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

Towards a Unified Approach in Autoimmune Fibrotic Signalling Pathways

Autoimmunity is a chronic process resulting in inflammation, tissue damage, and subsequent tissue remodelling and organ fibrosis. In contrast to acute inflammatory reactions, pathogenic fibrosis typically results from the chronic inflammatory reactions characterizing autoimmune diseases. Despite having obvious aetiological and clinical outcome distinctions, most chronic autoimmune fibrotic disorders have in common a persistent and sustained production of growth factors, proteolytic enzymes, angiogenic factors, and fibrogenic cytokines, which together stimulate the deposition of connective tissue elements or epithelial to mesenchymal transformation (EMT) that progressively remodels and destroys normal tissue architecture leading to organ failure. Despite its enormous impact on human health, there are currently no approved treatments that directly target the molecular mechanisms of fibrosis. The primary goal of this review is to discuss the most recent identified mechanisms of chronic autoimmune diseases characterized by a fibrotic evolution with the aim to identify possible common and unique mechanisms of fibrogenesis that might be exploited in the development of effective antifibrotic therapies.

Adjuvant Probiotics of Lactobacillus salivarius subsp. salicinius AP-32, L. johnsonii MH-68, and Bifidobacterium animalis subsp. lactis CP-9 Attenuate Glycemic Levels and Inflammatory Cytokines in Patients With Type 1 Diabetes Mellitus

INTRODUCTION

Type 1 diabetes mellitus (T1DM) is characterized by autoimmune destruction of pancreatic β cells. Previous study has discovered that probiotic strains residing in the gut play essential roles in host immune regulation. However, few clinical results demonstrated probiotic would actually benefit in attenuating glycated hemoglobin (HbA1c) along with inflammatory cytokine levels of the T1DM patients and analyzed their gut microbiota profile at the same time. In this clinical trial, we evaluated the therapeutic efficacy of probiotics on HbA1c along with inflammatory cytokine levels of T1DM patients to determine an alternative administration mode for T1DM medication. The probiotics changed T1DM gut microbiota profile will be measured by next-generation sequencing (NGS).

RESEARCH DESIGN AND METHODS

A randomized, double-blind, placebo-controlled trial was performed at China Medical University Hospital. T1DM patients between 6 and 18 years of age were enrolled. 27 patients were administered regular insulin therapy plus capsules containing probiotic strains Lactobacillus salivarius subsp. salicinius AP-32, L. johnsonii MH-68, and Bifidobacterium animalis subsp. lactis CP-9 daily for 6 months, and 29 patients were administered insulin therapy without extra probiotic supplement as placebo group. The variations of fasting blood glucose and HbA1c in these patients were analyzed. In addition, serum levels of inflammatory cytokines and anti-inflammatory cytokine were assessed using enzyme-linked immunosorbent assay. Patients' stool microbiota were all subjects to NGS analysis.

RESULTS

NGS data showed elevated populations of Bifidobacterium animalis, Akkermansia muciniphila and Lactobacillus salivarius in the gut of patients with T1DM who were taking probiotics. Patients with T1DM who were administered probiotics showed significantly reduced fasting blood glucose levels compared with the before-intervention levels. The HbA1c levels of the patients also improved after administration of probiotics. The concentrations of IL-8, IL-17, MIP-1β, RANTES, and TNF-α were significantly reduced and were associated with an increased TGF-β1 expression after probiotic intervention. The persistence effect of glycemic control and immunomodulation were observed even 3 months after discontinuation of the probiotics.

CONCLUSIONS

Here, we found that conventional insulin therapy plus probiotics supplementation attenuated T1DM symptoms than receiving insulin treatment only. Probiotics supplementation with insulin treatment changed gut microbiota and revealed better outcome in stabilizing glycemic levels and reducing HbA1c levels in patients with T1DM through beneficial regulation of immune cytokines.

CLINICAL TRIAL REGISTRATION

ClinicalTrials.gov, identifier NCT03880760.

Organ Fibrosis and Autoimmunity: The Role of Inflammation in TGFβ-Dependent EMT

Recent advances in our understanding of the molecular pathways that control the link of inflammation with organ fibrosis and autoimmune diseases point to the epithelial to mesenchymal transition (EMT) as the common association in the progression of these diseases characterized by an intense inflammatory response. EMT, a process in which epithelial cells are gradually transformed to mesenchymal cells, is a major contributor to the pathogenesis of fibrosis. Importantly, the chronic inflammatory microenvironment has emerged as a decisive factor in the induction of pathological EMT. Transforming growth factor-β (TGF-β), a multifunctional cytokine, plays a crucial role in the induction of fibrosis, often associated with chronic phases of inflammatory diseases, contributing to marked fibrotic changes that severely impair normal tissue architecture and function. The understanding of molecular mechanisms underlying EMT-dependent fibrosis has both a basic and a translational relevance, since it may be useful to design therapies aimed at counteracting organ deterioration and failure. To this end, we reviewed the recent literature to better elucidate the molecular response to inflammatory/fibrogenic signals in autoimmune diseases in order to further the specific regulation of EMT-dependent fibrosis in more targeted therapies.

Transforming Growth Factor β1 in Patients with Type 2 Diabetes Mellitus After Fetal Pancreatic Stem Cell Transplant

OBJECTIVES

Our objective was to determine transforming growth factor β1 levels in patients with type 2 diabetes mellitus after fetal pancreatic stem cell transplant.

MATERIALS AND METHODS

We examined 10 patients (age range, 41-65 y) with type 2 diabetes mellitus, which we subsequently divided into 2 groups. Group 1 comprised 5 patients who received fetal pancreatic stem cell transplant (cells were 16-18 wk gestation) performed by intravenous infusion. Group 2 comprised 5 patients (control group) who were on hypoglycemic tablet therapy or insulin therapy. The quantity of fetal stem cells infused was 5 to 6 × 106. We analyzed transforming growth factor β1, C-peptide, and glycated hemoglobin levels in patients before and 3 months after fetal pancreatic stem cell transplant.

RESULTS

In patients with type 2 diabetes mellitus, fetal pancreatic stem cell transplant led to a significant increase in transforming growth factor β1 levels, from 16 364.8 to 35 730.4 ng/mL (P = .008), with trend in decreased glycated hemoglobin levels, from 7.96% to 6.98% (P = .088) after 3 months.

CONCLUSIONS

Transforming growth factor β1 levels increased significantly within 3 months after fetal pancreatic stem cell transplant in patients with type 2 diabetes mellitus.

Clostridium butyricum CGMCC0313.1 Protects against Autoimmune Diabetes by Modulating Intestinal Immune Homeostasis and Inducing Pancreatic Regulatory T Cells

Recent evidence indicates that indigenous Clostridium species induce colonic regulatory T cells (Tregs), and gut lymphocytes are able to migrate to pancreatic islets in an inflammatory environment. Thus, we speculate that supplementation with the well-characterized probiotics Clostridium butyricum CGMCC0313.1 (CB0313.1) may induce pancreatic Tregs and consequently inhibit the diabetes incidence in non-obese diabetic (NOD) mice. CB0313.1 was administered daily to female NOD mice from 3 to 45 weeks of age. The control group received an equal volume of sterile water. Fasting glucose was measured twice a week. Pyrosequencing of the gut microbiota and flow cytometry of mesenteric lymph node (MLN), pancreatic lymph node (PLN), pancreatic and splenic immune cells were performed to investigate the effect of CB0313.1 treatment. Early oral administration of CB0313.1 mitigated insulitis, delayed the onset of diabetes, and improved energy metabolic dysfunction. Protection may involve increased Tregs, rebalanced Th1/Th2/Th17 cells and changes to a less proinflammatory immunological milieu in the gut, PLN, and pancreas. An increase of α4β7+ (the gut homing receptor) Tregs in the PLN suggests that the mechanism may involve increased migration of gut-primed Tregs to the pancreas. Furthermore, 16S rRNA gene sequencing revealed that CB0313.1 enhanced the Firmicutes/Bacteroidetes ratio, enriched Clostridium-subgroups and butyrate-producing bacteria subgroups. Our results provide the basis for future clinical investigations in preventing type 1 diabetes by oral CB0313.1 administration.

Role of TGF-β in Self-Peptide Regulation of Autoimmunity

Transforming growth factor (TGF)-β has been implicated in regulation of the immune system, including autoimmunity. We have found that TGF-β is readily produced by T cells following immunization with self-peptide epitopes that downregulate autoimmune responses in type 1 diabetes (T1D) prone nonobese diabetic (NOD) mice. These include multiple peptide epitopes derived from the islet β-cell antigens GAD65 (GAD65 p202-221, GAD65 p217-236), GAD67 (GAD67 p210-229, GAD67 p225-244), IGRP (IGRP p123-145, IGRP p195-214) and insulin B-chain (Ins. B:9-23) that protected NOD mice from T1D. Immunization of NOD mice with the self-MHC class II I-A^g7 β-chain-derived peptide, I-Aβ^g7 p54-76 also induced large amounts of TGF-β and also protected these mice from diabetes development. These results indicate that peptides derived from disease related self-antigens and MHC class II molecules primarily induce TGF-β producing regulatory Th3 and Tr1-like cells. TGF-β produced by these cells could enhance the differentiation of induced regulatory iTreg and iTreg17 cells to prevent induction and progression of autoimmune diseases. We therefore suggest that peripheral immune tolerance could be induced and maintained by immunization with self-peptides that induce TGF-β producing T cells.

TGF-β engineered mesenchymal stem cells (TGF-β/MSCs) for treatment of Type 1 diabetes (T1D) mice model

OBJECTIVE

Mesenchymal stem cells (MSCs) are advantageous candidates for cell therapy of Type 1 diabetes (T1D). Considering immunomodulatory effect of MSC, in this study, we engineered MSCs with TGF-β gene to increase MSC potency for T1D therapy in mouse model.

MATERIALS AND METHODS

Two plans were designed for prevention and treatment of diabetes, respectively. In both of them, MSCs were injected i.v. and then, the diabetes features including serum insulin, blood glucose, glucose tolerance, splenocytes proliferation, and IL-4/IFN-γ production were evaluated.

RESULTS

TGF-β/MSCs treatment program resulted in the restoration of serum glucose after 3weeks, while prevention program could delay diabetes progression for two weeks. TGF-β/MSCs treatment elevated the levels of serum insulin and Th2 cytokine shift on 5th week after start of treatment. TGF-β/MSCs (and MSCs alone) could also diminish body weight and enhance mice survival comparing to untreated diabetic mice.

CONCLUSION

Engineered TGF-β/MSCs could restore some T1D features, including the regulation of adverse immune responses and could be potent tools for cell therapy of T1D comparing MSCs alone.

Autoimmune Diabetes: An Overview of Experimental Models and Novel Therapeutics

Type 1 diabetes (T1D) results from a chronic and selective destruction of insulin-secreting β-cells within the islets of Langerhans of the pancreas by autoreactive CD4(+) and CD8(+) T lymphocytes. The use of animal models of T1D was instrumental for deciphering the steps of the autoimmune process leading to T1D. The non-obese diabetic (NOD) mouse and the bio-breeding (BB) rat spontaneously develop the disease similar to the human pathology in terms of the immune responses triggering autoimmune diabetes and of the genetic and environmental factors influencing disease susceptibility. The generation of genetically modified models allowed refining our understanding of the etiology and the pathogenesis of the disease. In the present review, we provide an overview of the experimental models generated and used to gain knowledge on the molecular and cellular mechanisms underlying the breakdown of self-tolerance in T1D and the progression of the autoimmune response. Immunotherapeutic interventions designed in these animal models and translated into the clinical arena in T1D patients will also be discussed.

Alteration of regulatory T cells in type 1 diabetes mellitus: a comprehensive review

Type 1 diabetes mellitus (T1DM) is a T cell-mediated autoimmune disease characterized by the destruction of pancreatic β cells. Numerous studies have demonstrated the key role of CD4(+)CD25(+)FoxP3(+) regulatory T cells (Tregs) in the development of T1DM. However, the changes in Treg expression and function as well as the regulation of these activities are not clearly elucidated. Most studies on the role of Tregs in T1DM were performed on peripheral blood rather than pancreas or pancreatic lymph nodes. Tissue-based studies are more difficult to perform, and there is a lack of histological data to support the role of Tregs in T1DM. In spite of this, strategies to increase Treg cell number and/or function have been viewed as potential therapeutic approaches in treating T1DM, and several clinical trials using these strategies have already emerged. Notably, many trials fail to demonstrate clinical response even when Treg treatment successfully boosts Tregs. In view of this, whether a failure of Tregs does exist and contribute to the development of T1DM and whether more Tregs would be clinically beneficial to patients should be carefully taken into consideration before applying Tregs as treatments in T1DM.

Serum IL-17, IL-23, and TGF-β levels in type 1 and type 2 diabetic patients and age-matched healthy controls

Type 1 diabetes is recognized as an autoimmune inflammatory disease and low grade inflammation is also observed in type 2 diabetic patients. Interleukin 17 (IL-17) is a new player in inflammation. Th17 cells, as the main source of IL-17, require transforming growth factor β (TGF-β) and interleukin 23 (IL-23). The aim of this study was to investigate serum IL-17, IL-23 and TGF-β levels in diabetic patients and controls. In this case-control study, serum levels of IL-17, IL-23, and TGF-β were measured in 24 type 1 diabetic patients and 30 healthy controls using the ELISA method. Simultaneously, the same methodology was used to compare serum concentration of these three cytokines in 38 type 2 diabetic patients and 40 healthy controls. There was no significant difference between serum levels of IL-17 and IL-23 cytokines between cases and controls. However, TGF-β was significantly lower in type 1 diabetic patients (P < 0.001). Serum IL-17 and IL-23 levels demonstrate no association with type 1 and type 2 diabetes, but, in line with previous studies, TGF-β levels were lower in type 1 diabetic patients.

Therapeutic use of a selective S1P1 receptor modulator ponesimod in autoimmune diabetes

In the present study, we investigated the therapeutic potential of a selective S1P₁ receptor modulator, ponesimod, to protect and reverse autoimmune diabetes in non-obese diabetic (NOD) mice. Ponesimod was administered orally to NOD mice starting at 6, 10, 13 and 16 weeks of age up to 35 weeks of age or to NOD mice showing recent onset diabetes. Peripheral blood and spleen B and T cell counts were significantly reduced after ponesimod administration. In pancreatic lymph nodes, B lymphocytes were increased and expressed a transitional 1-like phenotype. Chronic oral ponesimod treatment efficiently prevented autoimmune diabetes in 6, 10 and 16 week-old pre-diabetic NOD mice. Treatment withdrawal led to synchronized disease relapse. Ponesimod did not inhibit the differentiation of autoreactive T cells as assessed by adoptive transfer of lymphocytes from treated disease-free NOD mice. In addition, it did not affect the migration, proliferation and activation of transgenic BDC2.5 cells into the target tissue. However, ponesimod inhibited spreading of the T cell responses to islet-specific glucose-6-phosphatase catalytic subunit-related protein (IGRP). Treatment of diabetic NOD mice with ponesimod induced disease remission. However, here again, upon treatment cessation, the disease rapidly recurred. This recurrence was effectively prevented by combination treatment with a CD3 antibody leading to the restoration of self-tolerance. In conclusion, treatment with a selective S1P₁ modulator in combination with CD3 antibody represents a promising therapeutic approach for the treatment of autoimmune diabetes.

Dietary gluten alters the balance of pro-inflammatory and anti-inflammatory cytokines in T cells of BALB/c mice

Several studies have documented that dietary modifications influence the development of type 1 diabetes. However, little is known about the interplay of dietary components and the penetration of diabetes incidence. In this study we tested if wheat gluten is able to induce differences in the cytokine pattern of Foxp3(+) regulatory T cells, as well as Foxp3(-) T cells, isolated from intestinal mucosal lymphoid tissue and non-mucosal lymphoid compartments in BALB/c mice. The gluten-containing standard diet markedly changed the cytokine expression within Foxp3(-) T cells, in all lymphoid organs tested, towards a higher expression of pro-inflammatory interferon-γ (IFN-γ), interleukin-17 (IL-17) and IL-2. In Foxp3(+) regulatory T cells, gluten ingestion resulted in a mucosal increase in IL-17 and IL-2 and an overall increase in IFN-γ and IL-4. The gluten-free diet induced an anti-inflammatory cytokine profile with higher proportion of transforming growth factor-β (TGF-β)(+) Foxp3(-) T cells in all tested lymphoid tissues and higher IL-10 expression within non-T cells in spleen, and a tendency towards a mucosal increase in TGF-β(+) Foxp3(+) regulatory T cells. Our data shows that the gluten-containing standard diet modifies the cytokine pattern of both Foxp3(-) T cells and Foxp3(+) regulatory T cells towards a more inflammatory cytokine profile. This immune profile may contribute to the higher type 1 diabetes incidence associated with gluten intake.

Nonviral-mediated hepatic expression of IGF-I increases Treg levels and suppresses autoimmune diabetes in mice

In type 1 diabetes, loss of tolerance to β-cell antigens results in T-cell-dependent autoimmune destruction of β cells. The abrogation of autoreactive T-cell responses is a prerequisite to achieve long-lasting correction of the disease. The liver has unique immunomodulatory properties and hepatic gene transfer results in tolerance induction and suppression of autoimmune diseases, in part by regulatory T-cell (Treg) activation. Hence, the liver could be manipulated to treat or prevent diabetes onset through expression of key genes. IGF-I may be an immunomodulatory candidate because it prevents autoimmune diabetes when expressed in β cells or subcutaneously injected. Here, we demonstrate that transient, plasmid-derived IGF-I expression in mouse liver suppressed autoimmune diabetes progression. Suppression was associated with decreased islet inflammation and β-cell apoptosis, increased β-cell replication, and normalized β-cell mass. Permanent protection depended on exogenous IGF-I expression in liver nonparenchymal cells and was associated with increased percentage of intrapancreatic Tregs. Importantly, Treg depletion completely abolished IGF-I-mediated protection confirming the therapeutic potential of these cells in autoimmune diabetes. This study demonstrates that a nonviral gene therapy combining the immunological properties of the liver and IGF-I could be beneficial in the treatment of the disease.

Targeting regulatory T cells in the treatment of type 1 diabetes mellitus

Type 1 diabetes mellitus (T1DM) is a T cell-mediated autoimmune disease resulting in islet β cell destruction, hypoinsulinemia, and severely altered glucose homeostasis. T1DM has classically been attributed to the pathogenic actions of auto-reactive effector T cells(Teffs) on the β cell. Recent literature now suggests that a failure of a second T cell subtype, known as regulatory T cells (Tregs), plays a critical role in the development of T1DM. During immune homeostasis, Tregs counterbalance the actions of autoreactive Teff cells, thereby participating in peripheral tolerance. An imbalance in the activity between Teff and Tregs may be crucial in the breakdown of peripheral tolerance, leading to the development of T1DM. In this review, we summarize our current understanding of Treg function in health and in T1DM, and examine the effect of experimental therapies for T1DM on Treg cell number and function in both mice and humans.

Clinical immunologic interventions for the treatment of type 1 diabetes

Type 1 diabetes is an autoimmune disease, hence the rationale for immunotherapy to halt disease progression. Based on knowledge gained from other autoimmune diseases and from transplantation, the first immunointervention trials used immunosuppressive drugs, e.g., cyclosporin, in patients with recently diagnosed type 1 diabetes. Although remarkable, the effect vanished following drug withdrawal. Efforts were then devoted to devise strategies to induce/restore self-tolerance and avoid chronic immunosuppression. Various approaches were identified from work in spontaneous models of autoimmune diabetes, including the use of β-cell autoantigens and monoclonal antibodies directed at relevant immune molecules such as costimulatory ligands, T-cell receptor molecules such as CD3, and B cells. Phase II and phase III trials were launched, results of which are now available. Although the endeavor is challenging, the experience gained indicates that immunotherapy appears as the real hope of inducing long-term remission of the disease provided the treatment is started early and that protocols are adapted based on lessons from the past.

Targeting Janus tyrosine kinase 3 (JAK3) with an inhibitor induces secretion of TGF-β by CD4+ T cells

Regulatory T cells (Tregs) are critical for the peripheral maintenance of the autoreactive T cells in autoimmune disorders such as type 1 diabetes (T1D). Pharmacological inhibition of Janus tyrosine kinase 3 (JAK3) has been proposed as a basis for new treatment modalities against autoimmunity and allogeneic responses. Targeting JAK3 with an inhibitor has previously been shown to exhibit protective action against the development of T1D in non-obese diabetic (NOD) mice. As the mechanism of such preventative action has been unknown, we hypothesized that JAK3 inhibition induces generation of Tregs. Here, we show that the JAK3 inhibitor 4-(4'-hydroxyphenyl)-amino-6,7-dimethoxyquinazoline (WHI-P131) suppresses proliferation of short-term cultured NOD CD4(+) T cells through induction of apoptosis, while promoting survival of a particular population of long-term cultured cells. It was found that the surviving cells were not of the CD4(+)CD25(+)FoxP3(+) phenotype. They secreted decreased amounts of IL-10, IL-4 and interferon (IFN)-γ compared to the cells not exposed to the optimal concentrations of JAK3 inhibitor. However, an elevated transforming growth factor (TGF)-β secretion was detected in their supernatants. In vivo treatment of prediabetic NOD mice with WHI-P131 did not affect the frequency and number of splenic and pancreatic lymph node CD4(+)FoxP3(+) Tregs, while generating an elevated numbers of CD4(+)FoxP3(-) TGF-β-secreting T cells. In conclusion, our data suggest an induction of TGF-β-secreting CD4(+) T cells as the underlying mechanism for antidiabetogenic effects obtained by the treatment with a JAK3 inhibitor. To our knowledge, this is the first report of the JAK3 inhibitor activity in the context of the murine Tregs.

T cell receptor transgenic lymphocytes infiltrating murine tumors are not induced to express foxp3

Regulatory T cells (Treg) that express the transcription factor Foxp3 are enriched within a broad range of murine and human solid tumors. The ontogeny of these Foxp3 Tregs - selective accumulation or proliferation of natural thymus-derived Treg (nTreg) or induced Treg (iTreg) converted in the periphery from naïve T cells - is not known. We used several strains of mice in which Foxp3 and EGFP are coordinately expressed to address this issue. We confirmed that Foxp3-positive CD4 T cells are enriched among tumor-infiltrating lymphocytes (TIL) and splenocytes (SPL) in B16 murine melanoma-bearing C57BL/6 Foxp3^EGFP mice. OT-II Foxp3^EGFP mice are essentially devoid of nTreg, having transgenic CD4 T cells that recognize a class II-restricted epitope derived from ovalbumin; Foxp3 expression could not be detected in TIL or SPL in these mice when implanted with ovalbumin-transfected B16 tumor (B16-OVA). Likewise, TIL isolated from B16 tumors implanted in Pmel-1 Foxp3^EGFP mice, whose CD8 T cells recognize a class I-restricted gp100 epitope, were not induced to express Foxp3. All of these T cell populations - wild-type CD4, pmel CD8 and OTII CD4 - could be induced in vitro to express Foxp3 by engagement of their T cell receptor (TCR) and exposure to transforming growth factor β (TGFβ). B16 melanoma produces TGFβ and both pmel CD8 and OTII CD4 express TCR that should be engaged within B16 and B16-OVA respectively. Thus, CD8 and CD4 transgenic T cells in these animal models failed to undergo peripheral induction of Foxp3 in a tumor microenvironment.

Otelixizumab in the treatment of Type 1 diabetes mellitus

Anti-CD3 antibodies have been demonstrated in both animal and human studies to be able to reverse autoimmune diseases; for example Type 1 diabetes. Not only does treatment with anti-CD3 antibodies result in the removal of pathogenic T cells but evidence suggests that a state of operational tolerance can be induced through the effects on regulatory T cells. The clinical use of anti-CD3 antibodies has been hampered by their safety profile. However, the introduction of humanized, nonmitogenic, aglycosylated anti-CD3 antibodies, such as otelixizumab, and promising results reported in newly-diagnosed patients with Type 1 diabetes, have renewed the interest for these antibodies in the treatment of autoimmune diseases.

Human CD3 transgenic mice: preclinical testing of antibodies promoting immune tolerance

Monoclonal antibodies have proven to be potent agents to promote immunological tolerance in animal models of autoimmune disease and transplantation. However, optimal clinical application and pharmaceutical development have been limited by the species specificity of therapeutic antibodies, as well exemplified in the case of anti-CD3 antibodies. Compelling evidence in the nonobese diabetic (NOD) mouse, recently translated to clinical autoimmune insulin-dependent diabetes, demonstrates that a short CD3 antibody treatment effectively and durably controls disease progression. We established transgenic mice expressing the human ε chain of the CD3 complex bred onto the NOD background. These mice developed a high incidence of spontaneous autoimmune diabetes and harbored T cells sensitive both in vitro and in vivo to anti-human CD3 antibodies. Treatment of diabetic transgenic mice with otelixizumab, an anti-human CD3 antibody that has proven effective in the clinic, resulted in durable disease remission dependent on transferable T cell-mediated tolerance. This model should enable the evaluation of anti-human CD3 antibodies to determine their potential clinical utility.

Viral infection prevents diabetes by inducing regulatory T cells through NKT cell-plasmacytoid dendritic cell interplay

Type 1 diabetes (T1D) is an autoimmune disease resulting from T cell-mediated destruction of insulin-producing β cells, and viral infections can prevent the onset of disease. Invariant natural killer T cells (iNKT cells) exert a regulatory role in T1D by inhibiting autoimmune T cell responses. As iNKT cell-plasmacytoid dendritic cell (pDC) cooperation controls viral replication in the pancreatic islets, we investigated whether this cellular cross talk could interfere with T1D development during viral infection. Using both virus-induced and spontaneous mouse models of T1D, we show that upon viral infection, iNKT cells induce TGF-β-producing pDCs in the pancreatic lymph nodes (LNs). These tolerogenic pDCs convert naive anti-islet T cells into Foxp3(+) CD4(+) regulatory T cells (T reg cells) in pancreatic LNs. T reg cells are then recruited into the pancreatic islets where they produce TGF-β, which dampens the activity of viral- and islet-specific CD8(+) T cells, thereby preventing T1D development in both T1D models. These findings reveal a crucial cooperation between iNKT cells, pDCs, and T reg cells for prevention of T1D by viral infection.

Natural and induced T CD4+CD25+FOXP3+ regulatory T cells

Evidence has been accumulated to show that the forkhead/winged-helix transcription factor Foxp3 is a good marker for specialized CD4+ T cells that regulate immune responses to self as well as to a variety of foreign antigens including infectious or tumor antigens, alloantigens, allergens, and commensal antigens. It is now well established that CD4+CD25+Foxp3+ regulatory T cells encompass two categories of lymphocytes that are distinct in their origin, antigen specificity, as well as the stimuli driving their differentiation and homeostasis. Natural CD4+CD25+Foxp3+ regulatory T cells are an independent lineage generated in the thymus through major histocompatibility class II molecules-dependent MHC class high avidity interactions with their T cell receptor. They are specific for self-antigens. Adaptive or induced CD4+CD25+Foxp3+ regulatory T cells stem from mature CD4+CD25-Foxp3-precursors at the periphery following adequate stimulation. They have been shown to develop in vivo following suboptimal antigen stimulation, in situations characterized by chronic inflammation (autoimmunity, allergy, immune responses to tumors and transplants) and also as physiological actors of the mucosal immune system. Although major progress has been accomplished over the last years in our understanding of the central role of CD4+CD25+Foxp3+ regulatory T cells in the control of immune responses, major issues are still elusive. In particular, there are still no reliable phenotypic or functional markers that make it possible to distinguish between natural and induced CD25+Foxp3+ regulatory T cells.

Autoantigen-specific regulatory T cells induced in patients with type 1 diabetes mellitus by insulin B-chain immunotherapy

There is a growing body of evidence to suggest that the autoimmunity observed in type 1 diabetes mellitus (T1DM) is the result of an imbalance between autoaggressive and regulatory cell subsets. Therapeutics that supplement or enhance the existing regulatory subset are therefore a much sought after goal in this indication. Here, we report the results of a double blind, placebo controlled, phase I clinical trial of a novel antigen-specific therapeutic in 12 subjects with recently diagnosed T1DM. Our primary objective was to test its safety. The study drug, human insulin B-chain in incomplete Freund's adjuvant (IFA) was administered as a single intramuscular injection, with subjects followed for 2 years. All subjects completed therapy and all follow-up visits. The therapy was generally safe and well-tolerated. Mixed meal stimulated C-peptide responses, measured every 6 months, showed no statistical differences between arms. All patients vaccinated with the autoantigen, but none who received placebo, developed robust insulin-specific humoral and T cell responses. Up to two years following the single injection, in peripheral blood from subjects in the experimental arm, but not the control arm, insulin B-chain-specific CD4+ T cells could be isolated and cloned that showed phenotypic and functional characteristics of regulatory T cells. The induction of a lasting, robust immune response generating autoantigen-specific regulatory T cells provides strong justification for further testing of this therapy in type 1 diabetes. (clinicaltrials.gov identifier NCT00057499).

Recent insights into CD4+ T-cell specificity and function in type 1 diabetes

Type 1 diabetes (T1D) is caused by T-cell-mediated destruction of the insulin-producing beta-cells in the pancreas. Genetic and immunological evidence from humans and mouse models indicates that CD4(+) T cells play a crucial role in the development and prevention of T1D. The dichotomy between CD4(+) T regulatory and effector T cells has encouraged research into the role of these cell subsets in T1D. New antigens and epitopes recognized by CD4(+) T cells in affected individuals have been identified. Growing knowledge of T-cell specificity and function is helping to develop new assays for analyzing islet antigen-specific CD4(+) T cells from human blood. Here we discuss, with particular reference to human studies, advances in our understanding of CD4(+) T-cell responses in T1D.

99th Dahlem conference on infection, inflammation and chronic inflammatory disorders: immune therapies of type 1 diabetes: new opportunities based on the hygiene hypothesis

Insulin-dependent (type 1) diabetes is a prototypic organ-specific autoimmune disease resulting from the selective destruction of insulin-secreting beta cells within pancreatic islets of Langerhans by an immune-mediated inflammation involving autoreactive CD4(+) and CD8(+) T lymphocytes which infiltrate pancreatic islets. Current treatment is substitutive, i.e. chronic use of exogenous insulin which, in spite of significant advances, is still associated with major constraints (multiple daily injections, risks of hypoglycaemia) and lack of effectiveness over the long term in preventing severe degenerative complications. Finding a cure for autoimmune diabetes by establishing effective immune-based therapies is a real medical health challenge, as the disease incidence increases steadily in industrialized countries. As the disease affects mainly children and young adults, any candidate immune therapy must therefore be safe and avoid a sustained depression of immune responses with the attendant problems of recurrent infection and drug toxicity. Thus, inducing or restoring immune tolerance to target autoantigens, controlling the pathogenic response while preserving the host reactivity to exogenous/unrelated antigens, appears to be the ideal approach. Our objective is to review the major progress accomplished over the last 20 years towards that aim. In addition, we would like to present another interesting possibility to access new preventive strategies based on the 'hygiene hypothesis', which proposes a causal link between the increasing incidence of autoimmune diseases, including diabetes, and the decrease of the infectious burden. The underlying rationale is to identify microbial-derived compounds mediating the protective activity of infections which could be developed therapeutically.

New insights into the role of VIP on the ratio of T-cell subsets during the development of autoimmune diabetes

Type I diabetes is an autoimmune T-cell-mediated disease associated with overexpression of inflammatory mediators and the disturbance of different T-cell subsets. Vasoactive intestinal peptide (VIP) is a potent anti-inflammatory agent with regulatory effects on activated T cells. As the equilibrium between different T-cell subsets is involved in the final outcome, leading to tolerance or autoimmunity, we studied the evolution of markers for T cells in nonobese diabetic (NOD) mice. The study of different transcription factors, cytokines or cytokine receptors, shows that VIP interferes with functional phase of T helper 17 (Th17) cells and prevents the increase in the proportion of Th1 to Th17 cells. On the other hand, VIP-treated NOD mice show an increase in the proportion of CD4(+)CD25(+) cells in the spleen. Thus, VIP switches the Tregs/Th17 ratio leading to tolerance in NOD mice. Similarly, VIP reverses the ratio of Th1-/Th2-cell subsets associated with autoimmune pathology. All these effects on the ratio of T-cell subsets and the anti-inflammatory effect of VIP in decreasing proinflammatory mediators result in a reduction of β-cell destruction in pancreas. Taken together, these results show that VIP provides significant protection against spontaneous diabetes by modulating T-cell subsets and counterbalancing tolerance and immunity.

Immune therapy for type 1 diabetes mellitus-what is unique about anti-CD3 antibodies?

Type 1 diabetes mellitus (T1DM) is a prototypic organ-specific autoimmune disease that results from selective destruction of insulin-secreting beta-cells by immune-mediated inflammation (insulitis), that is, the infiltration of pancreatic islets by autoreactive CD4(+) and CD8(+) T lymphocytes. Current treatment is substitutive-chronic use of exogenous insulin-which, in spite of considerable advances, is still associated with constraints and lack of effectiveness over the long-term in relation to the prevention of vascular and neurological complications. Finding a cure for T1DM is an important medical health challenge, as the disease's incidence is steadily increasing in industrialized countries and projections of future prevalence are alarming. Crucially, as T1DM mainly affects children and young adults, any candidate immune therapy must be safe and avoid chronic use of immunosuppressants that promote sustained depression of immune responses. The ideal approach would, therefore, involve induction or, in the case of established T1DM, restoration of immune tolerance to target autoantigens. This Review presents, in particular, two strategies that are still in clinical development but hold great promise. These strategies are focused on the use of candidate autoantigens and anti-CD3 monoclonal antibodies.

Consecutive low doses of cyclophosphamide preferentially target Tregs and potentiate T cell responses induced by DNA PLG microparticle immunization

Cyclophosphamide in combination with immunotherapeutic approaches preferentially impinges on T(reg) activity and allows for robust generation of T cell effectors. Reduced dosages of cyclophosphamide are necessary to restrict its cytotoxic effects to the negative regulatory cell populations while sparing effector lymphocytes. We investigated cyclophosphamide dosing in combination with ZYC300, a PLG-encapsulated plasmid DNA vaccine which encodes the cytochrome P450 family member, CYP1B1, a known human tumor-associated antigen. In mice, three consecutive, low doses of cyclophosphamide comprised a superior regimen in enhancing the magnitude, diversity of epitopes, and avidity to individual epitopes of specific T cell responses when compared to regimens that used either a single low or a single high dose. Consecutive low doses of cyclophosphamide predominantly targeted T(regs) while sparing overall T lymphocyte counts. Thus, we report the synergistic activity of pharmacologic T(reg) depletion with cyclophosphamide on quantitatively and qualitatively increasing T cell responses to a known human tumor-associated antigen.

New insights into T cell biology and T cell-directed therapy for autoimmunity, inflammation, and immunosuppression

T cell-directed therapies have become mainstays in the management of various autoimmune diseases and organ transplantation. The understanding of T cell biology has expanded greatly since the development of most agents currently in use. Here we discuss important recent discoveries pertaining to T helper cell differentiation, lineage commitment, and function. Within this context, we examine existing T cell-directed therapies, including new agents being evaluated in clinical and preclinical studies. We also use recent findings to speculate on novel targets.

Progress towards the clinical use of CD3 monoclonal antibodies in the treatment of autoimmunity

PURPOSE OF REVIEW

A major problem in the field of clinical transplantation, as well as in autoimmunity, is that conventional treatments rely on chronic immunosuppression that is not specific for the antigens involved and that increases the risk of infections and tumours. A major need and challenge is, therefore, to achieve 'operational tolerance', namely an inhibition of pathogenic responses in the absence of chronic immunosuppression.

RECENT FINDINGS

Here we review data showing that monoclonal antibodies to the CD3 complex, the signal transducing element of the T cell receptor, promote immune tolerance. This strategy has been the matter of extensive experimental studies in models of autoimmunity and has recently led to a successful clinical translation.

SUMMARY

Results from controlled trials in autoimmune insulin-dependent diabetes showed that CD3 monoclonal antibodies afford long-term effects following a short administration. The present challenge is to build on these results, first, to set the use of CD3 monoclonal antibodies as an established therapy in well selected subsets of patients with autoimmunity, and second, given the similarities of immune mechanisms underlying T cell-mediated autoimmune diseases and allograft rejection, to address if and how this therapeutic strategy could be extended to organ transplantation in the not-too-distant future.

Regulatory T cells enter the pancreas during suppression of type 1 diabetes and inhibit effector T cells and macrophages in a TGF-beta-dependent manner

Treg can suppress autoimmune diseases such as type 1 diabetes, but their in vivo activity during suppression remains poorly characterized. In type 1 diabetes, Treg activity has been demonstrated in the pancreatic lymph node, but little has been studied in the pancreas, the site of autoimmune islet destruction. In this study we induced islet-specific Treg from the BDC-6.9 TCR transgenic mouse by activation of T cells in the presence of TGF-beta. These Treg can suppress spontaneous diabetes as well as transfer of diabetes into NOD.scid mice by diabetic NOD spleen cells or activated BDC-2.5 TCR transgenic Th1 effector T cells. In the latter transfer model, we observed infiltration of the pancreas by both effector T cells and Treg, suggesting that Treg are active in the inflammatory site and are not just restricted to the draining lymph node. Within the pancreas, we demonstrate that Treg transfer causes a reduction in the number of effector Th1 T cells and macrophages, and also inhibits effector T-cell cytokine and chemokine production. Although we found no role for TGF-beta in vitro, transfection of effector T cells with a dominant-negative TGF-beta receptor demonstrated that in vivo suppression of diabetes by TGF-beta-induced Treg is TGF-beta-dependent.

Combination therapy with glucagon-like peptide-1 and gastrin restores normoglycemia in diabetic NOD mice

OBJECTIVE

Glucagon-like peptide-1 (GLP-1) and gastrin promote pancreatic beta-cell function, survival, and growth. Here, we investigated whether GLP-1 and gastrin can restore the beta-cell mass and reverse hyperglycemia in NOD mice with autoimmune diabetes.

RESEARCH DESIGN AND METHODS

Acutely diabetic NOD mice were treated with GLP-1 and gastrin, separately or together, twice daily for 3 weeks. Blood glucose was measured weekly and for a further 5 weeks after treatments, after which pancreatic insulin content and beta-cell mass, proliferation, neogenesis, and apoptosis were measured. Insulin autoantibodies were measured, and adoptive transfer of diabetes and syngeneic islet transplant studies were done to evaluate the effects of GLP-1 and gastrin treatment on autoimmunity.

RESULTS

Combination therapy with GLP-1 and gastrin, but not with GLP-1 or gastrin alone, restored normoglycemia in diabetic NOD mice. The GLP-1 and gastrin combination increased pancreatic insulin content, beta-cell mass, and insulin-positive cells in pancreatic ducts, and beta-cell apoptosis was decreased. Insulin autoantibodies were reduced in GLP-1- and gastrin-treated NOD mice, and splenocytes from these mice delayed adoptive transfer of diabetes in NOD-scid mice. Syngeneic islet grafts in GLP-1 -and gastrin-treated NOD mice were infiltrated by leukocytes with a shift in cytokine expression from interferon-gamma to transforming growth factor-beta1, and beta-cells were protected from apoptosis.

CONCLUSIONS

Combination therapy with GLP-1 and gastrin restores normoglycemia in diabetic NOD mice by increasing the pancreatic beta-cell mass and downregulating the autoimmune response.

TGF-beta expression by allogeneic bone marrow stromal cells ameliorates diabetes in NOD mice through modulating the distribution of CD4+ T cell subsets

BMSCs could promote the regeneration of islet beta-cell, but the status of BMSCs under diabetes is still unknown. Our study verified the effect of allogeneic BMSCs (ICR) transferred into NOD mice on blood glucose and CD4+ T cells subsets function. In vivo experiment, BMSCs could decrease blood glucose, weaken lymphocytes proliferation. In vitro experiment, the distribution of CD4+ T cell subsets was changed after co-culture with BMSCs, resulting in a greater frequency of Treg cells and reduced representation of Th17 cells. After TGF-beta blockade, CD4+ T cells differentiated along a route favoring development of Th17, but not Treg cells. Thus, NOD can be treated by BMSCs which changes the distribution of CD4+ T cells, increases the number of Treg cells, and inhibits the differentiation of Th17 cells. And the positive effects of allogeneic BMSCs in the treatment of NOD mice depend on the regulation of TGF-beta secreted by BMSCs.

Regulatory T cells and human disease

The main function of our immune system is to protect us from invading pathogens and microorganisms by destroying infected cells, while minimizing collateral damage to tissues. In order to maintain this balance between immunity and tolerance, current understanding of the immune system attributes a major role to regulatory T cells (Tregs) in controlling both immunity and tolerance. Various subsets of Tregs have been identified based on their expression of cell surface markers, production of cytokines, and mechanisms of action. In brief, naturally occurring thymic-derived CD4+CD25+ Tregs are characterized by constitutive expression of the transcription factor FOXP3, while antigen-induced or adaptive Tregs are mainly identified by expression of immunosuppressive cytokines (interleukin-10 (IL-10) and/or transforming growth factor-beta (TGF-beta)). While Tregs in normal conditions regulate ongoing immune responses and prevent autoimmunity, imbalanced function or number of these Tregs, either enhanced or decreased, might lead, respectively, to decreased immunity (e.g., with tumor development or infections) or autoimmunity (e.g., multiple sclerosis). This review will discuss recent research towards a better understanding of the biology of Tregs, their interaction with other immune effector cells, such as dendritic cells, and possible interventions in human disease.

Regulatory T-cells protect from type 1 diabetes after induction by coxsackievirus infection in the context of transforming growth factor-beta

OBJECTIVE

Coxsackievirus infections have long been associated with the induction of type 1 diabetes. Infection with coxsackievirus B4 (CB4) enhances type 1 diabetes onset in NOD mice by accelerating the presentation of beta-cell antigen to autoreactive T-cells. It has been reported that a progressive defect in regulatory T-cell (Treg) function is, in part, responsible for type 1 diabetes onset in NOD mice. This defect may contribute to susceptibility to viral-induced type 1 diabetes. We asked whether the immune response after CB4 infection could be manipulated to reestablish peripheral tolerance while maintaining the immune response to virus.

RESEARCH DESIGN AND METHODS

NOD mice expressing transforming growth factor-beta (TGF-beta) specifically in the beta-cells were infected with CB4, and the functional role of Tregs in disease protection was measured. Systemic treatments with TGF-beta were used to assess its therapeutic potential.

RESULTS

Here, we report that Tregs induced after CB4 infection in the presence of TGF-beta prevented type 1 diabetes. The capacity to directly infect pancreatic beta-cells correlated with increased numbers of pancreatic Tregs, suggesting that presentation of beta-cell antigen is integral to induction of diabetogenic protective Tregs. Furthermore, the presence of these viral induced Tregs correlated with protection from type 1 diabetes without altering the antiviral response. Finally, when TGF-beta was administered systemically to NOD mice after infection, the incidence of type 1 diabetes was reduced, thereby signifying a potential therapeutic role for TGF-beta.

CONCLUSIONS

We demonstrate manipulations of the immune response that result in Treg-mediated protection from type 1 diabetes without concomitant loss of the capacity to control viral infection.

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.

The Foxp3+ regulatory T cell: a jack of all trades, master of regulation

The function of regulatory T cells (T(reg) cells) has been attributed to a growing number of diverse pathways, molecules and processes. Seemingly contradictory conclusions regarding the mechanisms underlying T(reg) cell suppressive activity have revitalized skeptics in the field who challenge the core validity of the idea of T(reg) cells as central immune regulators. However, we note that a consensus may be emerging from the data: that multiple T(reg) cell functions act either directly or indirectly at the site of antigen presentation to create a regulatory milieu that promotes bystander suppression and infectious tolerance. Thus, the versatility and adaptability of the Foxp3+ T(reg) cells may in fact be the best argument that these cells are 'multitalented masters of immune regulation'.

The use of CD3-specific antibodies in autoimmune diabetes: a step toward the induction of immune tolerance in the clinic

CD3-specific monoclonal antibodies were the first rodent monoclonals introduced in clinical practice in the mid 1980s as approved immunosuppressants to prevent and treat organ allograft rejection. Since then compelling evidence has been accumulated to suggest that in addition to their immunosuppressive properties, CD3-specific antibodies can also afford inducing immune tolerance especially in the context of ongoing immune responses. Thus, they are highly effective at restoring self-tolerance in overt autoimmunity, a capacity first demonstrated in the experimental setting, which was recently transferred to the clinic with success.

Pathobiology of transforming growth factor beta in cancer, fibrosis and immunologic disease, and therapeutic considerations

Transforming growth factor beta (TGF-beta) is a highly pleiotropic cytokine that plays an important role in wound healing, angiogenesis, immunoregulation and cancer. The cells of the immune system produce the TGF-beta1 isoform, which exerts powerful anti-inflammatory functions, and is a master regulator of the immune response. However, this is context dependent, because TGF-beta can contribute to the differentiation of both regulatory (suppressive) T cells (Tr cells) and inflammatory Th17 cells. While TGF-beta might be underproduced in some autoimmune diseases, it is overproduced in many pathological conditions. This includes pulmonary fibrosis, glomerulosclerosis, renal interstitial fibrosis, cirrhosis, Crohn's disease, cardiomyopathy, scleroderma and chronic graft-vs-host disease. In neoplastic disease, TGF-beta suppresses the progression of early lesions, but later this effect is lost and cancer cells produce TGF-beta, which then promotes metastasis. This cytokine also contributes to the formation of the tumor stroma, angiogenesis and immunosuppression. In view of this, several approaches are being studied to inhibit TGF-beta activity, including neutralizing antibodies, soluble receptors, receptor kinase antagonist drugs, antisense reagents and a number of less specific drugs such as angiotensin II antagonists and tranilast. It might be assumed that TGF-beta blockade would result in severe inflammatory disease, but this has not been the case, presumably because the neutralization is only partial. In contrast, the systemic administration of TGF-beta for therapeutic purposes is limited by toxicity and safety concerns, but local administration appears feasible, especially to promote wound healing. Immunotherapy or vaccination stimulating TGF-beta production and/or Tr differentiation might be applied to the treatment of autoimmune diseases. The benefits of new therapies targeting TGF-beta are under intense investigation.

Expansion and characteristics of human T regulatory type 1 cells in co-cultures simulating tumor microenvironment

OBJECTIVE

Chronic inflammation and cancer development are associated with dysregulated immune responses and the presence of regulatory T cells (T(reg)). To study the role of T(reg) in tumor cell escape from immune surveillance, an in vitro model simulating the tumor microenvironment and promoting the induction and expansion of IL-10(+) T(reg )type 1 (Tr1) was established.

METHODS

An in vitro co-culture system (IVA) included an irradiated head and neck squamous cell carcinoma cell line, immature dendritic cells (iDC), CD4(+)CD25(- )T cells and cytokines, IL-2 (10 IU/ml), IL-10 (20 IU/ml), IL-15 (20 IU/ml) +/- 1 nM rapamycin. Autologous iDC and CD4(+)CD25(-) T cells were obtained from the peripheral blood of 15 normal donors. Co-cultures were expanded for 10 days. Proliferating lymphocytes were phenotyped by multi-color flow cytometry. Their suppressor function was measured in CFSE inhibition assays +/- neutralizing anti-IL-10 mAb and using transwell cultures. Culture supernatants were tested for IL-4, IL-10, TGF-beta and IFN-gamma in ELISA.

RESULTS

In the IVA, low doses of IL-2, IL-10 and IL-15 promoted induction and expansion of CD3(+)CD4(+)CD25(-)IL2Rbeta(+)IL2Rgamma(+)FoxP3(+)CTLA-4(+)IL-10(+) cells with suppressor activity (mean suppression +/- SD = 58 +/- 12%). These suppressor cells produced IL-10 (mean +/- SD = 535 +/- 12 pg/ml) and TGF-beta (mean +/- SD = 512 +/- 38 pg/ml), but no IL-4 or IFN-gamma. Suppressor function of co-cultures correlated with the percent of expanding IL-10(+) Tr1 cells (r (2 )=( )0.9; P < 0.001). The addition of rapamycin enriched Tr1 cells in all co-cultures. Neutralizing anti-IL-10 mAb abolished suppressive activity. Suppression was cell-contact independent.

CONCLUSION

The tumor microenvironment promotes generation of Tr1 cells which have the phenotype distinct from that of CD4(+)CD25(high)FoxP3(+) nTreg and mediate IL-10 dependent immune suppression in a cell-contact independent manner. Tr1 cells may play a critical role in cancer progression.

CD3-specific antibodies: a portal to the treatment of autoimmunity

Targeted immunotherapies hold great promise for the treatment and cure of autoimmune diseases. The efficacy of CD3-specific monoclonal antibody therapy in mice and humans stems from its ability to re-establish immune homeostasis in treated individuals. This occurs through modulation of the T-cell receptor (TCR)-CD3 complex (also termed antigenic modulation) and/or induction of apoptosis of activated autoreactive T cells, which leaves behind 'space' for homeostatic reconstitution that favours selective induction, survival and expansion of adaptive regulatory T cells, which establishes long-term tolerance. This Review summarizes the pre-clinical and clinical studies of CD3-specific monoclonal antibody therapy and highlights future opportunities to enhance the efficacy of this potent immunotherapeutic.

Cutting Edge: Proinflammatory and Th2 cytokines synergize to induce thymic stromal lymphopoietin production by human skin keratinocytes

Thymic stromal lymphopoietin (TSLP) is an epithelial cell-derived cytokine that strongly activates dendritic cells (DC) and can initiate allergic inflammation. The factors inducing the production of human TSLP are not known. In this study, we show that proinflammatory (TNF-alpha or IL-1alpha) and Th2 (IL-4 or IL-13) cytokines synergized to induce the production of TSLP in human skin explants. TSLP production in situ was restricted to epidermal keratinocytes of the suprabasal layer. TSLP production could not be inhibited by factors regulating Th2 inflammation, such as IL-10, TGF-beta, or IFN-gamma. Cytokine-treated skin culture supernatants induced the maturation of blood CD11c(+) DC in a TSLP-dependent manner. Our data provide the first evidence of TSLP induction and subsequent DC activation in human skin. Blocking TSLP-inducing cytokines could represent a novel strategy for the treatment of allergic diseases.

Functional Foxp3+ CD4+ CD25(Bright+) "natural" regulatory T cells are abundant in rabbit conjunctiva and suppress virus-specific CD4+ and CD8+ effector T cells during ocular herpes infection

We studied the phenotype and distribution of "naturally" occurring CD4(+) CD25(+) T regulatory cells (CD4(+) CD25(+) nT(reg) cells) resident in rabbit conjunctiva, the main T-cell inductive site of the ocular mucosal immune system, and we investigated their suppressive capacities using herpes simplex virus type 1 (HSV-1)-specific effector T (T(eff)) cells induced during ocular infection. The expression of CD4, CD25, CTLA4, GITR, and Foxp3 was examined by reverse transcription-PCR, Western blotting, and fluorescence-activated cell sorter analysis in CD45(+) pan-leukocytes isolated from conjunctiva, spleen, and peripheral blood monocyte cells (PBMC) of HSV-1-infected and uninfected rabbits. Normal conjunctiva showed a higher frequency of CD4(+) CD25((Bright+)) T cells than did spleen and PBMC. These cells expressed high levels of Foxp3, GITR, and CTLA4 molecules. CD4(+) CD25((Bright+)) T cells were localized continuously along the upper and lower palpebral and bulbar conjunctiva, throughout the epithelium and substantia propria. Conjunctiva-derived CD4(+) CD25((Bright+)) T cells, but not CD4(+) CD25((low)) T cells, efficiently suppressed HSV-specific CD4(+) and CD8(+) T(eff) cells. The CD4(+) CD25((Bright+)) T-cell-mediated suppression was effective on both peripheral blood and conjunctiva infiltrating T(eff) cells and was cell-cell contact dependent but independent of interleukin-10 and transforming growth factor beta. Interestingly, during an ocular herpes infection, there was a selective increase in the frequency and suppressive capacity of Foxp3(+) CD4(+) CD25((Bright+)) T cells in conjunctiva but not in the spleen or in peripheral blood. Altogether, these results provide the first evidence that functional Foxp3(+) CD4(+) CD25((Bright+)) T(reg) cells accumulate in the conjunctiva. It remains to be determined whether conjunctiva CD4(+) CD25(+) nT(reg) cells affect the topical/mucosal delivery of subunit vaccines that stimulate the ocular mucosal immune system.