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      Harnessing the power of regulatory T-cells to control autoimmune diabetes: overview and perspective

      1 , 1 , 1 , 2

      Immunology

      Wiley

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          Abstract

          Type 1 diabetes (T1D) is a T-cell-mediated autoimmune disease resulting in islet β-cell destruction, hypoinsulinaemia and severely altered glucose homeostasis. Although the mechanisms that initiate T1D still remain elusive, a breakdown of immune tolerance between effector T-cells (Teff) and regulatory T-cells (Treg) is considered to be the crucial component leading to autoimmunity. As such, strategies have been developed to boost the number and/or function of Treg in the hope of specifically hampering the pathogenic Teff activity. In this review, we will summarize the current understanding of biomarkers and functions of both forkhead box protein 3 (FoxP3)+ Treg and type 1 regulatory T (Tr1) cells in health and in T1D, examine the outcome of experimental therapies in both animal models and humans via manipulation of Treg responses and also provide an outlook on the potential of Treg-based immunotherapies in the prevention and treatment of this disease. Discussed immunotherapies include adoptive transfer of ex-vivo expanded FoxP3+ Treg, manipulation of Treg cells via the interleukin (IL)‐2/IL-2R pathway and induction of Treg by tolerogenic peptides, tolerogenic dendritic cells or altered gut microbiota.

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          Most cited references 83

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          IDO expression by dendritic cells: tolerance and tryptophan catabolism.

           David Munn,  L Mellor (2004)
          Indoleamine 2,3-dioxygenase (IDO) is an enzyme that degrades the essential amino acid tryptophan. The concept that cells expressing IDO can suppress T-cell responses and promote tolerance is a relatively new paradigm in immunology. Considerable evidence now supports this hypothesis, including studies of mammalian pregnancy, tumour resistance, chronic infections and autoimmune diseases. In this review, we summarize key recent developments and propose a unifying model for the role of IDO in tolerance induction.
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            The inhibitory cytokine IL-35 contributes to regulatory T-cell function.

            Regulatory T (T(reg)) cells are a critical sub-population of CD4+ T cells that are essential for maintaining self tolerance and preventing autoimmunity, for limiting chronic inflammatory diseases, such as asthma and inflammatory bowel disease, and for regulating homeostatic lymphocyte expansion. However, they also suppress natural immune responses to parasites and viruses as well as anti-tumour immunity induced by therapeutic vaccines. Although the manipulation of T(reg) function is an important goal of immunotherapy, the molecules that mediate their suppressive activity remain largely unknown. Here we demonstrate that Epstein-Barr-virus-induced gene 3 (Ebi3, which encodes IL-27beta) and interleukin-12 alpha (Il12a, which encodes IL-12alpha/p35) are highly expressed by mouse Foxp3+ (forkhead box P3) T(reg) cells but not by resting or activated effector CD4+ T (T(eff)) cells, and that an Ebi3-IL-12alpha heterodimer is constitutively secreted by T(reg) but not T(eff) cells. Both Ebi3 and Il12a messenger RNA are markedly upregulated in T(reg) cells co-cultured with T(eff) cells, thereby boosting Ebi3 and IL-12alpha production in trans. T(reg)-cell restriction of this cytokine occurs because Ebi3 is a downstream target of Foxp3, a transcription factor that is required for T(reg)-cell development and function. Ebi3-/- and Il12a-/- T(reg) cells have significantly reduced regulatory activity in vitro and fail to control homeostatic proliferation and to cure inflammatory bowel disease in vivo. Because these phenotypic characteristics are distinct from those of other IL-12 family members, this novel Ebi3-IL-12alpha heterodimeric cytokine has been designated interleukin-35 (IL-35). Ectopic expression of IL-35 confers regulatory activity on naive T cells, whereas recombinant IL-35 suppresses T-cell proliferation. Taken together, these data identify IL-35 as a novel inhibitory cytokine that may be specifically produced by T(reg) cells and is required for maximal suppressive activity.
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              Interleukin 10 (IL-10) and viral IL-10 strongly reduce antigen-specific human T cell proliferation by diminishing the antigen-presenting capacity of monocytes via downregulation of class II major histocompatibility complex expression

              Interleukin 10 (IL-10) and viral IL-10 (v-IL-10) strongly reduced antigen-specific proliferation of human T cells and CD4+ T cell clones when monocytes were used as antigen-presenting cells. In contrast, IL- 10 and v-IL-10 did not affect the proliferative responses to antigens presented by autologous Epstein-Barr virus-lymphoblastoid cell line (EBV-LCL). Inhibition of antigen-specific T cell responses was associated with downregulation of constitutive, as well as interferon gamma- or IL-4-induced, class II MHC expression on monocytes by IL-10 and v-IL-10, resulting in the reduction in antigen-presenting capacity of these cells. In contrast, IL-10 and v-IL-10 had no effect on class II major histocompatibility complex (MHC) expression on EBV-LCL. The reduced antigen-presenting capacity of monocytes correlated with a decreased capacity to mobilize intracellular Ca2+ in the responder T cell clones. The diminished antigen-presenting capacities of monocytes were not due to inhibitory effects of IL-10 and v-IL-10 on antigen processing, since the proliferative T cell responses to antigenic peptides, which did not require processing, were equally well inhibited. Furthermore, the inhibitory effects of IL-10 and v-IL-10 on antigen-specific proliferative T cell responses could not be neutralized by exogenous IL-2 or IL-4. Although IL-10 and v-IL-10 suppressed IL-1 alpha, IL-1 beta, tumor necrosis factor alpha (TNF- alpha), and IL-6 production by monocytes, it was excluded that these cytokines played a role in antigen-specific T cell proliferation, since normal antigen-specific responses were observed in the presence of neutralizing anti-IL-1, -IL-6, and -TNF-alpha mAbs. Furthermore, addition of saturating concentrations of IL-1 alpha, IL-1 beta, IL-6, and TNF-alpha to the cultures had no effect on the reduced proliferative T cell responses in the presence of IL-10, or v-IL-10. Collectively, our data indicate that IL-10 and v-IL-10 can completely prevent antigen-specific T cell proliferation by inhibition of the antigen-presenting capacity of monocytes through downregulation of class II MHC antigens on monocytes.
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                Author and article information

                Journal
                Immunology
                Immunology
                Wiley
                00192805
                February 2018
                February 2018
                December 11 2017
                : 153
                : 2
                : 161-170
                Affiliations
                [1 ]Department of Immunobiology; Yale University; New Haven CT USA
                [2 ]Howard Hughes Medical Institute; Yale University; New Haven CT USA
                Article
                10.1111/imm.12867
                5765377
                29155454
                © 2017

                http://doi.wiley.com/10.1002/tdm_license_1.1

                http://onlinelibrary.wiley.com/termsAndConditions#vor

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