CD4+CD25+ T regulatory cells control anti-islet CD8+ T cells through TGF-beta-TGF-beta receptor interactions in type 1 diabetes

Pancreatic lymph node-derived CD4+CD25+ T regulatory (Treg) cells inhibit in situ differentiation of islet-reactive CD8+ T cells into cytotoxic T lymphocytes, thereby preventing diabetes progression. The mechanism by which these Treg cells suppress anti-islet CD8+ T cells is unknown. Here, we show by using a CD8+ T cell-mediated model of type 1 diabetes that transforming growth factor (TGF)-beta-TGF-beta receptor signals are critical for CD4+CD25+ Treg cell regulation of autoreactive islet-specific cytotoxic T lymphocytes. Transgenic expression of tumor necrosis factor alpha from birth to 25 days of age in the islets of B6 mice that constitutively express CD80 on their beta cells results in accumulation of CD4+CD25+TGF-beta+ cells exclusively in the islets and pancreatic lymph nodes, which delays diabetes progression. In contrast, expression of tumor necrosis factor alpha until 28 days of age prevents islet accumulation of CD4+CD25+TGF-beta+ Treg cells, resulting in acceleration to diabetes. Furthermore, adoptive transfer experiments demonstrated that CD4+CD25+ Treg cells could not control na?ve or activated islet-reactive CD8+ T cells bearing a dominant negative TGF-beta receptor type II. Our data demonstrate that, in vivo, TGF-beta signaling in CD8+ T cells is critical for CD4+CD25+ Treg cell suppression of islet-reactive CD8+ T cells in type 1 diabetes.     

The immunosuppressive drug FK778 induces regulatory activity in stimulated human CD4+ CD25- T cells

The induction of transplantation tolerance involves a T-cell-mediated process of immune regulation. In clinical transplantation, the use of immunosuppressive drugs that promote or facilitate this process would be highly desirable. Here, we investigated the tolerance-promoting potential of the immunosuppressive drug FK778, currently under development for clinical therapy. Using a human allogeneic in vitro model we showed that, upon T-cell receptor (TCR) triggering, FK778 induced a regulatory phenotype in CD4+ CD25- T cells. Purified CD4+ CD25- T cells primed in the presence of FK778 showed hyporesponsiveness upon restimulation with alloantigen in the absence of the drug. This anergic state was reversible by exogenous interleukin-2 (IL-2) and was induced independent of naturally occurring CD4+ CD25+ regulatory T cells. Pyrimidine restriction was a crucial requirement for the de novo induction of regulatory activity by FK778. The FK778-induced anergic cells showed suppressor activity in a cell-cell contact-dependent manner; were CD25(high), CD45RO+, CD27-, and CD62L-; and expressed cytotoxic T-lymphocyte-associated antigen-4 (CTLA-4), glucocorticoid-induced tumor necrosis factor receptor (GITR), and FoxP3. The cells revealed delayed p27(kip1) degradation and enhanced phosphorylation of STAT3. In conclusion, the new drug FK778 shows tolerizing potential through the induction of a regulatory T-cell subset in CD4+ CD25- T cells.     

CD28 disruption exacerbates inflammation in Tgf-beta1-/- mice: in vivo suppression by CD4+CD25+ regulatory T cells independent of autocrine TGF-beta1

Tgf-beta1-/- mice develop a progressive, lethal, inflammatory syndrome, but mechanisms leading to the spontaneous activation of Tgf-beta1-/- T cells remain unclear. Here we show the disruption of CD28 gene expression accelerates disease in Tgf-beta1-/- mice, and we link this increase in severity to a reduction in the number of CD4+CD25+ regulatory T cells. CD4+CD25+ T cells develop normally in Tgf-beta1-/- mice and display characteristic expression of cytotoxic T lymphocyte-associated antigen 4 (CTLA-4), glucocorticoid-induced tumor necrosis factor receptor (GITR), alpha(E)beta7 integrin, and Foxp3. Adoptive transfer of Tgf-beta1-/- splenocytes to Tgf-beta1+/+/Rag2-/- mice induced an autoimmune inflammatory disease with features similar to those of the Tgf-beta1-/- phenotype, and disease transfer was accelerated by the depletion of Tgf-beta1-/- CD4+CD25+ T cells from donor splenocytes. Cotransfer of Tgf- beta1-/- CD4+CD25+ T cells clearly attenuated disease in Rag2-/- recipients of CD25+-depleted Tgf-beta1-/- spleen and lymph node cells, but suppression was incomplete when compared with Tgf-beta1+/+ CD4+CD25+ T cells. These data demonstrate that CD4+CD25+ regulatory T cells develop in complete absence of endogenous transforming growth factor-beta1 (TGF-beta1) expression and that autocrine TGF-beta1 expression is not essential for these cells to suppress inflammation in vivo.     

Glucose transporter 1 expression identifies a population of cycling CD4+ CD8+ human thymocytes with high CXCR4-induced chemotaxis

GLUT1, the major glucose transporter in peripheral T lymphocytes, is induced upon T cell receptor activation. However, the role of GLUT1 during human thymocyte differentiation remains to be evaluated. Our identification of GLUT1 as the human T lymphotrophic virus (HTLV) receptor has enabled us to use tagged HTLV-receptor-binding domain fusion proteins to specifically monitor surface GLUT1 expression. Here, we identify a unique subset of CD4+ CD8+ double-positive (DP) thymocytes, based on their GLUT1 surface expression. Whereas these cells express variable levels of CD8, they express uniformly high levels of CD4. Glucose uptake was 7-fold higher in CD4(hi) DP thymocytes than in CD4(lo) DP thymocytes (P = 0.0002). Further analyses indicated that these GLUT1+ thymocytes are early post-beta-selection, as demonstrated by low levels of T cell receptor (TCR)alphabeta and CD3. This population of immature GLUT1+ DP cells is rapidly cycling and can be further distinguished by specific expression of the transferrin receptor. Importantly, the CXCR4 chemokine receptor is expressed at 15-fold higher levels on GLUT1+ DP thymocytes, as compared with the DP GLUT1- subset, and the former cells show enhanced chemotaxis to the CXCR4 ligand CXCL12. Thus, during human thymopoiesis, GLUT1 is up-regulated after beta-selection, and these immature DP cells constitute a population with distinct metabolic and chemotactic properties.     

Th2 cells are less susceptible than Th1 cells to the suppressive activity of CD25+ regulatory thymocytes because of their responsiveness to different cytokines

T-cell clones generated from both CD4+CD25+ and CD8+CD25+ human thymocytes were assessed for their ability to suppress the proliferative response to allogeneic stimulation of type 1 T-helper (Th1) or type 2 T-helper (Th2) clones derived from autologous CD4+CD25- thymocytes. Both CD4+ and CD8+ T-regulatory (Treg) cells completely suppressed the proliferation of Th1 clones but exhibited significantly lower suppressive activity on the proliferation of Th2 clones. The partial suppressive effect on Th2 cells was further reduced by the addition in culture of interleukin-4 (IL-4), whereas it was increased in the presence of an anti-IL-4 monoclonal antibody (mAb). The suppressive activity on Th2 clones was also completely inhibited by the addition of IL-7, IL-9, and IL-15 but not of IL-2, whereas the suppressive effect on Th1 clones was only reverted by the addition of IL-15. Of note, Th2 clones expressed significantly higher amounts of mRNA for IL-4 receptor (IL-4R) and IL-9R alpha chains than Th1 clones, whereas the expression of mRNA for IL-2R, IL-7R, and IL-15R alpha chains was comparable. Taken together, these findings demonstrate that Th2 cells have a lower susceptibility than Th1 cells to the suppressive activity of human CD25+ regulatory thymocytes, because they are able to produce, and to respond to, growth factors distinct from IL-2, such as IL-4 and IL-9.     

Modulation of tryptophan catabolism by human leukemic cells results in the conversion of CD25- into CD25+ T regulatory cells

Indoleamine 2,3-dioxygenase (IDO) is a novel immunosuppressive agent expressed in some subsets of normal and neoplastic cells, including acute myeloid leukemia (AML) cells. Here, we show that IDO expression correlates with increased circulating CD4+CD25+FOXP3+ T cells in patients with AML at diagnosis. In vitro, IDO+ AML cells increase the number of CD4+ CD25+ T cells expressing surface CTLA-4 and FOXP3 mRNA, and this effect is completely abrogated by the IDO inhibitor, 1-methyl tryptophan (1-MT). Purified CD4+CD25+ T cells obtained from coculture with IDO+ AML cells act as T regulatory (T(reg)) cells because they do not proliferate, do not produce interleukin (IL)-2, and inhibit naive T-cell proliferation. Coculture with IDO+AML cells results in the conversion of CD4+CD25- into CD4+CD25+ T cells, which is completely abrogated by 1-MT. Moreover, in mice, intrasplenic injection of IDO+ leukemia/ lymphoma A20 cells induces the expansion of bona fide T(reg) cells by conversion of CD4+CD25- T cells; this effect is counteracted by 1-MT treatment. These data indicate that AML cells induce T-cell tolerance by directly converting CD4+CD25- T cells into CD4+CD25+ T(reg) cells through an IDO-dependent mechanism.     

强直性脊柱炎患者外周血CD4+CD25+调节性T细胞的研究

目的 观察强直性脊柱炎(AS)患者外周血CD4+CD25调节性T细胞(Treg)的数量、功能及肿瘤坏死因子(TNF)-a 抑制剂治疗的影响.方法 活动性AS患者25例,10例给予etanercept治疗12周,健康对照21名,分离外周血单个核细胞(PBMC),流式细胞术检测CD4+CD25high T细胞比例;实时定量聚合酶链反应检测FOXP3 mRNA表达;免疫磁珠法去除CD25+细胞,可溶性噻唑盐(WST-1)法检测T细胞增殖.结果 活动性AS组CD4+CD25high T细胞比例与对照组差异尤统计学意义,但FOXP3 mRNA表达明显低于对照组(P＜0.01),并与C反应蛋白(CRP)呈负相关(P＜0.01).两组的CD4+CD25+细胞体外均能抑制T细胞增殖(P均＜0.01). Etanercept治疗明显增加CD4+CD25highT细胞比例和FOXP3 mRNA表达(P均＜0.01),与CRP降低呈负相关(P＜0.05;P＜0.01).结论 AS患者外周血表达FOXP3的CD4+CD25+Treg细胞异常,可能参与AS发生和发展;Etanercept治疗上调Treg细胞,可能是抗TNF-α治疗的一个机制.     

TGF-beta regulates in vivo expansion of Foxp3-expressing CD4+CD25+ regulatory T cells responsible for protection against diabetes

CD4+CD25+ regulatory T cells are essential in the protection from organ-specific autoimmune diseases. In the pancreas, they inhibit actions of autoreactive T cells and thereby prevent diabetes progression. The signals that control the generation, the maintenance, or the expansion of regulatory T cell pool in vivo remain poorly understood. Here we show that a transient pulse of transforming growth factor beta (TGF-beta) in the islets during the priming phase of diabetes is sufficient to inhibit disease onset by promoting the expansion of intraislet CD4+CD25+ T cell pool. Approximately 40-50% of intraislet CD4+ T cells expressed the CD25 marker and exhibited characteristics of regulatory T cells including small size, high level of intracellular CTLA-4, expression of Foxp3, and transfer of protection against diabetes. Results from in vivo incorporation of BrdUrd revealed that the generation of a high frequency of regulatory T cells in the islets is due to in situ expansion upon TGF-beta expression. Thus, these findings demonstrate a previously uncharacterized mechanism by which TGF-beta inhibits autoimmune diseases via regulation of the size of the CD4+CD25+ regulatory T cell pool in vivo.     

Intratumoral CD4+CD25+ regulatory T-cell-mediated suppression of infiltrating CD4+ T cells in B-cell non-Hodgkin lymphoma

Most non-Hodgkin lymphomas (NHLs) are of B-cell origin, but the tumor tissue can be variably infiltrated with T cells. In the present study, we have identified a subset of CD4(+)CD25(+) T cells with high levels of CTLA-4 and Foxp3 (intratumoral T(reg) cells) that are overrepresented in biopsy specimens of B-cell NHL (median of 17% in lymphoma biopsies, 12% in inflammatory tonsil, and 6% in tumor-free lymph nodes; P = .001). We found that these CD4(+)CD25(+) T cells suppressed the proliferation and cytokine (IFN-gamma and IL-4) production of infiltrating CD4(+)CD25(-) T cells in response to PHA stimulation. PD-1 was found to be constitutively and exclusively expressed on a subset of infiltrating CD4(+)CD25(-) T cells, and B7-H1 could be induced on intratumoral CD4(+)CD25(+) T cells in B-cell NHL. Anti-B7-H1 antibody or PD-1 fusion protein partly restored the proliferation of infiltrating CD4(+)CD25(-) T cells when cocultured with intratumoral T(reg) cells. Finally, we found that CCL22 secreted by lymphoma B cells is involved in the chemotaxis and migration of intratumoral T(reg) cells that express CCR4, but not CCR8. Taken together, our results suggest that T(reg) cells are highly represented in the area of B-cell NHL and that malignant B cells are involved in the recruitment of these cells into the area of lymphoma.     

Effects of inhaled fluticasone propionate on CTLA-4-positive CD4+CD25+ cells in induced sputum in mild asthmatics

Background and objective: Cytotoxic T-lymphocyte antigen 4 (CTLA-4) signalling of regulatory T cells regulates mucosal lymphocyte tolerance and differentiation, and may therefore have a beneficial effect in allergic diseases such as asthma. The aim of this study was to evaluate the effects of fluticasone propionate (FP) on CD4+CD25+ T cell co-expression of CTLA-4 in the sputum of mild asthmatic subjects. Methods: Eleven mild, stable asthmatic subjects completed a double-blind, randomized, cross-over, placebo-controlled study to compare the effects of 14 days 200 µg twice daily FP and placebo. Before and after treatment, airway hyperresponsiveness was measured, and sputum was induced for measurements of CTLA-4+CD4+CD25+ cells, eosinophils and levels of IL-10, IL-13 and transforming growth factor (TGF)-β Results: FP treatment increased co-expression of CTLA-4 on sputum CD4+CD25+ cells from a mean (SEM) of 7.9% (1.8) to 12.7% (3.3) after 14 days treatment (P < 0.05) compared with placebo. FP treatment also significantly increased IL-10 levels, reduced per cent sputum eosinophils, and reduced airway hyperresponsiveness (P < 0.05). There was a significant negative correlation between the change in airway hyperresponsiveness and per cent sputum eosinophils (P < 0.01), but no correlation with changes in CTLA-4+CD4+CD25+ cells (P > 0.05). There was no change in the levels of sputum IL-13 or TGF-β Conclusions: The percentage of airway CTLA-4+CD4+CD25+ cells increased after FP treatment, coincident with improvements in airway inflammation and hyperresponsiveness. Whether improved asthma assessments are related to the increase in CTLA-4+CD4+CD25+ cells and thus improved regulation of T-cell tolerance and differentiation will require a larger sample size to determine. The normalization of CTLA-4+CD4+CD25+ cells in asthma may contribute to the management of this disease.     

A dual altered peptide ligand down-regulates myasthenogenic T cell responses by up-regulating CD25- and CTLA-4-expressing CD4+ T cells

Immunization of mice with two myasthenogenic peptides, p195-212 and p259-271, which are sequences of the human acetylcholine receptor, resulted in myasthenia gravis (MG)-associated immune responses. A dual altered peptide ligand (APL) composed of the two APLs of the myasthenogenic peptides inhibited, in vitro and in vivo, those responses. The aims of this study were to further elucidate the mechanism/s by which the dual APL down-regulates MG-associated responses in vivo and characterize the cell population/s involved in this immunomodulatory suppressive effect. We have shown here that s.c. administration of the dual APL activates CD4CD25-expressing cells in lymph nodes (LN) of SJL mice. Furthermore, depletion of these cells diminished significantly the inhibitory effect of the APL on p195-212-specific proliferative responses. Depletion of the CD4+CD25+ cells was accompanied with a decrease in the secretion of the immunosuppressive cytokine, transforming growth factor (TGF)-beta. Administration of the dual APL resulted also in the up-regulation of the expression of cytotoxic T lymphocyte antigen (CTLA)-4 and in a down-regulated expression of CD28 on LN cells. Blockade of the CTLA-4 function, in vitro, abrogated the inhibitory effect of the dual APL on the proliferative responses specific to p195-212. Thus, our results suggest that the active suppression exerted by the dual APL is mediated by the CD4+CD25+ immunoregulatory cell population, either directly through the CTLA-4 molecule expressed on these cells, and/or indirectly by causing the differentiation of other regulatory T cell population/s that secrete immunosuppressive cytokines.     

Induction of CD4+/CD25+ regulatory T cells by targeting of antigens to immature dendritic cells

Coupling of ovalbumin (OVA) to anti-DEC-205 monoclonal antibody (mAb) (alphaDEC) induced the proliferation of OVA-specific T cells in vivo. Expansion was short-lived, caused by dendritic cells (DCs), and rendered T cells anergic thereafter. Phenotypic analysis revealed the induction of CD25+/CTLA-4+ T cells suppressing proliferation and interleukin-2 (IL-2) production of effector CD4+ T cells. The findings were supported by 2 disease models: (1) CD4+ T-cell-mediated hypersensitivity reactions were suppressed by the injection of alphaDEC-OVA and (2) the application of hapten-coupled alphaDEC-205 reduced CD8+ T-cell-mediated allergic reactions. Thus, targeting of antigens to immature DCs through alphaDEC antibodies led to the induction of regulatory T cells, providing the basis for novel strategies to induce regulatory T cells in vivo.     

Precommitment of CD4+CD8+ thymocytes to either CD4 or CD8 lineages.

CD4+ and CD8+ mature T cells arise from CD4+CD8+ precursors in the thymus. During this process, cells expressing T-cell receptors (TCRs) reactive with self major histocompatibility complex (MHC) class I or II molecules are positively selected to the CD8 or CD4 lineage, respectively. It is controversial whether lineage commitment of CD4+CD8+ thymocytes is controlled directly by TCR specificity for MHC (instructional model) or, alternatively, by processes that operate independently of TCR specificity (stochastic model). We show here that CD4+CD8+ thymocytes bearing a MHC class I-restricted transgenic TCR can be subject to two alternative developmental fates. One population of CD4+CD8+ cells is positively selected by MHC class I molecules to the CD8 lineage as expected, whereas the other CD4+CD8+ population rearranges endogenous TCR genes and is positively selected by MHC class II molecules to the CD4 lineage. Blocking TCR-MHC class II interactions in vivo does not interfere with the generation of CD4+CD8+ cells expressing endogenous TCRs but does prevent their subsequent maturation to CD4+ cells. These data support a version of the stochastic model in which CD4+CD8+ thymocytes are precommitted to the CD4 or CD8 lineage independently of TCR specificity for MHC and prior to positive selection.     

Tumor necrosis factor-alpha regulation of CD4+CD25+ T cell levels in NOD mice

The mechanism by which tumor necrosis factor-alpha (TNF) differentially modulates type I diabetes mellitus in the nonobese diabetic (NOD) mouse is not well understood. CD4+CD25+ T cells have been implicated as mediators of self-tolerance. We show (i) NOD mice have a relative deficiency of CD4+CD25+ T cells in thymus and spleen; (ii) administration of TNF or anti-TNF to NOD mice can modulate levels of this population consistent with their observed differential age-dependent effects on diabetes in the NOD mouse; (iii) CD4+CD25+ T cells from NOD mice treated neonatally with TNF show compromised effector function in a transfer system, whereas those treated neonatally with anti-TNF show no alteration in ability to prevent diabetes; and (iv) repeated injection of CD4+CD25+ T cells into neonatal NOD mice delays diabetes onset for as long as supplementation occurred. These data suggest that alterations in the number and function of CD4+CD25+ T cells may be one mechanism by which TNF and anti-TNF modulate type I diabetes mellitus in NOD mice.     

Innate CD4+CD25+ regulatory T cells are required for oral tolerance and inhibition of CD8+ T cells mediating skin inflammation

To elucidate the role of CD4+CD25+ regulatory T cells in oral tolerance, we used the model of contact hypersensitivity (CHS) to 2,4-dinitrofluorobenzene (DNFB), which is mediated by CD8+ Tc1 effector cells independently of CD4+ T-cell help. Conversely to normal mice, invariant chain knock-out (KO) (Ii degrees / degrees ) mice, which are deficient in CD4+ T cells, cannot be orally tolerized and develop a chronic hapten-specific CHS response. Transfer of naive CD4+ T cells before hapten gavage into Ii degrees / degrees mice restores oral tolerance by a mechanism independent of interleukin-10 (IL-10) production by CD4+ T cells. That naturally occurring CD4+CD25+ T cells are critical for oral tolerance induction is demonstrated by the finding that (1) transfer of CD4+CD25+ but not CD4+CD25- T cells into Ii degrees / degrees recipients completely prevents the CHS response and skin infiltration by CD8+ T cells, by blocking development of hapten-specific CD8+ T cells; (2) in vivo depletion of CD4+CD25+ cells by antibody treatment in normal mice impairs oral tolerance; and (3) CD4+CD25+ T cells inhibit hapten-specific CD8+ T-cell proliferation and interferon gamma (IFN gamma) production, in vitro. These data show that naturally occurring CD4+CD25+ T cells are instrumental for orally induced tolerance and are key actors for the control of antigen-specific CD8+ T-cell effectors mediating skin inflammation.     

Role for CTLA-4 but not CD25+ T cells during Schistosoma mansoni infection of mice

Schistosoma mansoni infection of mice increases the frequency of cells that are CD4+ CD25+ in the acute (4 and 8 weeks) and chronic (16 week) stages of infection. Depletion of > 85% of CD25+ cells in the acute or chronic stages of schistosome infection caused no overt changes in morbidity or immunological responses. The absence of effect in mice with CD25+ cells depleted may be due to the preferential expression of IL-4 and IL-10, two cytokines that are protective in schistosome infection, on CD25- CD4+ cells. We also assessed infection-induced changes of other regulatory markers, GITR, CD103 and CTLA-4 on CD4+ cells. We identified a marked expansion of CTLA-4+ population on CD25- CD4+ cells in acute and chronic infection. Blocking of CTLA-4 during acute, but not chronic infection, caused significant weight loss and altered the type 2 cytokine response of mice, with increased IL-4 and IL-5 production associated with significantly more Th2 cells and eosinophils in the liver granuloma. This study illustrates the complexity of regulation of T cells in schistosome infection and highlights a specific role for CTLA-4+, but not CD25+ cells, in the regulation of Th2 responses in helminth infection.     

Negative selection of CD4+ CD8+ thymocytes by T-cell receptor peptide antagonists.

Antigen-induced activation of T cells can be specifically inhibited by antigen analogs that have been termed T-cell receptor peptide antagonists. These antagonists appear to act by inducing the formation of nonstimulatory or partially stimulatory complexes between T-cell receptors and the major histocompatibility complex molecules presenting the peptides. Herein, we have investigated the effect of T-cell receptor peptide antagonists on thymocyte negative selection. First, peptide antagonists were identified for the cytochrome c-specific T-cell clone AD10. These peptides were then tested for their ability to induce negative selection in an in vitro model system using thymocytes from mice transgenic for the AD10 T-cell receptor. Though unable to induce mature T-cell activation, the T-cell receptor peptide antagonists induced deletion of CD4+ CD8+ thymocytes. These results suggest that negative selection of CD4+ CD8+ thymocytes can be induced by T-cell receptor interactions of a lower affinity than those required for mature T-cell activation.