Low CD86 expression in the nonobese diabetic mouse results in the impairment of both T cell activation and CTLA-4 up-regulation

An injectable subcutaneous colon-specific immune niche for the treatment of ulcerative colitis

As a chronic autoinflammatory condition, ulcerative colitis is often managed via systemic immunosuppressants. Here we show, in three mouse models of established ulcerative colitis, that a subcutaneously injected colon-specific immunosuppressive niche consisting of colon epithelial cells, decellularized colon extracellular matrix and nanofibres functionalized with programmed death-ligand 1, CD86, a peptide mimic of transforming growth factor-beta 1, and the immunosuppressive small-molecule leflunomide, induced intestinal immunotolerance and reduced inflammation in the animals' lower gastrointestinal tract. The bioengineered colon-specific niche triggered autoreactive T cell anergy and polarized pro-inflammatory macrophages via multiple immunosuppressive pathways, and prevented the infiltration of immune cells into the colon's lamina propria, promoting the recovery of epithelial damage. The bioengineered niche also prevented colitis-associated colorectal cancer and eliminated immune-related colitis triggered by kinase inhibitors and immune checkpoint blockade.

Immune checkpoint modulators in early clinical development for the treatment of type 1 diabetes

INTRODUCTION

Despite the improvements of insulin therapy, people with type 1 diabetes (T1D) still suffer from a decreased quality of life and life expectancy. The search toward a cure for T1D is therefore still a scorching open field of research.

AREAS COVERED

Tackling the immune checkpoint signaling pathways has gained importance in the field of cancer immunotherapy. The same pathways can be targeted in autoimmunity with an opposite principle: to dampen the exaggerated immune response. In this review, we report a comprehensive excursus on the cellular and molecular mechanisms that lead to loss of immunological tolerance, and recent evidence on the role of immune checkpoint molecules in the development of T1D and their potential application for the mitigation of autoimmune diabetes.

EXPERT OPINION

Contrasting results about the efficacy of immune checkpoint modulators for T1D have been published, with very few molecules from preclinical studies eligible for use in humans. The heterogeneous and complex pathophysiology of T1D may explain the conflicting evidence. Designing clinical trials that acknowledge the pathophysiological and clinical complexity of T1D and that forecast the need of simultaneously tackling different disease pathways will be crucial to enhance the benefits which may be gained by such compounds.

A better understanding of the role of the CTLA-CD80/86 axis in the treatment of autoimmune diseases

Autoimmune diseases are diseases in which the regulatory mechanisms of the immune response are disturbed. As a result, the body loses self-tolerance. Since one of the main regulatory mechanisms of the immune response is the CTLA4-CD80/86 axis, this hypothesis suggests that autoimmune diseases potentially share a similar molecular basis of pathogenesis. Hence, investigating the CTLA4-CD80/86 axis may be helpful in finding an appropriate treatment strategy. Therefore, this study aims to investigate the molecular basis of the CTLA4-CD80/86 axis in the regulation of the immune response, and then its role in developing some autoimmune diseases, including systemic lupus erythematosus, rheumatoid arthritis, type 1 diabetes, and multiple sclerosis. As well, the main therapeutic strategies affecting the CTLA4-CD80/86 axis have been summarized to highlight the importance of this axis in management of autoimmune diseases.

Recent advances in developing active targeting and multi-functional drug delivery systems via bioorthogonal chemistry

Bioorthogonal chemistry reactions occur in physiological conditions without interfering with normal physiological processes. Through metabolic engineering, bioorthogonal groups can be tagged onto cell membranes, which selectively attach to cargos with paired groups via bioorthogonal reactions. Due to its simplicity, high efficiency, and specificity, bioorthogonal chemistry has demonstrated great application potential in drug delivery. On the one hand, bioorthogonal reactions improve therapeutic agent delivery to target sites, overcoming off-target distribution. On the other hand, nanoparticles and biomolecules can be linked to cell membranes by bioorthogonal reactions, providing approaches to developing multi-functional drug delivery systems (DDSs). In this review, we first describe the principle of labeling cells or pathogenic microorganisms with bioorthogonal groups. We then highlight recent breakthroughs in developing active targeting DDSs to tumors, immune systems, or bacteria by bioorthogonal chemistry, as well as applications of bioorthogonal chemistry in developing functional bio-inspired DDSs (biomimetic DDSs, cell-based DDSs, bacteria-based and phage-based DDSs) and hydrogels. Finally, we discuss the difficulties and prospective direction of bioorthogonal chemistry in drug delivery. We expect this review will help us understand the latest advances in the development of active targeting and multi-functional DDSs using bioorthogonal chemistry and inspire innovative applications of bioorthogonal chemistry in developing smart DDSs for disease treatment.

Immune Checkpoint-Bioengineered Beta Cell Vaccine Reverses Early-Onset Type 1 Diabetes

Type 1 diabetes mellitus (T1DM) is a chronic autoimmune disease that results from autoreactive T cells destroying insulin-producing pancreatic beta (β) cells. The development of T1DM is associated with the deficiency of co-inhibitory immune checkpoint ligands (e.g., PD-L1, CD86, and Gal-9) in β cells. Here, a new translational approach based on metabolic glycoengineering and bioorthogonal click chemistry, which bioengineers β cells with co-inhibitory immune checkpoint molecules that induce antigen-specific immunotolerance and reverse early-onset hyperglycemia is reported. To achieve this goal, a subcutaneous injectable acellular pancreatic extracellular matrix platform for localizing the bioengineered β cells while creating a pancreas-like immunogenic microenvironment, in which the autoreactive T cells can interface with the β cells, is devised.

B cell depletion reduces T cell activation in pancreatic islets in a murine autoimmune diabetes model

AIMS/HYPOTHESIS

Type 1 diabetes is a T cell-mediated autoimmune disease characterised by the destruction of beta cells in the islets of Langerhans, resulting in deficient insulin production. B cell depletion therapy has proved successful in preventing diabetes and restoring euglycaemia in animal models of diabetes, as well as in preserving beta cell function in clinical trials in the short term. We aimed to report a full characterisation of B cell kinetics post B cell depletion, with a focus on pancreatic islets.

METHODS

Transgenic NOD mice with a human CD20 transgene expressed on B cells were injected with an anti-CD20 depleting antibody. B cells were analysed using multivariable flow cytometry.

RESULTS

There was a 10 week delay in the onset of diabetes when comparing control and experimental groups, although the final difference in the diabetes incidence, following prolonged observation, was not statistically significant (p = 0.07). The co-stimulatory molecules CD80 and CD86 were reduced on stimulation of B cells during B cell depletion and repopulation. IL-10-producing regulatory B cells were not induced in repopulated B cells in the periphery, post anti-CD20 depletion. However, the early depletion of B cells had a marked effect on T cells in the local islet infiltrate. We demonstrated a lack of T cell activation, specifically with reduced CD44 expression and effector function, including IFN-γ production from both CD4⁺ and CD8⁺ T cells. These CD8⁺ T cells remained altered in the pancreatic islets long after B cell depletion and repopulation.

CONCLUSIONS/INTERPRETATION

Our findings suggest that B cell depletion can have an impact on T cell regulation, inducing a durable effect that is present long after repopulation. We suggest that this local effect of reducing autoimmune T cell activity contributes to delay in the onset of autoimmune diabetes.

Co-stimulatory and Co-inhibitory Pathways in Autoimmunity

The immune system is guided by a series of checks and balances, a major component of which is a large array of co-stimulatory and co-inhibitory pathways that modulate the host response. Although co-stimulation is essential for boosting and shaping the initial response following signaling through the antigen receptor, inhibitory pathways are also critical for modulating the immune response. Excessive co-stimulation and/or insufficient co-inhibition can lead to a breakdown of self-tolerance and thus to autoimmunity. In this review, we will focus on the role of co-stimulatory and co-inhibitory pathways in two systemic (systemic lupus erythematosus and rheumatoid arthritis) and two organ-specific (multiple sclerosis and type 1 diabetes) emblematic autoimmune diseases. We will also discuss how mechanistic analysis of these pathways has led to the identification of potential therapeutic targets and initiation of clinical trials for autoimmune diseases, as well as outline some of the challenges that lie ahead.

Impaired dendritic cell function in a spontaneous autoimmune polyneuropathy

Spontaneous autoimmune polyneuropathy (SAP) in B7-2 knockout NOD mice mimics the progressive form of chronic inflammatory demyelinating polyradiculoneuropathy, and is mediated by myelin protein zero (P0)-reactive Th1 cells. In this study, we focused on the effect of B7-2 deletion on the function of dendritic cells (DCs) within the context of SAP. We found that development of SAP was associated with a preponderance or increase of CD11b(+) DCs in peripheral lymph nodes and sciatic nerves. B7-2 deletion led to altered immunophenotypic properties that differ between CD11b(+) DCs and CD8α(+) DCs. Both DC subsets from B7-2 knockout NOD mice exhibited impaired capacity to capture fluorophore-labeled myelin P0, but diminished Ag-presenting function was observed only in CD11b(+) DCs. Clinical assessment, electrophysiologic studies, and splenocyte proliferation studies revealed that absence of B7-2 on DCs was sufficient to cause impaired ability to induce tolerance to P0, which could be overcome by preconditioning with IL-10. Tolerance induction by Ag-pulsed wild-type NOD DCs was dependent on IL-10 and was associated with increased CD4(+) regulatory T cells, whereas tolerance induction by IL-10-conditioned B7-2-deficient DCs was associated with increased percentages of both regulatory T cells and B10 cells in the spleen. We conclude that B7-2 deletion has an impact on the distribution of DC subsets in lymphoid organs and alters the expression of costimulatory molecules, but functional consequences are not uniform across DC subsets. Defective tolerance induction in the absence of B7-2 can be restored by preconditioning of DCs with IL-10.

Prevention of autoimmune diabetes by DNA vaccination

DNA vaccination with antigen expression plasmids has been introduced as a simple method of inducing immunity to the antigens of infectious agents or tumors. Although DNA vaccination is generally immunostimulatory, it is possible to design suppressive vaccines that protect against autoimmune diseases such as Type 1 diabetes. In mice prone to diabetes, investigators have delivered a plasmid encoding an islet-cell antigen such as insulin B chain, glutamic acid decarboxylase, or antigen/immunoglobulin G-Fc fusion constructs, with or without co-delivery of another gene encoding a cytokine or other immunoregulatory molecule. This approach has led to protection against disease, related to the generation of regulatory T-cells and increased production of regulatory cytokines. DNA vaccination is a promising approach to autoimmune disease prevention.

Characterisation of the T cell and dendritic cell repertoire in a murine model of mucopolysaccharidosis I (MPS I)

BACKGROUND

Mucopolysaccharidosis I (MPS I) is a metabolic disorder caused by α-L-Iduronidase (IDUA) deficiency, resulting in lysosomal accumulation of heparan (HS) and dermatan sulphate (DS). This has been reported in microglia, yet currently the effect of IDUA deficiency on T cells and dendritic cells (DC) and their functionality in disease pathogenesis remains unclear.

METHODS

Peripheral blood was collected from 3 month old C57BL/6 MPS I (n = 11) and wildtype (WT) (n = 6) mice. T cell and DC phenotype and functional characteristics were identified by flow cytometry.

RESULTS

MPS I mice exhibited a reduction in DC (p = <0.001) along with CD8+ cytotoxic (p = 0.01) and CD4+ T helper (p = 0.032) cells, compared to WT controls. MPS I DC displayed a significant decrease in cell surface CD123 (p = 0.02) and CD86 (p = 0.006) expression. Furthermore, CD45RB expression was significantly reduced on T helper cells in the MPS I population (p = 0.019).

CONCLUSION

We report a reduction in circulating DC and T cells in the MPS I mouse; indicative of adaptive immune dysfunction. DC reduction may occur in response to down-regulation of the IL-3 receptor (CD123), necessary for DC survival. We also report down-regulation of cell surface CD86, a molecule required for T cell co-stimulation. T helper cell down-regulation of CD45RB is redolent of an anti-inflammatory phenotype with poor proliferative capacity. The definitive causes of our findings and the consequences and role that these findings play in the pathogenesis of MPS are unclear, but may be in response to lysosomal storage of unmetabolized HS and DS.

Th17 cells in type 1 diabetes

T1D is an autoimmune disorder, which involves the CD4(+) as well as CD8(+) T-cell-mediated destruction of β cells. Recently, another population of T cells (Th17) is found to be involved in T1D pathology. This review will discuss the characteristics of Th17 cells and the mechanism of Th17-mediated T1D development. Th17 cell expansion is unstrained under T1D condition. Certain Treg cells are defective in T1D and lose the control of Th17 expansion. In addition, the altered function of APCs and a subset of monocytes which spontaneously secrete IL-1β and IL-6 in T1D determine the abnormal expansion of Th17 as well. The pathogenic Th17 cells can cause the imbalance between Teff and Treg cells. Conversion from Th17 to Th1 phenotype and Th17 stimulated CTL responses may play an accessory role in T1D as well. Due to the effects of Th17 on T1D, therapeutic strategies designed to inhibit these cells are applicable and the positive effects are obvious. Taken together, Th17 may exert essential effects on the development of T1D. Identification of the underlying mechanism may inspire new viewpoints for the therapy of this disease.

Differential IL-21 signaling in APCs leads to disparate Th17 differentiation in diabetes-susceptible NOD and diabetes-resistant NOD.Idd3 mice

Type 1 diabetes (T1D) is an autoimmune disease that shows familial aggregation in humans and likely has genetic determinants. Disease linkage studies have revealed many susceptibility loci for T1D in mice and humans. The mouse T1D susceptibility locus insulin-dependent diabetes susceptibility 3 (Idd3), which has a homologous genetic interval in humans, encodes cytokine genes Il2 and Il21 and regulates diabetes and other autoimmune diseases; however, the cellular and molecular mechanisms of this regulation are still being elucidated. Here we show that T cells from NOD mice produce more Il21 and less Il2 and exhibit enhanced Th17 cell generation compared with T cells from NOD.Idd3 congenic mice, which carry the protective Idd3 allele from a diabetes-resistant mouse strain. Further, APCs from NOD and NOD.Idd3 mice played a central role in this differential Th17 cell development, and IL-21 signaling in APCs was pivotal to this process. Specifically, NOD-derived APCs showed increased production of pro-Th17 mediators and dysregulation of the retinoic acid (RA) signaling pathway compared with APCs from NOD.Idd3 and NOD.Il21r-deficient mice. These data suggest that the protective effect of the Idd3 locus is due, in part, to differential RA signaling in APCs and that IL-21 likely plays a role in this process. Thus, we believe APCs provide a new candidate for therapeutic intervention in autoimmune diseases.

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

OBJECTIVE

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

MATERIALS AND METHODS

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

RESULTS

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

CONCLUSIONS

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

NOD dendritic cells stimulated with Lactobacilli preferentially produce IL-10 versus IL-12 and decrease diabetes incidence

Dendritic cells (DCs) from NOD mice produced high levels of IL-12 that induce IFNγ-producing T cells involved in diabetes development. We propose to utilize the microorganism ability to induce tolerogenic DCs to abrogate the proinflammatory process and prevent diabetes development. NOD DCs were stimulated with Lactobacilli (nonpathogenic bacteria targeting TLR2) or lipoteichoic acid (LTA) from Staphylococcus aureus (TLR2 agonist). LTA-treated DCs produced much more IL-12 than IL-10 and accelerated diabetes development when transferred into NOD mice. In contrast, stimulation of NOD DCs with L. casei favored the production of IL-10 over IL-12, and their transfer decreased disease incidence which anti-IL-10R antibodies restored. These data indicated that L. casei can induce NOD DCs to develop a more tolerogenic phenotype via production of the anti-inflammatory cytokine, IL-10. Evaluation of the relative production of IL-10 and IL-12 by DCs may be a very useful means of identifying agents that have therapeutic potential.

Emerging roles for B lymphocytes in Type 1 diabetes

Self-reactive B lymphocytes play two main pathological roles in autoimmune diseases: as secretors of autoantibodies and as specialized antigen-presenting cells that present self-components to autoreactive T lymphocytes. In recognition of these roles, recent clinical trials have utilized B-lymphocyte-depleting monoclonal antibodies to treat various autoimmune diseases, with encouraging results in those where humoral autoimmunity is clearly important. Surprisingly, recent results in animal models suggest that B-lymphocyte depletion may also be effective in the treatment of T-lymphocyte-mediated autoimmune diseases, such as Type 1 diabetes (T1D). This article reviews the experimental evidence that has uncovered pathogenic as well as regulatory roles for B lymphocytes in the prodrome of T1D and how this information is being used to develop novel therapeutic strategies to treat the disease.

Dendritic cell-directed CTLA-4 engagement during pancreatic beta cell antigen presentation delays type 1 diabetes

The levels of expression of alternatively spliced variants of CTLA-4 and insufficient CTLA-4 signaling have been implicated in type 1 diabetes. Hence, we hypothesized that increasing CTLA-4-specific ligand strength on autoantigen-presenting dendritic cells (DCs) can enhance ligation of CTLA-4 on T cells and lead to modulation of autoreactive T cell response. In this study, we show that DC-directed enhanced CTLA-4 engagement upon pancreatic beta cell Ag presentation results in the suppression of autoreactive T cell response in NOD mice. The T cells from prediabetic NOD mice treated with an agonistic anti-CTLA-4 Ab-coated DC (anti-CTLA-4-Ab DC) showed significantly less proliferative response and enhanced IL-10 and TGF-beta1 production upon exposure to beta cell Ags. Furthermore, these mice showed increased frequency of Foxp3+ and IL-10+ T cells, less severe insulitis, and a significant delay in the onset of hyperglycemia compared with mice treated with control Ab-coated DCs. Further analyses showed that diabetogenic T cell function was modulated primarily through the induction of Foxp3 and IL-10 expression upon Ag presentation by anti-CTLA-4-Ab DCs. The induction of Foxp3 and IL-10 expression appeared to be a consequence of increased TGF-beta1 production by T cells activated using anti-CTLA-4-Ab DCs, and this effect could be enhanced by the addition of exogenous IL-2 or TGF-beta1. Collectively, this study demonstrates the potential of a DC-directed CTLA-4 engagement approach not only in treating autoimmunity in type 1 diabetes, but also in altering diabetogenic T cell function ex vivo for therapy.

The potential utility of bone marrow or umbilical cord blood transplantation for the treatment of type I diabetes mellitus

The pathology of type 1 diabetes mellitus (T1D) involves the autoimmune destruction or malfunction of pancreatic β cells, leading to a lack of insulin. The absence of insulin is life-threatening, necessitating daily hormone injections from an exogenous source. Insulin injections do not adequately mimic the precise regulation of β cells on glucose homeostasis, however, eventually leading to complications in diabetic patients. There currently is no definitive cure for T1D. Pancreas transplantation, although quite successful, is an invasive intervention that is restricted to patients with advanced complications, requires constant immunosuppression, and is severely limited by donor availability. Recent progress in human islet cell isolation and immunosuppressive protocols has restored euglycemia in patients who received islet cells from 2 or 3 pancreas donors. However, because of the scarcity of cadaver pancreata and the low yield of islet cells obtained by the procedure, not all patients have access to this surgical intervention. Thus, other therapeutic approaches are needed to arrest immune aggression, preserve β cell mass, and provide efficient replacement. In this sense, bone marrow and umbilical cord blood transplantation are promising possibilities that merit exploration. In this review, we summarize multiple strategies that have been proposed and tested for potential therapeutic benefit in patients with T1D.

Invariant natural killer T-cell control of type 1 diabetes: a dendritic cell genetic decision of a silver bullet or Russian roulette

OBJECTIVE

In part, activation of invariant natural killer T (iNKT)-cells with the superagonist alpha-galactosylceramide (alpha-GalCer) inhibits the development of T-cell-mediated autoimmune type 1 diabetes in NOD mice by inducing the downstream differentiation of antigen-presenting dendritic cells (DCs) to an immunotolerogenic state. However, in other systems iNKT-cell activation has an adjuvant-like effect that enhances rather than suppresses various immunological responses. Thus, we tested whether in some circumstances genetic variation would enable activated iNKT-cells to support rather than inhibit type 1 diabetes development.

RESEARCH DESIGN AND METHODS

We tested whether iNKT-conditioned DCs in NOD mice and a major histocompatibility complex-matched C57BL/6 (B6) background congenic stock differed in capacity to inhibit type 1 diabetes induced by the adoptive transfer of pathogenic AI4 CD8 T-cells.

RESULTS

Unlike those of NOD origin, iNKT-conditioned DCs in the B6 background stock matured to a state that actually supported rather than inhibited AI4 T-cell-induced type 1 diabetes. The induction of a differing activity pattern of T-cell costimulatory molecules varying in capacity to override programmed death-ligand-1 inhibitory effects contributes to the respective ability of iNKT-conditioned DCs in NOD and B6 background mice to inhibit or support type 1 diabetes development. Genetic differences inherent to both iNKT-cells and DCs contribute to their varying interactions in NOD and B6.H2(g7) mice.

CONCLUSIONS

This great variability in the interactions between iNKT-cells and DCs in two inbred mouse strains should raise a cautionary note about considering manipulation of this axis as a potential type 1 diabetes prevention therapy in genetically heterogeneous humans.

Aberrancies in Antigen-presenting Cells and T Cells in Autoimmune Thyroid Disease. A Role in Faulty Tolerance Induction

Various thyrocyte, monocyte, macrophage, DC and T cell abnormalities exist in the animal models of spontaneously developing autoimmune thyroiditis and in patients with autoimmune thyroid disease. An aberrant interaction between such abnormal thyrocytes, abnormal professional antigen-presenting cells (APC) and abnormal T cells forms the basis for the atypical autoimmune reaction targeting thyroid antigens. In the atypical interaction more than one gene and various environmental factors are involved. The genetic and environmental factors must act together to induce full-blown disease. Although there is a general blueprint for the development of destructive autoimmune thyroiditis, thyrocyte and immune cell abnormalities differ between the various animal models and the various forms of autoimmune thyroid disease (either associated with type 1 diabetes, associated with bipolar disorder or not associated). This tells us that there are different etio-pathogenic forms of destructive autoimmune thyroiditis. Whether such heterogeneity is also the case for the etio-pathogenesis of Graves' disease remains unknown. Animal models of spontaneously developing Graves' disease would be helpful in unraveling this question. If indeed there are various etio-pathogenic routes in different patients that lead to destructive autoimmune thyroiditis, then tailor-made therapeutic approaches need to be carried out in attempts to correct the underlying immune abnormalities in individual patients or to prevent the development of destructive autoimmune thyroiditis in individuals at risk. While in some forms of destructive autoimmune thyroiditis (f.i. those associated with bipolar disorder) immune suppression should be the first choice of intervention, other forms (f.i. those associated with type 1 diabetes) may benefit from immune stimulation in certain pre-stages of the disease (to restore f.i. the faulty APC function characteristic of this condition). Obviously a more precise determination of the spectrum of cell-mediated immune abnormalities is required in individual cases of destructive autoimmune thyroiditis, before therapies that aim at correcting the immune abnormalities can be tested successfully.

Modulation of dendritic cells using granulocyte-macrophage colony-stimulating factor (GM-CSF) delays type 1 diabetes by enhancing CD4+CD25+ regulatory T cell function

Abnormalities in DC function are implicated in defective immune regulation that leads to type-1 diabetes (T1D) in NOD mice and humans. In this study, we used GM-CSF and Flt3-L to modulate DC function in NOD mice and observed the effects on T1D development. Treatment with either ligand at earlier stages of insulitis suppressed the development of T1D. Unlike Flt3-L, GM-CSF was more effective in suppressing T1D, even when administered at later stages of insulitis. In vitro studies and in vivo adoptive transfer experiments revealed that CD4+CD25+ T cells from GM-CSF-treated mice could suppress effector T cell response and T1D. This suppression is likely mediated through enhanced IL-10 and TGF-beta1 production. Adoptive transfer of GM-CSF exposed DCs to naive mice resulted in an expansion of Foxp3+ T cells and a significant delay in T1D onset. Our results indicate that GM-CSF acted primarily on DCs and caused an expansion of Foxp3+ Tregs which delayed the onset of T1D in NOD mice.

Clinical application of NKT cell biology in type I (autoimmune) diabetes mellitus

Type 1 natural killer T (NKT) cells are a population of CD1d-restricted, regulatory T cells that exhibit various NK cell characteristics and rapidly produce cytokines on stimulation with glycolipid antigen. In type I diabetes (TID), NKT cells are thought to have a tolerogenic function, evidenced by NKT cell numerical and functional deficiencies in the nonobese diabetic (NOD) mouse, which when corrected, can ameliorate disease. The mechanisms by which NKT cells can mediate their immunosuppressive effects in NOD mice are still poorly understood, which makes successful clinical translation of NKT- cell-based therapies challenging. However, new insights into the genetic control of NKT cell deficiencies have provided some understanding of the genes that may control NKT cell number and function, potentially offering a new avenue for assessing TID risk in humans. Here, we review the mechanisms by which NKT cells are thought to prevent TID, discuss the evidence for involvement of NKT cells in the regulation of human TID and examine the genetic control of NKT cell number and function. A greater understanding of these areas will increase the chances of successful clinical manipulation of NKT cells to prevent or treat TID.

Lowered expressions of the NF-kappaB family members in dendritic cells from NOD mice are associated with a reduced expression of GATA-2

In type 1 diabetes, dendritic cells (DCs) display defective phenotype and function and possibly play crucial roles in the pathogenesis of this disease. In the present study, we compared transcription profiles of CD11c(+) bone marrow (BM)-derived DCs from NOD mice with those from NON mice, focusing on the NF-kappaB/Rel family members and associated molecules. The BMDCs from NOD mice displayed reduced mRNA expressions of NF-kappaB components, p65, p50, p52, and RelB, compared to NON mice: the proportions of each molecule relative to those of NON DCs were 53.9, 54.1, 54.0, and 37.0%, respectively, which were accompanied with lowered expressions of downstream immunomodulatory molecules, including IL-6, CD80, CD86, 4-1BB, and CD40. The reduction of NF-kappaB components possibly underlies the defective phenotype and function of DCs from NOD mice, and could predispose to autoimmunity.

APC activation restores functional CD4(+)CD25(+) regulatory T cells in NOD mice that can prevent diabetes development

Background

Defects in APC and regulatory cells are associated with diabetes development in NOD mice. We have shown previously that NOD APC are not effective at stimulating CD4⁺CD25⁺ regulatory cell function in vitro. We hypothesize that failure of NOD APC to properly activate CD4⁺CD25⁺ regulatory cells in vivo could compromise their ability to control pathogenic cells, and activation of NOD APC could restore this defect, thereby preventing disease.

Methodology/Principal Findings

To test these hypotheses, we used the well-documented ability of complete Freund's adjuvant (CFA), an APC activator, to prevent disease in NOD mice. Phenotype and function of CD4⁺CD25⁺ regulatory cells from untreated and CFA-treated NOD mice were determined by FACS, and in vitro and in vivo assays. APC from these mice were also evaluated for their ability to activate regulatory cells in vitro. We have found that sick NOD CD4⁺CD25⁺ cells expressed Foxp3 at the same percentages, but decreased levels per cell, compared to young NOD or non-NOD controls. Treatment with CFA increased Foxp3 expression in NOD cells, and also increased the percentages of CD4⁺CD25⁺Foxp3⁺ cells infiltrating the pancreas compared to untreated NOD mice. Moreover, CD4⁺CD25⁺ cells from pancreatic LN of CFA-treated, but not untreated, NOD mice transferred protection from diabetes. Finally, APC isolated from CFA-treated mice increased Foxp3 and granzyme B expression as well as regulatory function by NOD CD4⁺CD25⁺ cells in vitro compared to APC from untreated NOD mice.

Conclusions/Significance

These data suggest that regulatory T cell function and ability to control pathogenic cells can be enhanced in NOD mice by activating NOD APC.

CD40 on NOD CD4 T cells contributes to their activation and pathogenicity

Our goals in this study were to investigate conditions under which T cells from NOD mice express CD40 and to determine how CD40 on autoreactive CD4 T cells contributes to their pathogenicity in T1D. Using CD40-positive diabetogenic T cell clones and CD4 T cells from NOD mice, we examined expression of CD40 upon activation through the TCR and costimulation through either CD28 or CD40. Our results indicate that CD40 expression is increased upon activation with antigen/MHC and that activation of NOD CD4 T cells through TCR/CD40 rapidly induced CD40 expression. Furthermore, CD40 costimulation promoted T cell proliferation to the same extent as costimulation through TCR/CD28. Importantly, costimulation of CD4 T cells through CD40 also interfered with T cell homeostasis by altering regulation of CTLA-4 expression. Through CD40-CD154 blocking studies, we demonstrated that signaling between T cells through CD40 and its ligand contributes to activation of pathogenic T cells and that blocking CD40 on T cells abrogates their ability to transfer diabetes. Thus, costimulation through CD40 on NOD T cells contributes to their pathogenicity by providing additional pathways for activation and by inhibiting upregulation of CTLA-4 during T cell activation.

Vitamin D and human health: lessons from vitamin D receptor null mice

The vitamin D endocrine system is essential for calcium and bone homeostasis. The precise mode of action and the full spectrum of activities of the vitamin D hormone, 1,25-dihydroxyvitamin D [1,25-(OH)(2)D], can now be better evaluated by critical analysis of mice with engineered deletion of the vitamin D receptor (VDR). Absence of a functional VDR or the key activating enzyme, 25-OHD-1alpha-hydroxylase (CYP27B1), in mice creates a bone and growth plate phenotype that mimics humans with the same congenital disease or severe vitamin D deficiency. The intestine is the key target for the VDR because high calcium intake, or selective VDR rescue in the intestine, restores a normal bone and growth plate phenotype. The VDR is nearly ubiquitously expressed, and almost all cells respond to 1,25-(OH)(2)D exposure; about 3% of the mouse or human genome is regulated, directly and/or indirectly, by the vitamin D endocrine system, suggesting a more widespread function. VDR-deficient mice, but not vitamin D- or 1alpha-hydroxylase-deficient mice, and man develop total alopecia, indicating that the function of the VDR and its ligand is not fully overlapping. The immune system of VDR- or vitamin D-deficient mice is grossly normal but shows increased sensitivity to autoimmune diseases such as inflammatory bowel disease or type 1 diabetes after exposure to predisposing factors. VDR-deficient mice do not have a spontaneous increase in cancer but are more prone to oncogene- or chemocarcinogen-induced tumors. They also develop high renin hypertension, cardiac hypertrophy, and increased thrombogenicity. Vitamin D deficiency in humans is associated with increased prevalence of diseases, as predicted by the VDR null phenotype. Prospective vitamin D supplementation studies with multiple noncalcemic endpoints are needed to define the benefits of an optimal vitamin D status.

Genetic background of IL-10(-/-) mice alters host-pathogen interactions with Campylobacter jejuni and influences disease phenotype

We hypothesized that particular genetic backgrounds enhance rates of colonization, increase severity of enteritis, and allow for extraintestinal spread when inbred IL-10(-/-) mice are infected with pathogenic C. jejuni. Campylobacter jejuni stably colonized C57BL/6 and NOD mice, while congenic strains lacking IL-10 developed typhlocolitis following colonization that mimicked human campylobacteriosis. However, IL-10 deficiency alone was not necessary for the presence of C. jejuni in extraintestinal sites. C3H/HeJ tlr4(-/-) mice that specifically express the Cdcs1 allele showed colonization and limited extraintestinal spread without enteritis implicating this interval in the clinical presentation of C. jejuni infection. Furthermore, when the IL-10 gene is inactivated as in C3Bir tlr4(-/-) IL-10(-/-) mice, enteritis and intensive extraintestinal spread were observed, suggesting that clinical presentations of C. jejuni infection are controlled by a complex interplay of factors. These data demonstrate that lack of IL-10 had a greater effect on C. jejuni induced colitis than other immune elements such as TLR4 (C3H/HeJ, C3Bir IL-10(-/-)), MHC H-2g7, diabetogenic genes, and CTLA-4 (NOD) and that host genetic background is in part responsible for disease phenotype. C3Bir IL-10(-/-) mice where Cdcs1 impairs gut barrier function provide a new murine model of C. jejuni and can serve as surrogates for immunocompromised patients with extraintestinal spread.

Impaired SLAM-SLAM homotypic interaction between invariant NKT cells and dendritic cells affects differentiation of IL-4/IL-10-secreting NKT2 cells in nonobese diabetic mice

The regulatory function of invariant NKT (iNKT) cells for tolerance induction and prevention of autoimmunity is linked to a specific cytokine profile that comprises the secretion of type 2 cytokines like IL-4 and IL-10 (NKT2 cytokine profile). The mechanism responsible for iNKT cell differentiation toward a type 2 phenotype is unknown. Herein we show that costimulatory signals provided by the surface receptor signaling lymphocytic activation molecule (SLAM) on myeloid dendritic cells (mDC) to iNKT cells is crucial for NKT2 orientation. Additionally, we demonstrate that the impaired acquisition of an NKT2 cytokine phenotype in nonobese diabetic (NOD) mice that spontaneously develop autoimmune diabetes is due to defective SLAM-induced signals generated by NOD mDC. Mature mDC of C57BL/6 mice express SLAM and induce C57BL/6 or NOD iNKT cells to acquire a predominant NKT2 cytokine phenotype in response to antigenic stimulation with the iNKT cell-specific Ag, the alpha-galactosylceramide. In contrast, mature NOD mDC express significantly lower levels of SLAM and are unable to promote GATA-3 (the SLAM-induced intracellular signal) up-regulation and IL-4/IL-10 production in iNKT cells from NOD or C57BL/6 mice. NOD mice carry a genetic defect of the Slamf1 gene that is associated with reduced SLAM expression on double-positive thymocytes and altered iNKT cell development in the thymus. Our data suggest that the genetic Slamf1 defect in NOD mice also affects SLAM expression on other immune cells such as the mDC, thus critically impairing the peripheral differentiation of iNKT cells toward a regulatory NKT2 type.

Autologous umbilical cord blood infusion for type 1 diabetes

OBJECTIVE

The physical, emotional, and economic costs of type 1 diabetes (T1D) mandate continued efforts to develop effective strategies to prevent or reverse the disease. Herein, we describe the scientific and therapeutic rationale underlying efforts utilizing umbilical cord blood (UCB) as a therapy for ameliorating the progression of this autoimmune disease.

MATERIALS AND METHODS

We recently embarked on a pilot study to document the safety and potential efficacy of autologous UCB infusion in subjects with T1D. Under this protocol, patients recently diagnosed with the disease and for whom autologous cord blood is stored, undergo infusion. Studies are performed before infusion and every 3 to 6 months postinfusion for immunologic and metabolic assessment. To date, 15 autologous infusions have been performed.

RESULTS

Preliminary observations suggest that autologous cord blood transfusion is safe and provides some slowing of the loss of endogenous insulin production in children with T1D. Mechanistic studies demonstrate that umbilical cord blood contains highly functional populations of regulatory T cells (Treg) and that increased Treg populations may be found in the peripheral blood of subjects more than 6 months after cord blood infusion. We provide the rationale for cord blood-based therapies, a summary of our initial protocol, and plans for future studies designed to explore the potential of cord blood-derived regulatory T cells to treat T1D.

CONCLUSIONS

Prolonged follow-up and additional mechanistic efforts are urgently needed to determine if umbilical cord blood-derived stem cells can be used as part of safe and effective therapies for T1D.

Unaltered diabetes presentation in NOD mice lacking the vitamin D receptor

OBJECTIVE

Vitamin D deficiency increases risk for type 1 diabetes in genetically predisposed individuals, while high doses of 1,25-dihydroxyvitamin D(3) [1,25(OH)(2)D(3)] prevent insulitis and diabetes in NOD mice.

RESEARCH DESIGN AND METHODS

Since 1,25(OH)(2)D(3) regulates gene transcription through the vitamin D receptor (VDR), we investigated the role of VDR in diabetes development by creating NOD mice without functional VDR.

RESULTS

VDR(-/-) NOD mice are rachitic and have lower numbers of putative regulator cells [TCR-alpha/beta(+)CD4(-)CD8(-) (natural killer T-cells) and CD4(+)CD25(+) T-cells [in central and peripheral immune organs compared with VDR(+/+) NOD littermates. Lipopolysaccharide-stimulated VDR(-/-) NOD macrophages expressed lower interleukin (IL)-1, IL-6, and CC chemokine ligand 2 mRNA, correlating with less nuclear translocation of p65 nuclear factor-kappaB compared with VDR(+/+) NOD macrophages. Thymic and lymph node dendritic cells from VDR(-/-) NOD mice displayed an even less mature CD11c(+)CD86(+) phenotype than VDR(+/+) NOD mice. Despite this immune phenotype linked to diabetes in NOD mice, VDR(-/-) NOD mice developed insulitis and diabetes at the same rate and incidence as VDR(+/+) NOD littermates.

CONCLUSIONS

Despite aggravating known immune abnormalities in NOD mice, disruption of VDR does not alter disease presentation in NOD mice in contrast to the more aggressive diabetes presentation in vitamin D-deficient NOD mice.

Insulin administration confers diabetes-preventive properties to NOD mice derived dendritic cells

Administration of autoantigen can be of value for prevention of autoimmune diabetes and it has been speculated that the control point of dendritic cells (DC) for the induction of peripheral tolerance may be highly relevant. We examined the properties of DC associated with immune suppression in NOD mice by insulin injection subcutaneously and the ability of which to suppress diabetes transfer by diabetogenic effector cells in secondary NOD-SCID recipients. Our data showed that the surface expressions of MHC II and CD86 on NOD-derived DC were increased after insulin treatment compared with those on PBS controlled mice. The dendritic cells with a mature phenotype and increased MLR stimulation adoptively transferred immune tolerogenic effects in secondary NOD-SCID mice, which were associated with significant greater IL-10, TGF-beta production and CD4(+)CD25(+)T differentiation from splenocytes compared with NOD-SCID control recipients. Moreover, treatment with DC remarkably decreased the incidence of diabetes in secondary recipients. These results suggest that a subtype of DC generated by insulin subcutaneous treated NOD mice confers potential protection from diabetes through polarizing the immune response towards a Th2 regulatory pathway.

Treg in type 1 diabetes

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

Regulation of type 1 diabetes by NKT cells

Type 1 diabetes is an autoimmune disease due to the destruction of insulin-producing pancreatic beta cells. Natural Killer T (NKT) cells are a T-cell subset that links the innate and adaptive immune systems. NKT cells play a key regulatory role in type 1 diabetes. The absence of NKT cells correlates with exacerbation of type 1 diabetes, whereas an increased frequency and/or activation of NKT cells prevents beta-cell autoimmunity. Various mechanisms are involved in the protective effect of NKT cells. The goal is now to translate knowledge gained from mouse models into human therapeutics.

Improved outcomes in NOD mice treated with a novel Th2 cytokine-biasing NKT cell activator

Activation of CD1d-restricted invariant NKT (iNKT) cells by alpha-galactosylceramide (alphaGalCer) significantly suppresses development of diabetes in NOD mice. The mechanisms of this protective effect are complex, involving both Th1 and Th2 cytokines and a network of regulatory cells including tolerogenic dendritic cells. In the current study, we evaluated a newly described synthetic alphaGalCer analog (C20:2) that elicits a Th2-biased cytokine response for its impact on disease progression and immunopathology in NOD mice. Treatment of NOD mice with alphaGalCer C20:2 significantly delayed and reduced the incidence of diabetes. This was associated with significant suppression of the late progression of insulitis, reduced infiltration of islets by autoreactive CD8(+) T cells, and prevention of progressive disease-related changes in relative proportions of different subsets of dendritic cells in the draining pancreatic lymph nodes. Multiple favorable effects observed with alphaGalCer C20:2 were significantly more pronounced than those seen in direct comparisons with a closely related analog of alphaGalCer that stimulated a more mixed pattern of Th1 and Th2 cytokine secretion. Unlike a previously reported Th2-skewing murine iNKT cell agonist, the alphaGalCer C20:2 analog was strongly stimulatory for human iNKT cells and thus warrants further examination as a potential immunomodulatory agent for human disease.

CD100 enhances dendritic cell and CD4+ cell activation leading to pathogenetic humoral responses and immune complex glomerulonephritis

CD100, a member of the semaphorin family, is a costimulatory molecule in adaptive immune responses by switching off CD72's negative signals. However, CD100's potential pathogenetic effects in damaging immune responses remain largely unexplored. We tested the hypothesis that CD100 plays a pathogenetic role in experimental immune complex glomerulonephritis. Daily injection of horse apoferritin for 14 days induced immune complex formation, mesangial proliferative glomerulonephritis and proteinuria in CD100-intact (CD100+/+) BALB/c mice. CD100-deficient (CD100-/-) mice were protected from histological and functional glomerular injury. They exhibited reduced deposition of Igs and C3 in glomeruli, reduced MCP-1 and MIP-2 intrarenal mRNA expression, and diminished glomerular macrophage accumulation. Attenuated glomerular injury was associated with decreased Ag-specific Ig production, reduced CD4+ cell activation and cytokine production. Following Ag injection, CD4+ cell CD100 expression was enhanced and dendritic cell CD86 expression was up-regulated. However, in CD100-/- mice, dendritic cell CD86 (but not CD80) up-regulation was significantly attenuated. Following i.p. immunization, CD86, but not CD80, promotes early Ag-specific TCR-transgenic DO11.10 CD4+ cell proliferation and IFN-gamma production, suggesting that CD100 expression enables full expression of CD86 and consequent CD4+ cell activation. Transfer of CD100+/+ DO11.10 cells into CD100-/- mice resulted in decreased proliferation demonstrating that CD100 from other sources in addition to CD100 from Ag-specific CD4+ cells plays a role in initial T cell proliferation. Although T cell-B cell interactions also may be relevant, these studies demonstrate that CD100 enhances pathogenetic humoral immune responses and promotes the activation of APCs by up-regulating CD86 expression.

Deficiency in NOD antigen-presenting cell function may be responsible for suboptimal CD4+CD25+ T-cell-mediated regulation and type 1 diabetes development in NOD mice

Various defects in antigen-presenting cells (APCs) and T-cells, including regulatory cells, have been associated with type 1 diabetes development in NOD mice. CD4(+)CD25(+) regulatory cells play a crucial role in controlling various autoimmune diseases, and a deficiency in their number or function could be involved in disease development. The current study shows that NOD mice had fewer CD4(+)CD25(+) regulatory cells, which expressed normal levels of glucocorticoid-induced tumor necrosis factor receptor and cytotoxic T-lymphocyte-associated antigen-4. We have also found that NOD CD4(+)CD25(+) cells regulate poorly in vitro after stimulation with anti-CD3 and NOD APCs in comparison with B6 CD4(+)CD25(+) cells stimulated with B6 APCs. Surprisingly, stimulation of NOD CD4(+)CD25(+) cells with B6 APCs restored regulation, whereas with the reciprocal combination, NOD APCs failed to activate B6 CD4(+)CD25(+) cells properly. Interestingly, APCs from disease-free (>30 weeks of age), but not diabetic, NOD mice were able to activate CD4(+)CD25(+) regulatory function in vitro and apparently in vivo because only spleens of disease-free NOD mice contained potent CD4(+)CD25(+) regulatory cells that prevented disease development when transferred into young NOD recipients. These data suggest that the failure of NOD APCs to activate CD4(+)CD25(+) regulatory cells may play an important role in controlling type 1 diabetes development in NOD mice.

B cells in the spotlight: innocent bystanders or major players in the pathogenesis of type 1 diabetes

It has long been established that type 1 diabetes (T1D) is a T cell-mediated autoimmune disease, with CD4+ and CD8+ T cells being largely responsible for the destruction of beta cells within the pancreatic islets of Langerhans. Although autoantibodies specific for islet cell proteins are regularly detected in individuals with T1D and can be utilized as effective markers for predicting the onset of disease, they are not believed to be directly pathogenic to beta cells. Thus, activation of autoantibody-secreting B cells has long been regarded as a secondary consequence of the ongoing self-reactive T cell response. However, recently, studies in the nonobese diabetic mouse model of disease have demonstrated that B cells are an important component in the development of T1D by virtue of their ability to act as the preferential antigen presenting cell population required for efficient expansion of diabetogenic CD4+ T cells. Furthermore, autoantibodies might also be responsible for mediating early beta cell pathogenesis in this model.

Differential MHC class II presentation of a pathogenic autoantigen during health and disease

Glucose-6-phosphate isomerase (GPI) is the target autoantigen recognized by KRN T cells in the K/BxN model of rheumatoid arthritis. T cell reactivity to this ubiquitous Ag results in the recruitment of anti-GPI B cells and subsequent immune complex-mediated arthritis. Because all APCs have the capacity to process and present this autoantigen, it is unclear why systemic autoimmunity with polyclonal B cell activation does not ensue. To this end, we examined how GPI is presented by B cells relative to other immunologically relevant APCs such as dendritic cells (DCs) and macrophages in the steady state, during different phases of arthritis development, and after TLR stimulation. Although all APCs can process and present the GPI:I-A(g7) complex, they do so with different efficiencies. DCs are the most potent at baseline and become progressively more potent with disease development correlating with immune complex uptake. Interestingly, in vivo and in vitro maturation of DCs did not enhance GPI presentation, suggesting that DCs use mechanisms to regulate the presentation of self-peptides. Non-GPI-specific B cells are the weakest APCs (100-fold less potent than DCs) and fail to productively engage KRN T cells at steady state and during arthritis. However, the ability to stimulate KRN T cells is strongly enhanced in B cells after TLR ligation and provides a mechanism whereby polyclonal B cells may be activated in the wake of an acute infection.

Altered phenotype and function of dendritic cells in children with type 1 diabetes

The importance of dendritic cells (DC) in the activation of T cells and in the maintenance of self-tolerance is well known. We investigated whether alterations in phenotype and function of DC may contribute to the pathogenesis of Type 1 diabetes (T1DM). Mature DC (mDC) from 18 children with T1DM and 10 age-matched healthy children were tested. mDC, derived from peripheral blood monocytes cultured for 6 days in presence of interleukin (IL)-4 and granulocyte-macrophage colony stimulating factor (GM-CSF) and stimulated with lipopolysaccharide (LPS) for the last 24 h, were phenotyped for the expression of the co-stimulatory molecules B7.1 and B7.2. In six patients and six controls allogenic mixed leucocyte reaction (AMLR) was performed using mDC and cord blood-derived naive T cells at a DC/T naive ratio of 1 : 200. Proliferation was assessed on day 7 by [(3)H]-thymidine incorporation assay. Mature DC derived from patients showed, compared with controls, a reduced expression of B7.1 [mean of fluorescence intensity (MFI): 36.2 +/- 14.3 versus 72.9 +/- 34.5; P = 0.004] and B7.2 (MFI: 122.7 +/- 67.5 versus 259.6 +/- 154.1; P = 0.02). We did not find differences in the HLA-DR expression (P = 0.07). Moreover, proliferative response of allogenic naive T cells cultured with mDC was impaired in the patients (13471 +/- 9917.2 versus 40976 +/- 24527.2 cpm, P = 0.04). We also measured IL-10 and IL-12 concentration in the supernatant of DC cultures. Interestingly, we observed in the patients a sevenfold higher level of IL-10 (P = 0.07) and a ninefold lower level of IL-12 (P = 0.01). Our data show a defect in the expression of the co-stimulatory molecules and an impairment of DC priming function, events that might contribute to T1DM pathogenesis.

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.

Aberrancies in the differentiation and maturation of dendritic cells from bone-marrow precursors are linked to various genes on chromosome 4 and other chromosomes of the BB-DP rat

BB-Diabetes Prone (BB-DP) rats, a model for endocrine autoimmune diseases, are severely lymphopenic, especially lacking ART2+ regulatory T cells. BB-Diabetes Resistant (DR) rats are not lymphopenic and do not develop autoimmunity. BB-DP and BB-DR rats only differ at the lymphopenia (lyp) gene (iddm2) on chromosome 4. Since BB-DP rats also show aberrancies in the differentiation of dendritic cells (DC) from bone-marrow precursors, we tested the hypothesis that F344 rats congenic for a BB-DP chromosome 4 region (42.5-93.6Mb; including the lyp gene, but also iddm4) display an in vitro DC differentiation different from normal F344 rats. Here we show that the 42.5-93.6Mb BB-DP chromosome 4 region is linked to an increased DC precursor apoptosis, a low MHC class II expression, a reduced IL-10 production and a reduced T cell stimulatory capacity of DC. From our previous report on DC differentiation defects in BB rats (only differing in iddm2) and the present report, we deduce that the abnormal apoptosis and low MHC class II expression is linked to iddm2. The reduced T cell stimulatory capacity is linked to other genes on chromosome 4 (candidate gene: iddm4). The reduced IL-10 production has a complex linkage pattern.

Of mice and men: use of animal models to identify possible interventions for the prevention of autoimmune type 1 diabetes in humans

Animal model and clinical studies indicate that type 1 diabetes (T1D) results from T cell-mediated autoimmune destruction of insulin-producing pancreatic beta-cells. This review discusses the knowledge gained from animal models about the nature of the autoreactive T cells that cause T1D and the possible basis for their development. Based on this information, the possible positive and negative aspects of various antigen-specific and non-specific immunotherapies, which could potentially prevent the onset of T1D in at risk individuals, are discussed.

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DNA vaccination with an insulin construct and a chimeric protein binding to both CTLA4 and CD40 ameliorates type 1 diabetes in NOD mice

Type 1 diabetes (T1D), a T-cell-mediated autoimmune disease, could be attributed to many defects in nonobese diabetic (NOD) mice, including deficient expressions of costimulatory molecules that impair antigen presentation. Thus, this deficient antigen presentation may result in a reduced ability to induce a tolerogenic response through negative selection/regulation of autoreactive T cells. Improperly activated T cells seem to be able to induce autoimmune responses causing diabetes. To re-establish tolerance to autoantigens by modulating costimulation, we constructed and tested a new type of DNA vaccine encoding a membrane-bound preproinsulin (mbPPI) and a chimeric gene vector encoding mutant B7.1/CD40L (mB7.1/CD40L) fusion protein. This mutant B7.1 binds CTLA4 but not CD28. We report that young NOD mice immunized with mbPPI along with mB7.1/CD40L DNA vectors significantly reduced diabetes incidence while treatment with CTLA4/IgG1 exacerbated diabetes. In conclusion, the combination of mbPPI and mB7.1/CD40L was able to protect against autoimmunity and diabetes in NOD mice possibly by promoting a more efficient presentation of autoantigen PPI and inducing specific tolerance to PPI by negatively regulating autoreactive T cells.

Defects in differentiation of bone-marrow derived dendritic cells of the BB rat are partly associated with IDDM2 (the lyp gene) and partly associated with other genes in the BB rat background

BB rats develop various organ-specific autoimmune diseases, e.g. autoimmune diabetes and thyroiditis and have proven important to dissect genetic factors that govern autoimmune disease development. The lymphopenia (lyp) gene (iddm2) is linked to autoimmune disease development and is a major genetic difference between diabetes-resistant (DR) and diabetes-prone (DP) BB rats. To study the effects of the lyp gene and other genes on dendritic cell (DC) differentiation from bone-marrow precursors, such differentiation was studied in BB-DP, BB-DR, Wistar and F344 control rats. DC of BB-DP rats showed a lower MHC class II expression as compared to BB-DR, Wistar and F344 rats. LPS-maturation did not restore this low MHC class II expression. DC of BB-DP rats also showed a poor capability to terminally differentiate into mature T cell stimulatory DC under the influence of LPS and produced significantly lower quantities of IL-10, yet these aberrancies were also found in BB-DR rats but did not occur in control rats. This study thus shows that various aberrancies exist in the differentiation of myeloid DC from bone-marrow precursors in the BB rat model of organ-specific autoimmunity. These aberrancies are multigenically determined and partly associated with iddm2 (lyp gene) and partly associated with other genes in the BB rat.

1α,25-Dihydroxyvitamin D3 restores thymocyte apoptosis sensitivity in non-obese diabetic (NOD) mice through dendritic cells

AIMS/HYPOTHESIS

Resistance of NOD thymocytes to apoptosis-inducing signals is restored by 1alpha,25-dihydroxyvitamin D3 (1alpha,25OH2D3), a therapy preventing diabetes in NOD mice. We studied whether modulation of thymocyte apoptosis is due to direct effects on thymic T lymphocytes or indirect effects via thymic dendritic cells, since both cell types constitute known targets for 1alpha,25OH2D3.

METHODS AND RESULTS

Female NOD mice were treated with 1alpha,25OH2D3 (5microg/kg/2d) from 21 to 70 days. Vehicle-treated NOD and NOR mice served as controls. Analysis of thymic T lymphocytes from 1alpha,25OH2D3)-treated mice revealed a decrease in number of apoptosis-resistant CD4+CD8+ and CD4+CD8-HSA(high) T lymphocyte subsets, higher pro-apoptotic IL-2 and FasL, and lower anti-apoptotic Bclx-L mRNA expression levels. Thymic dendritic cells from 1alpha,25OH2D3-treated NOD mice had increased CD8alpha+FasL+ and CD80+/86+ expression compared to control NOD mice. In a syngeneic co-culture system of thymocytes and thymic dendritic cells, apoptosis levels were 20% higher only in co-cultures where both T cell- and dendritic cell-compartments originated from 1alpha,25OH2D3-treated mice. Activation-induced cell death-sensitivity in peripheral T lymphocytes was comparable to levels present in NOR mice, confirming better thymic selection in 1alpha,25OH2D3-treated mice.

CONCLUSION/INTERPRETATION

We conclude that 1alpha,25OH2D3 needs both thymic T cell- and dendritic cell-compartments to exert its apoptosis-restorative effects in NOD thymocytes.