26,933 research outputs found

    Imaging regulatory T cell dynamics and CTLA4-mediated suppression of T cell priming

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    Foxp3(+) regulatory T cells (Tregs) maintain immune homoeostasis through mechanisms that remain incompletely defined. Here by two-photon (2P) imaging, we examine the cellular dynamics of endogenous Tregs. Tregs are identified as two non-overlapping populations in the T-zone and follicular regions of the lymph node (LN). In the T-zone, Tregs migrate more rapidly than conventional T cells (Tconv), extend longer processes and interact with resident dendritic cells (DC) and Tconv. Tregs intercept immigrant DCs and interact with antigen-induced DC: Tconv clusters, while continuing to form contacts with activated Tconv. During antigen-specific responses, blocking CTLA4-B7 interactions reduces Treg-Tconv interaction times, increases the volume of DC: Tconv clusters and enhances subsequent Tconv proliferation in vivo. Our results demonstrate a role for altered cellular choreography of Tregs through CTLA4-based interactions to limit T-cell priming

    Immunity to self co-generates regulatory T cells

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    Immune responses to self are kept in check by tolerance mechanisms, including suppression by regulatory T cells (Tregs). The defective generation of Tregs specific for self-antigens may lead to autoimmune disease. We identified a novel population of human CD4^+^ Tregs, characterized by high surface expression of CD52, which is co-generated in response to autoantigen. Blood CD4^+^CD52^hi^ T cells were generated preferentially in response to low-dose autoantigen and suppressed proliferation and interferon-[gamma] production by other T cells. Depletion of resting CD4^+^CD52^hi^ T cells enhanced the T-cell response to autoantigen. CD4^+^CD52^hi^ Tregs were neither derived from nor distinguished by markers of conventional resting CD4^+^CD25^+^ Tregs. In response to the pancreatic islet autoantigens glutamic acid decarboxylase, the generation of CD4^+^CD52^hi^ Tregs was impaired in individuals with and at-risk for type 1 diabetes, compared to healthy controls and individuals with type 2 diabetes. CD4^+^CD52^hi^ Tregs co-generated to self-antigen may therefore contribute to immune homeostasis and protect against autoimmune disease

    Controversies concerning thymus-derived regulatory T cells: fundamental issues and a new perspective

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    Thymus-derived regulatory T cells (Tregs) are considered to be a distinct T-cell lineage that is genetically programmed and specialised for immunosuppression. This perspective is based on the key evidence that CD25(+) Tregs emigrate to neonatal spleen a few days later than other T cells and that thymectomy of 3-day-old mice depletes Tregs only, causing autoimmune diseases. Although widely believed, the evidence has never been reproduced as originally reported, and some studies indicate that Tregs exist in neonates. Thus we examine the consequences of the controversial evidence, revisit the fundamental issues of Tregs and thereby reveal the overlooked relationship of T-cell activation and Foxp3-mediated control of the T-cell system. Here we provide a new model of Tregs and Foxp3, a feedback control perspective, which views Tregs as a component of the system that controls T-cell activation, rather than as a distinct genetically programmed lineage. This perspective provides new insights into the roles of self-reactivity, T cell–antigen-presenting cell interaction and T-cell activation in Foxp3-mediated immune regulation

    Regulatory T Cells in Arterivirus and Coronavirus Infections: Do They Protect Against Disease or Enhance it?

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    Regulatory T cells (Tregs) are a subset of T cells that are responsible for maintaining peripheral immune tolerance and homeostasis. The hallmark of Tregs is the expression of the forkhead box P3 (FoxP3) transcription factor. Natural regulatory T cells (nTregs) are a distinct population of T cells that express CD4 and FoxP3. nTregs develop in the thymus and function in maintaining peripheral immune tolerance. Other CD4+, CD4-CD8-, and CD8+CD28- T cells can be induced to acquire regulatory function by antigenic stimulation, depending on the cytokine milieu. Inducible (or adaptive) Tregs frequently express high levels of the interleukin 2 receptor (CD25). Atypical Tregs express FoxP3 and CD4 but have no surface expression of CD25. Type 1 regulatory T cells (Tr1 cells) produce IL-10, while T helper 3 cells (Th3) produce TGF-β. The function of inducible Tregs is presumably to maintain immune homeostasis, especially in the context of chronic inflammation or infection. Induction of Tregs in coronaviral infections protects against the more severe forms of the disease attributable to the host response. However, arteriviruses have exploited these T cell subsets as a means to dampen the immune response allowing for viral persistence. Treg induction or activation in the pathogenesis of disease has been described in both porcine reproductive and respiratory syndrome virus, lactate dehydrogenase elevating virus, and mouse hepatitis virus. This review discusses the development and biology of regulatory T cells in the context of arteriviral and coronaviral infection

    Immune Regulatory 1 Cells: A Novel and Potent Subset of Human T Regulatory Cells

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    A subset of T regulatory cells (Tregs), identified by TIRC7 (T cell immune response cDNA 7) expression is designated as Immune Regulatory 1 Cells (IR1 cells). TIRC7 is an immune checkpoint inhibitor, co-localized with the T- cell receptor, HLA-DR and CTLA-4 during T-cell activation, which delivers regulatory signals via binding to its ligand, HLA-DR α2 domain. IR1 cells express FOXP3, and multiple other markers associated with immune suppression. They constitute as much as 10% of Tregs. IR1 cells strongly inhibit proliferation in mixed lymphocyte reactions, where they express high levels of IL-10. Ex vivo expansion of Tregs over 2 weeks in the presence of an agonist TIRC7 antibody disproportionately expands the IR1 Treg subset, while maintaining high expression of suppressive markers including CD39, IL-10, LAP and GARP. Ex vivo expanded IR1 cells are a potent, homogeneous, stable set of suppressor Tregs with the potential to modulate immune dysregulation. The characteristics of IR1 cells suggest a therapeutic advantage over polyclonal Tregs for therapeutic interventions. Early restoration of immune homeostasis using IR1 cells has the potential to fundamentally alter the natural history of conditions characterized by abnormalities in the T regulatory cell compartment

    Role of LAG-3 in Regulatory T Cells

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    AbstractRegulatory T cells (Tregs) limit autoimmunity but also attenuate the magnitude of antipathogen and antitumor immunity. Understanding the mechanism of Treg function and therapeutic manipulation of Tregs in vivo requires identification of Treg-selective receptors. A comparative analysis of gene expression arrays from antigen-specific CD4+ T cells differentiating to either an effector/memory or a regulatory phenotype revealed Treg-selective expression of LAG-3, a CD4-related molecule that binds MHC class II. Antibodies to LAG-3 inhibit suppression by induced Tregs both in vitro and in vivo. Natural CD4+CD25+ Tregs express LAG-3 upon activation, which is significantly enhanced in the presence of effector cells, whereas CD4+CD25+ Tregs from LAG-3−/− mice exhibit reduced regulatory activity. Lastly, ectopic expression of LAG-3 on CD4+ T cells significantly reduces their proliferative capacity and confers on them suppressor activity toward effector T cells. We propose that LAG-3 marks regulatory T cell populations and contributes to their suppressor activity

    Targeting EZH2 Reprograms Intratumoral Regulatory T Cells to Enhance Cancer Immunity.

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    Regulatory T cells (Tregs) are critical for maintaining immune homeostasis, but their presence in tumor tissues impairs anti-tumor immunity and portends poor prognoses in cancer patients. Here, we reveal a mechanism to selectively target and reprogram the function of tumor-infiltrating Tregs (TI-Tregs) by exploiting their dependency on the histone H3K27 methyltransferase enhancer of zeste homolog 2 (EZH2) in tumors. Disruption of EZH2 activity in Tregs, either pharmacologically or genetically, drove the acquisition of pro-inflammatory functions in TI-Tregs, remodeling the tumor microenvironment and enhancing the recruitment and function of CD8+ and CD4+ effector T cells that eliminate tumors. Moreover, abolishing EZH2 function in Tregs was mechanistically distinct from, more potent than, and less toxic than a generalized Treg depletion approach. This study reveals a strategy to target Tregs in cancer that mitigates autoimmunity by reprogramming their function in tumors to enhance anti-cancer immunity

    The characterisation of human regulatory T cell subsets in ageing and atopy

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    The immune system must be controlled to prevent damage caused by inappropriate responses and extended inflammation. Regulatory T cells (Tregs), known to be generated by the thymus, must be maintained in the face of an ever-increasing human lifespan and associated thymic atrophy in order to protect the host, but whether they are maintained by expansion of pre-existing Tregs or conversion of conventional T cells is not yet known. There are known to be two subsets of FOXP3+ regulatory T cells: naive and memory cells, expressing CD45RA and CD45RO respectively. In this work the characteristics of CD45RA+ and CD45RO+ regulatory T cells were investigated in healthy adults. We found proliferative and phenotypic differences between the two subsets, and evidence that CD45RA+ Tregs can replenish the memory Treg pool on activation. It is, however, becoming more accepted that CD45RO+ Tregs are also likely to be composed of many cells that were converted externally to the thymus from conventional T cells, and our work suggests a mechanism for this conversion: anergy induction. We also found that the two Treg subsets are able to migrate to disparate tissues. Investigation of cutaneous immune responses in vivo revealed the presence of a significant proportion of Tregs, their numbers rising and falling in concordance with the number of conventional T cells. Finally, these investigations of Treg subsets were extended to investigate atopic dermatitis (AD), a hypersensitivity condition in which Tregs are implicated. We found significantly fewer CD45RA+ Tregs among AD patients, with unexpectedly low rates of turnover of these cells in AD skin, despite the presence of high proportions of CD4+FOXP3+ cells. Overall, the findings from this study imply disparate roles for CD45RA+ and CD45RO+ Tregs, and provide further evidence supporting a role for dysregulated regulatory T cell function in the pathogenesis of atopic dermatitis

    Human and Mouse CD8+CD25+FOXP3+ Regulatory T Cells at Steady State and during Interleukin-2 Therapy

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    International audienceIn addition to CD4+ regulatory T cells (Tregs), CD8+ suppressor T cells are emerging as an important subset of regulatory T cells. Diverse populations of CD8+ T cells with suppressive activities have been described. Among them, a small population of CD8+CD25+FOXP3+ T cells is found both in mice and humans. In contrast to thymic-derived CD4+CD25+FOXP3+ Tregs, their origin and their role in the pathophysiology of autoimmune diseases (AIDs) are less understood. We report here the number, phenotype, and function of CD8+ Tregs cells in mice and humans, at the steady state and in response to low-dose interleukin-2 (IL-2). CD8+ Tregs represent approximately 0.4 and 0.1% of peripheral blood T cells in healthy humans and mice, respectively. In mice, their frequencies are quite similar in lymph nodes (LNs) and the spleen, but two to threefold higher in Peyer patches and mesenteric LNs. CD8+ Tregs express low levels of CD127. CD8+ Tregs express more activation or proliferation markers such as CTLA-4, ICOS, and Ki-67 than other CD8+ T cells. In vitro, they suppress effector T cell proliferation as well as or even better than CD4+ Tregs. Owing to constitutive expression of CD25, CD8+ Tregs are 20- to 40-fold more sensitive to in vitro IL-2 stimulation than CD8+ effector T cells, but 2–4 times less than CD4+ Tregs. Nevertheless, low-dose IL-2 dramatically expands and activates CD8+ Tregs even more than CD4+ Tregs, in mice and humans. Further studies are warranted to fully appreciate the clinical relevance of CD8+ Tregs in AIDs and the efficacy of IL-2 treatment

    Cross talk between NKT and regulatory T cells (Tregs) in prostatic tissue of patients with benign prostatic hyperplasia and prostate cancer

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    Background and Purpose: Regulatory T cells (Tregs) and NKT cells are two subpopulations of T lymphocytes that independently regulate innate and adaptive immunity, but there is some evidence for cross-talk between Tregs and NKT cells, which allow a new immunoregulatory networks. Activated NKT cells may modulate quantitatively and qualitatively the function of Tregs through IL-2-dependent mechanisms, while Tregs can suppress the proliferation, cytokine release and cytotoxic activity of NKT cells by cell-contact-dependent mechanisms. Tregs may control tumor expansion at the priming, as well as the effector’s phase of T immune responses. Tumor cells provide antigenic stimulation of T cells and interact with the tumor-infiltrated innate immune cells secreting cytokines that are crucial for T-cell differentiation. Patients and Methods: In this study we examined the prostate tissue infiltrating lymphocytes of patients with prostate cancer (PCa) and benign prostatic hyperplasia (BPH) by flow cytometric technique (FACSCalibur) for determine the number of T, B, NK, NKT and Tregs and investigate the local regulatory immunosurveillance which allows the tumor’s immuneescape. Results: Our results have shown the statistically significantly elevated number of Tregs in prostatic tissue and slightly diminished percentage of NKT cells in prostate cancer patients in comparison to patients with benign prostatic hyperplasia. Conclusion: Although the exact mechanism is still unknown, increased infiltration of prostate tissue with T regulatory cells seems that stimulate the tumor to secrete factors (chemokines) that attract these cells in the tissue of the prostate where they achieve their anti-tumor effect and thus may contribute the tumor progressio
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