ABSTRACT
Regulatory T (Treg) cells are an immunosuppressive population that are required to maintain peripheral tolerance and prevent tissue damage from immunopathology, via anti-inflammatory cytokines, inhibitor receptors and metabolic disruption. Here we show that Treg cells acquire an effector-like state, yet remain stable and functional, when exposed to interferon gamma (IFNγ) during infection with lymphocytic choriomeningitis and influenza A virus. Treg cell-restricted deletion of the IFNγ receptor (encoded by Ifngr1), but not the interleukin 12 (IL12) receptor (encoded by Il12rb2), prevented TH1-like polarization (decreased expression of T-bet, CXC motif chemokine receptor 3 and IFNγ) and promoted TH2-like polarization (increased expression of GATA-3, CCR4 and IL4). TH1-like Treg cells limited CD8+ T cell effector function, proliferation and memory formation during acute and chronic infection. These findings provide fundamental insights into how Treg cells sense inflammatory cues from the environment (such as IFNγ) during viral infection to provide guidance to the effector immune response. This regulatory circuit prevents prolonged immunoinflammatory responses and shapes the quality and quantity of the memory T cell response.
Subject(s)
Interferon-gamma , T-Lymphocytes, Regulatory , Interferon-gamma/metabolism , Cytokines/metabolism , CD8-Positive T-Lymphocytes , Antiviral Agents/metabolism , Th1 CellsABSTRACT
Ezrin, radixin, and moesin (ERM) family proteins regulate cytoskeletal responses by tethering the plasma membrane to the underlying actin cortex. Mutations in ERM proteins lead to severe combined immunodeficiency, but the function of these proteins in T cells remains poorly defined. Using mice in which T cells lack all ERM proteins, we demonstrate a selective role for these proteins in facilitating S1P-dependent egress from lymphoid organs. ERM-deficient T cells display defective S1P-induced migration in vitro, despite normal responses to standard protein chemokines. Analysis of these defects revealed that S1P promotes a fundamentally different mode of migration than chemokines, characterized by intracellular pressurization and bleb-based motility. ERM proteins facilitate this process, controlling directional migration by limiting blebbing to the leading edge. We propose that the distinct modes of motility induced by S1P and chemokines are specialized to allow T cell migration across lymphatic barriers and through tissue stroma, respectively.
Subject(s)
Cell Movement , Cytoskeletal Proteins/metabolism , Cytoskeletal Proteins/physiology , Cytoskeleton/physiology , Lymphocytes/metabolism , Lysophospholipids/metabolism , Membrane Proteins/metabolism , Microfilament Proteins/metabolism , Sphingosine/analogs & derivatives , Animals , Cell Membrane , Cytoskeletal Proteins/genetics , Female , Lymphocytes/cytology , Male , Membrane Proteins/genetics , Mice , Mice, Inbred C57BL , Mice, Knockout , Microfilament Proteins/genetics , Phosphorylation , Sphingosine/metabolismABSTRACT
X-linked moesin associated immunodeficiency (X-MAID) is a primary immunodeficiency disease in which patients suffer from profound lymphopenia leading to recurrent infections. The disease is caused by a single point mutation leading to a R171W amino acid change in the protein moesin (moesinR171W). Moesin is a member of the ERM family of proteins, which reversibly link the cortical actin cytoskeleton to the plasma membrane. Here, we describe a novel mouse model with global expression of moesinR171W that recapitulates multiple facets of patient disease, including severe lymphopenia. Further analysis reveals that these mice have diminished numbers of thymocytes and bone marrow precursors. X-MAID mice also exhibit systemic inflammation that is ameliorated by elimination of mature lymphocytes through breeding to a Rag1-deficient background. The few T cells in the periphery of X-MAID mice are highly activated and have mostly lost moesinR171W expression. In contrast, single-positive (SP) thymocytes do not appear activated and retain high expression levels of moesinR171W. Analysis of ex vivo CD4 SP thymocytes reveals defects in chemotactic responses and reduced migration on integrin ligands. While chemokine signaling appears intact, CD4 SP thymocytes from X-MAID mice are unable to polarize and rearrange cytoskeletal elements. This mouse model will be a valuable tool for teasing apart the complexity of the immunodeficiency caused by moesinR171W, and will provide new insights into how the actin cortex regulates lymphocyte function.
Subject(s)
Cell Movement/immunology , Microfilament Proteins/deficiency , T-Lymphocytes/immunology , X-Linked Combined Immunodeficiency Diseases/immunology , Animals , Cell Movement/genetics , Disease Models, Animal , Mice , Mice, Knockout , Microfilament Proteins/immunology , X-Linked Combined Immunodeficiency Diseases/geneticsABSTRACT
T cell activation by dendritic cells (DCs) involves forces exerted by the T cell actin cytoskeleton, which are opposed by the cortical cytoskeleton of the interacting antigen-presenting cell. During an immune response, DCs undergo a maturation process that optimizes their ability to efficiently prime naïve T cells. Using atomic force microscopy, we find that during maturation, DC cortical stiffness increases via a process that involves actin polymerization. Using stimulatory hydrogels and DCs expressing mutant cytoskeletal proteins, we find that increasing stiffness lowers the agonist dose needed for T cell activation. CD4+ T cells exhibit much more profound stiffness dependency than CD8+ T cells. Finally, stiffness responses are most robust when T cells are stimulated with pMHC rather than anti-CD3ε, consistent with a mechanosensing mechanism involving receptor deformation. Taken together, our data reveal that maturation-associated cytoskeletal changes alter the biophysical properties of DCs, providing mechanical cues that costimulate T cell activation.
Subject(s)
Dendritic Cells/physiology , Lymphocyte Activation/physiology , T-Lymphocytes/physiology , Animals , Cell Line , HEK293 Cells , Humans , Mice , Mice, Inbred C57BLABSTRACT
Herpes simplex virus 1 (HSV-1) causes a lifelong infection of neurons that innervate barrier sites like the skin and mucosal surfaces like the eye. After primary infection of the cornea, the virus enters latency within the trigeminal ganglion (TG), from which it can reactivate throughout the life of the host. Viral latency is maintained, in part, by virus-specific CD8+ T cells that nonlethally interact with infected neurons. When CD8+ T cell responses are inhibited, HSV-1 can reactivate, and these recurrent reactivation events can lead to blinding scarring of the cornea. In the C57BL/6 mouse, CD8+ T cells specific for the immunodominant epitope from glycoprotein B maintain functionality throughout latency, while CD8+ T cells specific for subdominant epitopes undergo functional impairment that is associated with the expression of the inhibitory checkpoint molecule programmed death 1 (PD-1). Here, we investigate the checkpoint molecule T cell immunoglobulin and mucin domain-containing 3 (Tim-3), which has traditionally been associated with CD8+ T cell exhaustion. Unexpectedly, we found that Tim-3 was preferentially expressed on highly functional ganglionic CD8+ T cells during acute and latent HSV-1 infection. This, paired with data that show that Tim-3 expression on CD8+ T cells in the latently infected TG is influenced by viral gene expression, suggests that Tim-3 is an indicator of recent T cell stimulation, rather than functional compromise, in this model. We conclude that Tim-3 expression is not sufficient to define functional compromise during latency; however, it may be useful in identifying activated cells within the TG during HSV-1 infection.IMPORTANCE Without an effective means of eliminating HSV-1 from latently infected neurons, efforts to control the virus have centered on preventing viral reactivation from latency. Virus-specific CD8+ T cells within the infected TG have been shown to play a crucial role in inhibiting viral reactivation, and with a portion of these cells exhibiting functional impairment, checkpoint molecule immunotherapies have presented a potential solution to enhancing the antiviral response of these cells. In pursuing this potential treatment strategy, we found that Tim-3 (often associated with CD8+ T cell functional exhaustion) is not upregulated on impaired cells but instead is upregulated on highly functional cells that have recently received antigenic stimulation. These findings support a role for Tim-3 as a marker of activation rather than exhaustion in this model, and we provide additional evidence for the hypothesis that there is persistent viral gene expression in the HSV-1 latently infected TG.
Subject(s)
CD8-Positive T-Lymphocytes/immunology , Epitopes, T-Lymphocyte/immunology , Gene Expression Regulation/immunology , Hepatitis A Virus Cellular Receptor 2/immunology , Herpesvirus 1, Human/physiology , Lymphocyte Activation , Programmed Cell Death 1 Receptor/immunology , Trigeminal Ganglion , Virus Latency/immunology , Animals , Biomarkers , CD8-Positive T-Lymphocytes/pathology , CD8-Positive T-Lymphocytes/virology , Female , Mice , Trigeminal Ganglion/immunology , Trigeminal Ganglion/pathology , Trigeminal Ganglion/virologyABSTRACT
ß-site amyloid precursor protein-cleaving enzyme 1 (BACE1) is best known for its role in Alzheimer's disease amyloid plaque formation but also contributes to neurodegenerative processes triggered by CNS injury. In this article, we report that BACE1 is expressed in murine CD4+ T cells and regulates signaling through the TCR. BACE1-deficient T cells have reduced IL-17A expression under Th17 conditions and reduced CD73 expression in Th17 and inducible T regulatory cells. However, induction of the Th17 and T regulatory transcription factors RORγt and Foxp3 was unaffected. BACE1-deficient T cells showed impaired pathogenic function in experimental autoimmune encephalomyelitis. These data identify BACE1 as a novel regulator of T cell signaling pathways that impact autoimmune inflammatory T cell function.
Subject(s)
Amyloid Precursor Protein Secretases/metabolism , Aspartic Acid Endopeptidases/metabolism , Autoimmunity/immunology , Encephalomyelitis, Autoimmune, Experimental/immunology , T-Lymphocytes, Regulatory/immunology , Th17 Cells/immunology , 5'-Nucleotidase/metabolism , Alzheimer Disease/pathology , Amyloid Precursor Protein Secretases/genetics , Animals , Aspartic Acid Endopeptidases/genetics , Disease Models, Animal , Encephalomyelitis, Autoimmune, Experimental/pathology , Forkhead Transcription Factors/biosynthesis , Interleukin-17/metabolism , Lymphocyte Activation/immunology , Mice , Mice, Inbred C57BL , Mice, Knockout , Nuclear Receptor Subfamily 1, Group F, Member 3/biosynthesisABSTRACT
While T cells are important for the pathogenesis of systemic lupus erythematosus (SLE) and lupus nephritis, little is known about how T cells function after infiltrating the kidney. The current paradigm suggests that kidney-infiltrating T cells (KITs) are activated effector cells contributing to tissue damage and ultimately organ failure. Herein, we demonstrate that the majority of CD4+ and CD8+ KITs in 3 murine lupus models are not effector cells, as hypothesized, but rather express multiple inhibitory receptors and are highly dysfunctional, with reduced cytokine production and proliferative capacity. In other systems, this hypofunctional profile is linked directly to metabolic and specifically mitochondrial dysfunction, which we also observed in KITs. The T cell phenotype was driven by the expression of an "exhausted" transcriptional signature. Our data thus reveal that the tissue parenchyma has the capability of suppressing T cell responses and limiting damage to self. These findings suggest avenues for the treatment of autoimmunity based on selectively exploiting the exhausted phenotype of tissue-infiltrating T cells.
Subject(s)
Autoimmunity , CD4-Positive T-Lymphocytes , CD8-Positive T-Lymphocytes , Lupus Nephritis , Animals , CD4-Positive T-Lymphocytes/immunology , CD4-Positive T-Lymphocytes/metabolism , CD4-Positive T-Lymphocytes/pathology , CD8-Positive T-Lymphocytes/immunology , CD8-Positive T-Lymphocytes/pathology , Kidney , Lupus Nephritis/genetics , Lupus Nephritis/immunology , Lupus Nephritis/metabolism , Lupus Nephritis/pathology , Mice , Mice, Inbred BALB C , Mice, Inbred MRL lpr , Mice, KnockoutABSTRACT
Tim-3 is highly expressed on a subset of T cells during T cell exhaustion in settings of chronic viral infection and tumors. Using lymphocytic choriomeningitis virus (LCMV) Clone 13, a model for chronic infection, we found that Tim-3 was neither necessary nor sufficient for the development of T cell exhaustion. Nonetheless, expression of Tim-3 was sufficient to drive resistance to PD-L1 blockade therapy during chronic infection. Strikingly, expression of Tim-3 promoted the development of short-lived effector T cells, at the expense of memory precursor development, after acute LCMV infection. These effects were accompanied by increased Akt/mTOR signaling in T cells expressing endogenous or ectopic Tim-3. Conversely, Akt/mTOR signaling was reduced in effector T cells from Tim-3-deficient mice. Thus, Tim-3 is essential for optimal effector T cell responses, and may also contribute to exhaustion by restricting the development of long-lived memory T cells. Taken together, our results suggest that Tim-3 is actually more similar to costimulatory receptors that are up-regulated after T cell activation than to a dominant inhibitory protein like PD-1. These findings have significant implications for the development of anti-Tim-3 antibodies as therapeutic agents.
Subject(s)
Hepatitis A Virus Cellular Receptor 2/immunology , Lymphocyte Activation/immunology , Signal Transduction/immunology , T-Lymphocyte Subsets/immunology , Animals , Chronic Disease , Hepatitis A Virus Cellular Receptor 2/genetics , Lymphocytic Choriomeningitis , Lymphocytic choriomeningitis virus/immunology , Mice , Phenotype , Receptors, Antigen, T-Cell/immunology , TOR Serine-Threonine Kinases/metabolismABSTRACT
There is growing appreciation that cellular metabolic and bioenergetic pathways do not play merely passive roles in activated leukocytes. Rather, metabolism has important roles in controlling cellular activation, differentiation, survival, and effector function. Much of this work has been performed in T cells; however, there is still very little information regarding mast cell metabolic reprogramming and its effect on cellular function. Mast cells perform important barrier functions and help control type 2 immune responses. In this study we show that murine bone marrow-derived mast cells rapidly alter their metabolism in response to stimulation through the FcεRI. We also demonstrate that specific metabolic pathways appear to be differentially required for the control of mast cell function. Manipulation of metabolic pathways may represent a novel point for the manipulation of mast cell activation.
Subject(s)
Mast Cells/immunology , Mast Cells/metabolism , Animals , Cell Differentiation/immunology , Cells, Cultured , Mice , Mice, Inbred C57BLABSTRACT
Programmed Death 1 (PD-1) and T cell Ig and mucin domain-3 protein (Tim-3) are immune checkpoint receptors highly expressed on tumor infiltrating T lymphocytes (TIL). PD-1 inhibits T cell activation and type-1 T cell responses, while Tim-3 is proposed to mark more extensively exhausted cells, although the mechanisms underlying Tim-3 function are not clear. Trials of anti-PD-1 therapy have identified a large subset of non-responder patients, likely due to expression of alternative checkpoint molecules like Tim-3. We investigated the phenotypic and functional characteristics of T cells with differential expression of PD-1 (high/low) and Tim-3 (positive/negative), using TIL directly isolated from head and neck squamous cell carcinomas (HNSCC). Unexpectedly, we found that expression of Tim-3 alone does not necessarily mark TIL as dysfunctional/exhausted. In Tim-3-TIL, PD-1 levels correlate with T cell dysfunction, with a PD-1low/intermed phenotype identifying recently activated and still functional cells, whereas PD-1hiTim-3- T cells are actually exhausted. Nonetheless, PD-1intermed cells are still potently suppressed by PD-L1. PD-1 expression was associated with reduced phosphorylation of ribosomal protein S6 (pS6), whereas Tim-3 expression was associated with increased pS6. Using a novel mouse model for inducible Tim-3 expression, we confirmed that expression of Tim-3 does not necessarily render T cells refractory to further activation. These results suggest the existence of PD-1 and Tim-3 crosstalk in regulating antitumor T cell responses, with important implications for anti-PD-1 immunotherapy.
ABSTRACT
T cell (or transmembrane) immunoglobulin and mucin domain protein 3 (Tim-3) has attracted significant attention as a novel immune checkpoint receptor (ICR) on chronically stimulated, often dysfunctional, T cells. Antibodies to Tim-3 can enhance antiviral and antitumor immune responses. Tim-3 is also constitutively expressed by mast cells, NK cells and specific subsets of macrophages and dendritic cells. There is ample evidence for a positive role for Tim-3 in these latter cell types, which is at odds with the model of Tim-3 as an inhibitory molecule on T cells. At this point, little is known about the molecular mechanisms by which Tim-3 regulates the function of T cells or other cell types. We have focused on defining the effects of Tim-3 ligation on mast cell activation, as these cells constitutively express Tim-3 and are activated through an ITAM-containing receptor for IgE (FcεRI), using signaling pathways analogous to those in T cells. Using a variety of gain- and loss-of-function approaches, we find that Tim-3 acts at a receptor-proximal point to enhance Lyn kinase-dependent signaling pathways that modulate both immediate-phase degranulation and late-phase cytokine production downstream of FcεRI ligation.
Subject(s)
Mast Cells/metabolism , Receptors, IgE/metabolism , Receptors, Virus/metabolism , Signal Transduction , Animals , Antibodies/pharmacology , Antigens/immunology , Bone Marrow Cells/cytology , Carcinoembryonic Antigen/metabolism , Cell Degranulation/drug effects , Cross-Linking Reagents/pharmacology , Cytokines/biosynthesis , Hepatitis A Virus Cellular Receptor 2 , Immunoglobulin E/immunology , Interleukin-6/biosynthesis , Intracellular Signaling Peptides and Proteins/metabolism , Mast Cells/drug effects , Mice, Inbred C57BL , Mice, Knockout , Molecular Chaperones/metabolism , Nuclear Proteins/metabolism , Nuclear Receptor Subfamily 4, Group A, Member 1/metabolism , Phospholipase C gamma/metabolism , Phosphorylation/drug effects , Phosphotyrosine/metabolism , Protein Subunits/metabolism , Protein-Tyrosine Kinases/metabolism , Receptors, Virus/chemistry , Ribosomal Protein S6/metabolism , Signal Transduction/drug effects , Syk Kinase , Transcriptional Activation/drug effects , Tumor Necrosis Factor-alpha/biosynthesis , src-Family Kinases/metabolismABSTRACT
IL-10 production during intracellular bacterial infections is generally thought to be detrimental because of its role in suppressing protective T-helper cell 1 (Th1) responses. Francisella tularensis is a facultative intracellular bacterium that activates both Th1 and Th17 protective immune responses. Herein, we report that IL-10-deficient mice (Il10(-/-)), despite having increased Th1 and Th17 responses, exhibit increased mortality after pulmonary infection with F. tularensis live vaccine strain. We demonstrate that the increased mortality observed in Il10(-/-)-infected mice is due to exacerbated IL-17 production that causes increased neutrophil recruitment and associated lung pathology. Thus, although IL-17 is required for protective immunity against pulmonary infection with F. tularensis live vaccine strain, its production is tightly regulated by IL-10 to generate efficient induction of protective immunity without mediating pathology. These data suggest a critical role for IL-10 in maintaining the delicate balance between host immunity and pathology during pulmonary infection with F. tularensis live vaccine strain.