RESUMO
Immune cells use a variety of membrane-disrupting proteins [complement, perforin, perforin-2, granulysin, gasdermins, mixed lineage kinase domain-like pseudokinase (MLKL)] to induce different kinds of death of microbes and host cells, some of which cause inflammation. After activation by proteolytic cleavage or phosphorylation, these proteins oligomerize, bind to membrane lipids, and disrupt membrane integrity. These membrane disruptors play a critical role in both innate and adaptive immunity. Here we review our current knowledge of the functions, specificity, activation, and regulation of membrane-disrupting immune proteins and what is known about the mechanisms behind membrane damage, the structure of the pores they form, how the cells expressing these lethal proteins are protected, and how cells targeted for destruction can sometimes escape death by repairing membrane damage.
Assuntos
Citotoxicidade Imunológica , Interações Hospedeiro-Patógeno/imunologia , Imunidade , Proteínas Citotóxicas Formadoras de Poros/metabolismo , Animais , Apoptose/genética , Apoptose/imunologia , Biomarcadores , Membrana Celular/imunologia , Membrana Celular/metabolismo , Complexo de Ataque à Membrana do Sistema Complemento , Proteínas do Sistema Complemento/imunologia , Proteínas do Sistema Complemento/metabolismo , Regulação da Expressão Gênica , Humanos , Sistema Imunitário/imunologia , Sistema Imunitário/metabolismo , Metabolismo dos Lipídeos , Necroptose/genética , Necroptose/imunologia , Necrose/genética , Necrose/imunologia , Necrose/metabolismo , Proteínas Citotóxicas Formadoras de Poros/química , Proteínas Citotóxicas Formadoras de Poros/genética , Relação Estrutura-AtividadeRESUMO
The human body generates 10-100 billion cells every day, and the same number of cells die to maintain homeostasis in our body. Cells infected by bacteria or viruses also die. The cell death that occurs under physiological conditions mainly proceeds by apoptosis, which is a noninflammatory, or silent, process, while pathogen infection induces necroptosis or pyroptosis, which activates the immune system and causes inflammation. Dead cells generated by apoptosis are quickly engulfed by macrophages for degradation. Caspases are a large family of cysteine proteases that act in cascades. A cascade that leads to caspase 3 activation mediates apoptosis and is responsible for killing cells, recruiting macrophages, and presenting an "eat me" signal(s). When apoptotic cells are not efficiently engulfed by macrophages, they undergo secondary necrosis and release intracellular materials that represent a damage-associated molecular pattern, which may lead to a systemic lupus-like autoimmune disease.
Assuntos
Apoptose/imunologia , Fagocitose/imunologia , Animais , Biomarcadores , Caspases/metabolismo , Morte Celular , Humanos , Lisossomos/metabolismo , Macrófagos/imunologia , Macrófagos/metabolismo , Fosfatidilserinas/metabolismo , Proteínas de Transferência de Fosfolipídeos/metabolismo , Receptores de Morte Celular/metabolismo , Transdução de Sinais , Especificidade por SubstratoRESUMO
Caspases regulate cell death, immune responses, and homeostasis. Caspase-6 is categorized as an executioner caspase but shows key differences from the other executioners. Overall, little is known about the functions of caspase-6 in biological processes apart from apoptosis. Here, we show that caspase-6 mediates innate immunity and inflammasome activation. Furthermore, we demonstrate that caspase-6 promotes the activation of programmed cell death pathways including pyroptosis, apoptosis, and necroptosis (PANoptosis) and plays an essential role in host defense against influenza A virus (IAV) infection. In addition, caspase-6 promoted the differentiation of alternatively activated macrophages (AAMs). Caspase-6 facilitated the RIP homotypic interaction motif (RHIM)-dependent binding of RIPK3 to ZBP1 via its interaction with RIPK3. Altogether, our findings reveal a vital role for caspase-6 in facilitating ZBP1-mediated inflammasome activation, cell death, and host defense during IAV infection, opening additional avenues for treatment of infectious and autoinflammatory diseases and cancer.
Assuntos
Caspase 6/imunologia , Caspase 6/metabolismo , Inflamassomos/imunologia , Animais , Apoptose/imunologia , Morte Celular/imunologia , Imunidade Inata , Inflamassomos/metabolismo , Inflamassomos/fisiologia , Inflamação/imunologia , Inflamação/metabolismo , Inflamação/patologia , Macrófagos/imunologia , Macrófagos/metabolismo , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Proteína 3 que Contém Domínio de Pirina da Família NLR/metabolismo , Necroptose/imunologia , Ligação Proteica , Piroptose/imunologia , Proteínas de Ligação a RNA/metabolismo , Proteína Serina-Treonina Quinases de Interação com Receptores/metabolismoRESUMO
Fibroblastic reticular cells (FRCs) are specialized stromal cells that define tissue architecture and regulate lymphocyte compartmentalization, homeostasis, and innate and adaptive immunity in secondary lymphoid organs (SLOs). In the present study, we used single-cell RNA sequencing (scRNA-seq) of human and mouse lymph nodes (LNs) to identify a subset of T cell-zone FRCs defined by the expression of Gremlin1 (Grem1) in both species. Grem1-CreERT2 knock-in mice enabled localization, multi-omics characterization and genetic depletion of Grem1+ FRCs. Grem1+ FRCs primarily localize at T-B cell junctions of SLOs, neighboring pre-dendritic cells and conventional dendritic cells (cDCs). As such, their depletion resulted in preferential loss and decreased homeostatic proliferation and survival of resident cDCs and compromised T cell immunity. Trajectory analysis of human LN scRNA-seq data revealed expression similarities to murine FRCs, with GREM1+ cells marking the endpoint of both trajectories. These findings illuminate a new Grem1+ fibroblastic niche in LNs that functions to maintain the homeostasis of lymphoid tissue-resident cDCs.
Assuntos
Células Dendríticas Foliculares/imunologia , Fibroblastos/imunologia , Linfonodos/imunologia , Células Estromais/imunologia , Idoso , Animais , Apoptose/genética , Apoptose/imunologia , Proliferação de Células/genética , Sobrevivência Celular/genética , Sobrevivência Celular/imunologia , Células Dendríticas Foliculares/metabolismo , Feminino , Fibroblastos/metabolismo , Regulação da Expressão Gênica/imunologia , Técnicas de Introdução de Genes , Humanos , Imunidade Celular/genética , Peptídeos e Proteínas de Sinalização Intercelular/genética , Peptídeos e Proteínas de Sinalização Intercelular/metabolismo , Linfonodos/citologia , Masculino , Camundongos , Camundongos Transgênicos , RNA-Seq , Análise de Célula Única , Células Estromais/metabolismo , Linfócitos T/imunologia , Linfócitos T/metabolismoRESUMO
Ptpn6 is a cytoplasmic phosphatase that functions to prevent autoimmune and interleukin-1 (IL-1) receptor-dependent, caspase-1-independent inflammatory disease. Conditional deletion of Ptpn6 in neutrophils (Ptpn6∆PMN) is sufficient to initiate IL-1 receptor-dependent cutaneous inflammatory disease, but the source of IL-1 and the mechanisms behind IL-1 release remain unclear. Here, we investigate the mechanisms controlling IL-1α/ß release from neutrophils by inhibiting caspase-8-dependent apoptosis and Ripk1-Ripk3-Mlkl-regulated necroptosis. Loss of Ripk1 accelerated disease onset, whereas combined deletion of caspase-8 and either Ripk3 or Mlkl strongly protected Ptpn6∆PMN mice. Ptpn6∆PMN neutrophils displayed increased p38 mitogen-activated protein kinase-dependent Ripk1-independent IL-1 and tumor necrosis factor production, and were prone to cell death. Together, these data emphasize dual functions for Ptpn6 in the negative regulation of p38 mitogen-activated protein kinase activation to control tumor necrosis factor and IL-1α/ß expression, and in maintaining Ripk1 function to prevent caspase-8- and Ripk3-Mlkl-dependent cell death and concomitant IL-1α/ß release.
Assuntos
Apoptose/imunologia , Caspase 8/imunologia , Neutrófilos/imunologia , Proteínas Quinases/imunologia , Proteína Tirosina Fosfatase não Receptora Tipo 6/metabolismo , Proteína Serina-Treonina Quinases de Interação com Receptores/imunologia , Animais , Caspase 8/genética , Células Cultivadas , Deleção de Genes , Inflamação/imunologia , Interleucina-1/imunologia , Interleucina-1alfa/metabolismo , Interleucina-1beta/metabolismo , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Proteína Tirosina Fosfatase não Receptora Tipo 6/genética , Receptores Tipo I de Interleucina-1/imunologia , Fator de Necrose Tumoral alfa/metabolismo , Proteínas Quinases p38 Ativadas por Mitógeno/metabolismoRESUMO
Tissue-resident memory T cells (TRM cells) are critical for cellular immunity to respiratory pathogens and reside in both the airways and the interstitium. In the present study, we found that the airway environment drove transcriptional and epigenetic changes that specifically regulated the cytolytic functions of airway TRM cells and promoted apoptosis due to amino acid starvation and activation of the integrated stress response. Comparison of airway TRM cells and splenic effector-memory T cells transferred into the airways indicated that the environment was necessary to activate these pathways, but did not induce TRM cell lineage reprogramming. Importantly, activation of the integrated stress response was reversed in airway TRM cells placed in a nutrient-rich environment. Our data defined the genetic programs of distinct lung TRM cell populations and show that local environmental cues altered airway TRM cells to limit cytolytic function and promote cell death, which ultimately leads to fewer TRM cells in the lung.
Assuntos
Linfócitos T CD8-Positivos/imunologia , Reprogramação Celular/genética , Reprogramação Celular/imunologia , Epigênese Genética/imunologia , Memória Imunológica/genética , Pulmão/imunologia , Animais , Apoptose/imunologia , Linfócitos T CD8-Positivos/citologia , Sobrevivência Celular/genética , Sobrevivência Celular/imunologia , Microambiente Celular/genética , Microambiente Celular/imunologia , Feminino , Pulmão/citologia , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Infecções por Orthomyxoviridae/genética , Infecções por Orthomyxoviridae/imunologia , Infecções por Orthomyxoviridae/patologiaRESUMO
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-ß 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.
Assuntos
Antígenos CD36/imunologia , Neoplasias/imunologia , Linfócitos T Reguladores/imunologia , Animais , Apoptose/imunologia , Antígenos CD36/deficiência , Antígenos CD36/genética , Linhagem Celular Tumoral , Feminino , Homeostase/imunologia , Humanos , Imunoterapia , Metabolismo dos Lipídeos/genética , Linfócitos do Interstício Tumoral/imunologia , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Neoplasias/metabolismo , Neoplasias/patologia , PPAR beta/imunologia , Transdução de Sinais/imunologia , Linfócitos T Reguladores/metabolismo , Linfócitos T Reguladores/patologia , Microambiente Tumoral/imunologiaRESUMO
Rheumatoid arthritis is characterized by progressive joint inflammation and affects ~1% of the human population. We noted single-nucleotide polymorphisms (SNPs) in the apoptotic cell-engulfment genes ELMO1, DOCK2, and RAC1 linked to rheumatoid arthritis. As ELMO1 promotes cytoskeletal reorganization during engulfment, we hypothesized that ELMO1 loss would worsen inflammatory arthritis. Surprisingly, Elmo1-deficient mice showed reduced joint inflammation in acute and chronic arthritis models. Genetic and cell-biology studies revealed that ELMO1 associates with receptors linked to neutrophil function in arthritis and regulates activation and early neutrophil recruitment to the joints, without general inhibition of inflammatory responses. Further, neutrophils from the peripheral blood of human donors that carry the SNP in ELMO1 associated with arthritis display increased migratory capacity, whereas ELMO1 knockdown reduces human neutrophil migration to chemokines linked to arthritis. These data identify 'noncanonical' roles for ELMO1 as an important cytoplasmic regulator of specific neutrophil receptors and promoter of arthritis.
Assuntos
Proteínas Adaptadoras de Transdução de Sinal/imunologia , Artrite Experimental/imunologia , Artrite Reumatoide/imunologia , Neutrófilos/imunologia , Proteínas Adaptadoras de Transdução de Sinal/genética , Animais , Apoptose/imunologia , Artrite Experimental/diagnóstico , Artrite Experimental/genética , Artrite Experimental/patologia , Artrite Reumatoide/diagnóstico , Artrite Reumatoide/genética , Artrite Reumatoide/patologia , Quimiotaxia/genética , Quimiotaxia/imunologia , Colágeno/imunologia , Complemento C5a/imunologia , Complemento C5a/metabolismo , Citoplasma/imunologia , Citoplasma/metabolismo , Modelos Animais de Doenças , Feminino , Perfilação da Expressão Gênica , Voluntários Saudáveis , Humanos , Microscopia Intravital , Articulações/citologia , Articulações/imunologia , Leucotrieno B4/imunologia , Leucotrieno B4/metabolismo , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Neutrófilos/metabolismo , Polimorfismo de Nucleotídeo Único , Proteômica , Índice de Gravidade de Doença , Transdução de Sinais/imunologia , Imagem com Lapso de TempoRESUMO
The transcription factor AhR modulates immunity at multiple levels. Here we report that phagocytes exposed to apoptotic cells exhibited rapid activation of AhR, which drove production of the cytokine IL-10. Activation of AhR was dependent on interactions between apoptotic-cell DNA and the pattern-recognition receptor TLR9 that was required for the prevention of immune responses to DNA and histones in vivo. Moreover, disease progression in mouse systemic lupus erythematosus (SLE) correlated with strength of the AhR signal, and the disease course could be altered by modulation of AhR activity. Deletion of AhR in the myeloid lineage caused systemic autoimmunity in mice, and an enhanced AhR transcriptional signature correlated with disease in patients with SLE. Thus, AhR activity induced by apoptotic cell phagocytes maintains peripheral tolerance.
Assuntos
Apoptose/imunologia , Tolerância Imunológica/imunologia , Lúpus Eritematoso Sistêmico/imunologia , Macrófagos/imunologia , Receptores de Hidrocarboneto Arílico/imunologia , Animais , Humanos , Camundongos , Transdução de Sinais/imunologia , Receptor Toll-Like 9/imunologiaRESUMO
Activation-induced cell death (AICD) of T lymphocytes can be exploited by cancers to escape immunological destruction. We demonstrated that tumor-specific cytotoxic T lymphocytes (CTLs) and type 1 helper T (TH1) cells, rather than type 2 helper T cells and regulatory T cells, were sensitive to AICD in breast and lung cancer microenvironments. NKILA, an NF-κB-interacting long noncoding RNA (lncRNA), regulates T cell sensitivity to AICD by inhibiting NF-κB activity. Mechanistically, calcium influx in stimulated T cells via T cell-receptor signaling activates calmodulin, thereby removing deacetylase from the NKILA promoter and enhancing STAT1-mediated transcription. Administering CTLs with NKILA knockdown effectively inhibited growth of breast cancer patient-derived xenografts in mice by increasing CTL infiltration. Clinically, NKILA overexpression in tumor-specific CTLs and TH1 cells correlated with their apoptosis and shorter patient survival. Our findings underscore the importance of lncRNAs in determining tumor-mediated T cell AICD and suggest that engineering lncRNAs in adoptively transferred T cells might provide a novel antitumor immunotherapy.
Assuntos
Carcinoma/imunologia , RNA Longo não Codificante/imunologia , Linfócitos T Citotóxicos/imunologia , Células Th1/imunologia , Evasão Tumoral/genética , Animais , Apoptose/imunologia , Neoplasias da Mama/genética , Neoplasias da Mama/imunologia , Neoplasias da Mama/patologia , Carcinoma/genética , Carcinoma/patologia , Feminino , Xenoenxertos , Humanos , Neoplasias Pulmonares/genética , Neoplasias Pulmonares/imunologia , Neoplasias Pulmonares/patologia , Masculino , Camundongos Endogâmicos NOD , Camundongos SCID , RNA Longo não Codificante/genéticaRESUMO
Neutrophils migrate rapidly to damaged tissue and play critical roles in host defense and tissue homeostasis. Here we investigated the mechanisms whereby neutrophils participate in tissue repair. In an intestinal epithelia injury model, neutrophil depletion exacerbated colitis and associated with reduced interleukin (IL)-22 and limited activation of type 3 innate lymphoid cells (ILC3s). Co-culture with neutrophils activated ILC3s in a manner dependent on neutrophil apoptosis. Metabolomic analyses revealed that lysophosphatidylserine (LysoPS) from apoptotic neutrophils directly stimulated ILC3 activation. ILC3-specific deletion of Gpr34, encoding the LysoPS receptor GPR34, or inhibition of downstream PI3K-AKT or ERK suppressed IL-22 production in response to apoptotic neutrophils. Gpr34-/- mice exhibited compromised ILC3 activation and tissue repair during colon injury, and neutrophil depletion abrogated these defects. GPR34 deficiency in ILC3s limited IL-22 production and tissue repair in vivo in settings of colon and skin injury. Thus, GPR34 is an ILC3-expressed damage-sensing receptor that triggers tissue repair upon recognition of dying neutrophils.
Assuntos
Apoptose/imunologia , Imunidade Inata/imunologia , Linfócitos/imunologia , Lisofosfolipídeos/imunologia , Neutrófilos/imunologia , Receptores de Lisofosfolipídeos/imunologia , Animais , Células Cultivadas , Colite/imunologia , Colo/imunologia , Homeostase/imunologia , Humanos , Interleucinas/imunologia , Mucosa Intestinal/imunologia , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Fosfatidilinositol 3-Quinases/imunologia , Interleucina 22RESUMO
Two sets of innate immune proteins detect pathogens. Pattern recognition receptors (PRRs) bind microbial products, whereas guard proteins detect virulence factor activities by the surveillance of homeostatic processes within cells. While PRRs are well known for their roles in many types of infections, the role of guard proteins in most infectious contexts remains less understood. Here, we demonstrated that inhibition of protein synthesis during viral infection is sensed as a virulence strategy and initiates pyroptosis in human keratinocytes. We identified the BCL-2 family members MCL-1 and BCL-xL as sensors of translation shutdown. Virus- or chemical-induced translation inhibition resulted in MCL-1 depletion and inactivation of BCL-xL, leading to mitochondrial damage, caspase-3-dependent cleavage of gasdermin E, and release of interleukin-1α (IL-1α). Blocking this pathway enhanced virus replication in an organoid model of human skin. Thus, MCL-1 and BCL-xL can act as guard proteins within barrier epithelia and contribute to antiviral defense.
Assuntos
Apoptose/imunologia , Células Epiteliais/imunologia , Proteínas Proto-Oncogênicas c-bcl-2/imunologia , Piroptose/imunologia , Receptores de Estrogênio/imunologia , Vírus/imunologia , Animais , Proteínas Reguladoras de Apoptose/imunologia , Caspase 3/imunologia , Linhagem Celular , Chlorocebus aethiops , Células HEK293 , Humanos , Interleucina-1alfa/imunologia , Camundongos , Mitocôndrias/imunologia , Células NIH 3T3 , Células Vero , Replicação Viral/imunologia , Proteína bcl-X/imunologiaRESUMO
Loss of lymphocytes, particularly T cell apoptosis, is a central pathological event after severe tissue injury that is associated with increased susceptibility for life-threatening infections. The precise immunological mechanisms leading to T cell death after acute injury are largely unknown. Here, we identified a monocyte-T cell interaction driving bystander cell death of T cells in ischemic stroke and burn injury. Specifically, we found that stroke induced a FasL-expressing monocyte population, which led to extrinsic T cell apoptosis. This phenomenon was driven by AIM2 inflammasome-dependent interleukin-1ß (IL-1ß) secretion after sensing cell-free DNA. Pharmacological inhibition of this pathway improved T cell survival and reduced post-stroke bacterial infections. As such, this study describes inflammasome-dependent monocyte activation as a previously unstudied cause of T cell death after injury and challenges the current paradigms of post-injury lymphopenia.
Assuntos
Coinfecção/imunologia , Proteínas de Ligação a DNA/imunologia , Tolerância Imunológica/imunologia , Inflamassomos/imunologia , Transdução de Sinais/imunologia , Animais , Apoptose/imunologia , Infecções Bacterianas/imunologia , Queimaduras/imunologia , Queimaduras/microbiologia , Coinfecção/microbiologia , Humanos , Interleucina-1beta/imunologia , Camundongos , Camundongos Endogâmicos C57BL , Monócitos/imunologia , Acidente Vascular Cerebral/imunologia , Acidente Vascular Cerebral/microbiologia , Linfócitos T/imunologiaRESUMO
Apoptosis can potently defend against intracellular pathogens by directly killing microbes and eliminating their replicative niche. However, the reported ability of Mycobacterium tuberculosis to restrict apoptotic pathways in macrophages in vitro has led to apoptosis being dismissed as a host-protective process in tuberculosis despite a lack of in vivo evidence. Here we define crucial in vivo functions of the death receptor-mediated and BCL-2-regulated apoptosis pathways in mediating protection against tuberculosis by eliminating distinct populations of infected macrophages and neutrophils and priming T cell responses. We further show that apoptotic pathways can be targeted therapeutically with clinical-stage compounds that antagonize inhibitor of apoptosis (IAP) proteins to promote clearance of M. tuberculosis in mice. These findings reveal that any inhibition of apoptosis by M. tuberculosis is incomplete in vivo, advancing our understanding of host-protective responses to tuberculosis (TB) and revealing host pathways that may be targetable for treatment of disease.
Assuntos
Apoptose/imunologia , Macrófagos/imunologia , Mycobacterium tuberculosis/imunologia , Neutrófilos/imunologia , Tuberculose Pulmonar/imunologia , Animais , Caspase 8/genética , Caspase 8/metabolismo , Linhagem Celular , Dipeptídeos/uso terapêutico , Humanos , Indóis/uso terapêutico , Ativação Linfocitária/imunologia , Macrófagos/microbiologia , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Neutrófilos/microbiologia , Proteínas Quinases/genética , Proteínas Quinases/metabolismo , Proteínas Proto-Oncogênicas c-bcl-2/genética , Proteínas Proto-Oncogênicas c-bcl-2/metabolismo , Linfócitos T/imunologia , Tiazóis/uso terapêutico , Tuberculose Pulmonar/tratamento farmacológicoRESUMO
Live regulatory T cells (Treg cells) suppress antitumor immunity, but how Treg cells behave in the metabolically abnormal tumor microenvironment remains unknown. Here we show that tumor Treg cells undergo apoptosis, and such apoptotic Treg cells abolish spontaneous and PD-L1-blockade-mediated antitumor T cell immunity. Biochemical and functional analyses show that adenosine, but not typical suppressive factors such as PD-L1, CTLA-4, TGF-ß, IL-35, and IL-10, contributes to apoptotic Treg-cell-mediated immunosuppression. Mechanistically, apoptotic Treg cells release and convert a large amount of ATP to adenosine via CD39 and CD73, and mediate immunosuppression via the adenosine and A2A pathways. Apoptosis in Treg cells is attributed to their weak NRF2-associated antioxidant system and high vulnerability to free oxygen species in the tumor microenvironment. Thus, the data support a model wherein tumor Treg cells sustain and amplify their suppressor capacity through inadvertent death via oxidative stress. This work highlights the oxidative pathway as a metabolic checkpoint that controls Treg cell behavior and affects the efficacy of therapeutics targeting cancer checkpoints.
Assuntos
Apoptose/imunologia , Antígeno B7-H1/metabolismo , Tolerância Imunológica/imunologia , Neoplasias Ovarianas/imunologia , Estresse Oxidativo/fisiologia , Linfócitos T Reguladores/imunologia , 5'-Nucleotidase/genética , 5'-Nucleotidase/metabolismo , Adenosina/metabolismo , Animais , Antígenos CD/metabolismo , Apirase/metabolismo , Antígeno CTLA-4/metabolismo , Feminino , Proteínas Ligadas por GPI/genética , Humanos , Interleucina-10/metabolismo , Interleucinas/metabolismo , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Fator 2 Relacionado a NF-E2/metabolismo , Oxigênio/metabolismo , Receptor A2A de Adenosina/metabolismo , Fator de Crescimento Transformador beta/metabolismo , Células Tumorais Cultivadas , Microambiente Tumoral/imunologiaRESUMO
The immune system monitors the health of cells and is stimulated by necrosis. Here we examined the receptors and ligands driving this response. In a targeted screen of C-type lectin receptors, a Clec2d reporter responded to lysates from necrotic cells. Biochemical purification identified histones, both free and bound to nucleosomes or neutrophil extracellular traps, as Clec2d ligands. Clec2d recognized poly-basic sequences in histone tails and this recognition was sensitive to post-translational modifications of these sequences. As compared with WT mice, Clec2d-/- mice exhibited reduced proinflammatory responses to injected histones, and less tissue damage and improved survival in a hepatotoxic injury model. In macrophages, Clec2d localized to the plasma membrane and endosomes. Histone binding to Clec2d did not stimulate kinase activation or cytokine production. Rather, histone-bound DNA stimulated endosomal Tlr9-dependent responses in a Clec2d-dependent manner. Thus, Clec2d binds to histones released upon necrotic cell death, with functional consequences to inflammation and tissue damage.
Assuntos
Histonas/metabolismo , Lectinas Tipo C/imunologia , Lectinas Tipo C/metabolismo , Fígado/lesões , Necrose/patologia , Receptores de Superfície Celular/imunologia , Receptores de Superfície Celular/metabolismo , Animais , Apoptose/imunologia , Endossomos/metabolismo , Células HEK293 , Humanos , Células Jurkat , Lectinas Tipo C/genética , Macrófagos/imunologia , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Neutrófilos/imunologia , Receptores de Superfície Celular/genética , Receptor Toll-Like 9/imunologiaRESUMO
Programmed cell death contributes to host defense against pathogens. To investigate the relative importance of pyroptosis, necroptosis, and apoptosis during Salmonella infection, we infected mice and macrophages deficient for diverse combinations of caspases-1, -11, -12, and -8 and receptor interacting serine/threonine kinase 3 (RIPK3). Loss of pyroptosis, caspase-8-driven apoptosis, or necroptosis had minor impact on Salmonella control. However, combined deficiency of these cell death pathways caused loss of bacterial control in mice and their macrophages, demonstrating that host defense can employ varying components of several cell death pathways to limit intracellular infections. This flexible use of distinct cell death pathways involved extensive cross-talk between initiators and effectors of pyroptosis and apoptosis, where initiator caspases-1 and -8 also functioned as executioners when all known effectors of cell death were absent. These findings uncover a highly coordinated and flexible cell death system with in-built fail-safe processes that protect the host from intracellular infections.
Assuntos
Apoptose/imunologia , Macrófagos/imunologia , Necroptose/imunologia , Piroptose/imunologia , Infecções por Salmonella/imunologia , Salmonella/imunologia , Animais , Caspase 1/deficiência , Caspase 1/genética , Caspase 12/deficiência , Caspase 12/genética , Caspase 8/genética , Caspases Iniciadoras/deficiência , Caspases Iniciadoras/genética , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Proteína Serina-Treonina Quinases de Interação com Receptores/deficiência , Proteína Serina-Treonina Quinases de Interação com Receptores/genéticaRESUMO
Effector CD8+ T cells are important mediators of adaptive immunity, and receptor-ligand interactions that regulate their survival may have therapeutic potential. Here, we identified a subset of effector CD8+ T cells that expressed the inhibitory fragment crystallizable (Fc) receptor FcγRIIB following activation and multiple rounds of division. CD8+ T cell-intrinsic genetic deletion of Fcgr2b increased CD8+ effector T cell accumulation, resulting in accelerated graft rejection and decreased tumor volume in mouse models. Immunoglobulin G (IgG) antibody was not required for FcγRIIB-mediated control of CD8+ T cell immunity, and instead, the immunosuppressive cytokine fibrinogen-like 2 (Fgl2) was a functional ligand for FcγRIIB on CD8+ T cells. Fgl2 induced caspase-3/7-mediated apoptosis in Fcgr2b+, but not Fcgr2b-/-, CD8+ T cells. Increased expression of FcγRIIB correlated with freedom from rejection following withdrawal from immunosuppression in a clinical trial of kidney transplant recipients. Together, these findings demonstrate a cell-intrinsic coinhibitory function of FcγRIIB in regulating CD8+ T cell immunity.
Assuntos
Apoptose/imunologia , Linfócitos T CD8-Positivos/imunologia , Fibrinogênio/imunologia , Receptores de IgG/imunologia , Adulto , Idoso , Animais , Caspase 3/imunologia , Caspase 7/imunologia , Linhagem Celular Tumoral , Feminino , Fibrinogênio/genética , Rejeição de Enxerto/imunologia , Humanos , Imunoglobulina G/imunologia , Terapia de Imunossupressão , Masculino , Melanoma Experimental , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Pessoa de Meia-Idade , Receptores de IgG/genética , Adulto JovemRESUMO
Fibrosis is an incurable disorder of unknown etiology. Segregated-nucleus-containing atypical monocytes (SatMs) are critical for the development of fibrosis. Here we examined the mechanisms that recruit SatMs to pre-fibrotic areas. A screen based on cytokine expression in the fibrotic lung revealed that the chemokine Cxcl12, which is produced by apoptotic nonhematopoietic cells, was essential for SatM recruitment. Analyses of lung tissues at fibrosis onset showed increased expression of Rbm7, a component of the nuclear exosome targeting complex. Rbm7 deletion suppressed bleomycin-induced fibrosis and at a cellular level, suppressed apoptosis of nonhematopoietic cells. Mechanistically, Rbm7 bound to noncoding (nc)RNAs that form subnuclear bodies, including Neat1 speckles. Dysregulated expression of Rbm7 resulted in the nuclear degradation of Neat1 speckles, the dispersion of the DNA repair protein BRCA1, and the triggering of apoptosis. Thus, Rbm7 in epithelial cells plays a critical role in the development of fibrosis by regulating ncRNA decay and thereby the production of chemokines that recruit SatMs.
Assuntos
Apoptose/imunologia , Núcleo Celular/imunologia , Exossomos/imunologia , Fibrose Pulmonar/imunologia , Proteínas de Ligação a RNA/imunologia , Animais , Apoptose/genética , Núcleo Celular/genética , Núcleo Celular/metabolismo , Quimiocina CXCL12/imunologia , Quimiocina CXCL12/metabolismo , Exossomos/genética , Exossomos/metabolismo , Regulação da Expressão Gênica/imunologia , Células HEK293 , Humanos , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Camundongos Transgênicos , Monócitos/imunologia , Monócitos/metabolismo , Células NIH 3T3 , Fibrose Pulmonar/genética , Fibrose Pulmonar/metabolismo , Proteínas de Ligação a RNA/genética , Proteínas de Ligação a RNA/metabolismoRESUMO
Epithelial tissues continually undergo apoptosis. Commensal organisms that inhabit the epithelium influence tissue homeostasis, in which regulatory T cells (Treg cells) have a central role. However, the physiological importance of epithelial cell apoptosis and how the number of Treg cells is regulated are both incompletely understood. Here we found that apoptotic epithelial cells negatively regulated the commensal-stimulated proliferation of Treg cells. Gut commensals stimulated CX3CR1(+)CD103(-)CD11b(+) dendritic cells (DCs) to produce interferon-ß (IFN-ß), which augmented the proliferation of Treg cells in the intestine. Conversely, phosphatidylserine exposed on apoptotic epithelial cells suppressed IFN-ß production by the DCs via inhibitory signaling mediated by the cell-surface glycoprotein CD300a and thus suppressed Treg cell proliferation. Our findings reveal a regulatory role for apoptotic epithelial cells in maintaining the number of Treg cell and tissue homeostasis.