Diversity of regulatory CD4+T cells controlling distinct organ-specific autoimmune diseases

Icos gene disruption in non-obese diabetic mice elicits myositis associated with anti-troponin T3 autoantibodies

AIMS

Idiopathic inflammatory myopathies (IIM) are autoimmune inflammatory disorders leading to skeletal muscle weakness and disability. The pathophysiology of IIM is poorly understood due to the scarcity of animal disease models. Genetic deletion of Icos or Icosl (inducible T cell co-stimulator/ligand) in non-obese diabetic (NOD) mice leads to muscle disease. Our aim was to characterise Icos^-/- NOD myopathy and to search for novel autoantibodies (aAbs) in this model.

METHODS

Diabetes, weight, myopathy incidence/clinical score and grip strength were assessed over time. Locomotor activity was analysed with the Catwalk XT gait analysis system. Muscle histology was evaluated in haematoxylin/eosin and Sirius red-stained sections, and immune infiltrates were characterised by immunofluorescence and flow cytometry. 2D gel electrophoresis of muscle protein extracts and mass spectrometry were used to identify novel aAbs. NOD mice were immunised with troponin T3 (TNNT3) in incomplete Freund's adjuvant (IFA) and R848. An addressable laser bead immunoassay (ALBIA) was developed to measure aAb IgG serum levels.

RESULTS

Icos^-/- NOD mice did not exhibit diabetes but developed spontaneous progressive myositis with decreased muscle strength and altered locomotor activity. Muscle from these mice exhibited myofibre necrosis, myophagocytosis, central nuclei, fibrosis and perimysial and endomysial cell infiltrates with macrophages and T cells. We identified anti-TNNT3 aAbs in diseased mice. Immunisation of NOD mice with murine TNNT3 protein led to myositis development, supporting its pathophysiological role.

CONCLUSIONS

These data show that Icos^-/- NOD mice represent a spontaneous model of myositis and the discovery of anti-TNNT3 aAb suggests a new autoantigen in this model.

Single-Cell Characterization of the Immune Microenvironment of Melanoma Brain and Leptomeningeal Metastases

PURPOSE

Melanoma brain metastases (MBM) and leptomeningeal melanoma metastases (LMM) are two different manifestations of melanoma CNS metastasis. Here, we used single-cell RNA sequencing (scRNA-seq) to define the immune landscape of MBM, LMM, and melanoma skin metastases.

EXPERIMENTAL DESIGN

scRNA-seq was undertaken on 43 patient specimens, including 8 skin metastases, 14 MBM, and 19 serial LMM specimens. Detailed cell type curation was performed, the immune landscapes were mapped, and key results were validated by IHC and flow cytometry. Association analyses were undertaken to identify immune cell subsets correlated with overall survival.

RESULTS

The LMM microenvironment was characterized by an immune-suppressed T-cell landscape distinct from that of brain and skin metastases. An LMM patient with long-term survival demonstrated an immune repertoire distinct from that of poor survivors and more similar to normal cerebrospinal fluid (CSF). Upon response to PD-1 therapy, this extreme responder showed increased levels of T cells and dendritic cells in their CSF, whereas poor survivors showed little improvement in their T-cell responses. In MBM patients, therapy led to increased immune infiltrate, with similar T-cell transcriptional diversity noted between skin metastases and MBM. A correlation analysis across the entire immune landscape identified the presence of a rare population of dendritic cells (DC3) that was associated with increased overall survival and positively regulated the immune environment through modulation of activated T cells and MHC expression.

CONCLUSIONS

Our study provides the first atlas of two distinct sites of melanoma CNS metastases and defines the immune cell landscape that underlies the biology of this devastating disease.

Gata3 hypermethylation and Foxp3 hypomethylation are associated with sustained protection and bystander effect following epicutaneous immunotherapy in peanut-sensitized mice

Background

Epicutaneous immunotherapy (EPIT) is a promising method for treating food allergies. In animal models, EPIT induces sustained unresponsiveness and prevents further sensitization mediated by Tregs. Here, we elucidate the mechanisms underlying the therapeutic effect of EPIT, by characterizing the kinetics of DNA methylation changes in sorted cells from spleen and blood and by evaluating its persistence and bystander effect compared to oral immunotherapy (OIT).

Methods

BALB/c mice orally sensitized to peanut proteins (PPE) were treated by EPIT using a PPE‐patch or by PPE‐OIT. Another set of peanut‐sensitized mice treated by EPIT or OIT were sacrificed following a protocol of sensitization to OVA. DNA methylation was analyzed during immunotherapy and 8 weeks after the end of treatment in sorted cells from spleen and blood by pyrosequencing. Humoral and cellular responses were measured during and after immunotherapy.

Results

Analyses showed a significant hypermethylation of the Gata3 promoter detectable only in Th2 cells for EPIT from the 4th week and a significant hypomethylation of the Foxp3 promoter in CD62L⁺ Tregs, which was sustained only for EPIT. In addition, mice treated with EPIT were protected from subsequent sensitization and maintained the epigenetic signature characteristic for EPIT.

Conclusions

Our study demonstrates that EPIT leads to a unique and stable epigenetic signature in specific T‐cell compartments with downregulation of Th2 key regulators and upregulation of Treg transcription factors, likely explaining the sustainability of protection and the observed bystander effect.

Mechanisms of autoimmunity in the non-obese diabetic mouse: effector/regulatory cell equilibrium during peak inflammation

Immune imbalance in autoimmune disorders such as type 1 diabetes may originate from aberrant activities of effector cells or dysfunction of suppressor cells. All possible defective mechanisms have been proposed for diabetes-prone species: (i) quantitative dominance of diabetogenic cells and decreased numbers of regulatory T cells, (ii) excessive aggression of effectors and defective function of suppressors, (iii) perturbed interaction between effector and suppressor cells, and (iv) variations in sensitivity to negative regulation. The experimental evidence available to date presents conflicting information on these mechanisms, with identification of perturbed equilibrium on the one hand and negation of critical role of each mechanism in propagation of diabetic autoimmunity on the other hand. In our analysis, there is no evidence that inherent abnormalities in numbers and function of effector and suppressor T cells are responsible for the immune imbalance responsible for propagation of type 1 diabetes as a chronic inflammatory process. Possibly, the experimental tools for investigation of these features of immune activity are still underdeveloped and lack sufficient resolution, in the presence of the extensive biological viability and functional versatility of effector and suppressor elements.

Immunotherapy of rat glioma without accumulation of CD4(+)CD25(+)FOXP3(+) regulatory T cells

Immunotherapy may be used for the treatment of glioblastoma multiforme; however, the induced immune response is inadequate when either T cells or dendritic cells are used alone. In this study, we established a novel vaccine procedure in rats, using dendritic cells pulsed with C6 tumor cell lysates in combination with adoptive transfer of T lymphocytes from syngenic donors. On day 21 after tumor inoculation, all the rats were sacrificed, the brains were harvested for calculation of glioma volume, cytolytic T lymphocyte responses were measured by cytotoxic assay, and the frequency of regulatory T lymphocytes (CD4⁺CD25⁺FOXP3⁺) in the peripheral blood was investigated by flow cytometric analysis. The survival rate of rats bearing C6 glioma was observed. Results showed that the co-immunization strategy had significant anti-tumor potential against the pre-established C6 glioma, and induced a strong cytolytic T lymphocyte response in rats. The frequency of peripheral blood CD4⁺CD25⁺FOXP3⁺ regulatory T lymphocytes was significantly decreased following the combination therapy, and the rats survived for a longer period. Experimental findings indicate that the combined immunotherapy of glioma cell lysate-pulsed dendritic cell vaccination following adoptive transfer of T cells can effectively inhibit the growth of gliomas in rats, boost anti-tumor immunity and produce a sustained immune response while avoiding the accumulation of CD4⁺CD25⁺FOXP3⁺ regulatory T lymphocytes.

Experimental myocardial infarction induces altered regulatory T cell hemostasis, and adoptive transfer attenuates subsequent remodeling

Background

Ischemic 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 Results

The 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.

Conclusion

Treg 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.

Thymic epithelium determines a spontaneous chronic neuritis in Icam1(tm1Jcgr)NOD mice

The NOD mouse strain spontaneously develops autoimmune diabetes. A deficiency in costimulatory molecules, such as B7-2, on the NOD genetic background prevents diabetes but instead triggers an inflammatory peripheral neuropathy. This constitutes a shift in the target of autoimmunity, but the underlying mechanism remains unknown. In this study, we demonstrate that NOD mice deficient for isoforms of ICAM-1, which comediate costimulatory functions, spontaneously develop a chronic autoimmune peripheral neuritis instead of diabetes. The disease is transferred by CD4(+) T cells, which infiltrate peripheral nerves together with macrophages and B cells and are autoreactive against peripheral myelin protein zero. These Icam1(tm1Jcgr)NOD mice exhibit unaltered numbers of regulatory T cells, but increased IL-17-producing T cells, which determine the severity, but not the target specificity, of autoimmunity. Ab-mediated ICAM-1 blockade triggers neuritis only in young NOD mice. Thymic epithelium from Icam1(tm1Jcgr)NOD mice features an altered expression of costimulatory molecules and induces neuritis and myelin autoreactivity after transplantation into nude mice in vivo. Icam1(tm1Jcgr)NOD mice exhibit a specifically altered TCR repertoire. Our findings introduce a novel animal model of chronic inflammatory neuropathies and indicate that altered expression of ICAM-1 on thymic epithelium shifts autoimmunity specifically toward peripheral nerves. This improves our understanding of autoimmunity in the peripheral nervous system with potential relevance for human diseases.

The potential role of dendritic cells in the therapy of Type 1 diabetes

Type 1 diabetes (T1D) is the result of T-cell mediated autoimmune destruction of pancreatic islet β-cells. The two current treatments for T1D are based on insulin or islet-cell replacement rather than the pathogenesis of T1D and remain problematic. Islet/pancreas transplantation does not cater for the majority of sufferers due to the lack of supply of organs and the need for continuous immunosuppression regimens. The mainstay treatment is insulin replacement, but this is disruptive to lifestyle and does not protect against severe long-term complications. An early vaccination and long-term restoration of immune tolerance to self-antigens in T1D patients (reversing the immunopathogenesis of the disease) would be preferable. Dendritic cells (DCs) are potent APCs and play an important role in inducing and maintaining immune tolerance. Targeting DCs through different DC surface molecules shows effective modulation of immune responses. Their feasibility for immunotherapy to prolong transplant survival and cancer immunotherapy has been demonstrated. Therefore, DCs could potentially be used in the treatment of autoimmune diseases. This review summarizes new insights into DCs as a potential therapeutic target for the treatment of T1D.

Miltefosine suppresses inflammation in a mouse model of inflammatory bowel disease

BACKGROUND

The repertoire of immunomodulators that can be used for the treatment of inflammatory bowel disease is limited. The use of these drugs is further restricted by the occurrence of side effects in a proportion of patients. Miltefosine (hexadecylphosphocholine) is a lipid drug developed in the 1980s for the treatment of cancer but is nowadays best known for its application in the oral treatment of leishmaniasis. Although the exact mechanism of action of miltefosine has yet to be elucidated, the drug has previously been shown to inhibit phospholipases and protein kinase C, both key components of proproliferative signal transduction in T cells.

METHODS

Stimulated peripheral blood lymphocyte were treated with miltefosine, and proliferation was measured. We use the CD45RB T-cell transfer colitis model to investigate the effect of miltefosine treatment on intestinal inflammation. Effects on the severity of colitis were studied by histochemical and immunohistochemical staining, and cytokine levels were determined using a cytokine bead array.

RESULTS

Miltefosine inhibited T-cell proliferation in vitro. In the transfer model, miltefosine significantly ameliorated the severity of colitis as measured by clinical, (immuno)histochemical, and biochemical parameters.

CONCLUSIONS

Miltefosine inhibits T-cell proliferation and effectively reduces inflammation in the T-cell transfer model. The drug may therefore be a candidate immunomodulator for inflammatory bowel disease.

An alternative role for Foxp3 as an effector T cell regulator controlled through CD40

The BDC2.5 T cell clone is highly diabetogenic, but the transgenic mouse generated from that clone is surprisingly slow in diabetes development. Although defining pathogenic effector T cells in autoimmunity has been inconsistent, CD4(+) cells expressing the CD40 receptor (Th40 cells) are highly diabetogenic in NOD mice, and NOD.BDC2.5.TCR.Tg mice possess large numbers of these cells. Given the importance of CD40 for pathogenic T cell development, BDC2.5.CD40(-/-) mice were created. Regulatory T cells, CD4(+)CD25(hi)Foxp3(+), develop normally, but pathogenic effector cells are severely reduced in number. Th40 cells from diabetic BDC2.5 mice rapidly induce diabetes in NOD.scid recipients, but Th40 cells from prediabetic mice transfer diabetes very slowly. Demonstrating an important paradigm shift, effector Th40 cells from prediabetic mice are Foxp3(+). As mice age, moving to type 1 diabetes development, Th40 cells lose Foxp3. When Th40 cells that are Foxp3(+) are transferred to NOD.scid recipients, disease is delayed. Th40 cells that are Foxp3(-) rapidly transfer disease. Th40 cells from BDC2.5.CD40(-/-) mice do not transfer disease nor do they lose Foxp3 expression. Mechanistically, Foxp3(+) cells produce IL-17 but do not produce IFN-γ, whereas Foxp3(-) Th40 cells produce IFN-γ and IL-2. This poses a new consideration for the function of Foxp3, as directly impacting effector T cell function.

Regulatory cells and transplantation tolerance

Transplantation tolerance is a continuing therapeutic goal, and it is now clear that a subpopulation of T cells with regulatory activity (Treg) that express the transcription factor foxp3 are crucial to this aspiration. Although reprogramming of the immune system to donor-specific transplantation tolerance can be readily achieved in adult mouse models, it has yet to be successfully translated in human clinical practice. This requires that we understand the fundamental mechanisms by which donor antigen-specific Treg are induced and function to maintain tolerance, so that we can target therapies to enhance rather than impede these regulatory processes. Our current understanding is that Treg act via numerous molecular mechanisms, and critical underlying components such as mTOR inhibition, are only now emerging.

Differentiation and transplantation of functional pancreatic beta cells generated from induced pluripotent stem cells derived from a type 1 diabetes mouse model

The nonobese diabetic (NOD) mouse is a classical animal model for autoimmune type 1 diabetes (T1D), closely mimicking features of human T1D. Thus, the NOD mouse presents an opportunity to test the effectiveness of induced pluripotent stem cells (iPSCs) as a therapeutic modality for T1D. Here, we demonstrate a proof of concept for cellular therapy using NOD mouse-derived iPSCs (NOD-iPSCs). We generated iPSCs from NOD mouse embryonic fibroblasts or NOD mouse pancreas-derived epithelial cells (NPEs), and applied directed differentiation protocols to differentiate the NOD-iPSCs toward functional pancreatic beta cells. Finally, we investigated whether the NPE-iPSC-derived insulin-producing cells could normalize hyperglycemia in transplanted diabetic mice. The NOD-iPSCs showed typical embryonic stem cell-like characteristics such as expression of markers for pluripotency, in vitro differentiation, teratoma formation, and generation of chimeric mice. We developed a method for stepwise differentiation of NOD-iPSCs into insulin-producing cells, and found that NPE-iPSCs differentiate more readily into insulin-producing cells. The differentiated NPE-iPSCs expressed diverse pancreatic beta cell markers and released insulin in response to glucose and KCl stimulation. Transplantation of the differentiated NPE-iPSCs into diabetic mice resulted in kidney engraftment. The engrafted cells responded to glucose by secreting insulin, thereby normalizing blood glucose levels. We propose that NOD-iPSCs will provide a useful tool for investigating genetic susceptibility to autoimmune diseases and generating a cellular interaction model of T1D, paving the way for the potential application of patient-derived iPSCs in autologous beta cell transplantation for treating diabetes.

The immunoregulatory role of CD4⁺ FoxP3⁺ CD25⁻ regulatory T cells in lungs of mice infected with Bordetella pertussis

The identification of regulatory T (Treg) cells was originally based on CD25 expression; however, CD25 is also expressed by activated effector T cells. FoxP3 is a more definitive marker of Treg cells, and CD4(+) FoxP3(+) CD25(+) T cells are considered the dominant natural Treg (nTreg) population. It has been suggested that certain CD4(+) FoxP3(+) Treg cells do not express CD25. In this study, we used a murine model of respiratory infection with Bordetella pertussis to examine the role of Treg cells in protective immunity in the lung. We first demonstrated that CD4(+) FoxP3(+) CD25(-) cells are the dominant Treg population in the lung, gut and liver. Pre-activated lung CD4(+) FoxP3(+) CD25(-) cells suppressed CD4(+) effector T cells in vitro, which was partly mediated by IL-10 and not dependent on cell contact. Furthermore, CD4(+) FoxP3(+) CD25(-) IL-10(+) T cells were found in the lungs of mice at the peak of infection with B. pertussis. The rate of bacterial clearance was not affected by depletion of CD25(+) cells or in IL-10-deficient (IL-10(-/-) ) mice, but was compromised in CD25-depleted IL-10(-/-) mice. Our findings suggest that IL-10-producing CD4(+) FoxP3(+) CD25(-) T cells represent an important regulatory cell in the lung.

Neoplastic "Black Ops": cancer's subversive tactics in overcoming host defenses

Metastatic cancer is usually an incurable disease. Cancers have a broad repertoire of subversive tactics to defeat the immune system. They mimic self, they down-regulate MHC molecules so that T cells are blind to their presence, they interfere with antigen presentation, and they produce factors that can kill T cells or paralyze their response to antigens. Furthermore, the same powerful machinery designed to prevent harmful autoimmune responses is also acting to protect cancers. In particular, cancer is protected with the help of so-called regulatory immune cells. These unique subsets of cells, represented by almost every immune cell type, function to control responses of effector immune cells. In this review, we will discuss the evidence that cancer actively promotes cross-talk of regulatory immune cells to evade immunosurveillance. We will also discuss the role of a newly described cell type, regulatory B cells, by emphasizing their importance in suppression of antitumor immune responses. Thus, cancer not only directly suppresses immune function, but also recruits components of the immune system to become traitors and protect the tumor from immune attack.

Human CD4+CD25(high)CD127 (low/neg) regulatory T cells

CD4+CD25(high)CD127(low/neg) regulatory T cells (Tregs) play a critical role in the maintenance of peripheral tolerance and in controlling the development of autoimmune diseases. A combination of surface and intracellular markers, namely, CD25, CD39/CD73, CD62L, CD45RO, CD127, glucocorticoid-induced tumor necrosis factor receptor (GITR), CTLA-4, and the forkhead/winged helix transcription factor (FOXP3), has been used to characterize Tregs. Tregs suppress T effector responses mainly in a direct cell-cell contact manner. However, other mechanisms independent from this manner cannot be excluded entirely. It has been shown that Tregs can undergo limited expansion in vitro after the stimulation of TCR in the presence of exogenous cytokines, e.g., IL-2. Expanded Tregs retain their suppression function. Human Tregs have demonstrated their great potential to be used as a therapeutic intervention in preventing graft rejection and treating autoimmune diseases. In this chapter, we have given a review on how to characterize, isolate, expand Tregs and assess their suppressive functions.

Differential outcomes in prediabetic vs. overtly diabetic NOD mice nonmyeloablatively conditioned with costimulatory blockade

OBJECTIVE

Autoimmune diabetes can be reversed with mixed chimerism. However, the myelotoxic agents currently required to establish chimerism have prevented the translation of this approach to the clinic. Here, we investigated whether multimodal costimulatory blockade would enhance chimerism and promote islet allograft tolerance in spontaneously diabetic nonobese diabetic (NOD) mice.

MATERIALS AND METHODS

Prediabetic and spontaneously diabetic NOD mice were preconditioned with anti-CD8 monoclonal antibody before conditioning with 500 cGy total body irradiation and transplantation with 30 × 10(6) B10.BR bone marrow cells. Overtly diabetic animals were conditioned similarly and transplanted with 300 to 400 B10.BR islets. After irradiation, both groups of recipients were treated with anti-CD154, anti-OX40L, and anti-inducible T-cell costimulatory monoclonal antibodies. Urine, blood glucose levels, and chimerism were monitored.

RESULTS

Conditioning of NOD mice with costimulatory blockade significantly enhanced engraftment, with 61% of mice engrafting at 1 month. Eleven of 12 chimeric animals with engraftment at 1 month remained diabetes-free over a 12-month follow-up, whereas nonchimeric animals progressed to diabetes. In contrast, similar conditioning prolonged islet allograft survival in only 2 of 11 overtly diabetic NOD recipients. Chimerism levels in the 9 islet rejector animals were 0%.

CONCLUSIONS

Although nonmyeloablative conditioning reversed the autoimmune process in prediabetic NOD mice, the same regimen was significantly less effective in establishing chimerism and reversing autoimmune diabetes in spontaneously diabetic NOD mice.

The soluble CTLA-4 splice variant protects from type 1 diabetes and potentiates regulatory T-cell function

OBJECTIVE

CTLA4 gene variation associates with multiple autoimmune disorders, including type 1 diabetes. The CTLA4 susceptibility allele was found to generate decreased levels of mRNA encoding soluble CTLA-4 (sCTLA-4) relative to the full-length isoform, the functional consequence of which is as yet unknown. In this study, we investigated the contribution of sCTLA-4 to immune regulation with the aim to elucidate the functional basis of the disease association of CTLA4.

RESEARCH DESIGN AND METHODS

To model the disease-associated splicing variation of CTLA4, we generated NOD mice in which sCTLA-4 mRNA is silenced by RNA interference.

RESULTS

We found that loss of sCTLA-4 impairs the function of regulatory T (Treg) cells. This functional defect could be attributed, at least in part, to the failure of sCTLA-4 knockdown (KD) Treg cells to downregulate dendritic cell costimulation. sCTLA-4 KD Treg cells, in contrast with wild-type Treg cells, failed to inhibit colitis induced by transfer of CD4(+)CD45RB(hi) cells into NOD.SCID animals. Furthermore, diminished sCTLA-4 expression accelerated the onset of autoimmune diabetes in transgenic mice.

CONCLUSIONS

Our results demonstrate that sCTLA-4 participates in immune regulation by potentiating the function of Treg cells. The functional outcome of silencing this splice variant in the NOD model provides an explanation for the association of CTLA4 variation with autoimmunity. Lower sCTLA-4 expression from the susceptibility allele may directly affect the suppressive capacity of Treg cells and thereby modulate disease risk. Our unprecedented approach establishes the feasibility of modeling splicing variations relevant to autoimmunity.

Tissue-based class control: the other side of tolerance

In this Essay, we offer a new perspective on how immune responses are regulated. We do not cover how they are turned on and off, but focus instead on the second major aspect of an immune response: the control of effector class. Although it is generally thought that the class of an immune response is tailored to fit the invading pathogen, we suggest here that it is primarily tailored to fit the tissue in which the response occurs. To this end, we cover such topics as the nature of T helper (T(H)) cell subsets (current and yet to be discovered), the nature of privileged sites, the difference between oral tolerance and oral vaccination, why the route of immunization matters, whether the T(H)1-type response is really the immune system's primary defense, and whether there might be a different role for some regulatory T cells.

The effect of regulatory T-cell depletion on the spectrum of organ-specific autoimmune diseases in nonobese diabetic mice at different ages

The nonobese diabetic (NOD) mouse spontaneously develops several autoimmune diseases, including type 1 diabetes and to a lesser extent thyroiditis and sialitis. Imbalance between effector T cells (Teffs) and regulatory T cells (Tregs) has recently been proposed as a mechanism for the disease pathogenesis in NOD mice, but previous studies have shown the various outcomes by different timing and methods of Treg-depletion. This study was, therefore, designed to compare the consequences of Treg-depletion by the same method (anti-CD25 antibody) on the spectrum of organ-specific autoimmune diseases in NOD mice of different ages. Treg-depletion by anti-CD25 antibody at 10 days of age accelerated development of all three diseases we examined (insulitis/diabetes, thyroiditis, and sialitis); Treg-depletion at 4 weeks of age accelerated only diabetes but not thyroiditis or sialitis; and Treg-depletion at 12 weeks of age hastened only development of thyroiditis and exhibited little influence on diabetes or sialitis. Increased levels of insulin autoantibodies (IAA) were, however, observed in mice depleted of Tregs at 10 days of age, not in those at 4 weeks. Thus, the consequences of Treg-depletion on the spectrum of organ-specific autoimmune diseases depend on the timing of anti-CD25 antibody injection in NOD mice. Aging gradually tips balance between Teffs and Tregs toward Teff-dominance for diabetes, but this balance for thyroiditis and sialitis likely alters more intricately. Our data also suggest that the levels of IAA are not necessarily correlated with diabetes development.

Pioglitazone modulates the balance of effector and regulatory T cells in apolipoprotein E deficient mice

BACKGROUND AND AIMS

Pioglitazone (PIO) affects T cell-mediated immunity through actions of peroxisome proliferator activated receptor γ (PPARγ). Effector and regulatory T cells control the development of atherosclerosis, a chronic inflammatory disease affecting the arterial blood vessels. The aim of this study was to examine whether PIO ameliorates atherosclerosis by altering the balance of effector and regulatory T cells.

METHODS AND RESULTS

To explore the effect of PIO on early and advanced atherosclerosis, apolipoprotein E deficient (ApoE-/-) mice were fed western diet and received PIO (20 mg/kg/day) by gastric gavage at 6 or 14 weeks of age, respectively for 8 weeks. Data showed PIO markedly inhibited early fatty streak formation. Further, although the advanced fibrofatty plaque sizes were not significantly reduced, the numbers of smooth muscle cells within lesions were increased and higher collagen concentrations were produced. In general, macrophage expression in lesions was decreased. Additionally, the expression of Foxp3(+) cells was increased in lesions and spleens in mice at all PIO treatment stages, whereas the CD4(+)IFN-γ(+)/CD4(+)IL-4(+) cell ratios were reduced.

CONCLUSION

PIO inhibited early atherosclerotic lesion formation and increased the stability of advanced atherosclerotic plaques in ApoE-/- mice, which was associated with altering the balance of effector and regulatory T cells.

Much ado about adenosine: adenosine synthesis and function in regulatory T cell biology

Recent studies have reported that adenosine is a significant mediator of regulatory T cell (Treg) function. Indeed, activation of the adenosine receptor subtypes expressed by a broad range of immune and inflammatory cells attenuates inflammation in several disease models. This anti-inflammatory response is associated with an increase in intracellular cAMP that inhibits cytokine responses of many immune/inflammatory cells, including T cells and APCs. Thus, adenosine produced by Tregs can provide a paracrine feedback that shapes the host response following an immunologic provocation. This review discusses the evidence that adenosine is an integral part of Treg biology and presents some of the mechanisms that may account for its contribution to the resolution of inflammation and the regulation of the immune/inflammatory cell phenotype.

Mathematical modelling of immune regulation of type 1 diabetes

Type 1 diabetes is a disease characterized by progressive loss of β cell function due to an autoimmune reaction affecting the islets of Langerhans. Two types of T cells are involved in diabetes: turncoat auto-reactive T cells, or T cells gone bad, that kill the insulin-producing cells, and regulatory T cells that are unable to control the auto-reactive T cells. We formulate a mathematical model that incorporates the role of cytotoxic T cells and regulatory T cells in type 1 diabetes. This study shows that onset of type 1 diabetes is due to a collective, dynamical instability, rather than being caused by a single etiological factor. It is also a numbers game between regulatory T cells and auto-reactive T cells. The problem in the onset of this disease is that there are not enough of the regulatory cells that suppress the immune response against the body's insulin-producing pancreatic islet cells.

Human antigen-specific regulatory T cells generated by T cell receptor gene transfer

Background

Therapies directed at augmenting regulatory T cell (Treg) activities in vivo as a systemic treatment for autoimmune disorders and transplantation may be associated with significant off-target effects, including a generalized immunosuppression that may compromise beneficial immune responses to infections and cancer cells. Adoptive cellular therapies using purified expanded Tregs represents an attractive alternative to systemic treatments, with results from animal studies noting increased therapeutic potency of antigen-specific Tregs over polyclonal populations. However, current methodologies are limited in terms of the capacity to isolate and expand a sufficient quantity of endogenous antigen-specific Tregs for therapeutic intervention. Moreover, FOXP3+ Tregs fall largely within the CD4+ T cell subset and are thus routinely MHC class II-specific, whereas class I-specific Tregs may function optimally in vivo by facilitating direct tissue recognition.

Methodology/Principal Findings

To overcome these limitations, we have developed a novel means for generating large numbers of antigen-specific Tregs involving lentiviral T cell receptor (TCR) gene transfer into in vitro expanded polyclonal natural Treg populations. Tregs redirected with a high-avidity class I-specific TCR were capable of recognizing the melanoma antigen tyrosinase in the context of HLA-A*0201 and could be further enriched during the expansion process by antigen-specific reactivation with peptide loaded artificial antigen presenting cells. These in vitro expanded Tregs continued to express FOXP3 and functional TCRs, and maintained the capacity to suppress conventional T cell responses directed against tyrosinase, as well as bystander T cell responses. Using this methodology in a model tumor system, murine Tregs designed to express the tyrosinase TCR effectively blocked antigen-specific effector T cell (Teff) activity as determined by tumor cell growth and luciferase reporter-based imaging.

Conclusions/Significance

These results support the feasibility of class I-restricted TCR transfer as a promising strategy to redirect the functional properties of Tregs and provide for a more efficacious adoptive cell therapy.

Key role of the GITR/GITRLigand pathway in the development of murine autoimmune diabetes: a potential therapeutic target

Background

The cross-talk between pathogenic T lymphocytes and regulatory T cells (Tregs) plays a major role in the progression of autoimmune diseases. Our objective is to identify molecules and/or pathways involved in this interaction and representing potential targets for innovative therapies. Glucocorticoid-induced tumor necrosis factor receptor (GITR) and its ligand are key players in the T effector/Treg interaction. GITR is expressed at low levels on resting T cells and is significantly up-regulated upon activation. Constitutive high expression of GITR is detected only on Tregs. GITR interacts with its ligand mainly expressed on antigen presenting cells and endothelial cells. It has been suggested that GITR triggering activates effector T lymphocytes while inhibiting Tregs thus contributing to the amplification of immune responses. In this study, we examined the role of GITR/GITRLigand interaction in the progression of autoimmune diabetes.

Methods and Findings

Treatment of 10-day-old non-obese diabetic (NOD) mice, which spontaneously develop diabetes, with an agonistic GITR-specific antibody induced a significant acceleration of disease onset (80% at 12 weeks of age). This activity was not due to a decline in the numbers or functional capacity of CD4⁺CD25⁺Foxp3⁺ Tregs but rather to a major activation of ‘diabetogenic’ T cells. This conclusion was supported by results showing that anti-GITR antibody exacerbates diabetes also in CD28^−/− NOD mice, which lack Tregs. In addition, treatment of NOD mice, infused with the diabetogenic CD4⁺BDC2.5 T cell clone, with GITR-specific antibody substantially increased their migration, proliferation and activation within the pancreatic islets and draining lymph nodes. As a mirror image, blockade of the GITR/GITRLigand pathway using a neutralizing GITRLigand-specific antibody significantly protected from diabetes even at late stages of disease progression. Experiments using the BDC2.5 T cell transfer model suggested that the GITRLigand antibody acted by limiting the homing and proliferation of pathogenic T cells in pancreatic lymph nodes.

Conclusion

GITR triggering plays an important costimulatory role on diabetogenic T cells contributing to the development of autoimmune responses. Therefore, blockade of the GITR/GITRLigand pathway appears as a novel promising clinically oriented strategy as GITRLigand-specific antibody applied at an advanced stage of disease progression can prevent overt diabetes.

Tregs utilize beta-galactoside-binding protein to transiently inhibit PI3K/p21ras activity of human CD8+ T cells to block their TCR-mediated ERK activity and proliferation

Regulatory T cells (Tregs) and beta-galactoside-binding protein (betaGBP), a regulatory protein often found expressed at sites of immunological privilege, have similar functions. Their presence affects the outcome of harmful autoimmunity and cancers, including experimental autoimmune encephalomyelitis and malignant gliomas. Here we report a novel pathway by which Tregs express and utilize betaGBP to control CD8(+) T cell responses partially activating TCR signaling but blocking PI3K activity. As a result, this leads to a loss of p21(ras), ERK and Akt activities despite activation of TCR proximal signals, such as phosphorylation of CD3zeta, Zap70, Lat and PKCtheta. Although non-processive TCR signaling often leads to cell anergy, Tregs/betaGBP did not affect cell viability. Instead, betaGBP/Tregs transiently prevented activation of CD8(+) T cells with self-antigens, while keeping their responses to xenogeneic antigens unaffected.

Upregulation of CD4+CD25+T lymphocyte by adenovirus-mediated gene transfer of CTLA4Ig fusion protein in experimental autoimmune myocarditis

OBJECTIVE

To explore the effects of adenovirus vector-mediated gene transfer of CTLA4Ig fusion protein on CD4+CD25+ T cells in experimental autoimmune myocarditis (EAM).

METHODS

EAM was induced by porcine cardiac myosin as previously described. Adenovirus vector-mediated CTLA4Ig gene was administrated intravenously in EAM rats on days 1, 4 and 7, with EGFP as control. On day 21, myocardium histopathology was examined and CD4+CD25+ T cells were isolated. Proliferation and suppression assays were used to evaluate the suppressive capacity of CD4+CD25+ T cells in vitro. Relative mRNA level of Foxp3 and TGF-beta was determined by quantitative real-time RT-PCR; expression of CTLA-4, B7-1 and B7-2 protein was compared with Western blot in CD4+CD25+ Tregs.

RESULTS

Severe inflammatory lesions were observed in the hearts of EGFP-treated EAM rats and the untreated ones, while Ad-CMV-CTLA4Ig alleviated the myocarditis histologically. Adenovirus vector-mediated CTLA4Ig gene transfer up-regulated the proportion of CD4+CD25+ Tregs significantly. T cell proliferation was greatly inhibited in the CTLA4Ig group compared with the untreated and EGFP-treated groups in vitro. CTLA-4 and B7-2 proteins were down-regulated in the CTLA4Ig group, Foxp3 and TGF-beta mRNA was up-regulated significantly by CTLA4Ig treatment.

CONCLUSIONS

Adenovirus vector-mediated CTLA4Ig gene transfer alleviated inflammation in EAM, one of the potential mechanisms is up-regulation of CD4+CD25+ Tregs.

CD 4+ T cells in the pathobiology of neurodegenerative disorders

CD4+ T cells orchestrate innate and adaptive immunity. In the central nervous system they modulate immune responses including cell trafficking and glial neuroregulatory functions through an array of soluble molecules cell-cell interactions affecting tissue homeostasis. During disease their roles evolve to an auto-aggressive or, alternatively, protective phenotype. How such a balance is struck in the setting of neurodegenerative disorders may reflect a dichotomy between regulatory T cell, anti-inflammatory and neuroprotective activities versus effector T cell inflammation and neurodegeneration. Interestingly, such roles may show commonalities amongst neurodegenerative diseases. Herein we focus on strategies to modulate such CD4+ T cell responses for therapeutic gain.

Germinated barley foodstuff ameliorates inflammation in mice with colitis through modulation of mucosal immune system

OBJECTIVE

Germinated barley foodstuff (GBF) is a prebiotic product made from malt which contains glutamine-rich protein and hemicellulose-rich fiber. Although GBF has been observed to attenuate colonic mucosal inflammation and bowel movements in ulcerative colitis, both experimentally and clinically, the details of the immune response remain elusive. The aim of this study was to investigate the effects of GBF on the colonic epithelium immune response in a CD45RB(high) T cell chronic colitis model.

MATERIAL AND METHODS

Colitis was induced by transferring CD4+ CD45RB(high) T cells to severe combined immunodeficiency (SCID) mice (control n=8, GBF n=8) and the effects of GBF on the colitis were evaluated. The evaluation included measurement of body-weight, occult blood tests, histological examination, mucosal cytokine reverse transcription-polymerase chain reaction (RT-PCR) analysis (interferon-gamma (IFN-gamma), transforming growth factor-beta (TGF-beta)) as well as IL-6 measurements.

RESULTS

Seven weeks after transferring the above cells, body-weight loss and occult blood were significantly reduced in the mice that had been fed with GBF. In these mice, there were also significant reductions in IFN-gamma mRNA expressions and IL-6 in the colonic mucosa, as compared with the control group. GBF also significantly attenuated, mucosal damage and mucin positive goblet cell depletion. Conversely, TGF-beta expression significantly increased in the GBF group, compared with the control group.

CONCLUSIONS

In this preliminary study using an experimental model in which colitis was induced by transferring CD4+ CD45RB(high) T cells to SCID mice, GBF reduced inflammation by modulating the colonic microflora.

Ly49 cluster sequence analysis in a mouse model of diabetes: an expanded repertoire of activating receptors in the NOD genome

The mouse Ly49 and human killer cell immunoglobulin-like receptors (KIR) gene clusters encode activating and inhibitory class I MHC receptors on natural killer (NK) cells. A direct correlation between the presence of multiple activating KIR and various human autoimmune diseases including diabetes has been shown. Previous studies have implicated NK cell receptors in the development of diabetes in the non-obese diabetic (NOD) inbred mouse strain. To assess the contribution of Ly49 to NOD disease acceleration the Ly49 gene cluster of these mice was sequenced. Remarkably, the NOD Ly49 haplotype encodes the largest haplotype and the most functional activating Ly49 of any known mouse strain. These activating Ly49 include three Ly49p-related and two Ly49h-related genes. The NOD cluster contains large regions highly homologous to both C57BL/6 and 129 haplotypes, suggesting unequal crossing over as a mechanism of Ly49 haplotype evolution. Interestingly, the 129-like region has duplicated in the NOD genome. Thus, the NOD Ly49 cluster is a unique mix of elements seen in previously characterized Ly49 haplotypes resulting in a disproportionately large number of functional activating Ly49 genes. Finally, the functionality of activating Ly49 in NOD mice was confirmed in cytotoxicity assays.

Targeting of pancreatic glia in type 1 diabetes

OBJECTIVE

Type 1 diabetes reflects autoimmune destruction of beta-cells and peri-islet Schwann cells (pSCs), but the mechanisms of pSC death and the T-cell epitopes involved remain unclear.

RESEARCH DESIGN AND METHODS

Primary pSC cultures were generated and used as targets in cytotoxic T-lymphocyte (CTL) assays in NOD mice. Cognate interaction between pSC and CD8(+) T-cells was assessed by transgenic restoration of beta2-microglobulin (beta2m) to pSC in NOD.beta2m(-/-) congenics. I-A(g7) and K(d) epitopes in the pSC antigen glial fibrillary acidic protein (GFAP) were identified by peptide mapping or algorithms, respectively, and the latter tested by immunotherapy.

RESULTS

pSC cultures did not express major histocompatibility complex (MHC) class II and were lysed by ex vivo CTLs from diabetic NOD mice. In vivo, restoration of MHC class I in GFAP-beta2m transgenics significantly accelerated adoptively transferred diabetes. Target epitopes in the pSC autoantigen GFAP were mapped to residues 79-87 and 253-261 for K(d) and 96-110, 116-130, and 216-230 for I-A(g7). These peptides were recognized spontaneously in NOD spleens as early as 2.5 weeks of age, with proliferative responses peaking around weaning and detectable lifelong. Several were also recognized by T-cells from new-onset type 1 diabetic patients. NOD mouse immunotherapy at 8 weeks with the CD8(+) T-cell epitope, GFAP 79-87 but not 253-261, significantly inhibited type 1 diabetes and was associated with reduced gamma-interferon production to whole protein GFAP.

CONCLUSIONS

Collectively, these findings elucidate a role for pSC-specific CD8(+) T-cells in islet inflammation and type 1 diabetes pathogenesis, further supporting neuronal involvement in beta-cell demise.

Characterization of in vitro antimurine thymocyte globulin-induced regulatory T cells that inhibit graft-versus-host disease in vivo

Antithymocyte/antilymphocyte globulins are polyclonal antihuman T-cell antibodies used clinically to treat acute transplant rejection. These reagents deplete T cells, but a rabbit antihuman thymocyte globulin has also been shown to induce regulatory T cells in vitro. To examine whether antithymocyte globulin-induced regulatory cells might be functional in vivo, we generated a corresponding rabbit antimurine thymocyte globulin (mATG) and tested its ability to induce regulatory cells in vitro and whether those cells can inhibit acute graft-versus-host disease (GVHD) in vivo upon adoptive transfer. In vitro, mATG induces a population of CD4(+)CD25(+) T cells that express several cell surface molecules representative of regulatory T cells. These cells do not express Foxp3 at either the protein or mRNA level, but do show suppressive function both in vitro and in vivo when adoptively transferred into a model of GVHD. These results demonstrate that in a murine system, antithymocyte globulin induces cells with suppressive activity that also function in vivo to protect against acute GVHD. Thus, in both murine and human systems, antithymocyte globulins not only deplete T cells, but also appear to generate regulatory cells. The in vitro generation of regulatory cells by anti-thymocyte globulins could provide ad-ditional therapeutic modalities for immune-mediated disease.

Treg in type 1 diabetes

At the time of this writing, a major void exists; the lack of a method to prevent and/or reverse type 1 diabetes in humans. We believe this void to a large extent is the result of our lack in understanding the mechanisms of autoimmunity that underlie beta cell destruction, a failure to understand the immunologic factors that contribute to type 1 diabetes, and the absence of immunologic tools which would allow for a better understanding of the mechanisms underlying disease development and monitoring of therapeutic interventions. Due to this, an intense degree of research interest has recently been generated to understand the mechanisms that regulate the immune response and form a state of immunological tolerance. While some progress has been made towards these goals, additional investigations are needed to address the aforementioned knowledge voids including the role for regulatory T cells (Treg), defined by their co-expression of CD4 and CD25 as well as the transcription factor FOXP3, in the pathogenesis and natural history of type 1 diabetes. We and others have recently reported findings related to the frequency and function of Treg cells in type 1 diabetes, yet the resulting literature represents a somewhat conflicting body of findings. Our studies did not support the notion that altered Treg frequencies are associated with type 1 diabetes, but rather did identify alterations in the functional (i.e., suppressive) activities of these cells in subjects with the disease. The need to bring resolution to the aforementioned published discrepancies in frequency and function of Treg in type 1 diabetes represents the impetus for this critical review. In addition, we hope to highlight the need for expanded studies that address specific knowledge gaps regarding the cellular and molecular mechanism(s) related to the frequency and function of Treg.

Rapamycin enriches for CD4(+) CD25(+) CD27(+) Foxp3(+) regulatory T cells in ex vivo-expanded CD25-enriched products from healthy donors and patients with multiple sclerosis

BACKGROUND

CD4(+) CD25(bright+) regulatory T cells (Treg) can be expanded to clinical doses using CD3/CD28 Ab-coated beads plus IL-2. However, this method requires high purity of the starting population to prevent overgrowth by non-regulatory T cells. Rapamycin, an agent that inhibits T-cell proliferation but selectively spares Treg, may be a means to expand Treg from less pure CD25-enriched cells.

METHODS

CD25-enriched cells were prepared by a single-step immunomagnetic-selection using anti-CD25 microbeads. The cells were activated with a single addition of anti-CD3/CD28 beads and expanded in ex vivo 15-5% HS and autologous CD4(+) CD25(-) feeder cells,+/-rapamycin (0.01-20 ng/mL). IL-2 was added on day 3. Cells were rested for 2 days in ex vivo 15-5% HS and tested for phenotype, intracellular Foxp3 protein and suppressor activity.

RESULTS

In the absence of rapamycin, CD25-enriched fractions expanded >17 000-fold by 21 days. Although suppressor activity was detected to day 14, it declined significantly by 21 days as non-regulatory cells expanded. The addition of rapamycin inhibited expansion of non-regulatory T cells at doses > or =1 ng/mL while increasing suppressor activity and the percentage of CD4(+) CD25(+) CD27(+) Foxp3(+) cells. Rapamycin did not enrich for Foxp3(+) cells in expanded cultures of CD4(+) CD25(-) cells. Treg were also readily expanded in cultures of CD25-enriched cells obtained from patients with multiple sclerosis in the presence of rapamycin.

DISCUSSION

The addition of 1-20 ng/mL rapamycin to CD25-enriched cultures increased the purity of cells with the phenotype and function of Treg. This approach may alleviate the need for rigorous enrichment of Treg prior to activation and expansion for potential clinical use.

Minor antigen h60-mediated aplastic anemia is ameliorated by immunosuppression and the infusion of regulatory T cells

Human bone marrow (BM) failure mediated by the immune system can be modeled in mice. In the present study, infusion of lymph node (LN) cells from C57BL/6 mice into C.B10-H2(b)/LilMcd (C.B10) recipients that are mismatched at multiple minor histocompatibility Ags, including the immunodominant Ag H60, produced fatal aplastic anemia. Declining blood counts correlated with marked expansion and activation of CD8 T cells specific for the immunodominant minor histocompatibility Ag H60. Infusion of LN cells from H60-matched donors did not produce BM failure in C.B10 mice, whereas isolated H60-specific CTL were cytotoxic for normal C.B10 BM cells in vitro. Treatment with the immunosuppressive drug cyclosporine abolished H60-specific T cell expansion and rescued animals from fatal pancytopenia. The development of BM failure was associated with a significant increase in activated CD4+CD25+ T cells that did not express intracellular FoxP3, whereas inclusion of normal CD4+CD25+ regulatory T cells in combination with C57BL/6 LN cells aborted H60-specific T cell expansion and prevented BM destruction. Thus, a single minor histocompatibility Ag H60 mismatch can trigger an immune response leading to massive BM destruction. Immunosuppressive drug treatment or enhancement of regulatory T cell function abrogated this pathophysiology and protected animals from the development of BM failure.

Human peripheral blood T regulatory cells (Tregs), functionally primed CCR4+ Tregs and unprimed CCR4- Tregs, regulate effector T cells using FasL

Regulatory CD25(+)CD4(+) T cells (Tregs) play an important role in the control of peripheral tolerance. In this study we demonstrate that human peripheral blood Tregs can be divided into two distinct populations based on the expression of CCR4. The majority ( approximately 75%) of freshly isolated Tregs express CCR4 and presumably represent memory-type Tregs. Interestingly, CCR4(-) Tregs require anti-CD3 Ab-mediated activation to acquire a regulatory activity, while CCR4(+) Tregs appear to be already primed to suppress the proliferation of CD8(+) T cells. CCR4 is also expressed on CD25(low)CD4(+) T cells (CCR4(+) non-Tregs) that mostly suppress Th1-type polarization without affecting T cell proliferation, presumably via the production of immunomodulatory cytokines like IL-10. In contrast, CCR4(+) Tregs express FasL to primarily regulate T cell proliferation via a contact-mediated process involving FasL/Fas signaling, a major regulatory pathway of T cell homeostasis. Finally, we also demonstrate that the depletion of CCR4(+) T cells leads to Th1-type polarization of CD4(+) T cells and augmentation of CD8(+) T cell responses to tumor Ags.

Clinical utilization of chemokines to combat cancer: the double-edged sword

Chemokines are a small group of related chemo-attractant peptides that play an essential role in the homeostatic maintenance of the immune system. They control the recruitment of cells needed for the induction and activation of innate and adaptive immune responses. However, tumors also utilize chemokines to actively progress and evade immunosurveillance. In fact, chemokines are involved directly or indirectly in almost every aspect of tumorigenesis. They mediate survival and metastatic spread of tumors, promote new blood vessel formation (neovascularization) and induce an immunosuppressive microenvironment via recruitment of immunosuppressive cells. As a result, a number of therapeutic strategies have been proposed to target almost every step of the chemokine/chemokine receptor involvement in tumors. Yet, despite occasional success stories, most of them appear to be ineffective or impractical, presumably due to 'nonspecific' harm of cells needed for the elimination of tumor escapees and maintenance of immunological memory. The strategy would only be effective if it also promoted antitumor adaptive immune responses capable of combating a residual disease and tumor relapse.

An early age-related increase in the frequency of CD4+ Foxp3+ cells in BDC2.5NOD mice

The role of regulatory T cells (Treg) in maintaining tolerance to self has been intensively scrutinized, particularly since the discovery of Foxp3 as a Treg-specific transcription factor. The BDC2.5NOD transgenic mouse is an excellent model of immunoregulation because it has a very low incidence of diabetes despite a highly autoreactive T-cell repertoire. It has previously been shown that reactivity against islets decreases with age in BDC2.5NOD mice. Here we show that there is a markedly higher frequency of Foxp3(+) Treg in the CD4(+) subset of 16-20-week-old mice compared with 4- or 8-week-old mice. This phenomenon can be observed in the spleen, thymus, pancreatic draining lymph nodes and the pancreas itself. We show that this early age-related increase in the frequency of Foxp3(+) cells does not occur in wild-type NOD, BALB/c or C57BL/6 mice. Further, we show that, in contrast to some reports on Treg in wild-type NOD mice, the suppressive function of BDC2.5NOD Treg from 16- to 20-week-old mice is intact and comparable to that from 4- to 8-week-old mice both in vitro and in vivo. Our data offer insights into the long-term protection of BDC2.5NOD mice from diabetes and an explanation for the age-related decrease in anti-islet responses seen in BDC2.5NOD mice.

PREDNOD, a prediction server for peptide binding to the H-2g7 haplotype of the non-obese diabetic mouse

The non-obese diabetic (NOD) mouse is a widely used animal model for study of autoimmune diseases, in particular human type 1 diabetes mellitus (T1DM). Identification of the subset of peptides that bind MHC molecules comprising the H-2g7 haplotype of NOD mouse and thereby representing potential NOD T-cell epitopes is important for research into the pathogenesis and immunotherapy of T1DM. The H-2g7 haplotype comprises the MHC class-I molecules Kd and Db and a single class-II molecule I-Ag7. We have developed a prediction system, PREDNOD, for accurate identification of peptides that bind the MHC molecules constituting the H-2g7 haplotype. PREDNOD is accessible at http://antigen.i2r.a-star.edu.sg/Ag7.

Role of naturally occurring CD4+ CD25+ regulatory T cells in experimental atherosclerosis

OBJECTIVE

Naturally occurring CD4+ CD25+ regulatory T cells (Tregs) exert suppressive effects on effector CD4 cells and downregulate experimental autoimmune disorders. We investigated the importance and potential role of Tregs in murine atherogenesis.

METHODS AND RESULTS

Tregs were investigated comparatively between aged and young apolipoprotein E-knockout (ApoE-KO) mice and age-matched C57BL/6 littermates. The effect of oxidized LDL (oxLDL) was tested on the functional suppressive properties of Tregs from ApoE-KO and C57BL/6 mice. Tregs, CD4+ CD25- cells, and saline were infused into ApoE-KO mice to study their effects on atherogenesis. Treg numbers were reduced in atherosclerotic compared with nonatherosclerotic ApoE-KO mice. The functional suppressive properties of Tregs from ApoE-KO mice were compromised in comparison with those from their C57BL/6 littermates. Thus, oxLDL attenuated the suppressive properties of Tregs from C57BL/6 mice and more so in ApoE-KO mice. Transfer of Tregs from age-matched ApoE-KO mice resulted in significant attenuation of atherosclerosis compared with that after delivery of CD4+ CD25+/- T cells or phosphate-buffered saline.

CONCLUSIONS

CD4+ CD25+ Tregs may play a protective role in the progression of atherosclerosis and could be considered a therapeutic tool if results from human studies can solidify observations in murine models.

Immune Regulatory T Cells in Siblings of Children Suffering from Type 1 Diabetes Mellitus

Patients with type 1 diabetes are suffering from defects in immune regulatory cells. Their siblings may be at increased risk of type 1 diabetes especially if they are carriers of certain human leucocyte antigen (HLA) alleles. In a prospective non-randomized study, we intended to evaluate 31 healthy siblings of paediatric patients with type 1 diabetes and explore immune regulatory populations of CD4+CD25+ T cells and natural killer (NK) T cells. Tested siblings of type 1 diabetes patients were stratified according to the HLA-associated risk of possible diabetes development. Immune regulatory function of CD4+CD25+ T cells was tested in vitro. Significant differences in CD4+CD25+ but not in NK T cells have been identified. Siblings of type 1 diabetes patients carrying high risk HLA alleles (DQA1*05, DQB1*0201, DQB1*0302) had significantly lower number of immune regulatory CD4+CD25+ T cells than the age-matched healthy controls or siblings carrying low-risk HLA alleles (DQB1*0301, DQB1*0603, DQB1*0602). Regulatory function of CD4+CD25+ T cells demonstrated a dose-escalation effect. In siblings of type 1 diabetes patients, the defect in immune regulatory CD4+CD25+ T cells exists in association with genetic HLA-linked risk for type 1 diabetes.

Short-Term Treatment With Anti-CD3 Antibody Reduces the Development and Progression of Atherosclerosis in Mice

Background— Atherosclerosis is a chronic inflammatory disease of the large arteries that is the primary cause of heart disease and stroke. Anti-CD3–specific antibodies suppress immune responses by antigenic modulation of the CD3 antibody/T-cell receptor complex. Their unique capacity to restore self-tolerance in a mouse model of diabetes and, importantly, in patients with recent-onset type 1 diabetes involves transforming growth factor-β–dependent mechanisms via expansion and/or activation of regulatory T cells. We hypothesized that treatment with anti-CD3–specific antibodies might inhibit atherosclerosis development and progression in mice.

Methods and Results— Low-density lipoprotein receptor–deficient mice were fed a high-cholesterol diet for 13 or 24 weeks. Anti-CD3 antibody was administered on 5 consecutive days beginning 1 week before or 13 weeks after the high-cholesterol diet was initiated, respectively. Control mice were injected in parallel with phosphate-buffered saline. Anti-CD3 antibody therapy reduced plaque development when administered before a high-cholesterol diet and markedly decreased lesion progression in mice with already established atherosclerosis. We found increased production of the antiinflammatory cytokine transforming growth factor-β in concanavalin A–stimulated lymph node cells and enhanced expression of the regulatory T-cell marker Foxp3 in spleens of anti-CD3 antibody–treated mice. A higher percentage of apoptotic cells within the plaques of anti-CD3 antibody–treated mice was also observed.

Conclusions— Altered disease progression, combined with the emergence of this particular cytokine pattern, indicates that short-term treatment with an anti-CD3 antibody induces a regulatory T-cell phenotype that restores self-tolerance in a mouse model of atherosclerosis.

Tryptophan catabolism generates autoimmune-preventive regulatory T cells

Tryptophan catabolism is a tolerogenic effector system in regulatory T cell function, yet the general mechanisms whereby tryptophan catabolism affects T cell responses remain unclear. We provide evidence that its effects include the emergence of a regulatory phenotype in naive CD4(+)CD25(-) cells via the general control non-depressing 2 (GCN2) protein kinase mediated induction of the forkhead transcription factor Foxp3. These cells are capable of effective control of diabetogenic T cells in vivo.

Transforming growth factor-beta and T-cell-mediated immunoregulation in the control of autoimmune diabetes

It is now well-established that CD4+ regulatory T cells are instrumental in controlling immune responses both to self-antigens and to non-self-antigens. However, the precise modalities involved in their differentiation and survival, their mode of action and their antigen specificity are only partially understood. We have been particularly interested in the study of regulatory T cells controlling autoimmune insulin-dependent diabetes. Here, we provide evidence to support the phenotypic and functional diversity of regulatory T cells mediating transferable 'active' or 'dominant' peripheral tolerance in the non-obese diabetic mouse model (NOD). They include natural and adaptive regulatory T cells that are operational both in unmanipulated NOD mice and in animals undergoing treatments aimed at inducing/restoring tolerance to self-beta-cell antigens. At least in our hands, the differential cytokine-dependency appears as a major distinctive feature of regulatory T cells subsets. Among immunoregulatory cytokines, transforming growth factor-beta(TGF-beta) appeared to play a key role. Herein we discuss these results and the working hypothesis they evoke in the context of the present literature, where the role of TGF-beta-dependent T-cell-mediated immunoregulation is still debated.

Regulatory T-cell physiology and application to treat autoimmunity

Endowed with the ability to actively suppress an immune response, regulatory T cells (Tregs) hold the promise of halting ongoing pathogenic autoimmunity and restoring self-tolerance in patients suffering from autoimmune diseases. Through many in vitro and in vivo studies, we have learned that Tregs can function in the lymph nodes as well as in the peripheral tissues. In vivo, Tregs act through dendritic cells to limit autoreactive T-cell activation, thus preventing their differentiation and acquisition of effector functions. By limiting the supply of activated pathogenic cells, Tregs prevent or slow down the progression of autoimmune diseases. However, this protective mechanism appears insufficient in autoimmune individuals, likely because of a shortage of Tregs cells and/or the development and accumulation of Treg-resistant pathogenic T cells over the long disease course. Thus, restoration of self-tolerance in these patients will likely require purging of pathogenic T cells along with infusion of Tregs with increased ability to control ongoing tissue injury. In this review, we highlight advances in dissecting Treg function in vivo in autoimmune settings and summarize multiple studies that have overcome the limitations of the low abundance of Tregs and their hypoproliferative phenotype to develop Treg-based therapies.

Resetting the functional capacity of regulatory T cells: a novel immunotherapeutic strategy to promote immune tolerance

Over the last few years, there has been a re-emergence of the concept of suppressor/regulatory T cells among the central players of immune mechanisms controlling a wide variety of immune responses from physiological autoreactivity (i.e., response to self-antigens) to responses to transplants, tumours and infectious antigens. Regulatory T cells are diverse in their phenotypes, antigen specificity, mode of action and immunopathological relevance. This review briefly summarises studies from the authors' group showing that specialised subsets of regulatory T cells are instrumental in the control of autoimmune diseases and more specifically of Type 1 diabetes. In addition, this review will provide evidence supporting the notion that CD3-specific monoclonal antibodies are representatives of a new category of immunotherapeutic agents that possess the unique capacity to promote immunological tolerance (an antigen-specific unresponsiveness in the absence of long-term generalised immunosuppression) through their ability to induce immunoregulatory T cells.

Ex vivo activated OVA specific and non-specific CD4+CD25+ regulatory T cells exhibit comparable suppression to OVA mediated T cell responses

CD4+CD25+ regulatory T cells (Tr) are important in maintaining immune tolerance to self-antigen (Ag) and preventing autoimmunity. Reduced number and inadequate function of Tr are observed in chronic autoimmune diseases. Adoptively transferred Tr effectively suppress ongoing autoimmune disease in multiple animal models. Therefore, strategies to modulate Tr have become an attractive approach to control autoimmunity. Activation of Tr is necessary for their optimal immune regulatory function. However, due to the low ratio of Tr to any given antigen (Ag) and the unknown nature of Ag in many autoimmune diseases, specific activation is not practical for potential therapeutic intervention. It has been shown in animal models that once activated, Tr can exhibit immune suppression in a bystander Ag-non-specific fashion, suggesting the effector phase of Tr is Ag independent. To investigate whether the immune suppression by activated bystander Tr is as potent as that of the Ag specific Tr, Tr cells were isolated from BALB/c or ovalbumin (OVA) specific T cell receptor (TCR) transgenic mice (DO11.10) and their immune suppression of an OVA specific T cell response was compared. We found that once activated ex vivo, Tr from BALB/c and DO11.10 mice exhibited comparable inhibition on OVA specific T cell responses as determined by T cell proliferation and cytokine production. Furthermore, their immune suppression function was compared in a delayed type hypersensitivity (DTH) model induced by OVA specific T cells. Again, OVA specific and non-specific Tr exhibited similar inhibition of the DTH response. Taken together, the results indicate that ex vivo activated Ag-non-specific Tr are as efficient as Ag specific Tr in immune suppression, therefore our study provides additional evidence suggesting the possibility of applying ex vivo activated Tr therapy for the control of autoimmunity.

Regulatory T cells in human autoimmune thyroid disease

CONTEXT

T regulatory cells have a key role in the pathogenesis of autoimmune diseases in different animal models. However, less information is available regarding these cells in human autoimmune thyroid diseases (AITD).

OBJECTIVE

The objective of the study was to analyze different regulatory T cell subsets in patients with AITD.

DESIGN

We studied by flow cytometry and immunohistochemistry different T regulatory cell subsets in peripheral blood mononuclear cells (PBMCs) and thyroid cell infiltrates from 20 patients with AITD. In addition, the function of T(REG) lymphocytes was assessed by cell proliferation assays. Finally, TGF-beta mRNA in thyroid tissue and its in vitro synthesis by thyroid mononuclear cells (TMCs) was determined by RNase protection assay and quantitative PCR.

RESULTS

PBMCs from AITD patients showed an increased percent of CD4+ lymphocytes expressing glucocorticoid-induced TNF receptor (GITR), Foxp3, IL-10, TGF-beta, and CD69 as well as CD69+CD25(bright), CD69+TGF-beta, and CD69+IL-10+ cells, compared with controls. TMCs from these patients showed an increased proportion of CD4+GITR+, CD4+CD69+, and CD69+ cells expressing CD25(bright), GITR, and Foxp3, compared with autologous PBMCs. Furthermore, a prominent infiltration of thyroid tissue by CD69+, CD25+, and GITR+ cells, with moderate levels of Foxp3+ lymphocytes, was observed. The suppressive function of peripheral blood T(REG) cells was defective in AITD patients. Finally, increased levels of TGF-beta mRNA were found in thyroid tissue, and thyroid cell infiltrates synthesized in vitro significant levels of TGF-beta upon stimulation through CD69.

CONCLUSIONS

Although T regulatory cells are abundant in inflamed thyroid tissue, they are apparently unable, in most cases, to downmodulate the autoimmune response and the tissue damage seen in AITD.