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DNA threads released by activated CD4+ T lymphocytes provide autocrine costimulation.

ABSTRACT: The extrusion of DNA traps contributes to a key mechanism in which innate immune cells clear pathogens or induce sterile inflammation. Here we provide evidence that CD4+ T cells, a critical regulator of adaptive immunity, release extracellular threads of DNA on activation. These DNA extrusions convey autocrine costimulatory signals to T lymphocytes and can be detected in lymph nodes isolated during the priming phase of experimental autoimmune encephalomyelitis (EAE), a CD4+ T cell-driven mouse model of multiple sclerosis. Pharmacologic inhibition of mitochondrial reactive oxygen species (mtROS) abolishes the extrusion of DNA by CD4+ T cells, reducing cytokine production in vitro and T cell priming against myelin in vivo. Moreover, mtROS blockade during established EAE markedly ameliorates disease severity, dampening autoimmune inflammation of the central nervous system. Taken together, these experimental results elucidate a mechanism of intrinsic immune costimulation mediated by DNA threads released by activated T helper cells, and identify a potential therapeutic target for such disorders as multiple sclerosis, neuromyelitis optica, and CD4+ T cell-mediated disorders.

SUBMITTER: Costanza M

PROVIDER: S-EPMC6500139 | biostudies-literature | 2019 Apr

REPOSITORIES: biostudies-literature

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DNA threads released by activated CD4+ T lymphocytes provide autocrine costimulation.

Costanza Massimo M Poliani Pietro L PL Portararo Paola P Cappetti Barbara B Musio Silvia S Pagani Francesca F Steinman Lawrence L Colombo Mario P MP Pedotti Rosetta R Sangaletti Sabina S

Proceedings of the National Academy of Sciences of the United States of America 20190415 18

The extrusion of DNA traps contributes to a key mechanism in which innate immune cells clear pathogens or induce sterile inflammation. Here we provide evidence that CD4+ T cells, a critical regulator of adaptive immunity, release extracellular threads of DNA on activation. These DNA extrusions convey autocrine costimulatory signals to T lymphocytes and can be detected in lymph nodes isolated during the priming phase of experimental autoimmune encephalomyelitis (EAE), a CD4+ ...[more]

PMID: 30988194

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Project description:BackgroundMicrovesicles are vesicles shed by plasma membranes following cell activation and apoptosis. The role of lymphocyte-derived microvesicles in endothelial function remains poorly understood.MethodsCD4+ T cells isolated from peripheral blood of healthy human donors were stimulated using anti-CD3/anti-CD28-coated beads. Proteomic profiling of microvesicles was performed using linear discriminant analysis (LDA) from activated T cells (MV.Act) and nonactivated T cells (MV.NAct). In addition, data processing analysis was performed using MaxQUANT workflow. Differentially expressed proteins found in MV.Act or MV.NAct samples with identification frequency = 100%, which were selected by both LDA (p < .01) and MaxQUANT (p < .01) workflows, were defined as "high-confidence" differentially expressed proteins. Functional effects of MV.Act on human primary microvascular endothelial cells were analysed.ResultsT cells released large amounts of microvesicles upon stimulation. Proteomic profiling of microvesicles using LDA identified 2279 proteins (n = 2110 and n = 851 proteins in MV.Act and MV.NAct, respectively). Protein-protein interaction network models reconstructed from both differentially expressed proteins (n = 594; LDA p ≤ .01) and "high-confidence" differentially expressed proteins (n = 98; p ≤ .01) revealed that MV.Act were enriched with proteins related to immune responses, protein translation, cytoskeleton organisation and TNFα-induced apoptosis. For instance, MV.Act were highly enriched with IFN-γ, a key proinflammatory pathway related to effector CD4+ T cells. Endothelial cell incubation with MV.Act induced superoxide generation, apoptosis, endothelial wound healing impairment and endothelial monolayer barrier disruption.ConclusionsT cell receptor-mediated activation of CD4+ T cells stimulates the release of microvesicles enriched with proteins involved in immune responses, inflammation and apoptosis. T cell-derived microvesicles alter microvascular endothelial function and barrier permeability, potentially promoting tissue inflammation.

Project description:The nutritional status of dairy cows and the metabolism of specific nutrients are critical regulators of immune cell function. Around the time of parturition, mobilization of body lipid and muscle helps compensate for the decrease in nutrient intake and the increased requirements of the mammary gland for lactation. An end-result of these processes is the marked increase in circulating concentrations of fatty acids (FA), which are a major risk factor for immune dysfunction. In food animal species such as dairy cows, any disturbance in nutritional or immunological homeostasis leads to deleterious feedback loops that can further risk health, efficiency of nutrient use, and compromise availability of safe and nutritious dairy foods for humans. Despite substantial progress with respect to regulation of innate immunity, such knowledge for adaptive immunity is scarce. To help bridge this gap in knowledge, we sought to study the role of calcium release-activated calcium modulator ORAI1 activation in T cells systemic immune function in vivo. CD4+ T cells were isolated from peripheral blood of dairy cows diagnosed as healthy or with ketosis, a common metabolic disorder of FA metabolism. Results revealed that levels of intracellular Ca2+ and reactive oxygen species (ROS) along with the abundance of store-operated Ca2+ entry (SOCE) moiety increased during ketosis. Further, plasma concentrations of inflammatory cytokines were elevated, the balance of Th17/Treg cells was disrupted, mitochondrial function impaired, and the abundance of mitophagy-related proteins in CD4+ T cells altered during ketosis. Molecular characterization of the direct effects of FA was evaluated in CD4+ T cells isolated from the spleen of 1-day-old calves. Enhanced supply of FA increased intracellular Ca2+ and ROS concentrations, upregulated the abundance of proteins associated with mitochondrial dynamics and ORAI1. Intermediates of mitophagy accumulated and the balance of Th17/Treg cells also was affected by the supply of FA. These negative effects were attenuated by silencing or inhibition of ORAI1 in CD4+ T cells. Together, data indicated that physiological states that lead to increases in systemic concentrations of FA could impact adaptive immunity negatively through ORAI1 regulated intracellular Ca2+, ROS balance, and increased effector functions of Th17 cells.

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DNA threads released by activated CD4+ T lymphocytes provide autocrine costimulation.

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DNA threads released by activated CD4<sup>+</sup> T lymphocytes provide autocrine costimulation.

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