Showing papers in "Nature Immunology in 2020"
TL;DR: The identification of T cell responses associated with milder disease will support an understanding of protective immunity and highlights the potential of including non-spike proteins within future COVID-19 vaccine design.
Abstract: The development of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccines and therapeutics will depend on understanding viral immunity. We studied T cell memory in 42 patients following recovery from COVID-19 (28 with mild disease and 14 with severe disease) and 16 unexposed donors, using interferon-γ-based assays with peptides spanning SARS-CoV-2 except ORF1. The breadth and magnitude of T cell responses were significantly higher in severe as compared with mild cases. Total and spike-specific T cell responses correlated with spike-specific antibody responses. We identified 41 peptides containing CD4+ and/or CD8+ epitopes, including six immunodominant regions. Six optimized CD8+ epitopes were defined, with peptide–MHC pentamer-positive cells displaying the central and effector memory phenotype. In mild cases, higher proportions of SARS-CoV-2-specific CD8+ T cells were observed. The identification of T cell responses associated with milder disease will support an understanding of protective immunity and highlights the potential of including non-spike proteins within future COVID-19 vaccine design. Questions have arisen as to whether patients with severe COVID-19 disease can generate a T cell response against SARS-CoV-2. Tao Dong and colleagues report that convalescent patients with COVID-19 harbor functional memory CD4+ and CD8+ T cells that recognize multiple epitopes that span the viral proteome. CD4+ T cells predominated the memory response in patients with severe disease, whereas higher proportions of CD8+ T cells were found in patients with mild disease.
982 citations
TL;DR: The transgenic mice expressing the human angiotensin I-converting enzyme 2 (ACE2) receptor driven by the cytokeratin-18 (K18) gene promoter are evaluated as a model of SARS-CoV-2 infection to define the basis of lung disease and test immune and antiviral-based countermeasures.
Abstract: Although animal models have been evaluated for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection, none have fully recapitulated the lung disease phenotypes seen in humans who have been hospitalized. Here, we evaluate transgenic mice expressing the human angiotensin I-converting enzyme 2 (ACE2) receptor driven by the cytokeratin-18 (K18) gene promoter (K18-hACE2) as a model of SARS-CoV-2 infection. Intranasal inoculation of SARS-CoV-2 in K18-hACE2 mice results in high levels of viral infection in lungs, with spread to other organs. A decline in pulmonary function occurs 4 days after peak viral titer and correlates with infiltration of monocytes, neutrophils and activated T cells. SARS-CoV-2-infected lung tissues show a massively upregulated innate immune response with signatures of nuclear factor-κB-dependent, type I and II interferon signaling, and leukocyte activation pathways. Thus, the K18-hACE2 model of SARS-CoV-2 infection shares many features of severe COVID-19 infection and can be used to define the basis of lung disease and test immune and antiviral-based countermeasures.
653 citations
TL;DR: Overall, these findings strongly suggest a pathogenic role for immune activation in subsets of patients with COVID-19, and provide further evidence that targeted immunomodulatory therapy may be beneficial in specific patient subpopulations and can be informed by careful immune profiling.
Abstract: A wide spectrum of clinical manifestations has become a hallmark of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) COVID-19 pandemic, although the immunological underpinnings of diverse disease outcomes remain to be defined. We performed detailed characterization of B cell responses through high-dimensional flow cytometry to reveal substantial heterogeneity in both effector and immature populations. More notably, critically ill patients displayed hallmarks of extrafollicular B cell activation and shared B cell repertoire features previously described in autoimmune settings. Extrafollicular activation correlated strongly with large antibody-secreting cell expansion and early production of high concentrations of SARS-CoV-2-specific neutralizing antibodies. Yet, these patients had severe disease with elevated inflammatory biomarkers, multiorgan failure and death. Overall, these findings strongly suggest a pathogenic role for immune activation in subsets of patients with COVID-19. Our study provides further evidence that targeted immunomodulatory therapy may be beneficial in specific patient subpopulations and can be informed by careful immune profiling.
492 citations
TL;DR: Disulfiram, an FDA-approved drug for treating alcoholism, is identified as an inhibitor of pore formation by GSDMD but not other members of the GSDM family, providing new therapeutic indications for repurposing this safe drug to counteract inflammation.
Abstract: Cytosolic sensing of pathogens and damage by myeloid and barrier epithelial cells assembles large complexes called inflammasomes, which activate inflammatory caspases to process cytokines (IL-1β) and gasdermin D (GSDMD). Cleaved GSDMD forms membrane pores, leading to cytokine release and inflammatory cell death (pyroptosis). Inhibiting GSDMD is an attractive strategy to curb inflammation. Here we identify disulfiram, a drug for treating alcohol addiction, as an inhibitor of pore formation by GSDMD but not other members of the GSDM family. Disulfiram blocks pyroptosis and cytokine release in cells and lipopolysaccharide-induced septic death in mice. At nanomolar concentration, disulfiram covalently modifies human/mouse Cys191/Cys192 in GSDMD to block pore formation. Disulfiram still allows IL-1β and GSDMD processing, but abrogates pore formation, thereby preventing IL-1β release and pyroptosis. The role of disulfiram in inhibiting GSDMD provides new therapeutic indications for repurposing this safe drug to counteract inflammation, which contributes to many human diseases.
450 citations
TL;DR: The single-cell transcriptional landscape of moderate, severe and convalescent cases of patients with COVID-19 describes the dynamic nature of immune responses during disease progression, and shows a deranged interferon response, profound immune exhaustion with skewed T cell receptor repertoire and broad T cell expansion.
Abstract: In coronavirus disease 2019 (COVID-19), caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection, the relationship between disease severity and the host immune response is not fully understood. Here we performed single-cell RNA sequencing in peripheral blood samples of 5 healthy donors and 13 patients with COVID-19, including moderate, severe and convalescent cases. Through determining the transcriptional profiles of immune cells, coupled with assembled T cell receptor and B cell receptor sequences, we analyzed the functional properties of immune cells. Most cell types in patients with COVID-19 showed a strong interferon-α response and an overall acute inflammatory response. Moreover, intensive expansion of highly cytotoxic effector T cell subsets, such as CD4+ effector-GNLY (granulysin), CD8+ effector-GNLY and NKT CD160, was associated with convalescence in moderate patients. In severe patients, the immune landscape featured a deranged interferon response, profound immune exhaustion with skewed T cell receptor repertoire and broad T cell expansion. These findings illustrate the dynamic nature of immune responses during disease progression.
437 citations
TL;DR: A biomarker based on PD-1 positivity of effector and regulatory T cells in the tumor microenvironment that accurately predicts the effectiveness of checkpoint blockade in patients is developed.
Abstract: Immune checkpoint blockade has provided a paradigm shift in cancer therapy, but the success of this approach is very variable; therefore, biomarkers predictive of clinical efficacy are urgently required. Here, we show that the frequency of PD-1+CD8+ T cells relative to that of PD-1+ regulatory T (Treg) cells in the tumor microenvironment can predict the clinical efficacy of programmed cell death protein 1 (PD-1) blockade therapies and is superior to other predictors, including PD ligand 1 (PD-L1) expression or tumor mutational burden. PD-1 expression by CD8+ T cells and Treg cells negatively impacts effector and immunosuppressive functions, respectively. PD-1 blockade induces both recovery of dysfunctional PD-1+CD8+ T cells and enhanced PD-1+ Treg cell–mediated immunosuppression. A profound reactivation of effector PD-1+CD8+ T cells rather than PD-1+ Treg cells by PD-1 blockade is necessary for tumor regression. These findings provide a promising predictive biomarker for PD-1 blockade therapies. Checkpoint blockade is effective in only a subset of patients; therefore, biomarkers that can predict efficacy would be clinically highly valuable. Nishkawa and colleagues develop a biomarker based on PD-1 positivity of effector and regulatory T cells in the tumor microenvironment that accurately predicts the effectiveness of checkpoint blockade in patients.
342 citations
TL;DR: These data establish a reference model and general framework for studying neutrophil-related disease mechanisms, biomarkers and therapeutic targets at single-cell resolution and represent an evolved mechanism for fine-tuned regulation of an effective but balanced neutrophils response.
Abstract: The full neutrophil heterogeneity and differentiation landscape remains incompletely characterized. Here, we profiled >25,000 differentiating and mature mouse neutrophils using single-cell RNA sequencing to provide a comprehensive transcriptional landscape of neutrophil maturation, function and fate decision in their steady state and during bacterial infection. Eight neutrophil populations were defined by distinct molecular signatures. The three mature peripheral blood neutrophil subsets arise from distinct maturing bone marrow neutrophil subsets. Driven by both known and uncharacterized transcription factors, neutrophils gradually acquire microbicidal capability as they traverse the transcriptional landscape, representing an evolved mechanism for fine-tuned regulation of an effective but balanced neutrophil response. Bacterial infection reprograms the genetic architecture of neutrophil populations, alters dynamic transitions between subpopulations and primes neutrophils for augmented functionality without affecting overall heterogeneity. In summary, these data establish a reference model and general framework for studying neutrophil-related disease mechanisms, biomarkers and therapeutic targets at single-cell resolution. Luo and colleagues use single-cell RNA sequencing to provide a comprehensive transcriptional landscape of neutrophil maturation, function and fate decision in their steady state and during bacterial infection.
291 citations
TL;DR: It is found that CD36 was selectively upregulated in intrautumoral T reg cells as a central metabolic modulator and elicited additive antitumor responses with anti-programmed cell death protein 1 therapy.
Abstract: Depleting regulatory T cells (Treg cells) to counteract immunosuppressive features of the tumor microenvironment (TME) is an attractive strategy for cancer treatment; however, autoimmunity due to systemic impairment of their suppressive function limits its therapeutic potential. Elucidating approaches that specifically disrupt intratumoral Treg cells is direly needed for cancer immunotherapy. We found that CD36 was selectively upregulated in intrautumoral Treg cells as a central metabolic modulator. CD36 fine-tuned mitochondrial fitness via peroxisome proliferator-activated receptor-β signaling, programming Treg cells to adapt to a lactic acid-enriched TME. Genetic ablation of Cd36 in Treg cells suppressed tumor growth accompanied by a decrease in intratumoral Treg cells and enhancement of antitumor activity in tumor-infiltrating lymphocytes without disrupting immune homeostasis. Furthermore, CD36 targeting elicited additive antitumor responses with anti-programmed cell death protein 1 therapy. Our findings uncover the unexplored metabolic adaptation that orchestrates the survival and functions of intratumoral Treg cells, and the therapeutic potential of targeting this pathway for reprogramming the TME.
260 citations
TL;DR: Tsokos reviews how the genetic, epigenetic and microbial environments influence innate and adaptive immune cells to drive immunopathology and organ damage in systemic lupus erythematosus.
Abstract: Impressive progress has been made over the last several years toward understanding how almost every aspect of the immune system contributes to the expression of systemic autoimmunity. In parallel, studies have shed light on the mechanisms that contribute to organ inflammation and damage. New approaches that address the complicated interaction between genetic variants, epigenetic processes, sex and the environment promise to enlighten the multitude of pathways that lead to what is clinically defined as systemic lupus erythematosus. It is expected that each patient owns a unique 'interactome', which will dictate specific treatment.
250 citations
TL;DR: Newly discovered functions of m6A in controlling various aspects of immunity, including immune recognition, activation of innate and adaptive immune responses, and cell fate decisions are summarized.
Abstract: Protection from harmful pathogens depends on activation of the immune system, which relies on tight regulation of gene expression. Recently, the RNA modification N6-methyladenosine (m6A) has been found to play an essential role in such regulation. Here, we summarize newly discovered functions of m6A in controlling various aspects of immunity, including immune recognition, activation of innate and adaptive immune responses, and cell fate decisions. We then discuss some of the current challenges in the field and describe future directions for uncovering the immunological functions of m6A and its mechanisms of action.
224 citations
TL;DR: It is demonstrated that PD-L1 + T cells have diverse tolerogenic effects on tumor immunity and ‘back-signaling’ into T cells and macrophages can also dampen immune responses within the tumor microenvironment.
Abstract: Programmed cell death protein 1 (PD-1) ligation delimits immunogenic responses in T cells. However, the consequences of programmed cell death 1 ligand 1 (PD-L1) ligation in T cells are uncertain. We found that T cell expression of PD-L1 in cancer was regulated by tumor antigen and sterile inflammatory cues. PD-L1+ T cells exerted tumor-promoting tolerance via three distinct mechanisms: (1) binding of PD-L1 induced STAT3-dependent 'back-signaling' in CD4+ T cells, which prevented activation, reduced TH1-polarization and directed TH17-differentiation. PD-L1 signaling also induced an anergic T-bet-IFN-γ- phenotype in CD8+ T cells and was equally suppressive compared to PD-1 signaling; (2) PD-L1+ T cells restrained effector T cells via the canonical PD-L1-PD-1 axis and were sufficient to accelerate tumorigenesis, even in the absence of endogenous PD-L1; (3) PD-L1+ T cells engaged PD-1+ macrophages, inducing an alternative M2-like program, which had crippling effects on adaptive antitumor immunity. Collectively, we demonstrate that PD-L1+ T cells have diverse tolerogenic effects on tumor immunity.
TL;DR: How cytoprotective and cytotoxic signaling modules activated by radiation in specific cell populations reshape the immunological tumor microenvironment is discussed.
Abstract: Therapeutic irradiation of the tumor microenvironment causes differential activation of pro-survival and pro-death pathways in malignant, stromal, endothelial and immune cells, hence causing a profound cellular and biological reconfiguration via multiple, non-redundant mechanisms. Such mechanisms include the selective elimination of particularly radiosensitive cell types and consequent loss of specific cellular functions, the local release of cytokines and danger signals by dying radiosensitive cells, and altered cytokine secretion by surviving radioresistant cells. Altogether, these processes create chemotactic and immunomodulatory cues for incoming and resident immune cells. Here we discuss how cytoprotective and cytotoxic signaling modules activated by radiation in specific cell populations reshape the immunological tumor microenvironment.
TL;DR: It is necessary to intensify efforts to prevent and control vector-borne diseases and their impacts are likely to worsen in the face of ongoing climate change.
Abstract: Climate change is already affecting vector-borne disease transmission and spread, and its impacts are likely to worsen. In the face of ongoing climate change, we must intensify efforts to prevent and control vector-borne diseases.
TL;DR: New targets of the immune response to SARS-CoV-2 are identified and it is shown that nucleocapsid, open reading frame (ORF)8 and ORF3b elicit the strongest specific antibody responses.
Abstract: The SARS-CoV-2 virus emerged in December 2019 and has caused a worldwide pandemic due to the lack of any pre-existing immunity. Accurate serology testing is urgently needed to help diagnose infection, determine past exposure of populations and assess the response to a future vaccine. The landscape of antibody responses to SARS-CoV-2 is unknown. In this study, we utilized the luciferase immunoprecipitation system to assess the antibody responses to 15 different SARS-CoV-2 antigens in patients with COVID-19. We identified new targets of the immune response to SARS-CoV-2 and show that nucleocapsid, open reading frame (ORF)8 and ORF3b elicit the strongest specific antibody responses. ORF8 and ORF3b antibodies, taken together as a cluster of points, identified 96.5% of COVID-19 samples at early and late time points of disease with 99.5% specificity. Our findings could be used to develop second-generation diagnostic tests to improve serological assays for COVID-19 and are important in understanding pathogenicity.
TL;DR: The NK cell–cancer cycle is introduced to highlight recent advances in NK cell biology and to discuss the progress and problems of NK cell-based cancer immunotherapies.
Abstract: Natural killer (NK) cells belong to the innate immune system and contribute to protecting the host through killing of infected, foreign, stressed or transformed cells. Additionally, via cellular cross-talk, NK cells orchestrate antitumor immune responses. Hence, significant efforts have been undertaken to exploit the therapeutic properties of NK cells in cancer. Current strategies in preclinical and clinical development include adoptive transfer therapies, direct stimulation, recruitment of NK cells into the tumor microenvironment (TME), blockade of inhibitory receptors that limit NK cell functions, and therapeutic modulation of the TME to enhance antitumor NK cell function. In this Review, we introduce the NK cell–cancer cycle to highlight recent advances in NK cell biology and to discuss the progress and problems of NK cell–based cancer immunotherapies. In this Review, Smyth and colleagues provide an overview of recent advances in NK cell biology and discuss the progress and problems of NK cell–based cancer immunotherapies.
Ludwig Institute for Cancer Research1, University of Lausanne2, Austrian Academy of Sciences3, Duke University4, École Polytechnique Fédérale de Lausanne5, National Taiwan University6, University of Basel7, University Hospital of Basel8, National Health Research Institutes9, Medical University of Vienna10
TL;DR: It is reported that mitochondrial dysfunction and impaired mitophagy triggered by the tumor microenvironment lead to subsequent epigenetic changes and cause permanent T cell exhaustion and dysfunction.
Abstract: The metabolic challenges present in tumors attenuate the metabolic fitness and antitumor activity of tumor-infiltrating T lymphocytes (TILs). However, it remains unclear whether persistent metabolic insufficiency can imprint permanent T cell dysfunction. We found that TILs accumulated depolarized mitochondria as a result of decreased mitophagy activity and displayed functional, transcriptomic and epigenetic characteristics of terminally exhausted T cells. Mechanistically, reduced mitochondrial fitness in TILs was induced by the coordination of T cell receptor stimulation, microenvironmental stressors and PD-1 signaling. Enforced accumulation of depolarized mitochondria with pharmacological inhibitors induced epigenetic reprogramming toward terminal exhaustion, indicating that mitochondrial deregulation caused T cell exhaustion. Furthermore, supplementation with nicotinamide riboside enhanced T cell mitochondrial fitness and improved responsiveness to anti-PD-1 treatment. Together, our results reveal insights into how mitochondrial dynamics and quality orchestrate T cell antitumor responses and commitment to the exhaustion program.
TL;DR: It is shown that tumor cell autophagy opposes inflammatory cell death following radiation therapy and can be inhibited to enhance antitumor responses, suggesting that mitochondrial outer membrane permeabilization may represent a valid target for boosting radiation therapy immunogenicity in patients with breast cancer.
Abstract: Autophagy supports both cellular and organismal homeostasis. However, whether autophagy should be inhibited or activated for cancer therapy remains unclear. Deletion of essential autophagy genes increased the sensitivity of mouse mammary carcinoma cells to radiation therapy in vitro and in vivo (in immunocompetent syngeneic hosts). Autophagy-deficient cells secreted increased amounts of type I interferon (IFN), which could be limited by CGAS or STING knockdown, mitochondrial DNA depletion or mitochondrial outer membrane permeabilization blockage via BCL2 overexpression or BAX deletion. In vivo, irradiated autophagy-incompetent mammary tumors elicited robust immunity, leading to improved control of distant nonirradiated lesions via systemic type I IFN signaling. Finally, a genetic signature of autophagy had negative prognostic value in patients with breast cancer, inversely correlating with mitochondrial abundance, type I IFN signaling and effector immunity. As clinically useful autophagy inhibitors are elusive, our findings suggest that mitochondrial outer membrane permeabilization may represent a valid target for boosting radiation therapy immunogenicity in patients with breast cancer.
TL;DR: A population of meningeal γδ17 T cells are characterized that use IL-17a to elicit anxiety-like behavior through cortical glutamatergic neurons, suggesting an evolutionary bridge between this conserved anti-pathogen molecule and survival behavioral traits in vertebrates.
Abstract: Interleukin (IL)-17a has been highly conserved during evolution of the vertebrate immune system and widely studied in contexts of infection and autoimmunity. Studies suggest that IL-17a promotes behavioral changes in experimental models of autism and aggregation behavior in worms. Here, through a cellular and molecular characterization of meningeal γδ17 T cells, we defined the nearest central nervous system–associated source of IL-17a under homeostasis. Meningeal γδ T cells express high levels of the chemokine receptor CXCR6 and seed meninges shortly after birth. Physiological release of IL-17a by these cells was correlated with anxiety-like behavior in mice and was partially dependent on T cell receptor engagement and commensal-derived signals. IL-17a receptor was expressed in cortical glutamatergic neurons under steady state and its genetic deletion decreased anxiety-like behavior in mice. Our findings suggest that IL-17a production by meningeal γδ17 T cells represents an evolutionary bridge between this conserved anti-pathogen molecule and survival behavioral traits in vertebrates. IL-17a is an evolutionarily conserved cytokine with behavior-modulating roles in the central nervous system. Kipnis and colleagues characterize a population of meningeal γδ17 T cells that use IL-17a to elicit anxiety-like behavior through cortical glutamatergic neurons.
TL;DR: This Review addresses the emerging literature on regulation of the sensing of cytosolic DNA and RNA via cGAS and RLRs and offers a rich and largely unexplored source for new therapeutic targets.
Abstract: Pathogen-derived nucleic acids are crucial signals for innate immunity. Despite the structural similarity between those and host nucleic acids, mammalian cells have been able to evolve powerful innate immune signaling pathways that originate from the detection of cytosolic nucleic acid species, one of the most prominent being the cGAS-STING pathway for DNA and the RLR-MAVS pathway for RNA, respectively. Recent advances have revealed a plethora of regulatory mechanisms that are crucial for balancing the activity of nucleic acid sensors for the maintenance of overall cellular homeostasis. Elucidation of the various mechanisms that enable cells to maintain control over the activity of cytosolic nucleic acid sensors has provided new insight into the pathology of human diseases and, at the same time, offers a rich and largely unexplored source for new therapeutic targets. This Review addresses the emerging literature on regulation of the sensing of cytosolic DNA and RNA via cGAS and RLRs.
TL;DR: It is demonstrated that the nonclassical MHC molecule MR1 is expressed on a wide variety of cancer types and can be targeted by conventional T cells, and offers opportunities for HLA-independent, pan-cancer,pan-population immunotherapies.
Abstract: Human leukocyte antigen (HLA)-independent, T cell-mediated targeting of cancer cells would allow immune destruction of malignancies in all individuals. Here, we use genome-wide CRISPR-Cas9 screening to establish that a T cell receptor (TCR) recognized and killed most human cancer types via the monomorphic MHC class I-related protein, MR1, while remaining inert to noncancerous cells. Unlike mucosal-associated invariant T cells, recognition of target cells by the TCR was independent of bacterial loading. Furthermore, concentration-dependent addition of vitamin B-related metabolite ligands of MR1 reduced TCR recognition of cancer cells, suggesting that recognition occurred via sensing of the cancer metabolome. An MR1-restricted T cell clone mediated in vivo regression of leukemia and conferred enhanced survival of NSG mice. TCR transfer to T cells of patients enabled killing of autologous and nonautologous melanoma. These findings offer opportunities for HLA-independent, pan-cancer, pan-population immunotherapies.
TL;DR: This study lays the groundwork for resolving the origin of the SLE transcriptional signatures and the disease heterogeneity towards precision medicine applications by using single-cell RNA-seq analysis of peripheral whole-blood cells from adolescent patients with SLE.
Abstract: Patients with systemic lupus erythematosus (SLE) display a complex blood transcriptome whose cellular origin is poorly resolved. Using single-cell RNA sequencing, we profiled ~276,000 peripheral blood mononuclear cells from 33 children with SLE with different degrees of disease activity and 11 matched controls. Increased expression of interferon-stimulated genes (ISGs) distinguished cells from children with SLE from healthy control cells. The high ISG expression signature (ISGhi) derived from a small number of transcriptionally defined subpopulations within major cell types, including monocytes, CD4+ and CD8+ T cells, natural killer cells, conventional and plasmacytoid dendritic cells, B cells and especially plasma cells. Expansion of unique subpopulations enriched in ISGs and/or in monogenic lupus-associated genes classified patients with the highest disease activity. Profiling of ~82,000 single peripheral blood mononuclear cells from adults with SLE confirmed the expansion of similar subpopulations in patients with the highest disease activity. This study lays the groundwork for resolving the origin of the SLE transcriptional signatures and the disease heterogeneity towards precision medicine applications. Banchereau and colleagues provide a resource dataset that examines disease-related transcriptional profiles of peripheral whole-blood cells from adolescent patients with SLE by single-cell RNA-seq analysis.
TL;DR: Hexosaminidase subunit beta is identified to be specifically expressed by microglia and stable even under inflammatory conditions, and Prinz and colleagues provide valuable new genetic tools to specifically studymicroglia functions in the CNS.
Abstract: Microglia and central nervous system (CNS)-associated macrophages (CAMs), such as perivascular and meningeal macrophages, are implicated in virtually all diseases of the CNS. However, little is known about their cell-type-specific roles in the absence of suitable tools that would allow for functional discrimination between the ontogenetically closely related microglia and CAMs. To develop a new microglia gene targeting model, we first applied massively parallel single-cell analyses to compare microglia and CAM signatures during homeostasis and disease and identified hexosaminidase subunit beta (Hexb) as a stably expressed microglia core gene, whereas other microglia core genes were substantially downregulated during pathologies. Next, we generated HexbtdTomato mice to stably monitor microglia behavior in vivo. Finally, the Hexb locus was employed for tamoxifen-inducible Cre-mediated gene manipulation in microglia and for fate mapping of microglia but not CAMs. In sum, we provide valuable new genetic tools to specifically study microglia functions in the CNS.
TL;DR: It is shown that T RM cells can reenter the circulation, and exhibit considerable plasticity, although they retain a proclivity to reestablish themselves in their tissue of origin.
Abstract: Central memory T (TCM) cells patrol lymph nodes and perform conventional memory responses on restimulation: proliferation, migration and differentiation into diverse T cell subsets while also self-renewing. Resident memory T (TRM) cells are parked within single organs, share properties with terminal effectors and contribute to rapid host protection. We observed that reactivated TRM cells rejoined the circulating pool. Epigenetic analyses revealed that TRM cells align closely with conventional memory T cell populations, bearing little resemblance to recently activated effectors. Fully differentiated TRM cells isolated from small intestine epithelium exhibited the potential to differentiate into TCM cells, effector memory T cells and TRM cells on recall. Ex-TRM cells, former intestinal TRM cells that rejoined the circulating pool, heritably maintained a predilection for homing back to their tissue of origin on subsequent reactivation and a heightened capacity to redifferentiate into TRM cells. Thus, TRM cells can rejoin the circulation but are advantaged to re-form local TRM when called on.
TL;DR: It is revealed that loss of ATP production through oxidative phosphorylation limits T cell proliferation and effector function during chronic antigenic stimulation, and treatments that maintain redox balance promote T cell self-renewal and enhance anti-tumor immunity.
Abstract: The majority of tumor-infiltrating T cells exhibit a terminally exhausted phenotype, marked by a loss of self-renewal capacity. How repetitive antigenic stimulation impairs T cell self-renewal remains poorly defined. Here, we show that persistent antigenic stimulation impaired ADP-coupled oxidative phosphorylation. The resultant bioenergetic compromise blocked proliferation by limiting nucleotide triphosphate synthesis. Inhibition of mitochondrial oxidative phosphorylation in activated T cells was sufficient to suppress proliferation and upregulate genes linked to T cell exhaustion. Conversely, prevention of mitochondrial oxidative stress during chronic T cell stimulation allowed sustained T cell proliferation and induced genes associated with stem-like progenitor T cells. As a result, antioxidant treatment enhanced the anti-tumor efficacy of chronically stimulated T cells. These data reveal that loss of ATP production through oxidative phosphorylation limits T cell proliferation and effector function during chronic antigenic stimulation. Furthermore, treatments that maintain redox balance promote T cell self-renewal and enhance anti-tumor immunity. Thompson and colleagues show that repetitive antigenic stimulation within the tumor environment triggers mitochondrial dysfunction by inhibiting oxidative phosphorylation, which leads to T cell exhaustion.
TL;DR: A cell-intrinsic program that modified the neutrophil proteome in the circulation and caused the progressive loss of granule content and reduction of the NET-forming capacity was identified, which unveiled a ‘disarming’ strategy of neutrophils that depletes protein stores to reduce the magnitude of inflammation.
Abstract: The antimicrobial functions of neutrophils are facilitated by a defensive armamentarium of proteins stored in granules, and by the formation of neutrophil extracellular traps (NETs). However, the toxic nature of these structures poses a threat to highly vascularized tissues, such as the lungs. Here, we identified a cell-intrinsic program that modified the neutrophil proteome in the circulation and caused the progressive loss of granule content and reduction of the NET-forming capacity. This program was driven by the receptor CXCR2 and by regulators of circadian cycles. As a consequence, lungs were protected from inflammatory injury at times of day or in mouse mutants in which granule content was low. Changes in the proteome, granule content and NET formation also occurred in human neutrophils, and correlated with the incidence and severity of respiratory distress in pneumonia patients. Our findings unveil a ‘disarming’ strategy of neutrophils that depletes protein stores to reduce the magnitude of inflammation. Hidalgo and colleagues describe a cell-intrinsic program that induces changes in the proteome, granule content and NET-forming capacity of neutrophils and is driven by the chemokine receptor CXCR2 and regulators of the circadian clock.
TL;DR: New insights into lymph node stromal cells are reviewed, a heterogeneous cell population that serves distinct functions during development, in maintaining lymphocyte homeostasis, and in coordinating immune responses.
Abstract: Lymph nodes (LNs) are strategically positioned at dedicated sites throughout the body to facilitate rapid and efficient immunity. Central to the structural integrity and framework of LNs, and the recruitment and positioning of leukocytes therein, are mesenchymal and endothelial lymph node stromal cells (LNSCs). Advances in the last decade have expanded our understanding and appreciation of LNSC heterogeneity, and the role they play in coordinating immunity has grown rapidly. In this review, we will highlight the functional contributions of distinct stromal cell populations during LN development in maintaining immune homeostasis and tolerance and in the activation and control of immune responses.
Saarland University1, Rush University Medical Center2, RWTH Aachen University3, Erasmus University Rotterdam4, Leipzig University5, Medical University of Graz6, University of Zurich7, Heidelberg University8, Synlab Group9, Maastricht University10, ETH Zurich11, University of Bonn12, University of Massachusetts Medical School13
TL;DR: It is demonstrated that ApoC3 activates the NLRP3 inflammasome via a non-canonical pathway contributing to inflammation and development of atherosclerosis.
Abstract: NLRP3-inflammasome-driven inflammation is involved in the pathogenesis of a variety of diseases. Identification of endogenous inflammasome activators is essential for the development of new anti-inflammatory treatment strategies. Here, we identified that apolipoprotein C3 (ApoC3) activates the NLRP3 inflammasome in human monocytes by inducing an alternative NLRP3 inflammasome via caspase-8 and dimerization of Toll-like receptors 2 and 4. Alternative inflammasome activation in human monocytes is mediated by the Toll-like receptor adapter protein SCIMP. This triggers Lyn/Syk-dependent calcium entry and the production of reactive oxygen species, leading to activation of caspase-8. In humanized mouse models, ApoC3 activated human monocytes in vivo to impede endothelial regeneration and promote kidney injury in an NLRP3- and caspase-8-dependent manner. These data provide new insights into the regulation of the NLRP3 inflammasome and the pathophysiological role of triglyceride-rich lipoproteins containing ApoC3. Targeting ApoC3 might prevent organ damage and provide an anti-inflammatory treatment for vascular and kidney diseases.
TL;DR: This work simultaneously assess microbiota and single immune cells across the healthy, adult human colon, with paired characterization of immune cells in the mesenteric lymph nodes, to delineate colonic immune niches at steady state.
Abstract: Gastrointestinal microbiota and immune cells interact closely and display regional specificity; however, little is known about how these communities differ with location. Here, we simultaneously assess microbiota and single immune cells across the healthy, adult human colon, with paired characterization of immune cells in the mesenteric lymph nodes, to delineate colonic immune niches at steady state. We describe distinct helper T cell activation and migration profiles along the colon and characterize the transcriptional adaptation trajectory of regulatory T cells between lymphoid tissue and colon. Finally, we show increasing B cell accumulation, clonal expansion and mutational frequency from the cecum to the sigmoid colon and link this to the increasing number of reactive bacterial species.
TL;DR: It is shown that in interferon-γ-stimulated cells guanylate-binding proteins (GBPs) assemble on the surface of Gram-negative bacteria into polyvalent signaling platforms required for activation of caspase-4.
Abstract: Bacterial lipopolysaccharide triggers human caspase-4 (murine caspase-11) to cleave gasdermin-D and induce pyroptotic cell death. How lipopolysaccharide sequestered in the membranes of cytosol-invading bacteria activates caspases remains unknown. Here we show that in interferon-γ-stimulated cells guanylate-binding proteins (GBPs) assemble on the surface of Gram-negative bacteria into polyvalent signaling platforms required for activation of caspase-4. Caspase-4 activation is hierarchically controlled by GBPs; GBP1 initiates platform assembly, GBP2 and GBP4 control caspase-4 recruitment, and GBP3 governs caspase-4 activation. In response to cytosol-invading bacteria, activation of caspase-4 through the GBP platform is essential to induce gasdermin-D-dependent pyroptosis and processing of interleukin-18, thereby destroying the replicative niche for intracellular bacteria and alerting neighboring cells, respectively. Caspase-11 and GBPs epistatically protect mice against lethal bacterial challenge. Multiple antagonists of the pathway encoded by Shigella flexneri, a cytosol-adapted bacterium, provide compelling evolutionary evidence for the importance of the GBP-caspase-4 pathway in antibacterial defense.
TL;DR: Following viral clearance and clinical recovery, at 1 month after infection with influenza, mice are better protected from Streptococcus pneumoniae infection due to a population of monocyte-derived alveolar macrophages that produce increased interleukin-6.
Abstract: Despite the prevalence and clinical importance of influenza, its long-term effect on lung immunity is unclear. Here we describe that following viral clearance and clinical recovery, at 1 month after infection with influenza, mice are better protected from Streptococcus pneumoniae infection due to a population of monocyte-derived alveolar macrophages (AMs) that produce increased interleukin-6. Influenza-induced monocyte-derived AMs have a surface phenotype similar to resident AMs but display a unique functional, transcriptional and epigenetic profile that is distinct from resident AMs. In contrast, influenza-experienced resident AMs remain largely similar to naive AMs. Thus, influenza changes the composition of the AM population to provide prolonged antibacterial protection. Monocyte-derived AMs persist over time but lose their protective profile. Our results help to understand how transient respiratory infections, a common occurrence in human life, can constantly alter lung immunity by contributing monocyte-derived, recruited cells to the AM population. Respiratory infections occur throughout life but how this shapes the lung immune system through time is unclear. Wack and colleagues show that a previous influenza infection recruits monocytes to the lung, which then assume an alveolar macrophage-like phenotype and mediate long-term antibacterial protection.