Suppressive Activity Of Tregs Research Articles

Deciphering the role of TRIB1 in regulatory T-cells

The role of regulatory T-cells (Tregs) is crucial to maintain immune homoeostasis by controlling peripheral tolerance. A better understanding in the molecular mechanisms involved in the biology of these Tregs could improve their expansion and selection to treat immune-related diseases, achieve immunosuppression-free organ transplantation and to specifically target them in cancer. We reported on the overexpression of tribbles-1 (TRIB1) in Tregs compared with their counterpart naive T-cells and that TRIB1 interacts with the master molecule of Tregs, forkhead box P3 (FOXP3), a transcription factor essential for Treg suppressive activity. We demonstrated that these two molecules interact together in the nucleus of Tregs and TRIB1 overexpression is associated with a decrease in their proliferative capacities. Since TRIB1 was reported to be overexpressed in the blood of renal transplanted patients with chronic antibody-mediated rejection (CAMR), altogether, these results suggest TRIB1 could be linked to the decrease proportion of Tregs in patients exhibiting CAMR and a key player in Tregs through its FOXP3 interaction. In addition, yeast two-hybrid screening experiments highlighted that TRIB1 potentially interacts with molecules playing roles in intracellular events following T-cell activation and particularly cluster of differentiation (CD)4(+) T-cells. This suggests still non explored potential links between TRIB1 in Tregs. Our goal is thus to decipher the role of TRIB1 in the Treg biology, notably in pathways known to involved its partner and main transcriptional factor of Tregs, FOXP3 and to determine the role of TRIB1 in immune pathologies.

Decrease of CD4+ CD25+ CD127low FoxP3+ regulatory T cells with impaired suppressive function in untreated ulcerative colitis patients

Regulatory T (Treg) cells take part in immune homeostasis and play a pivotal role in maintaining peripheral tolerance. The aim of this study was to evaluate the frequency and function of Treg cells in active and untreated ulcerative colitis (UC) patients. Thirty-two subjects with newly diagnosed UC and 31 age-matched healthy controls were included in this survey. The frequency of Tregs was analyzed with flow cytometry using CD4, CD25, CD127 and FoxP3 markers. We used surface expression of CD4+, CD25+ and CD127low markers for isolation of a relatively pure Treg population. Suppressive activity of Tregs was determined by measuring their ability to inhibit the proliferation of T responder cells. UC patients had a lower frequency of CD4+ CD25+ CD127low FoxP3+ Treg cells. Additionally, Treg cell-mediated suppression was lower in UC patients compared to controls. The frequency and suppressive capacity of Tregs and MFI of FoxP3 were inversely correlated with disease activity. These results suggest that CD4+ CD25+ CD127low FoxP3+ Treg cells may contribute to immunopathogenesis of UC, and assessment of Treg cell frequency and function may have clinical value.

A phase 1b/2 study of the combination of the IDO pathway inhibitor indoximod and temozolomide for adult patients with temozolomide-refractory primary malignant brain tumors: Safety analysis and preliminary efficacy of the phase 1b component.

2070 Background: Indoleamine 2, 3-dioxygenase (IDO) is a key immune-modulatory enzyme within the IDO pathway that inhibits CD8+ T cells and enhances the suppressor activity of Tregs. IDO is express...

Regulatory T-cell subsets with acquired functional impairment: important indicators of disease severity in atopic dermatitis.

Our aim was to assess whether the presence of highly active effector T cells in atopic dermatitis (AD) is associated with changes in the number and/or function of regulatory T cells (Tregs). Flow cytometry was utilised to determine the percentage of CD4+ CD25bright CD127-/low FOXP3+ and skin-homing CLA+ CD4+ CD25bright FOXP3+ Tregs in healthy controls and AD patients. The correlation between disease severity and Treg percentages was estimated. Treg suppressor activity and cell proliferation were measured after T-cell stimulation. Significantly increased percentages of Tregs were found in AD patients compared to healthy individuals, and significant correlation between the frequency of Tregs and disease severity was also detected. The otherwise normal suppressor activity of Tregs decreased in the presence of Staphylococcus enterotoxin B (SEB). In conclusion, the continuous presence of SEB can trigger an acquired functional impairment of Tregs in AD patients and the correlation between the increased frequency of Tregs and disease severity supports their important role in AD pathogenesis.

Clinically-relevant cyclosporin and rapamycin concentrations enhance regulatory T cell function to a similar extent but with different mechanisms: an in-vitro study in healthy humans.

Evidence indicates that regulatory T cells (Tregs) are profoundly involved in promoting allograft tolerance after organ transplantation. Since a successful transplantation currently still requires a long-term immunosuppressive treatment, clarifying the specific impact of these drugs on Tregs may be of high clinical relevance. Conflicting results arise from the literature, particularly as concerns cyclosporine (CsA). The specific aim of this work was to evaluate in-vitro the direct effects of clinically-relevant drug concentrations of three widely used immunosuppressive drugs, i.e. CsA, rapamycin (RAPA) and mycophenolic acid (MPA), on Treg activity, number and forkhead/winged helix transcription factor (FoxP3) expression in humans. Tregs (CD4(+)CD25(+)) isolated from healthy donors were cultured in the presence of different concentrations of CsA, RAPA or MPA. The suppressive activity of Tregs was evaluated in mixed lymphocyte reactions with CD4(+)CD25(-) T cells. Phenotype analysis and FoxP3 expression were assessed by flow cytometry. Clinically-relevant CsA and RAPA concentrations significantly enhanced to a similar extent the suppressive activity of Tregs. Although this effect was associated with an increase in Treg number as well as in FoxP3 expression with both drugs, the driving mechanism seemed to be primarily quantitative (i.e. increase of the cell number) for RAPA, whereas mainly qualitative (i.e. increase in FoxP3 levels) for CsA, respectively. Conversely, MPA did not show any effect on Treg function and number. These findings suggest that both RAPA and CsA may be beneficial in promoting Treg-dependent allograft tolerance after organ transplantation.

Experimental Myocardial Infarction Induces Altered Regulatory T Cell Hemostasis, and Adoptive Transfer Attenuates Subsequent Remodeling

BackgroundIschemic cardiac damage is associated with upregulation of cardiac pro-inflammatory cytokines, as well as invasion of lymphocytes into the heart. Regulatory T cells (Tregs) are known to exert a suppressive effect on several immune cell types. We sought to determine whether the Treg pool is influenced by myocardial damage and whether Tregs transfer and deletion affect cardiac remodeling.Methods and ResultsThe number and functional suppressive activity of Tregs were assayed in mice subjected to experimental myocardial infarction. The numbers of splenocyte-derived Tregs in the ischemic mice were significantly higher after the injury than in the controls, and their suppressive properties were significantly compromised. Compared with PBS, adoptive Treg transfer to mice with experimental infarction reduced infarct size and improved LV remodeling and functional performance by echocardiography. Treg deletion with blocking anti-CD25 antibodies did not influence infarct size or echocardiographic features of cardiac remodeling.ConclusionTreg numbers are increased whereas their function is compromised in mice with that underwent experimental infarction. Transfer of exogeneous Tregs results in attenuation of myocardial remodeling whereas their ablation has no effect. Thus, Tregs may serve as interesting potential interventional targets for attenuating left ventricular remodeling.

Detection and functional assessment of regulatory T cells in clinical samples

Regulatory T cell (Treg)-mediated immunosuppression is considered a major obstacle for successful cancer immunotherapy. Given their profound effect on the outcome of immunotherapy trials, Treg frequency and function are being studied extensively. Unfortunately, no consensus has been reached about a) the (minimal number of) markers required to define human Tregs and b) which assay is the best to measure Treg suppressor function. We had organized a workshop on the detection and functional testing of (antigen-specific) Tregs. Based on the outcome of this workshop and subsequent discussions, we proposed the following essential marker set for flow cytometric Treg analysis: CD3, CD4, CD25, CD127, FoxP3, Ki67 and CD45RA. We have validated the use of this essential marker set in a series of PBMC from healthy donors and cancer patients, as well as in tumor draining lymph nodes and freshly isolated tumors. We here show that the CD3, CD4, CD25, CD127 and FoxP3 markers are the minimally required markers to define human Treg cells in peripheral blood, tumors and lymph nodes. Importantly, as Ki67 and CD45RA provide additional information on their activation status, we recommend to also include these markers in the essential Treg marker set. Similarly, the discussion on functional assays revealed that classical suppressor cell assays measuring the inhibition of responder cell proliferation or cytokine production in 3-7 day long assays required large numbers of Tregs and were technically challenging. Other assays, in particular an assay measuring Treg-mediated prevention of CD69 and CD154 up-regulation on CD4+ T cells was used as alternative and short (6-20h) assay for assessing human Treg suppressor function. We studied the ability of Tregs to inhibit CD25, CD69, CD154 and CD137 up-regulation on CD4+ and CD8+ T cells and compared this to the classical assay. Indeed Tregs were able to inhibit aCD3/CD28-bead-induced up-regulation of CD25, CD69 (on CD4 and CD8) and CD154 (on CD4), but not CD137 (on CD8) on responder T cells. Moreover, we showed that this excellently correlated with suppression of T cell proliferation. In conclusion, we have identified CD3, CD4, CD25, CD127, FoxP3, Ki67 and CD45RA as the minimally required marker to define Tregs and showed that the T cell activation marker assay is a simple, fast and robust assay to measure Treg suppressive activity. The proposed essential marker set will be used to launch proficiency panels and harmonize the phenotypic analysis of Tregs within the CIMT Immunoguiding Program (CIP) participating laboratories.

IT-36 * PHASE 1/2 STUDY OF THE COMBINATION OF INDOXIMOD AND TEMOZOLOMIDE FOR ADULT PATIENTS WITH TEMOZOLOMIDE-REFRACTORY PRIMARY MALIGNANT BRAIN TUMORS

BACKGROUND: Indoleamine 2, 3-dioxygenase (IDO) is a key immune-modulatory enzyme that inhibits CD8+ T cells and enhances the suppressor activity of Tregs. IDO is expressed in 50 to 90% of glioblastoma (GBM) and is correlated with poor prognosis. IDO pathway inhibitors such as indoximod (1-Methyl-D-tryptophan) can improve anti-tumor T cell response slowing the tumor growth in vivo. We have demonstrated a synergistic effect of indoximod when combined with temozolomide (TMZ) and radiation in a syngeneic orthotopic brain tumor model. This phase 1 study is designed to determine maximal tolerated dose (MTD) of indoximod in combination with TMZ in GBM followed by an expansion phase 2 testing the preliminary activity of the combination in relevant situations with the addition of bevacizumab or stereotactic radiosurgery. METHODS: After progression to standard front line-therapy, patients with GBM are enrolled in a dose escalation study of indoximod (600, 1000 or 1200 mg twice daily given orally) with a standard fixed dose of TMZ. In the phase 2 part, patients are separated into 3 cohorts: cohort 2a: indoximod with TMZ, cohort 2b: indoximod with TMZ and bevacizumab (for patients who are currently on bevacizumab), cohort 2c: indoximod with TMZ and stereotactic radiosurgery. STATISTICAL ANALYSIS: The study uses a 3 + 3 dose escalation design, until reaching the MTD or the maximal specified dose. Sample size in phase 2 is based on the primary endpoint of 6 months progression free survival (PFS). CORRELATIVE STUDIES: Assessment of primary tumor samples for IDO expression, evaluation of serum for potential biomarkers of IDO pathway activity (kynurenine and tryptophan) and a pharmacokinetic analysis will be performed. RESULTS: Study is ongoing. Updates are to be presented at the meeting.

Aberrant GITR expression on different T cell subsets and the regulation by glucocorticoid in systemic lupus erythematosus.

The dysfunction of T regulatory cells is important for the pathogenesis of systemic lupus erythematosus (SLE). Glucocorticoid-induced tumor necrosis factor receptor family-related protein (GITR) is expressed at low levels on resting responder T lymphocytes (Tresps) and is up-regulated on T regulatory cells (Tregs) and activated T cells, diminishing suppressive activity of Tregs and/or leading to resistance to suppression of Tregs by activated effector T cells. We aimed to explore whether SLE patients had an aberrant expression of GITR on Tregs and responder T cells (Tresps) and the regulation by glucocorticoids. The surface GITR expression on Tregs and Tresps cells were analyzed by flow cytometry in 32 patients and 15 normal controls. Purified Tregs or Tresps were cultured with glucocorticoid. Apoptosis of the cells were determined by the staining of Annexin V. Systemic lupus erythematosus patients had higher levels of GITR expressed on CD4(+) CD25(+) , CD4(+) CD25(high) and CD4(+) CD25(+) CD127(low/-) Tregs as well as on CD4(+) CD25(-) Tresps compared to healthy controls. The expression of GITR on Tregs and Tresps were positively correlated with score of SLE disease activity index (SLEDAI). In vitro glucocorticoid induced GITR expression on purified Tresp cells, but not on Tregs, and almost all of the GITR positive cells induced by glucocorticoid encountered apoptosis. Aberrant expression of GITR may contribute to SLE pathogenesis. Glucocorticoid may achieve its therapeutic effect partly by inducing GITR expression on Tresps rather than Tregs, which initiates the apoptosis of Tresp cells in SLE patients.

Target tissue ectoenzyme CD39/CD73-expressing Foxp3+ regulatory T cells in patients with psoriasis.

Psoriasis is a chronic, relapsing, inflammatory skin disease, in which regulatory T cells (Tregs) play an important role. Recently, human Treg ectoenzymes (CD39/CD73) have been reported to mediate the suppressive activity of Tregs. To investigate the proportions of CD39/CD73 expressing Foxp3(+) regulatory T cells in different types of psoriatic lesions. Immunohistochemical staining was used to analyse expression of Foxp3, CD39 and CD73 in biopsy tissue from healthy controls and from patients with different types of psoriasis. In normal control biopsies, CD39(+) cells were scattered throughout the epidermis and dermis, while CD73(+) cells were localized predominantly in the dermis. The proportion of cells that were both CD39(+) and Foxp3(+) was significantly lower in pustular psoriasis (PP) and erythrodermic psoriasis (EP) than in psoriasis vulgaris (PV) (25.0 ± 2.6%, 26.5 ± 2.0% and 45.1 ± 3.5%, respectively; P < 0.001). Likewise, CD73(+) Foxp3(+) cells were lower in PP and EP than in PV (6.2 ± 1.9%, 11.6 ± 2.8% and 17.7 ± 2.3% respectively, P < 0.001). There were no significant differences in the population size of double-staining cells in EP compared with PP. The relative reduced expressions of CD39 and CD73 within Foxp3(+) Tregs may imply a different immunopathogenesis for different psoriatic lesions.

Abstract 2564: Histone deacetylase 6 is a novel target for enhancing T-cell function during anti-tumor response and tumor-peptide vaccination

Abstract Histone deacetylases (HDACs) are a family of epigenetic regulators with emerging roles in both tumor and immune system biology. In particular, HDAC6 has been reported to modulate the acetylation HSP90, a regulator of regulatory T-cell (Treg) suppressive activity (de Zoeten, Mol Cel Biol, 2011). Here we report a novel role of HDAC6 in T-cell activation and response against tumor or peptide vaccine. Initially the relative expression of HDAC6 was evaluated in mouse and human T-cells, revealing decreased expression of this HDAC following CD3/CD28 stimulation. To further investigate the role(s) of HDAC6 in T-cell function, an HDAC6KO mouse model was utilized. Characterization of the T-cell compartments of the HDAC6KO mouse model showed a slight, but statistically significant increase in CD4+ T-cell population in the lymph nodes at the expense of a decreased percentage of CD8+ T-cells. Further investigation using isotype-specific HDAC6 inhibitors showed similar results when WT T-cells were activated and treated with an HDAC6 inhibitor. In addition to this population skewing, HDAC6 inhibition led to an enhanced expression of CD69 in WT CD4+ T-cells. This result was reproduced in human CD4+ T-cells, indicating a role of HDAC6 in regulating T-cell activation. To evaluate advantages of HDAC6 inhibition for tumor immunotherapy, melanoma-bearing mice were adoptively transferred with T-cells activated and treated with an HDAC6 inhibitor. Ex vivo analysis of memory T-cell distribution in the lymph nodes demonstrated an increased percent of CD44+CD62L+ T-cells upon HDAC6 inhibition, suggesting a role of HDAC6 in the formation or distribution of memory CD4+ and CD8+ T-cells. In a separate experiment, HDAC6KO mice inoculated with melanoma presented significantly delayed tumor growth. Additionally, in a tumor-peptide vaccination model, HDAC6KO mice displayed a remarkably reduced contraction phase in the antigen-specific CD8+ T-cell compartment when compared to WT mice after peptide vaccine administration. To further evaluate whether these in vivo responses were dependent on T-cells, WT or lympho-deficient, lymphoma-bearing mice were treated with an HDAC6 inhibitor. HDAC6 inhibition led to reduced tumor burden in WT mice, which was absent in lympho-deficient mice, highlighting the importance of lymphocytes in the aforementioned in vivo results. Thus, the role of HDAC6 in regulating immune cells during anti-tumor response appears to be more important than the previously reported role as a regulator of Treg function. The data presented demonstrates a positive effect of HDAC6 in T-cell activation, maintenance of anti-tumor response in vivo and persistence of reactive T-cells following peptide vaccination. The results herein described have revealed an unexplored role of HDAC6 with positive implications for cancer immunotherapy, warranting further investigation. Citation Format: Andressa S. Laino, David M. Woods, Fengdong Cheng, HongWei Wang, Eduardo M. Sotomayor. Histone deacetylase 6 is a novel target for enhancing T-cell function during anti-tumor response and tumor-peptide vaccination. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 2564. doi:10.1158/1538-7445.AM2014-2564

Evaluation of immunosuppressive function of regulatory T cells using a novel in vitro cytotoxicity assay.

Naturally occurring regulatory T cells (Tregs) play a pivotal role in the maintenance of self-tolerance due to their intrinsic immunosuppressive activity. Currently, a number of human clinical trials are being conducted to investigate the roles of Tregs in treating various immune-mediated disorders. Traditionally, the suppressive activity of Tregs is measured using either a thymidine incorporation assay, which is a radioactive assay; or CFSE based flow cytometry assay, which requires a relatively large number of cells. Consequently, there is an increasing need to develop novel alternative bioassays that can characterize various aspects of the immunosuppressive function of Tregs in vitro. In this study, using murine clonal CD8+ T cells specific for an islet antigen as responder T cells, we first established a novel, sensitive and quantitative in vitro luminescence based cell viability assay to measure cytotoxicity. Then we used this assay to measure if Tregs could inhibit the cytotoxicity of CD8 effector T cells. This assay does not involve the use of radioisotopes and only needs relatively low number of Tregs. Since normally Tregs only constitute 5-10% of peripheral CD4+ T cells, this advantage is noteworthy compared with other methods. With the assay we developed, we demonstrated that regulatory T cells (Tregs) could inhibit the antigen-specific killing of an adherent target cell monolayer by the CD8+ cytotoxic T cells. We observed more inhibition when Tregs and CD8 killer T cells were incubated during the in vitro activation (stimulation) stage of the cytotoxic T lymphocytes (CTL) than when they were added later at the start of the effector phase. Interestingly, Tregs from B6 mice demonstrated higher suppression of CD8+ T cell killing than Tregs from NOD mice. Moreover, IL-2/anti-IL-2 mAb complexes induced expansion of Tregs in vivo, as well as enhancing the Treg’s suppressive activity per cell.Therefore, this novel non-radioactive, luminescence based cytotoxicity assay mediated by clonal islet antigen-specific CD8 T cells can be used to measure, characterize, and quantitate the immunosuppressive activity of natural Tregs, representing a useful approach to characterize the functions of Tregs in the setting of autoimmune diseases and to elucidate the mechanisms for Treg cell-mediated immunoregulation.Electronic supplementary materialThe online version of this article (doi:10.1186/2045-3701-4-51) contains supplementary material, which is available to authorized users.

Increased production of interleukin-17 over interleukin-10 by treg cells implicates inducible costimulator molecule in experimental spondyloarthritis.

HLA-B27/human β2 -microglobulin (hβ2 m)-transgenic (B27-transgenic) rats develop an inflammatory disorder resembling spondyloarthritis, with accumulation of proinflammatory Th17 cells. Because Treg cells and Th17 cells have opposing effects in inflammatory disorders, we sought to determine whether biased expansion of Th17 cells could result from altered Treg cell frequency and/or function in B27-transgenic rats. We characterized the phenotype and function of Treg cells from B27-transgenic rats in comparison with those from control rats, by examining their expression of cell surface markers, suppressive activity, cytokine production, and differentiation pattern. In B27-transgenic rats, the preferential accumulation of CD4+ Teff cells over Treg cells was not associated with a defect in Treg cell differentiation or suppressive activity. The expression of Treg cell markers was similar between B27-transgenic and control rats, with the exception of the inducible costimulator (ICOS) molecule, which was overexpressed in B27-transgenic rats. High levels of ICOS are considered to be a hallmark of Treg cells with heightened suppressive activity and interleukin-10 (IL-10) expression. Paradoxically, the production of IL-10 by Treg cells was reduced in B27-transgenic rats, whereas the production of IL-17 was enhanced. Moreover, the addition of anti-ICOS monoclonal antibodies during Treg cell differentiation in the presence of dendritic cells from B27-transgenic rats reversed this cytokine profile, restoring the balance between IL-10 and IL-17 in Treg cells from B27-transgenic rats. We observed dysregulated production of IL-10 and IL-17 by Treg cells from B27-transgenic rats, which may contribute to disease development. Moreover, our data highlight a key role for ICOS signaling in the generation of imbalanced production of IL-10 and IL-17 by Treg cells in this experimental model of spondyloarthritis.

T-cell Immune Suppression in Patients with Hematologic Malignancies: Clinical Implications

SUMMARY The reversion of immune suppression and restoration of T-cell function against leukemia remains a significant clinical challenge. However, the advent of improved antileukemia-specific T-cell induction and the generation of gene-modified T cells has extended cellular immunotherapy to hematological malignancies. Numerous immunotherapeutic protocols have been developed aiming to enhance antileukemia T-cell immune function, eliminate leukemic cells and prevent relapse. By contrast, abnormal expression of CTLA-4 and PD1/PD-L1 plays a critical role in effector T-cell responses and increases Treg suppressive activity in patients with tumors; therefore, blocking CTLA-4, PD1 and PD-L1 is a novel approach for immunotherapy.

Liver injury in acute hepatitis A is associated with decreased frequency of regulatory T cells caused by Fas-mediated apoptosis

ObjectiveFoxp3+CD4+CD25+ regulatory T cells (Tregs) control immune responses, but their role in acute viral hepatitis remains elusive. Herein, we investigated alteration in the peripheral blood Treg population during acute hepatitis...

A phase I/II study of the combination of indoximod and temozolomide for adult patients with temozolomide-refractory primary malignant brain tumors.

TPS2107 Background: Indoleamine 2, 3-dioxygenase (IDO) is a key immune-modulatory endogenous enzyme that inhibits CD8+ T cells and enhances the suppressor activity of Tregs. IDO is expressed in a l...

CTLA-4+ regulatory T cells are increased in cetuximab treated head and neck cancer patients, suppress NK cell cytotoxicity and correlate with poor prognosis (TUM2P.916)

Abstract The EGFR-targeted antibody, cetuximab, is clinically effective against head and neck cancer (HNC) but only in 15 - 20% of patients. We hypothesized that regulatory T cells may have functional and clinical impact antitumor immunity induced in cetuximab-treated patients. Indeed, Treg frequency and expression of CTLA-4, CD39, and surface TGF-β were significantly increased after cetuximab-based therapy. These Treg were inversely associated with functional activity of intratumoral NK cells and with clinical outcome in cetuximab-treated HNC patients. Importantly, NK cells selectively eliminated intratumoral Treg in the presence of anti-CTLA mAb (ipilimumab), which overcame the Treg suppressive activity on cetuximab-mediated ADCC. These results suggest that differences in Treg-mediated suppression may play a role in the clinical response to cetuximab therapy, and that efficacy of cetuximab therapy could be enhanced by adding ipilimumab to eliminate Treg, thus promoting anti-tumor immunity.

Genetic and epigenetic basis of Treg cell development and function: from a FoxP3‐centered view to an epigenome‐defined view of natural Treg cells

Naturally occurring regulatory T (nTreg) cells, which specifically express the transcription factor Forkhead box protein P3 (FoxP3), are indispensable for the maintenance of immunological self-tolerance and homeostasis. Recent studies have shown that developing nTreg cells in the thymus acquire a Treg-specific and stable hypomethylation pattern in a limited number of genes, which encode key molecules including FoxP3, essential for Treg cell function. This epigenetic change is acquired via T-cell receptor (TCR) stimulation, beginning prior to FoxP3 expression. The Treg-specific DNA hypomethylated regions generally act as gene enhancers in steady state nTreg cells, contributing to the stable expression of Treg function-associated key genes including Ctla4, Il2ra, and Ikzf4 in addition to Foxp3. Upon TCR stimulation of mature nTreg cells, FoxP3 strongly represses many genes including Il2, contributing to Treg suppressive activity. Thus, the Treg-specific epigenome alteration can determine the heritable Treg-specific gene network including Foxp3 regulation. Considering physiological presence of non-suppressive FoxP3(+) T cells in the immune system and loss of FoxP3 in Treg cells under certain immunological conditions, functional nTreg cells can be more accurately defined as a T-cell subpopulation possessing the Treg-type epigenome, rather than FoxP3(+) T cells. This epigenome-based definition of Treg cells would enable better understanding of functional stability, plasticity, and heterogeneity of Treg cells.

Disruption of CD8+ Treg activity results in expansion of T follicular helper cells and enhanced antitumor immunity.

Tumor growth is associated with the inhibition of host antitumor immune responses that can impose serious obstacles to cancer immunotherapy. To define the potential contribution of Qa-1-restricted CD8 regulatory T cells (Treg) to the development of tumor immunity, we studied B6.Qa-1 D227K mice that harbor a point mutation in the MHC class Ib molecule Qa-1 that impairs CD8 Treg suppressive activity. Here, we report that the growth of B16 melanoma is substantially delayed in these Qa-1-mutant mice after therapeutic immunization with B16 melanoma cells engineered to express granulocyte macrophage colony-stimulating factor compared with Qa-1 B6-WT controls. Reduced tumor growth is associated with enhanced expansion of follicular T helper cells, germinal center B cells, and high titers of antitumor autoantibodies, which provoke robust antitumor immune responses in concert with tumor-specific cytolytic T cells. Analysis of tumor-infiltrating T cells revealed that the Qa-1 DK mutation was associated with an increase in the ratio of CD8(+) T effectors compared with CD8 Tregs. These data suggest that the CD8(+) T effector-Treg ratio may provide a useful prognostic index for cancer development and raise the possibility that depletion or inactivation of CD8 Tregs represents a potentially effective strategy to enhance antitumor immunity.

Regulatory T cell Itch reins in Th2 inflammation

Regulatory T cell Itch reins in Th2 inflammation