathogenic cells in mitosis more effectively than the same cells in other stages of the cell cycle. Thus, cells in mitosis warrant and undergo heightened surveillance, a novel strategy for immunologic assessment of danger. Recognition of cells in mitosis involved ligation of activating NK-cell receptors and binding to target-cell hyaluronan, a component of the pericellular matrix known to be increased during mitosis. Direct interaction between activating NK-cell receptors and hyaluronan is possible, but other mechanisms consistent with our data are also discussed.