SciCombinator

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Concept: Regulatory T cell

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Aberrant T-cell activation underlies many autoimmune disorders, yet most attempts to induce T-cell tolerance have failed. Building on previous strategies for tolerance induction that exploited natural mechanisms for clearing apoptotic debris, we show that antigen-decorated microparticles (500-nm diameter) induce long-term T-cell tolerance in mice with relapsing experimental autoimmune encephalomyelitis. Specifically, intravenous infusion of either polystyrene or biodegradable poly(lactide-co-glycolide) microparticles bearing encephalitogenic peptides prevents the onset and modifies the course of the disease. These beneficial effects require microparticle uptake by marginal zone macrophages expressing the scavenger receptor MARCO and are mediated in part by the activity of regulatory T cells, abortive T-cell activation and T-cell anergy. Together these data highlight the potential for using microparticles to target natural apoptotic clearance pathways to inactivate pathogenic T cells and halt the disease process in autoimmunity.

Concepts: Immune system, White blood cell, Protein, T cell, T cells, Major histocompatibility complex, Autoimmunity, Regulatory T cell

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Regulatory T cells (Tregs) prevent autoimmunity but limit antitumor immunity. The canonical NF-κB signaling pathway both activates immunity and promotes thymic Treg development. Here, we report that mature Tregs continue to require NF-κB signaling through IκB-kinase β (IKKβ) after thymic egress. Mice lacking IKKβ in mature Tregs developed scurfy-like immunopathology due to death of peripheral FoxP3(+) Tregs. Also, pharmacological IKKβ inhibition reduced Treg numbers in the circulation by ∼50% and downregulated FoxP3 and CD25 expression and STAT5 phosphorylation. In contrast, activated cytotoxic T lymphocytes (CTLs) were resistant to IKKβ inhibition because other pathways, in particular nuclear factor of activated T cells (NFATc1) signaling, sustained their survival and expansion. In a melanoma mouse model, IKKβ inhibition after CTL cross-priming improved the antitumor response and delayed tumor growth. In conclusion, prolonged IKKβ inhibition decimates circulating Tregs and improves CTL responses when commenced after tumor vaccination, indicating that IKKβ represents a druggable checkpoint.

Concepts: Immune system, Improve, Immunology, T cells, Autoimmunity, Mouse, Human cells, Regulatory T cell

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Protocols to use Foxp3+ T-regulatory (Treg) cells for cellular therapy, especially post-allogeneic stem cell transplantation, are currently being developed and tested by various groups. Inhibitors of DNA methyltransferase (Dnmt) enzymes have been advocated as a means to promote and stabilize Foxp3 expression in Tregs undergoing expansion in vitro, prior to their injection in vivo. We investigated the effects of conditionally deleting two Dnmt enzymes that co-immunoprecipitated with Foxp3 in Treg isolates. Deletion of Dnmt1, but not Dnmt3a, decreased the numbers and function of peripheral Tregs, and impaired conversion of conventional T cells into Foxp3+ Tregs under polarizing conditions. Importantly, mice with conditional deletion of Dnmt1 in their Tregs died from autoimmunity by 3-4 weeks of age unless rescued by perinatal transfer of wild-type Tregs. Conditional Dnmt1 deletion did not affect methylation of CpG-sites within Foxp3, but decreased global DNA methylation and altered Treg expression of several hundred pro-inflammatory and other genes. Hence, Dnmt1 is necessary for maintenance of the core gene program underlying Treg development and function, and its deletion within the Treg lineage leads to lethal autoimmunity. These data suggest that caution may be warranted when considering the use of DNMT inhibitors in development of Treg-based cellular therapies.

Concepts: DNA, Gene, Gene expression, Cell, Chromosome, DNA methylation, DNA methyltransferase, Regulatory T cell

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Along with their immunogenic role, dendritic cells (DCs) are also critical in maintaining tolerance to self-antigens by inducing regulatory T cells (Tregs) via the expression of the immunomodulatory enzyme indoleamine 2,3-dioxygenase 1 (IDO1). In turn, Tregs modulate the maturation and/or function of DCs. In immune thrombocytopenia (ITP), the interaction between DCs and Tregs has never been investigated although decreased number/function of Tregs as well as altered DCs have been described. Here, we ask whether, in ITP: (1) IDO1 expression/activity is decreased in mature DCs; (2) IDO1-mediated Treg generation is impaired; and (3) DC maturation is abnormally modulated by Tregs. We found that in ITP, DCs show reduced capability of upregulating the expression/activity of IDO1. This finding results in the reduced ability of mature DCs of converting T cells into Tregs. In turn, Tregs are characterized by decreased interleukin-10 production and show lower ability of inhibiting DC maturation. In conclusion, these data point out the role of IDO1 in the impaired regulatory T cell development of ITP patients and suggest that the cross-talk between Tregs and DCs is hampered and plays a pathogenetic role.

Concepts: Enzyme, T cell, T cells, Thrombocytopenia, Autoimmunity, Idiopathic thrombocytopenic purpura, Human cells, Regulatory T cell

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In a cross-sectional study, we assessed effects of calcineurin inhibitor (CNI) or rapamycin on T-regulatory (Treg) cells from children with stable liver (n = 53) or kidney (n = 9) allografts several years posttransplant. We analyzed Treg number, phenotype, suppressive function, and methylation at the Treg-specific demethylation region (TSDR) using Tregs and peripheral blood mononuclear cells. Forty-eight patients received CNI (39 as monotherapy) and 12 patients received rapamycin (9 as monotherapy). Treg numbers diminished over time on either regimen, but reached significance only with CNI (r =-0.424, p = 0.017). CNI levels inversely correlated with Treg number (r =-0.371, p = 0.026), and positively correlated with CD127+ expression by Tregs (r = 0.437, p = 0.023). Patients with CNI levels >3.6 ng/mL had weaker Treg function than those with levels <3.6 ng/mL, whereas rapamycin therapy positively correlated with Treg numbers (r = 0.628, p = 0.029) and their expression of CTLA4 (r = 0.726, p = 0.041). Overall, CTLA4 expression, TSDR demethylation and an absence of CD127 were important for Treg suppressive function. We conclude that rapamycin has beneficial effects on Treg biology, whereas long-term and high dose CNI use may impair Treg number, function and phenotype, potentially acting as a barrier to attaining host hyporesponsiveness to an allograft.

Concepts: DNA, Gene, Gene expression, Glucose, Organ transplant, Autoimmunity, PBMC, Regulatory T cell

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This study explores the consequences of deficiency in the autoimmune regulator (Aire) on the susceptibility to experimental autoimmune encephalomyelitis (EAE). Increased susceptibility to EAE was found in Aire knockout (KO) compared to wild type (WT) in 6month old mice. In contrast, 2month old Aire KO mice were less susceptible to EAE than WT mice, and this age-related resistance correlated with elevated proportions of T regulatory (Treg) cells in their spleen and brain. Combined with our previous findings in experimental autoimmune myasthenia gravis, we suggest an age-related association between Aire and Treg cells in the susceptibility to autoimmunity.

Concepts: Immune system, Gene, Immunology, Magnetic resonance imaging, Autoimmune diseases, Myasthenia gravis, Autoimmunity, Regulatory T cell

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OBJECTIVE.: Current approaches offer no cures for rheumatoid arthritis (RA). Accumulating evidence has revealed that manipulation of bone-marrow mesenchymal stem cells (BMSCs) may have the potential to treat RA. While BMSC-based therapy faces many challenges such as limited cell availability and reduced clinical feasibility, we herein demonstrate that substitution of gingival-derived mesenchymal stem cells (GMSCs) results in significantly improved therapeutic effects on established collagen-induced arthritis (CIA). METHODS.: CIA has been induced with the immunization of type II collagen (CII) and CFA in DBA/1J mice. GMSCs were injected i.v. into mice on day 14 after immunization. In some experiments, injection of PC61 (anti-CD25 antibody) i.p. was used to delete Tregs in arthritic mice. RESULTS.: Infusion of GMSCs in DBA/1J mice with CIA significantly decreased the severity of arthritis and pathology scores, and down-regulated inflammatory cytokine (IFN-γ, IL-17A) production. Infusion of GMSCs resulted in an increase in CD4(+) CD39(+) Foxp3(+) cells in arthritic mice. These increases were noted early in spleen and LN and later in synovial fluid. The increased frequency of Foxp3(+) Treg cells consisted of cells that were mainly Helios negative. Infusion of GMSCs partially interfered with the progress of CIA when Treg cells were depleted. Pre-treatment of GMSCs with CD39 or CD73 inhibitor significantly reversed the protective effect of GMSCs on CIA. CONCLUSION.: The role of GMSCs in controlling CIA pathology mostly depends upon CD39/CD73 signals and partially upon the induction of CD4(+) CD39(+) Foxp3(+) Treg cells. GMSCs provide a promising approach for the treatment of autoimmune diseases. © 2013 American College of Rheumatology.

Concepts: Stem cell, Mesenchymal stem cell, Bone marrow, Rheumatoid arthritis, Rheumatology, Arthritis, Autoimmunity, Regulatory T cell

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Objective To investigate the role of Th17/Treg unbalance in the pathogenesis of experimental autoimmune encephalomyelitis (EAE). Methods EAE was modeled in mice and the number of regulatory T cells (Tregs) in spleen of EAE mice was detected by flow cytometry. The expressions of Foxp3 and RoR-γt mRNA in the spleen of EAE mice and IL-17 mRNA in the brain of EAE mice were evaluated by real-time quantitative PCR and the levels of IL-6, TGF-β and IL-17 in the serum of EAE mice were examined by ELISA. Results Compared with control group, the number of CD4(+)CD25(+) Foxp3(+) Tregs and the expression of Foxp3 mRNA in the spleen of EAE mice dramatically decreased in the early and peak stage of EAE (P<0.05), but increased in chronic stage of EAE (P<0.05); the RoR-γt mRNA expression from mouse spleen at the early stage of EAE was significant raised (P<0.05), but was not significantly different at the peak and chronic stage of EAE from that in control group (P>0.05). The levels of IL-6 and TGF-β in the serum of EAE group dramatically increased compared with control group (P<0.05). With the development of EAE, the level of IL-6 gradually decreased, and there was no statistical difference in the chronic stage of EAE compared with control group (P>0.05). However, the level of TGF-β was higher than that in control group in the chronic stage of EAE (P<0.05). Compared with those in control group, the concentration of IL-17A and the expression of IL-17 mRNA dramatically increased in different stages of EAE group, especially in peak stage (P<0.05). Conclusion Th17/Treg unbalance may be involved in the pathogenesis of EAE.

Concepts: Gene expression, Polymerase chain reaction, Messenger RNA, Flow cytometry, Stage, Autoimmunity, Debut albums, Regulatory T cell

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The overwhelming body of research on T regulatory cells (Treg) has focused on CD4 + CD25 + Foxp3+ T cells. However, recent years have witnessed a resurgence in interest in CD4 - CD8+, CD4 - CD8- (double negative [DN]), and CD4 + Foxp3- type 1 Treg (Tr1) Treg and their role in controlling autoimmune diseases and in promoting the survival of organ allografts and xenografts. CD8+ and DN Treg can arise spontaneously (natural Treg) or can be induced in situ. Both CD8+ and DN Treg have been shown to enhance the survival of organ allografts and xenografts. Additionally, both can suppress alloimmune responses by contact-dependent mechanisms by either inducing apoptosis or mediating direct cytolysis of effector T cells. CD8+, DN, and Tr1 Treg can also act in a contact-independent manner by elaborating soluble immunosuppressive factors, such as TGF-β and IL-10. Applying CD8+, DN, and Tr1 Treg for enhancing the survival of organ allografts and xenografts is still in its infancy but holds significant potential. Furthermore, there is a need for a more comprehensive understanding of how current immunosuppressive therapies applied to organ transplantations affect the wide array of Treg populations.

Concepts: Immune system, Apoptosis, Immunology, T helper cell, T cells, Organ transplant, Regulatory T cell, Allotransplantation

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The concept of regulatory T cell (Treg) therapy in transplantation is now a reality. Significant advances in science and technology have enabled us to isolate human Tregs, expand them to clinically relevant numbers and infuse them into human transplant recipients. With several Phase I/II trials underway investigating Treg safety and efficacy it is now more crucial than ever to understand their complex biology. However, our journey is by no means complete, results from these trials will undoubtedly provoke both further knowledge and enquiry, which, alongside evolving science will continue to drive the optimization of Treg therapy in the pursuit of transplantation tolerance. In this review we will summarize current knowledge of Treg biology, explore novel technologies in the setting of Treg immunotherapy and address key prerequisites surrounding the clinical application of Tregs in transplantation. This article is protected by copyright. All rights reserved.

Concepts: Organ, T cells, Organ transplant, Autoimmunity, Technology, Human cells, Copyright, Regulatory T cell