RESUMO
Traditionally, the innate and adaptive immune systems are differentiated by their specificity and memory capacity. In recent years, however, this paradigm has shifted: Cells of the innate immune system appear to be able to gain memory characteristics after transient stimulation, resulting in an enhanced response upon secondary challenge. This phenomenon has been called trained immunity. Trained immunity is characterized by nonspecific increased responsiveness, mediated via extensive metabolic and epigenetic reprogramming. Trained immunity explains the heterologous effects of vaccines, which result in increased protection against secondary infections. However, in chronic inflammatory conditions, trained immunity can induce maladaptive effects and contribute to hyperinflammation and progression of cardiovascular disease, autoinflammatory syndromes, and neuroinflammation. In this review we summarize the current state of the field of trained immunity, its mechanisms, and its roles in both health and disease.
Assuntos
Memória Imunológica , Vacinas , Animais , Diferenciação Celular , Humanos , Sistema Imunitário , Imunidade InataRESUMO
The innate immune response is a rapid response to pathogens or danger signals. It is precisely activated not only to efficiently eliminate pathogens but also to avoid excessive inflammation and tissue damage. cis-Regulatory element-associated chromatin architecture shaped by epigenetic factors, which we define as the epiregulome, endows innate immune cells with specialized phenotypes and unique functions by establishing cell-specific gene expression patterns, and it also contributes to resolution of the inflammatory response. In this review, we focus on two aspects: (a) how niche signals during lineage commitment or following infection and pathogenic stress program epiregulomes by regulating gene expression levels, enzymatic activities, or gene-specific targeting of chromatin modifiers and (b) how the programed epiregulomes in turn mediate regulation of gene-specific expression, which contributes to controlling the development of innate cells, or the response to infection and inflammation, in a timely manner. We also discuss the effects of innate immunometabolic rewiring on epiregulomes and speculate on several future challenges to be encountered during the exploration of the master regulators of epiregulomes in innate immunity and inflammation.
Assuntos
Imunidade Inata , Inflamação , Animais , Epigênese Genética , Humanos , Imunidade Inata/genética , Inflamação/genéticaRESUMO
We comprehensively review memory B cells (MBCs), covering the definition of MBCs and their identities and subsets, how MBCs are generated, where they are localized, how they are maintained, and how they are reactivated. Whereas naive B cells adopt multiple fates upon stimulation, MBCs are more restricted in their responses. Evolving work reveals that the MBC compartment in mice and humans consists of distinct subpopulations with differing effector functions. We discuss the various approaches to define subsets and subset-specific roles. A major theme is the need to both deliver faster effector function upon reexposure and readapt to antigenically variant pathogens while avoiding burnout, which would be the result if all MBCs generated only terminal effector function. We discuss cell-intrinsic differences in gene expression and signaling that underlie differences in function between MBCs and naive B cells and among MBC subsets and how this leads to memory responses.
Assuntos
Subpopulações de Linfócitos B/imunologia , Linfócitos B/imunologia , Memória Imunológica , Vacinas/imunologia , Animais , Humanos , Imunidade Humoral , Ativação Linfocitária , Camundongos , TranscriptomaRESUMO
The medical burden of stroke extends beyond the brain injury itself and is largely determined by chronic comorbidities that develop secondarily. We hypothesized that these comorbidities might share a common immunological cause, yet chronic effects post-stroke on systemic immunity are underexplored. Here, we identify myeloid innate immune memory as a cause of remote organ dysfunction after stroke. Single-cell sequencing revealed persistent pro-inflammatory changes in monocytes/macrophages in multiple organs up to 3 months after brain injury, notably in the heart, leading to cardiac fibrosis and dysfunction in both mice and stroke patients. IL-1ß was identified as a key driver of epigenetic changes in innate immune memory. These changes could be transplanted to naive mice, inducing cardiac dysfunction. By neutralizing post-stroke IL-1ß or blocking pro-inflammatory monocyte trafficking with a CCR2/5 inhibitor, we prevented post-stroke cardiac dysfunction. Such immune-targeted therapies could potentially prevent various IL-1ß-mediated comorbidities, offering a framework for secondary prevention immunotherapy.
Assuntos
Lesões Encefálicas , Imunidade Inata , Memória Imunológica , Inflamação , Interleucina-1beta , Camundongos Endogâmicos C57BL , Monócitos , Animais , Camundongos , Interleucina-1beta/metabolismo , Lesões Encefálicas/imunologia , Humanos , Masculino , Monócitos/metabolismo , Monócitos/imunologia , Inflamação/imunologia , Macrófagos/imunologia , Macrófagos/metabolismo , Acidente Vascular Cerebral/complicações , Acidente Vascular Cerebral/imunologia , Cardiopatias/imunologia , Feminino , Receptores CCR2/metabolismo , Fibrose , Epigênese Genética , Imunidade TreinadaRESUMO
Multiple COVID-19 vaccines, representing diverse vaccine platforms, successfully protect against symptomatic COVID-19 cases and deaths. Head-to-head comparisons of T cell, B cell, and antibody responses to diverse vaccines in humans are likely to be informative for understanding protective immunity against COVID-19, with particular interest in immune memory. Here, SARS-CoV-2-spike-specific immune responses to Moderna mRNA-1273, Pfizer/BioNTech BNT162b2, Janssen Ad26.COV2.S, and Novavax NVX-CoV2373 were examined longitudinally for 6 months 100% of individuals made memory CD4+ T cells, with cTfh and CD4-CTL highly represented after mRNA or NVX-CoV2373 vaccination. mRNA vaccines and Ad26.COV2.S induced comparable CD8+ T cell frequencies, though only detectable in 60-67% of subjects at 6 months. A differentiating feature of Ad26.COV2.S immunization was a high frequency of CXCR3+ memory B cells. mRNA vaccinees had substantial declines in antibodies, while memory T and B cells were comparatively stable. These results may also be relevant for insights against other pathogens.
Assuntos
Vacinas contra COVID-19 , COVID-19 , Ad26COVS1 , Anticorpos Antivirais , Vacina BNT162 , COVID-19/prevenção & controle , Humanos , Imunidade Humoral , Memória Imunológica , SARS-CoV-2RESUMO
SARS-CoV-2 Omicron is highly transmissible and has substantial resistance to neutralization following immunization with ancestral spike-matched vaccines. It is unclear whether boosting with Omicron-matched vaccines would enhance protection. Here, nonhuman primates that received mRNA-1273 at weeks 0 and 4 were boosted at week 41 with mRNA-1273 or mRNA-Omicron. Neutralizing titers against D614G were 4,760 and 270 reciprocal ID50 at week 6 (peak) and week 41 (preboost), respectively, and 320 and 110 for Omicron. 2 weeks after the boost, titers against D614G and Omicron increased to 5,360 and 2,980 for mRNA-1273 boost and 2,670 and 1,930 for mRNA-Omicron, respectively. Similar increases against BA.2 were observed. Following either boost, 70%-80% of spike-specific B cells were cross-reactive against WA1 and Omicron. Equivalent control of virus replication in lower airways was observed following Omicron challenge 1 month after either boost. These data show that mRNA-1273 and mRNA-Omicron elicit comparable immunity and protection shortly after the boost.
Assuntos
COVID-19 , SARS-CoV-2 , Vacina de mRNA-1273 contra 2019-nCoV , Animais , Anticorpos Neutralizantes , Anticorpos Antivirais , COVID-19/prevenção & controle , Macaca , RNA MensageiroRESUMO
We examined antibody and memory B cell responses longitudinally for â¼9-10 months after primary 2-dose SARS-CoV-2 mRNA vaccination and 3 months after a 3rd dose. Antibody decay stabilized between 6 and 9 months, and antibody quality continued to improve for at least 9 months after 2-dose vaccination. Spike- and RBD-specific memory B cells remained durable over time, and 40%-50% of RBD-specific memory B cells simultaneously bound the Alpha, Beta, Delta, and Omicron variants. Omicron-binding memory B cells were efficiently reactivated by a 3rd dose of wild-type vaccine and correlated with the corresponding increase in neutralizing antibody titers. In contrast, pre-3rd dose antibody titers inversely correlated with the fold-change of antibody boosting, suggesting that high levels of circulating antibodies may limit the added protection afforded by repeat short interval boosting. These data provide insight into the quantity and quality of mRNA-vaccine-induced immunity over time through 3 or more antigen exposures.
Assuntos
Vacinas contra COVID-19 , COVID-19 , Anticorpos Neutralizantes , Anticorpos Antivirais , COVID-19/prevenção & controle , Humanos , RNA Mensageiro , SARS-CoV-2 , Vacinas Sintéticas , Vacinas de mRNARESUMO
The human fetal immune system begins to develop early during gestation; however, factors responsible for fetal immune-priming remain elusive. We explored potential exposure to microbial agents in utero and their contribution toward activation of memory T cells in fetal tissues. We profiled microbes across fetal organs using 16S rRNA gene sequencing and detected low but consistent microbial signal in fetal gut, skin, placenta, and lungs in the 2nd trimester of gestation. We identified several live bacterial strains including Staphylococcus and Lactobacillus in fetal tissues, which induced in vitro activation of memory T cells in fetal mesenteric lymph node, supporting the role of microbial exposure in fetal immune-priming. Finally, using SEM and RNA-ISH, we visualized discrete localization of bacteria-like structures and eubacterial-RNA within 14th weeks fetal gut lumen. These findings indicate selective presence of live microbes in fetal organs during the 2nd trimester of gestation and have broader implications toward the establishment of immune competency and priming before birth.
Assuntos
Bactérias/metabolismo , Desenvolvimento Embrionário , Feto/citologia , Feto/microbiologia , Leucócitos/citologia , Adulto , Bactérias/genética , Bactérias/ultraestrutura , Proliferação de Células , Células Dendríticas/metabolismo , Feminino , Feto/ultraestrutura , Trato Gastrointestinal/embriologia , Trato Gastrointestinal/ultraestrutura , Humanos , Memória Imunológica , Ativação Linfocitária/imunologia , Viabilidade Microbiana , Gravidez , Segundo Trimestre da Gravidez , RNA Bacteriano/genética , RNA Ribossômico 16S/genética , Reprodutibilidade dos Testes , Linfócitos T/citologiaRESUMO
Trained innate immunity, induced via modulation of mature myeloid cells or their bone marrow progenitors, mediates sustained increased responsiveness to secondary challenges. Here, we investigated whether anti-tumor immunity can be enhanced through induction of trained immunity. Pre-treatment of mice with ß-glucan, a fungal-derived prototypical agonist of trained immunity, resulted in diminished tumor growth. The anti-tumor effect of ß-glucan-induced trained immunity was associated with transcriptomic and epigenetic rewiring of granulopoiesis and neutrophil reprogramming toward an anti-tumor phenotype; this process required type I interferon signaling irrespective of adaptive immunity in the host. Adoptive transfer of neutrophils from ß-glucan-trained mice to naive recipients suppressed tumor growth in the latter in a ROS-dependent manner. Moreover, the anti-tumor effect of ß-glucan-induced trained granulopoiesis was transmissible by bone marrow transplantation to recipient naive mice. Our findings identify a novel and therapeutically relevant anti-tumor facet of trained immunity involving appropriate rewiring of granulopoiesis.
Assuntos
Granulócitos/imunologia , Imunidade Inata , Neoplasias/imunologia , Imunidade Adaptativa , Transferência Adotiva , Animais , Epigênese Genética , Interferon Tipo I/metabolismo , Camundongos Endogâmicos C57BL , Monócitos/metabolismo , Neoplasias/patologia , Neutrófilos/metabolismo , Fenótipo , Receptor de Interferon alfa e beta/deficiência , Receptor de Interferon alfa e beta/metabolismo , Transcrição Gênica , Transcriptoma/genética , beta-Glucanas/metabolismoRESUMO
Natural killer (NK) cells are present in the circulation and can also be found residing in tissues, and these populations exhibit distinct developmental requirements and are thought to differ in terms of ontogeny. Here, we investigate whether circulating conventional NK (cNK) cells can develop into long-lived tissue-resident NK (trNK) cells following acute infections. We found that viral and bacterial infections of the skin triggered the recruitment of cNK cells and their differentiation into Tcf1hiCD69hi trNK cells that share transcriptional similarity with CD56brightTCF1hi NK cells in human tissues. Skin trNK cells arose from interferon (IFN)-γ-producing effector cells and required restricted expression of the transcriptional regulator Blimp1 to optimize Tcf1-dependent trNK cell formation. Upon secondary infection, trNK cells rapidly gained effector function and mediated an accelerated NK cell response. Thus, cNK cells redistribute and permanently position at sites of previous infection via a mechanism promoting tissue residency that is distinct from Hobit-dependent developmental paths of NK cells and ILC1 seeding tissues during ontogeny.
Assuntos
Coinfecção , Humanos , Células Matadoras Naturais/metabolismo , Diferenciação CelularRESUMO
Plasma cells that emerge after infection or vaccination exhibit heterogeneous lifespans; most survive for days to months, whereas others persist for decades, providing antigen-specific long-term protection. We developed a mathematical framework to explore the dynamics of plasma cell removal and its regulation by survival factors. Analyses of antibody persistence following hepatitis A and B and HPV vaccination revealed specific patterns of longevity and heterogeneity within and between responses, implying that this process is fine-tuned near a critical "flat" state between two dynamic regimes. This critical state reflects the tuning of rates of the underlying regulatory network and is highly sensitive to variation in parameters, which amplifies lifespan differences between cells. We propose that fine-tuning is the generic outcome of competition over shared survival signals, with a competition-based mechanism providing a unifying explanation for a wide range of experimental observations, including the dynamics of plasma cell accumulation and the effects of survival factor deletion. Our theory is testable, and we provide specific predictions.
Assuntos
Longevidade , Plasmócitos , Anticorpos , Vacinação , AntígenosRESUMO
The immune system encodes information about the severity of a pathogenic threat in the quantity and type of memory cells it forms. This encoding emerges from lymphocyte decisions to maintain or lose self-renewal and memory potential during a challenge. By tracking CD8+ T cells at the single-cell and clonal lineage level using time-resolved transcriptomics, quantitative live imaging, and an acute infection model, we find that T cells will maintain or lose memory potential early after antigen recognition. However, following pathogen clearance, T cells may regain memory potential if initially lost. Mechanistically, this flexibility is implemented by a stochastic cis-epigenetic switch that tunably and reversibly silences the memory regulator, TCF1, in response to stimulation. Mathematical modeling shows how this flexibility allows memory T cell numbers to scale robustly with pathogen virulence and immune response magnitudes. We propose that flexibility and stochasticity in cellular decisions ensure optimal immune responses against diverse threats.
Assuntos
Linfócitos T CD8-Positivos , Células T de Memória , Epigênese Genética , Células Clonais , Memória Imunológica , Diferenciação CelularRESUMO
Innate immune cells can develop long-term memory after stimulation by microbial products during infections or vaccinations. Here, we report that metabolic signals can induce trained immunity. Pharmacological and genetic experiments reveal that activation of the cholesterol synthesis pathway, but not the synthesis of cholesterol itself, is essential for training of myeloid cells. Rather, the metabolite mevalonate is the mediator of training via activation of IGF1-R and mTOR and subsequent histone modifications in inflammatory pathways. Statins, which block mevalonate generation, prevent trained immunity induction. Furthermore, monocytes of patients with hyper immunoglobulin D syndrome (HIDS), who are mevalonate kinase deficient and accumulate mevalonate, have a constitutive trained immunity phenotype at both immunological and epigenetic levels, which could explain the attacks of sterile inflammation that these patients experience. Unraveling the role of mevalonate in trained immunity contributes to our understanding of the pathophysiology of HIDS and identifies novel therapeutic targets for clinical conditions with excessive activation of trained immunity.
Assuntos
Imunidade Inata , Memória Imunológica , Deficiência de Mevalonato Quinase/imunologia , Ácido Mevalônico/metabolismo , Monócitos/imunologia , Animais , Células Cultivadas , Humanos , Inibidores de Hidroximetilglutaril-CoA Redutases/farmacologia , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Monócitos/efeitos dos fármacos , Receptor IGF Tipo 1/metabolismoRESUMO
Trained innate immunity fosters a sustained favorable response of myeloid cells to a secondary challenge, despite their short lifespan in circulation. We thus hypothesized that trained immunity acts via modulation of hematopoietic stem and progenitor cells (HSPCs). Administration of ß-glucan (prototypical trained-immunity-inducing agonist) to mice induced expansion of progenitors of the myeloid lineage, which was associated with elevated signaling by innate immune mediators, such as IL-1ß and granulocyte-macrophage colony-stimulating factor (GM-CSF), and with adaptations in glucose metabolism and cholesterol biosynthesis. The trained-immunity-related increase in myelopoiesis resulted in a beneficial response to secondary LPS challenge and protection from chemotherapy-induced myelosuppression in mice. Therefore, modulation of myeloid progenitors in the bone marrow is an integral component of trained immunity, which to date, was considered to involve functional changes of mature myeloid cells in the periphery.
Assuntos
Imunidade Inata , Memória Imunológica , Células Progenitoras Mieloides/imunologia , Animais , Células Cultivadas , Fator Estimulador de Colônias de Granulócitos e Macrófagos/metabolismo , Interleucina-1beta/metabolismo , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Células Progenitoras Mieloides/efeitos dos fármacos , Mielopoese/imunologia , beta-Glucanas/farmacologiaRESUMO
Long-term epigenetic reprogramming of innate immune cells in response to microbes, also termed "trained immunity," causes prolonged altered cellular functionality to protect from secondary infections. Here, we investigated whether sterile triggers of inflammation induce trained immunity and thereby influence innate immune responses. Western diet (WD) feeding of Ldlr-/- mice induced systemic inflammation, which was undetectable in serum soon after mice were shifted back to a chow diet (CD). In contrast, myeloid cell responses toward innate stimuli remained broadly augmented. WD-induced transcriptomic and epigenomic reprogramming of myeloid progenitor cells led to increased proliferation and enhanced innate immune responses. Quantitative trait locus (QTL) analysis in human monocytes trained with oxidized low-density lipoprotein (oxLDL) and stimulated with lipopolysaccharide (LPS) suggested inflammasome-mediated trained immunity. Consistently, Nlrp3-/-/Ldlr-/- mice lacked WD-induced systemic inflammation, myeloid progenitor proliferation, and reprogramming. Hence, NLRP3 mediates trained immunity following WD and could thereby mediate the potentially deleterious effects of trained immunity in inflammatory diseases.
Assuntos
Reprogramação Celular , Dieta Ocidental , Epigênese Genética , Imunidade Inata , Memória Imunológica , Proteína 3 que Contém Domínio de Pirina da Família NLR/genética , Adulto , Idoso , Animais , Células Cultivadas , Feminino , Humanos , Lipoproteínas LDL/metabolismo , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Pessoa de Meia-Idade , Células Mieloides/imunologia , Proteína 3 que Contém Domínio de Pirina da Família NLR/metabolismo , Locos de Características Quantitativas , Receptores de LDL/genéticaRESUMO
Innate immune memory is an emerging area of research. However, innate immune memory at major mucosal sites remains poorly understood. Here, we show that respiratory viral infection induces long-lasting memory alveolar macrophages (AMs). Memory AMs are programed to express high MHC II, a defense-ready gene signature, and increased glycolytic metabolism, and produce, upon re-stimulation, neutrophil chemokines. Using a multitude of approaches, we reveal that the priming, but not maintenance, of memory AMs requires the help from effector CD8 T cells. T cells jump-start this process via IFN-γ production. We further find that formation and maintenance of memory AMs are independent of monocytes or bone marrow progenitors. Finally, we demonstrate that memory AMs are poised for robust trained immunity against bacterial infection in the lung via rapid induction of chemokines and neutrophilia. Our study thus establishes a new paradigm of immunological memory formation whereby adaptive T-lymphocytes render innate memory of mucosal-associated macrophages.
Assuntos
Linfócitos T CD8-Positivos/imunologia , Imunidade Inata , Pulmão/imunologia , Macrófagos Alveolares/imunologia , Linfócitos T Auxiliares-Indutores/imunologia , Animais , Linfócitos T CD8-Positivos/citologia , Memória Imunológica , Pulmão/citologia , Macrófagos Alveolares/citologia , Camundongos , Camundongos Endogâmicos BALB C , Camundongos Transgênicos , Monócitos/citologia , Monócitos/imunologia , Mucosa Respiratória/citologia , Mucosa Respiratória/imunologia , Linfócitos T Auxiliares-Indutores/citologiaRESUMO
Memory B cells (MBCs) can persist for a lifetime, but the mechanisms that allow their long-term survival remain poorly understood. Here, we isolated and analyzed human splenic smallpox/vaccinia protein B5-specific MBCs in individuals who were vaccinated more than 40 years ago. Only a handful of clones persisted over such an extended period, and they displayed limited intra-clonal diversity with signs of extensive affinity-based selection. These long-lived MBCs appeared enriched in a CD21hiCD20hi IgG+ splenic B cell subset displaying a marginal-zone-like NOTCH/MYC-driven signature, but they did not harbor a unique longevity-associated transcriptional or metabolic profile. Finally, the telomeres of B5-specific, long-lived MBCs were longer than those in patient-paired naive B cells in all the samples analyzed. Overall, these results imply that separate mechanisms such as early telomere elongation, affinity selection during the contraction phase, and access to a specific niche contribute to ensuring the functional longevity of MBCs.
Assuntos
Memória Imunológica , Células B de Memória , Linfócitos B/metabolismo , Centro Germinativo , Humanos , Imunoglobulina G/metabolismoRESUMO
The consumption of Western-type calorically rich diets combined with chronic overnutrition and a sedentary lifestyle in Western societies evokes a state of chronic metabolic inflammation, termed metaflammation. Metaflammation contributes to the development of many prevalent non-communicable diseases (NCDs), and these lifestyle-associated pathologies represent a rising public health problem with global epidemic dimensions. A better understanding of how modern lifestyle and Western diet (WD) activate immune cells is essential for the development of efficient preventive and therapeutic strategies for common NCDs. Here, we review the current mechanistic understanding of how the Western lifestyle can induce metaflammation, and we discuss how this knowledge can be translated to protect the public from the health burden associated with their selected lifestyle.
Assuntos
Dieta Ocidental , Sistema Imunitário/fisiologia , Animais , Dieta , Suscetibilidade a Doenças , Retroalimentação Fisiológica , Microbioma Gastrointestinal , Homeostase , Interações Hospedeiro-Patógeno/imunologia , Humanos , Imunidade Inata , Inflamação/etiologia , Inflamação/metabolismo , Especificidade de ÓrgãosRESUMO
Over the past decade, compelling evidence has unveiled previously overlooked adaptive characteristics of innate immune cells. Beyond their traditional role in providing short, non-specific protection against pathogens, innate immune cells can acquire antigen-agnostic memory, exhibiting increased responsiveness to secondary stimulation. This long-term de-facto innate immune memory, also termed trained immunity, is mediated through extensive metabolic rewiring and epigenetic modifications. While the upregulation of trained immunity proves advantageous in countering immune paralysis, its overactivation contributes to the pathogenesis of autoinflammatory and autoimmune disorders. In this review, we present the latest advancements in the field of innate immune memory followed by a description of the fundamental mechanisms underpinning trained immunity generation and different cell types that mediate it. Furthermore, we explore its implications for various diseases and examine current limitations and its potential therapeutic targeting in immune-related disorders.
Assuntos
Epigênese Genética , Imunidade Inata , Memória Imunológica , Humanos , Animais , Doenças Autoimunes/imunologia , Imunidade Adaptativa , Imunidade TreinadaRESUMO
Group 2 Innate Lymphoid Cells (ILC2s) are innate lymphocytes involved in type 2 immunity. ILC2s are abundant at the barrier tissues and upon allergen exposure, respond to epithelial-derived alarmins by producing type 2 cytokines (e.g., IL-5 and IL-13). Upon activation, some of these activated ILC2s acquire immunological memory and can mount enhanced responses upon further allergen encounters. Here, we review recent findings of the cellular and molecular mechanisms underlying immune memory in ILC2s both in mice and humans and discuss the implications of memory ILC2s in the context of allergic diseases.