Regulatory T cells and type 1 diabetes

Regulatory T cells targeting a pathogenic MHC class II: Insulin peptide epitope postpone spontaneous autoimmune diabetes

Introduction

In spontaneous type 1 diabetes (T1D) non-obese diabetic (NOD) mice, the insulin B chain peptide 9-23 (B:9-23) can bind to the MHC class II molecule (IAg7) in register 3 (R3), creating a bimolecular IAg7/InsulinB:9-23 register 3 conformational epitope (InsB:R3). Previously, we showed that the InsB:R3-specific chimeric antigen receptor (CAR), constructed using an InsB:R3-monoclonal antibody, could guide CAR-expressing CD8 T cells to migrate to the islets and pancreatic lymph nodes. Regulatory T cells (Tregs) specific for an islet antigen can broadly suppress various pathogenic immune cells in the islets and effectively halt the progression of islet destruction. Therefore, we hypothesized that InsB:R3 specific Tregs would suppress autoimmune reactivity in islets and efficiently protect against T1D.

Methods

To test our hypothesis, we produced InsB:R3-Tregs and tested their disease-protective effects in spontaneous T1D NOD.CD28-/- mice.

Results

InsB:R3-CAR expressing Tregs secrete IL-10 dominated cytokines upon engagement with InsB:R3 antigens. A single infusion of InsB:R3 Tregs delayed the onset of T1D in 95% of treated mice, with 35% maintaining euglycemia for two healthy lifespans, readily home to the relevant target whereas control Tregs did not. Our data demonstrate that Tregs specific for MHC class II: Insulin peptide epitope (MHCII/Insulin) protect mice against T1D more efficiently than polyclonal Tregs lacking islet antigen specificity, suggesting that the MHC II/insulin-specific Treg approach is a promising immune therapy for safely preventing T1D.

Ursolic acid regulates gut microbiota and corrects the imbalance of Th17/Treg cells in T1DM rats

Ursolic acid (UA), a natural pentacyclic triterpenoid obtained from fruit and several traditional Chinese medicinal plants, exhibits anti-inflammatory and hypoglycemic properties. However, its protective effects against type 1 diabetes mellitus (T1DM) have not been explored. In this study, streptozotocin-induced T1DM rat models were established and treated with UA for six weeks. T1DM rats treated with UA were used to observe the effects of UA on body weight and fasting blood glucose (FBG) levels. Pathological changes in the pancreas were observed using immunohistochemical staining. The gut microbiota distribution was measured using 16S rDNA high-throughput sequencing. The proportions of Th17 and Treg cells were examined using flow cytometry. Protein and mRNA expression of molecules involved in Th17/Treg cell differentiation were assessed by quantitative real-time PCR and western blotting. The correlation between gut microbiota and Th17/Treg cell differentiation in T1DM was analyzed using redundancy analysis (RDA) analysis. Compared with the model group, FBG levels declined, and the progressive destruction of pancreatic β cells was alleviated. The diversity and uniformity of gut microbiota in T1DM rats treated with UA increased significantly. Interestingly, the Th17/Treg cell differentiation imbalance was corrected and positively correlated with the expression of Foxp3 and IL-10, and negatively correlated with the expression of RORγt, IL-17A, and TNF-α. These findings suggest that UA can lower FBG levels in T1DM rats, delay the progressive destruction of pancreatic β-cells, and modulate gut microbiota homeostasis and immune function in streptozotocin-induced T1DM rats.

Type 1 Diabetes in STAT Protein Family Mutations: Regulating the Th17/Treg Equilibrium and Beyond

Improvements in the immunological, molecular, and genetic technologies such as next-generation sequencing have led to an exponential increase in the number of monogenic immune dysregulatory syndromes diagnosed, where type 1 diabetes (T1D) forms part of the autoimmune manifestations. Here, we reviewed the mutations in the signal transducer and activator of transcription (STAT) protein family, namely gain-of-function (GOF) mutations in STAT1 and STAT3 as well as STAT5b deficiency, that show strong association to T1D susceptibility. The equilibrium of T-helper 17 (Th17) and regulatory T cells (Tregs) is often found altered in patients affected by STAT GOF mutations. While the increased number of Th17 cells and the concomitant decrease in Treg cells may explain T1D in STAT3 GOF patients, the reduced number of Th17 cells found in those carrying STAT1 GOF mutations added a new level of complexity on the exact role of Th17 in the pathogenesis of T1D. Here, we describe the possible mechanisms through which STAT3 and STAT1 GOF mutations may perturb the fate and function of Th17 and Tregs and explore how this may lead to the development of T1D. We propose that the study of monogenic diseases, and in particular STAT mutations, may not only improve our understanding of the function of the human immune system but also shed light onto the pathogenic mechanisms of T1D and the genetic variants that confer predisposition to the disease.

Potential route of Th17/Treg cell dynamics in targeting type 1 diabetes and rheumatoid arthritis: an autoimmune disorder perspective

Cytokines, small secreted proteins, have a specific effect on the interactions and communications between cells. They play a pivotal role in the pathogenesis of autoimmune diseases. Factors in the breakdown of self-tolerance and the subsequent events leading to the induction of pathogenic responses remain unclear for most of the autoimmune diseases. Large numbers of studies have revealed a general scheme in which pro-inflammatory cytokines contribute to the initiation and propagation of autoimmune inflammation, whereas anti-inflammatory cytokines facilitate the regression of inflammation and thereby recovery from the disease. The interleukin (IL)-17/IL-23 axis that emerged as the new paradigm has compelled us to critically re-examine the cytokine-driven immune events in the pathogenesis and treatment of autoimmunity. T-helper 17 cells and Regulatory T cells are two lymphocyte subsets with opposing action. In this review, we discuss the mechanism that promotes development of these cells from common precursors and specific factors that impact their cell numbers and function. Also presented are findings that suggest how the equilibrium between pre-inflammatory T helper and regulatory T-cell subsets might be pharmacologically restored for therapeutic benefit, emphasising type-1 diabetes and rheumatoid arthritis. Furthermore, the emerging clinical data showing anti-IL-17 and anti-IL-23 treatments for their efficacy in treating immune-mediated inflammatory diseases are presented.

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

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

CD73-dependent generation of adenosine and endothelial Adora2b signaling attenuate diabetic nephropathy

Nucleotide phosphohydrolysis by the ecto-5'-nucleotidase (CD73) is the main source for extracellular generation of adenosine. Extracellular adenosine subsequently signals through four distinct adenosine A receptors (Adora1, Adora2a, Adora2b, or Adora3). Here, we hypothesized a functional role for CD73-dependent generation and concomitant signaling of extracellular adenosine during diabetic nephropathy. CD73 transcript and protein levels were elevated in the kidneys of diabetic mice. Genetic deletion of CD73 was associated with more severe diabetic nephropathy, whereas treatment with soluble nucleotidase was therapeutic. Transcript levels of renal adenosine receptors showed a selective induction of Adora2b during diabetic nephropathy. In a transgenic reporter mouse, Adora2b expression localized to the vasculature and increased after treatment with streptozotocin. Adora2b(-/-) mice experienced more severe diabetic nephropathy, and studies in mice with tissue-specific deletion of Adora2b in tubular epithelia or vascular endothelia implicated endothelial Adora2b signaling in protection from diabetic nephropathy. Finally, treatment with a selective Adora2b agonist (BAY 60-6583) conveyed potent protection from diabetes-associated kidney disease. Taken together, these findings implicate CD73-dependent production of extracellular adenosine and endothelial Adora2b signaling in kidney protection during diabetic nephropathy.

Treg cells in pancreatic lymph nodes: the possible role in diabetogenesis and β cell regeneration in a T1D model

Previously, we established a model in which physiologically adequate function of the autologous β cells was recovered in non-obese diabetic (NOD) mice after the onset of hyperglycemia by rendering them hemopoietic chimera. These mice were termed antea-diabetic. In the current study, we addressed the role of T regulatory (Treg) cells in the mechanisms mediating the restoration of euglycemia in the antea-diabetic NOD model. The data generated in this study demonstrated that the numbers of Treg cells were decreased in unmanipulated NOD mice, with the most profound deficiency detected in the pancreatic lymph nodes (PLNs). The impaired retention of the Treg cells in the PLNs correlated with the locally compromised profile of the chemokines involved in their trafficking, with the most prominent decrease observed in SDF-1. The amelioration of autoimmunity and restoration of euglycemia observed in the antea-diabetic mice was associated with restoration of the Treg cell population in the PLNs. These data indicate that the function of the SDF-1/CXCR4 axis and the retention of Treg cells in the PLNs have a potential role in diabetogenesis and in the amelioration of autoimmunity and β cell regeneration in the antea-diabetic model. We have demonstrated in the antea-diabetic mouse model that lifelong recovery of the β cells has a strong correlation with normalization of the Treg cell population in the PLNs. This finding offers new opportunities for testing the immunomodulatory regimens that promote accumulation of Treg cells in the PLNs as a therapeutic approach for type 1 diabetes (T1D).

Immunology in the Clinic Review Series; focus on metabolic diseases: development of islet autoimmune disease in type 2 diabetes patients: potential sequelae of chronic inflammation

Historically, the development of type 2 diabetes has been considered not to have an autoimmune component, in contrast to the autoimmune pathogenesis of type 1 diabetes. In this review we will discuss the accumulating data supporting the concept that islet autoreactivity and inflammation is present in type 2 diabetes pathogenesis, and the islet autoimmunity appears to be one of the factors associated with the progressive nature of the type 2 diabetes disease process.

Anti-TNF rescue CD4+Foxp3+ regulatory T cells in patients with type 1 diabetes from effects mediated by TNF

The presence of low-grade chronic inflammation is a known feature of long standing diabetes type 1. The association between serum level of several markers of inflammation and severity of DM1 was proven. Serum concentrations of TNF were reported to be elevated in diabetic patients, especially those who developed diabetic complications. Lately, it has been also shown that TNF may impair the subset of naturally arising regulatory T cells, which control autoimmunity. The presented study, for the first time, shows the regulatory T cells in the context of an inflammatory environment that is present in patients with type 1 diabetes. It indicates that TNF reduces the number and frequency of regulatory CD4(+)Foxp3(+) T cells in children with diabetes type 1 and that in vitro treatment with anti-TNF antibody seems to rescue this cell subset from its defective effects.

Cytokines in autoimmunity: role in induction, regulation, and treatment

Cytokines play a pivotal role in the pathogenesis of autoimmune diseases. The precise triggers for the breakdown of self-tolerance and the subsequent events leading to the induction of pathogenic autoimmune responses remain to be defined for most of the naturally occurring autoimmune diseases. Studies conducted in experimental models of human autoimmune diseases and observations in patients have revealed a general scheme in which proinflammatory cytokines contribute to the initiation and propagation of autoimmune inflammation, whereas anti-inflammatory cytokines facilitate the regression of inflammation and recovery from acute phase of the disease. This idea is embodied in the T helper (Th) 1/Th2 paradigm, which over the past two decades has had a major influence on our thinking about the role of cytokines in autoimmunity. Interestingly, over the past decade, the interleukin (IL)-17/IL-23 axis has rapidly emerged as the new paradigm that has compelled us to critically re-examine the cytokine-driven immune events in the pathogenesis and treatment of autoimmunity. In this 2-volume special issue of the journal, leading experts have presented their research findings and viewpoints on the role of cytokines in the context of specific autoimmune diseases.

Thymic self-antigen expression for the design of a negative/tolerogenic self-vaccine against type 1 diabetes

Before being able to react against infectious non-self-antigens, the immune system has to be educated in the recognition and tolerance of neuroendocrine proteins, and this critical process essentially takes place in the thymus. The development of the autoimmune diabetogenic response results from a thymus dysfunction in programming central self-tolerance to pancreatic insulin-secreting islet β cells, leading to the breakdown of immune homeostasis with an enrichment of islet β cell reactive effector T cells and a deficiency of β cell-specific natural regulatory T cells (nTreg) in the peripheral T-lymphocyte repertoire. Insulin-like growth factor 2 (IGF-2) is the dominant member of the insulin family expressed during fetal life by the thymic epithelium under the control of the autoimmune regulator (AIRE) gene/protein. Based on the close homology and cross-tolerance between insulin, the primary T1D autoantigen, and IGF-2, the dominant self-antigen of the insulin family, a novel type of vaccination, so-called “negative/tolerogenic self-vaccination”, is currently developed for prevention and cure of T1D. If this approach were found to be effective for reprogramming immunological tolerance in T1D, it could pave the way for the design of negative self-vaccines against autoimmune endocrine diseases, as well as other organ-specific autoimmune diseases.

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.

The honeymoon phase: intersection of metabolism and immunology

PURPOSE OF REVIEW

Even though the honeymoon phase in type 1 diabetes mellitus has been well known, its underlying pathogenic mechanisms remain poorly described. The common explanation that it occurs due to 'beta-cell rest' on initiation of insulin therapy seems inadequate based on recent observations and studies and its underlying immunological aspects overlooked.

RECENT FINDINGS

In this article, we will review the metabolic and immunological aspects of the honeymoon phase and we will present our current model of the pathophysiology of this phase. Our view is that it is one of many phases of remission occurring basically due to development of adaptive immune tolerance along the course of type 1 diabetes. We will also review new findings of the interplay between metabolic factors (ambient glucose level) and immune function.

SUMMARY

The honeymoon phase provides a unique model to understand the pathogenesis of type 1 diabetes. Research to unravel its immune pathogenesis is needed. It may turn out that the optimum form of intervention in type 1 diabetes is one that combines enhancement of antigen-specific adaptive immune tolerance with optimized metabolic control in order to keep cytotoxic T cells anergic.

An update on preventive and regenerative therapies in diabetes mellitus

Type 1A (immune-mediated) and type 2 diabetes mellitus are two of the most common severe chronic illnesses, affecting over 230 million people worldwide with an estimated global prevalence of 5.1%. Although type 1 and type 2 diabetes differ greatly in modes of pathogenesis, these illnesses share a common pathology and consequences characterized by loss of functional beta-cell mass and subsequent dysregulation of carbohydrate and lipid metabolism. Since therapy for diabetes and the associated complications poses enormous public health and economic burdens, novel preventive and regenerative therapies have emerged in the past decade with the aim to preserve beta-cell mass and delay the onset of diabetes. The goal of this review is to provide a comprehensive overview of current efforts in the fight against diabetes, and attempts to document all strategies that have emerged in clinical studies within the past 25 years. First, strategies to identify individuals at risk, ranging from whole-genome scans to autoantibody screening, will be discussed. Second, novel approaches to prevent or delay the onset of disease will be covered. Particular focus is given on emerging strategies for individuals at risk for type 1 diabetes that target T-cell regulation and induction of tolerance, while new pharmaceutical concepts in combination with lifestyle interventions are discussed within the scope of type 2 diabetes prevention. Lastly, important efforts to halt disease progression with emphasis on beta-cell regeneration are presented.

Advances in type I diabetes associated tolerance mechanisms

Type 1 diabetes (T1D) is an autoimmune disease resulting from the destruction of insulin-producing pancreatic beta cells by autoreactive T cells. The polygenic trait for T1D risk implicates many genes that have an impact on fundamental immunological processes such as central and peripheral tolerance. Several pieces of evidence have suggested that many of the genetic loci that are directly linked to type 1 diabetes susceptibility modulate the generation and/or the activation of autoreactive T-lymphocytes. We and others have proposed a critical role for medullary thymic epithelial cells (mTEC) forming the Hassall's corpuscles in T-cell tolerance. Indeed, mTEC have been found to express promiscuous self-antigens, used directly or through thymic dendritic cells to drive either negative selection of insulin-reacting precursors or their differentiation into naturally occurring regulatory Foxp3+ CD4+ CD25+ T cells. In the periphery, naturally occurring Foxp3+ CD4+ CD25+regulatory T (Treg) cells represent the master cells in dominant peripheral T-cell tolerance. The development and function of Treg cells are ultimately linked to IL-2 and Foxp3 expression. This review addresses recent literature and emerging concepts of central and peripheral T-cell tolerance with regards to T1D.

pConsensus peptide induces tolerogenic CD8+ T cells in lupus-prone (NZB x NZW)F1 mice by differentially regulating Foxp3 and PD1 molecules

Systemic lupus erythematosus is an autoimmune disease caused primarily by autoantibodies (including IgG anti-DNA) and immune complexes that cause tissue damage. After tolerization with an artificial peptide (pConsensus, pCons) based on murine anti-DNA IgG sequences containing MHC class I and class II T cell determinants, lupus-prone (NZB x NZW)F(1) female (BWF(1)) mice develop regulatory CD4+CD25+ T cells and inhibitory CD8+ T cells, both of which suppress anti-DNA Ig production and immune glomerulonephritis. In the present work, we show that splenocytes from BWF(1) mice treated with pCons had significant expansion of primarily CD8+ T cells. CD4+ T cells and B cells were each directly suppressed by CD8+ T cells from tolerized mice in a contact-independent manner. Both pCons-induced CD8+CD28+ and CD8+CD28- T cells suppressed production of anti-DNA in vitro. Silencing with small interfering RNA of Foxp3 abrogated the suppression mediated by both CD8+ T cell subsets. Additionally, CD8+ T cells from tolerized mice were weakly cytotoxic against syngeneic B cells from old anti-DNA-producing mice, but not from young mice. Importantly, pCons treatment had dual effects on CD8+ suppressor T cells from tolerized mice, increasing the intracellular expression of Foxp3 while decreasing the surface expression of PD1 molecules. Blocking PD1/PDL1 interactions in the CD8+ T cells from tolerized mice reduced their expression of Foxp3 and their ability to suppress CD4+CD25- proliferation. In contrast, blocking PD1/PDL1 in naive T cells increased Foxp3 expression. Our data suggest that tolerization with pCons activates different subsets of inhibitory/cytotoxic CD8+ T cells whose targets are both CD4+CD25- effector T cells and B cells.

Toward cell-based therapy of type I diabetes

Type 1 diabetes (T1D) is an autoimmune disease that results from the destruction of insulin-producing pancreatic islet cells owing to the aggressive effector function of autoreactive T cells. In addition to lifetime supply of exogenous insulin, whole-pancreas or islet transplantation is presently the only alternative therapy for severely ill patients. Here, we discuss the current status of the development of cell-based therapies that are based on essentially two options, i.e. replacement of islet cells by islet-like cells derived from embryonic or adult stem cells, and re-establishment of immunological tolerance to islet self-antigens through regulatory T cells and/or tolerance-promoting monocyte-derived cells. A combination of both approaches will be required to turn cell-based therapy of T1D into clinical success.

Circulating CD4+CD25 high regulatory T cells and natural killer T cells in children with newly diagnosed type 1 diabetes or with diabetes-associated autoantibodies

Type 1 diabetes is a T-cell-mediated autoimmune disease in which insufficient regulatory mechanisms are perceived to be involved in the pathogenesis. We used flow cytometry to analyze the proportion of CD4(+)CD25(high) regulatory T cells and natural killer T (NKT) cells in peripheral blood obtained from 25 children with newly diagnosed type 1 diabetes, 21 nondiabetic subjects positive for two or more diabetes-associated autoantibodies, and from 39 autoantibody-negative age- and HLA-matched control subjects. CD4(+)CD25(high) T cells were also stained for additional markers HLA-DR, CD69, and CD62L. As NKT cell markers, we used CD161, V beta 11, and V alpha 24. The frequency of CD4(+)CD25(high)HLA-DR(-) T cells was significantly higher in multiple autoantibody-positive children than in controls (P = 0.021). We also detected a significantly higher level of CD4(+)CD25(high)HLA-DR(-) and CD4(+)CD25(high)CD69(-) T cells among children expressing three to four autoantibodies when compared to the controls (P = 0.004 and P = 0.048, respectively). The proportions of CD161(+)V beta 11(+) or V alpha 24(+)V beta 11(+) NKT cells were similar in all three groups of children studied. Interestingly, children with only two autoantibodies had a higher level of CD161(+)V beta 11(+) NKT cells than the controls (P = 0.002). Our data might be interpreted as indicative of an intensified regulatory response of regulatory T cells and NKT cells during the preclinical phase of the disease.

Oxidant stress, immune dysregulation, and vascular function in type I diabetes

Although high glucose is an important contributor to diabetic vasculopathies, complications still occur in spite of tight glycemic control, suggesting that some critical event prior to or concurrent with hyperglycemia may contribute to early vascular changes. Utilizing previously published and new experimental evidence, this review will discuss how prior to the hyperglycemic state, an imbalance between oxidants and antioxidants may contribute to early vascular dysfunction and set in motion proinflammatory insults that are further amplified as the diabetes develops. This imbalance results from the resetting of the equilibrium between vessel superoxide/H(2)O(2) production and/or decreased antioxidant defenses. Such an imbalance may cause endothelial dysfunction, characterized by abnormal endothelium-dependent vasoreactivity, as the first sign of blood vessel damage, followed by morphological changes of the vessel wall and inflammation. As such, increased oxidant stress in preglycemic states may be a critically central initiating event that underlies the pathogenesis of life-threatening vascular diseases in autoimmune diabetes. This review focuses on the relationship between oxidative stress, immune dysregulation, and vascular injury in type 1 diabetes, and how the discovery of novel pathways of vascular disease in nonobese diabetic mice may direct future studies in patients with type 1 diabetes.

Mechanistic insights into targeting T cell membrane proteinase to promote islet beta-cell rejuvenation in type 1 diabetes

It has been well established that invasion-promoting membrane type-1 matrix metalloproteinase (MT1-MMP), a multifunctional membrane-tethered enzyme, functions in cancer cells as a mediator of pericellular proteolysis and directly cleaves several cell surface receptors, including CD44. In this report, we confirm that adhesion of diabetogenic T cells promotes the activation of endogenous MT1-MMP. Activated protease then cleaves CD44 in adherent T cells. We have validated that the T cell CD44 receptor is critical for the adhesion of diabetogenic insulin-specific, CD8-positive, K(d)-restricted cells to the matrix as well as for the subsequent transmigration of the adherent T cells through the endothelium and homing of the transmigrated T cells into the pancreatic islets. We have determined that the inhibition of MT1-MMP by low dosages of AG3340 (a subnanomolar range hydroxamate inhibitor of MMPs that has been widely tested in cancer patients) inhibited both T cell MT1-MMP activity and MT1-MMP-dependent shedding of CD44, immobilized T cells on the endothelium, repressed the homing of diabetogenic T cells into the pancreatic islets, reduced insulitis and mononuclear cell infiltration, and promoted either the recovery or the rejuvenation of the functional insulin-producing beta cells in diabetic NOD mice with freshly developed type I diabetes (IDDM). We believe our data constitute a mechanistic and substantive rationale for clinical trials of selected MT1-MMP inhibitors in the therapy of IDDM in humans.

Innate (over)immunity and adaptive autoimmune disease

Autoimmune disease is characterized by clinical symptoms mediated by adaptive (T cell and B cell) immune reactions towards autoantigen-expressing tissue. Here we discuss that autoimmune disease is often preceded by autoreactivity, meaning the priming of autoantigen-specific immune cells without relevant tissue damage. Recent experimental evidence has demonstrated that both the induction of autoreactivity and the conversion into autoimmune disease is controlled by the activation of the nonspecific innate immune system. Also, the "inflammatory status" of the target organ critically influences the onset of overt autoimmune disease.

Effects of polyinosinic-polycytidylic acid and adoptive transfer of immune cells in the Lew.1AR1-iddm rat and in its coisogenic LEW.1AR1 background strain

The importance of the cellular immune system for the development of T1DM in the LEW.1AR1-iddm rat was investigated by use of polyinosinic-polycytidylic acid (Poly I:C) and by adoptive transfer of concanavalin A (Con A) activated lymphocytes from diabetic LEW.1AR1-iddm rats and the coisogenic LEW.AR1 background strain. Poly I:C treatment induced diabetes, characterized morphologically by a diffuse infiltration of the pancreas, in up to 20% of the animals of the coisogenic LEW.1AR1 background strain. It did not increase the diabetes incidence of 30% of the LEW.1AR1-iddm strain. In contrast Poly I:C treatment induced diabetes in up to 80% of the animals of the Mhc congenic LEW.1WR1 strain. Adoptive transfer of lymphocytes activated by the T-cell mitogen Con A from diabetic donors doubled the incidence of diabetes, characterized morphologically by a focal insulitis, in diabetes prone LEW.1AR1-iddm recipients. In contrast, animals of the LEW.1AR1 background strain did not develop diabetes after adoptive transfer. Moreover, adoptive transfer of Con A activated lymphocytes from LEW.1AR1 rats to LEW.1AR1-iddm rats with 30 or 60% diabetes incidence, significantly decreased the incidence of diabetes in LEW.1AR1-iddm rats with 60% diabetes incidence. The results show that autoreactive lymphocytes induce beta cell destruction in the LEW.1AR1-iddm rat, while the LEW.AR1 background strain apparently contains regulatory potential, which is able to counteract the autoimmune response.

Inhibition of Membrane Type-1 Matrix Metalloproteinase by Cancer Drugs Interferes with the Homing of Diabetogenic T Cells into the Pancreas

We have discovered that clinically tested inhibitors of matrix metalloproteinases can control the functional activity of T cell membrane type-1 matrix metalloproteinase (MT1-MMP) and the onset of disease in a rodent model of type 1 diabetes in non-obese diabetic mice. We determined that MT1-MMP proteolysis of the T cell surface CD44 adhesion receptor affects the homing of T cells into the pancreas. We also determined that both the induction of the intrinsic T cell MT1-MMP activity and the shedding of cellular CD44 follow the adhesion of insulin-specific, CD8-positive, Kd-restricted T cells to the matrix. Conversely, inhibition of these events by AG3340 (a potent hydroxamate inhibitor that was widely used in clinical trials in cancer patents) impedes the transmigration of diabetogenic T cells into the pancreas and protects non-obese diabetic mice from diabetes onset. Overall, our studies have divulged a previously unknown function of MT1-MMP and identified a promising novel drug target in type I diabetes.

CD4+CD25+ regulatory T cells control the progression from periinsulitis to destructive insulitis in murine autoimmune diabetes

Non-obese diabetic (NOD) mice develop spontaneous T-cell responses against pancreatic beta-cells, leading to islet cell destruction and diabetes. Despite high genetic similarity, non-obese resistant (NOR) mice do not develop diabetes. We show here that spleen cells of both NOD and NOR mice respond to the islet cell antigen glutamic acid decarboxylase-65 in IFN-gamma-ELISPOT assays. Moreover, NOR-T cells induce periinsulitis in NOD SCID recipient mice. Thus, a potentially pathogenic islet cell-specific T-cell response arises in NOR and NOD mice alike; the mechanism that prevents the autoimmune progression of self-reactive T cells in NOR mice presumably acts at the level of effector function. Consistent with this hypothesis, CD4+CD25+ cell-depleted spleen cells from NOR mice mediated islet cell destruction and overt diabetes in NOD SCID mice. Therefore, islet cell-specific effector cells in NOR mice appear to be under the control of CD4+CD25+ regulatory T cells, confirming the importance of regulatory cells in the control of autoimmune diabetes.