Transcription factors RUNX1 and RUNX3 in the induction and suppressive function of Foxp3+ inducible regulatory T cells

Gene profile analysis of CD8(+) ILT3-Fc induced T suppressor cells

Gene profile analysis of ILT3-Fc-induced Ts revealed a significant upregulation of Zink finger proteins, most of which act as transcriptional repressors. Included among these repressors is BCL6, which was shown to play a critical role in the differentiation of ILT3-Fc-induced T suppressor (Ts) cells. Genes implicated in cell cycle progression were downregulated. Genes encoding numerous inflammatory cytokines and chemokines were also downregulated. In contrast, antiapoptotic genes, as well as members of the WNT and transforming growth factor-β pathways, were upregulated. This study elucidates certain important aspects of Ts differentiation and function.

Cytokines and Regulatory T Cells in Rheumatoid Arthritis and Their Relationship with Response to Corticosteroids

Objective.

To analyze circulating cytokines and regulatory T cells (Treg) in patients with rheumatoid arthritis (RA) of different durations, and their association with functional interleukin 10 (IL-10) and tumor necrosis factor-α (TNF-α) genotypes in patients treated with corticosteroids.

Methods.

Serum levels of IL-6, IL-10, IL-17, IL-18, TNF-α, and transforming growth factor-ß (TGF-ß) were quantified in 196 patients and 61 healthy controls. Percentage of CD4+CD25high cells was determined by flow cytometry and Foxp3 expression by real-time reverse-transcription polymerase chain reaction. Data were related to clinical measurements and presence of the genotype −1082GG IL-10/−308GG TNF-α, previously associated with good response to corticosteroids.

Results.

Levels of TNF-α, IL-6, and IL-18 were significantly higher in patients compared to controls, while TGF-ß and IL-10 were lower. Serum samples of patients at disease onset (n = 32) had increased IL-6 and decreased TGF-ß, but there were no differences in other cytokines. These patients also presented a higher percentage of CD4+CD25high cells than those with established disease, although no significant differences were detected in Foxp3. Patients under corticosteroid treatment who were carriers of the good responder genotype had higher levels of TGF-ß, Foxp3, and Treg compared to patients with other genotypes, while relatively lower levels of TNF-α and IL-17 were observed.

Conclusion.

Patients at onset of RA present fewer alterations in cytokine levels and Treg than those with longer disease duration, supporting the role of disease progression in subsequent changes. The antiinflammatory balance observed in high IL-10/low TNF-α patients treated with prednisone supports the use of these genetic polymorphisms as predictors of response to corticosteroid therapy.

Methylation matters: binding of Ets-1 to the demethylated Foxp3 gene contributes to the stabilization of Foxp3 expression in regulatory T cells

The forkhead-box protein P3 (Foxp3) is a key transcription factor for the development and suppressive activity of regulatory T cells (Tregs), a T cell subset critically involved in the maintenance of self-tolerance and prevention of over-shooting immune responses. However, the transcriptional regulation of Foxp3 expression remains incompletely understood. We have previously shown that epigenetic modifications in the CpG-rich Treg-specific demethylated region (TSDR) in the Foxp3 locus are associated with stable Foxp3 expression. We now demonstrate that the methylation state of the CpG motifs within the TSDR controls its transcriptional activity rather than a Treg-specific transcription factor network. By systematically mutating every CpG motif within the TSDR, we could identify four CpG motifs, which are critically determining the transcriptional activity of the TSDR and which serve as binding sites for essential transcription factors, such as CREB/ATF and NF-κB, which have previously been shown to bind to this element. The transcription factor Ets-1 was here identified as an additional molecular player that specifically binds to the TSDR in a demethylation-dependent manner in vitro. Disruption of the Ets-1 binding sites within the TSDR drastically reduced its transcriptional enhancer activity. In addition, we found Ets-1 bound to the demethylated TSDR in ex vivo isolated Tregs, but not to the methylated TSDR in conventional CD4(+) T cells. We therefore propose that Ets-1 is part of a larger protein complex, which binds to the TSDR only in its demethylated state, thereby restricting stable Foxp3 expression to the Treg lineage.

Conference Scene: Summary report from EAACI: London 2010

Immunotherapy is, to date, the only effective curative method for the treatment of allergic disorders. Great efforts have been made to improve the efficacy, safety and patient compliance with this method. The growing understanding of the immunological mechanisms underlying immunotherapy has led to new approaches for immunotherapy involving the routes of administration and the kinds of molecules used. In addition, new vaccines are being created that combine the advantageous immunological charasteristics of different substances, such as virus-like particles linked to allergens. Many new results from ongoing research into these topics were presented at the 29th congress of the European Academy of Allergy and Clinical Immunology in London.

The Ets-1 transcription factor controls the development and function of natural regulatory T cells

Regulatory T cells (T reg cells) constitute a population of CD4(+) T cells that limits immune responses. The transcription factor Foxp3 is important for determining the development and function of T reg cells; however, the molecular mechanisms that trigger and maintain its expression remain incompletely understood. In this study, we show that mice deficient for the Ets-1 transcription factor (Ets-1(-/-)) developed T cell-mediated splenomegaly and systemic autoimmunity that can be blocked by functional wild-type T reg cells. Spleens of Ets-1(-/-) mice contained mostly activated T cells, including Th2-polarized CD4(+) cells and had reduced percentages of T reg cells. Splenic and thymic Ets-1(-/-) T reg cells expressed low levels of Foxp3 and displayed the CD103 marker that characterizes antigen-experienced T reg cells. Thymic development of Ets-1(-/-) T reg cells appeared intrinsically altered as Foxp3-expressing cells differentiate poorly in mixed fetal liver reconstituted chimera and fetal thymic organ culture. Ets-1(-/-) T reg cells showed decreased in vitro suppression activity and did not protect Rag2(-/-) hosts from naive T cell-induced inflammatory bowel disease. Furthermore, in T reg cells, Ets-1 interacted with the Foxp3 intronic enhancer and was required for demethylation of this regulatory sequence. These data demonstrate that Ets-1 is required for the development of natural T reg cells and suggest a role for this transcription factor in the regulation of Foxp3 expression.

Approaches for immunological tolerance induction to stem cell-derived cell replacement therapies

The shortage of donors for organ transplantation and also to treat degenerative diseases has led to the development of the new field of regenerative medicine. One aim of this field, in addition to in vivo induction of endogenous tissue regeneration, is to utilize stem cells as a supplementary source of cells to repair or replace tissues or organs that have ceased to function owing to ageing or autoimmunity. Embryonic stem cells hold promise in this respect because of their developmental capacity to generate all tissues within the body. More recently, the discovery of induced pluripotent stem cells, somatic cells reprogrammed to a primitive embryonic-like state by the introduction of pluripotency factors, may also act as an important cell source for cell replacement therapy. However, before cell replacement therapy can become a reality, one must consider how to overcome the potential transplant rejection of stem cell-derived products. There are several potential ways to circumvent the hurdles presented by the immune system in this setting, not least the induction of immunological tolerance in the host. In this review, we consider this and other approaches for engendering acceptance of stem cell-derived tissues.

PI3 kinase signalling blocks Foxp3 expression by sequestering Foxo factors

Expression of the regulatory T (T reg) cell–associated transcription factor Foxp3 can be induced by signals from the T cell receptor (TCR), interleukin-2 (IL-2), and transforming growth factor (TGF)-β. These signals are integrated by a network involving phosphatidylinositol 3 kinase (PI3K), protein kinase B (PKB; here referred to as Akt), and the mammalian target of rapamycin (mTOR). New studies show that the Foxo proteins Foxo1 and Foxo3a, which are inactivated by Akt, drive Foxp3 expression. These studies therefore explain the negative regulation of Foxp3 by PI3K signaling, and add Foxo proteins to the growing list of nuclear factors capable of modulating Foxp3 expression.

Role of Treg in immune regulation of allergic diseases

Allergy is a Th2-mediated disease that involves the formation of specific IgE antibodies against innocuous environmental substances. The prevalence of allergic diseases has dramatically increased over the past decades, affecting up to 30% of the population in industrialized countries. The understanding of mechanisms underlying allergic diseases as well as those operating in non-allergic healthy responses and allergen-specific immunotherapy has experienced exciting advances over the past 15 years. Studies in healthy non-atopic individuals and several clinical trials of allergen-specific immunotherapy have demonstrated that the induction of a tolerant state in peripheral T cells represent a key step in healthy immune responses to allergens. Both naturally occurring thymus-derived CD4+CD25+FOXP3+ Treg and inducible type 1 Treg inhibit the development of allergy via several mechanisms, including suppression of other effector Th1, Th2, Th17 cells; suppression of eosinophils, mast cells and basophils; Ab isotype change from IgE to IgG4; suppression of inflammatory DC; and suppression of inflammatory cell migration to tissues. The identification of the molecules involved in these processes will contribute to the development of more efficient and safer treatment modalities.

Regulatory T cells protect mice against coxsackievirus-induced myocarditis through the transforming growth factor beta-coxsackie-adenovirus receptor pathway

BACKGROUND

Coxsackievirus B3 infection is an excellent model of human myocarditis and dilated cardiomyopathy. Cardiac injury is caused either by a direct cytopathic effect of the virus or through immune-mediated mechanisms. Regulatory T cells (Tregs) play an important role in the negative modulation of host immune responses and set the threshold of autoimmune activation. This study was designed to test the protective effects of Tregs and to determine the underlying mechanisms.

METHODS AND RESULTS

Carboxyfluorescein diacetate succinimidyl ester-labeled Tregs or naïve CD4(+) T cells were injected intravenously once every 2 weeks 3 times into mice. The mice were then challenged with intraperitoneal coxsackievirus B3 immediately after the last cell transfer. Transfer of Tregs showed higher survival rates than transfer of CD4(+) T cells (P=0.0136) but not compared with the PBS injection group (P=0.0589). Interestingly, Tregs also significantly decreased virus titers and inflammatory scores in the heart. Transforming growth factor-beta and phosphorylated AKT were upregulated in Tregs-transferred mice and coxsackie-adenovirus receptor expression was decreased in the heart compared with control groups. Transforming growth factor-beta decreased coxsackie-adenovirus receptor expression and inhibited coxsackievirus B3 infection in HL-1 cells and neonatal cardiac myocytes. Splenocytes collected from Treg-, CD4(+) T-cell-, and PBS-treated mice proliferated equally when stimulated with heat-inactivated virus, whereas in the Treg group, the proliferation rate was reduced significantly when stimulated with noninfected heart tissue homogenate.

CONCLUSIONS

Adoptive transfer of Tregs protected mice from coxsackievirus B3-induced myocarditis through the transforming growth factor beta-coxsackie-adenovirus receptor pathway and thus suppresses the immune response to cardiac tissue, maintaining the antiviral immune response.

Transcription factors Foxo3a and Foxo1 couple the E3 ligase Cbl-b to the induction of Foxp3 expression in induced regulatory T cells

The transcription factor Foxp3 is essential for optimal regulatory T (T reg) cell development and function. Here, we show that CD4⁺ T cells from Cbl-b RING finger mutant knockin or Cbl-b–deficient mice show impaired TGF-β–induced Foxp3 expression. These T cells display augmented Foxo3a phosphorylation, but normal TGF-β signaling. Expression of Foxo3a rescues Foxp3 expression in Cbl-b–deficient T cells, and Foxo3a deficiency results in defective TGF-β–driven Foxp3 induction. A Foxo3a-binding motif is present in a proximal region of the Foxp3 promoter, and is required for Foxo3a association. Foxo1 exerts similar effects as Foxo3a on Foxp3 expression. This study reveals that Foxo factors promote transcription of the Foxp3 gene in induced T reg cells, and thus provides new mechanistic insight into Foxo-mediated T cell regulation.

Molecular mechanisms regulating TGF-beta-induced Foxp3 expression

Molecular mechanisms regulating transforming growth factor-beta (TGF-beta) induction of Foxp3 (forkhead box P3) expression and thus induction of induced regulatory T cells (Tregs) have been the focus of a great deal of study in recent years. It has become clear that this process is influenced by a number of factors as perhaps might be predicted by the fact that there is an overarching need of the immune system to finetune response to environmental antigens. In this review we discuss these mechanisms, with the aim of presenting a broad picture of how the various observations fit together to form an integrated regulatory regime.

Differentiation of effector CD4 T cell populations (*)

CD4 T cells play critical roles in mediating adaptive immunity to a variety of pathogens. They are also involved in autoimmunity, asthma, and allergic responses as well as in tumor immunity. During TCR activation in a particular cytokine milieu, naive CD4 T cells may differentiate into one of several lineages of T helper (Th) cells, including Th1, Th2, Th17, and iTreg, as defined by their pattern of cytokine production and function. In this review, we summarize the discovery, functions, and relationships among Th cells; the cytokine and signaling requirements for their development; the networks of transcription factors involved in their differentiation; the epigenetic regulation of their key cytokines and transcription factors; and human diseases involving defective CD4 T cell differentiation.