The role of interferon alpha in initiation of type I diabetes in the NOD mouse.

Type 1 diabetes (T1D) is an autoimmune disease in both humans and the nonobese diabetic (NOD) mouse, in which the insulin-producing-cells of the pancreatic islets are destroyed by a beta islet cell-specific T cell immune response. We recently reported that interferon (IFN)-α is an early trigger of the T1D process in NOD mice. Here, we show that extensive blockade of IFN-α action by a monoclonal antibody specific to IFN-α receptor 1 results in nearly complete prevention of T1D in NOD mice. Whether professional IFN-α producing cells, plasmacytoid dendritic cells (pDCs), are responsible for the initiation of T1D has been unclear. Here we demonstrate that depletion of pDCs in NOD mice by a specific mAb given at 15-25 days of age significantly delays the onset and decreases the incidence of T1D. These findings indicate that pDC and pDC-derived IFN-α are the prime initiators of the pathogenesis of T1D in NOD mice.

Interferon-alpha initiates type 1 diabetes in nonobese diabetic mice.

With the goal of identifying changes in gene expression in CD4(+) T cells during the development of diabetes in the nonobese diabetic (NOD) mouse, we used DNA microarrays to analyze gene expression in CD4(+) T cells from the pancreatic draining lymph nodes of NOD/BDC 2.5 T cell receptor transgenic and WT NOD mice at different ages. At 4 and 6 weeks of age, we found up-regulation of a number of genes that are known to be induced by IFN-alpha. IFN-alpha levels and IFN-alpha-producing plasmacytoid dendritic cells were increased in the PLNs of 3- to 4-week-old NOD mice. Moreover, blockade of IFN-alpha receptor 1 in NOD mice by a neutralizing antibody at 2-3 weeks of age significantly delayed the onset and decreased the incidence of type 1 diabetes, increased the relative number of immature dendritic cells in the PLNs, and enhanced the ability of spleen CD4(+) T cells to produce IL-4 and IL-10. These findings demonstrate that IFN-alpha in the PLNs is an essential initiator in the pathogenesis of type 1 diabetes in NOD mice.

Genomic expression profiling of TNF-alpha-treated BDC2.5 diabetogenic CD4+ T cells.

TNF-alpha plays an important role in immune regulation, inflammation, and autoimmunity. Chronic TNF exposure has been shown to down-modulate T cell responses. In a mouse T cell hybridoma model, TNF attenuated T cell receptor (TCR) signaling. We have confirmed that chronic TNF and anti-TNF exposure suppressed and increased T cell responses, respectively. In adult TCR (BDC2.5) transgenic nonobese diabetic mice, DNA microarray analysis of global gene expression in BDC2.5 CD4(+) T cells in response to chronic TNF or anti-TNF exposure showed that genes involved in functional categories including T cell signaling, cell cycle, proliferation, ubiquitination, cytokine synthesis, calcium signaling, and apoptosis were modulated. Genes such as ubiquitin family genes, cytokine inducible Src homology 2-containing genes, cyclin-dependent kinase inhibitors p21, p57, calmodulin family genes (calmodulin-1, -2, and -3) and calcium channel voltage-dependent, N type alpha1B subunit (CaV2.2) were induced by TNF, whereas Vav2, Rho GTPase-activating protein, calcium channel voltage-dependent, L type alpha1C subunit (CaV1.2), IL-1 receptor-associated kinase-1 and -2, and IL enhancer binding factor 3 were reduced by TNF. Genes such as CaV1.2 and proliferating cell nuclear antigen, repressed by TNF, were induced by anti-TNF treatment. Further, we showed that chronic TNF exposure impaired NF-kappaB and adaptor protein 1 transactivation activity, leading to T cell unresponsiveness. Thus, our results present a detailed picture of transcriptional programs affected by chronic TNF exposure and provide candidate target genes that may function to mediate TNF-induced T cell unresponsiveness.

In vitro-expanded antigen-specific regulatory T cells suppress autoimmune diabetes.

The low number of CD4+ CD25+ regulatory T cells (Tregs), their anergic phenotype, and diverse antigen specificity present major challenges to harnessing this potent tolerogenic population to treat autoimmunity and transplant rejection. In this study, we describe a robust method to expand antigen-specific Tregs from autoimmune-prone nonobese diabetic mice. Purified CD4+ CD25+ Tregs were expanded up to 200-fold in less than 2 wk in vitro using a combination of anti-CD3, anti-CD28, and interleukin 2. The expanded Tregs express a classical cell surface phenotype and function both in vitro and in vivo to suppress effector T cell functions. Most significantly, small numbers of antigen-specific Tregs can reverse diabetes after disease onset, suggesting a novel approach to cellular immunotherapy for autoimmunity.

CD4(+) T cells from glutamic acid decarboxylase (GAD)65-specific T cell receptor transgenic mice are not diabetogenic and can delay diabetes transfer.

Glutamic acid decarboxylase (GAD)65 is an early and important antigen in both human diabetes mellitus and the nonobese diabetic (NOD) mouse. However, the exact role of GAD65-specific T cells in diabetes pathogenesis is unclear. T cell responses to GAD65 occur early in diabetes pathogenesis, yet only one GAD65-specific T cell clone of many identified can transfer diabetes. We have generated transgenic mice on the NOD background expressing a T cell receptor (TCR)-specific for peptide epitope 286-300 (p286) of GAD65. These mice have GAD65-specific CD4(+) T cells, as shown by staining with an I-A(g7)(p286) tetramer reagent. Lymphocytes from these TCR transgenic mice proliferate and make interferon gamma, interleukin (IL)-2, tumor necrosis factor (TNF)-alpha, and IL-10 when stimulated in vitro with GAD65 peptide 286-300, yet these TCR transgenic animals do not spontaneously develop diabetes, and insulitis is virtually undetectable. Furthermore, in vitro activated CD4 T cells from GAD 286 TCR transgenic mice express higher levels of CTL-associated antigen (CTLA)-4 than nontransgenic littermates. CD4(+) T cells, or p286-tetramer(+)CD4(+) Tcells, from GAD65 286-300-specific TCR transgenic mice delay diabetes induced in NOD.scid mice by diabetic NOD spleen cells. This data suggests that GAD65 peptide 286-300-specific T cells have disease protective capacity and are not pathogenic.

Characteristics of autoimmunity in type 1 diabetes and type 1.5 overlap with type 2 diabetes.

This presentation is an overview of mechanisms for developing and maintaining self-tolerance in mammalian organisms. Because this meeting is focused on type 1 diabetes and its mechanisms, the discussion deals primarily with mechanisms of T-cell tolerance, since type 1 diabetes in both effector and initiator phases is primarily a T-cell-mediated autoimmune disease. Emphasis is placed on more recently discovered mechanisms of maintaining self-tolerance (autoimmune regulator [AIRE]) and a new defect in T-cell negative selection. The emerging picture is that of a polygenic disease with various combinations of different alleles of many genes with important roles in the normal immune response or normal immune responses.

Severe anaphylactic reactions to glutamic acid decarboxylase (GAD) self peptides in NOD mice that spontaneously develop autoimmune type 1 diabetes mellitus.

BACKGROUND: Insulin dependent (i.e., "type 1") diabetes mellitus (T1DM) is considered to be a T cell mediated disease in which TH1 and Tc autoreactive cells attack the pancreatic islets. Among the beta-cell antigens implicated in T1DM, glutamic acid decarboxylase (GAD) 65 appears to play a key role in the development of T1DM in humans as well as in non-obese diabetic (NOD) mice, the experimental model for this disease. It has been shown that shifting the immune response to this antigen from TH1 towards TH2, via the administration of GAD65 peptides to young NOD mice, can suppress the progression to overt T1DM. Accordingly, various protocols of "peptide immunotherapy" of T1DM are under investigation. However, in mice with experimental autoimmune encephalomyelitis (EAE), another autoimmune TH1 mediated disease that mimics human multiple sclerosis, anaphylactic shock can occur when the mice are challenged with certain myelin self peptides that initially were administered with adjuvant to induce the disease. RESULTS: Here we show that NOD mice, that spontaneously develop T1DM, can develop fatal anaphylactic reactions upon challenge with preparations of immunodominant GAD65 self peptides after immunization with these peptides to modify the development of T1DM. CONCLUSIONS: These findings document severe anaphylaxis to self peptide preparations used in an attempt to devise immunotherapy for a spontaneous autoimmune disease. Taken together with the findings in EAE, these results suggest that peptide therapies designed to induce a TH1 to TH2 shift carry a risk for the development of anaphylactic reactivity to the therapeutic peptides.

Selection of aberrant class II restricted CD8+ T cells in NOD mice expressing a glutamic acid decarboxylase (GAD)65-specific T cell receptor transgene.

We previously described the generation of non-obese diabetic (NOD) mice expressing a transgenic T cell receptor (TCR) specific for peptide epitope 286-300 of the diabetes related self antigen, glutamic acid decarboxylase (GAD)65 in the context of I-A(g7) class II MHC, that are paradoxically protected from diabetes. In this report, we examine the atypical CD8+ cells in these mice. Unlike typical class II restricted TCR transgenic mice, GAD286 mice have normal numbers of CD8+ cells, half of which express high levels of the transgenic TCR. These MHC mismatched CD8+ cells persist in the periphery and proliferate to GAD286-300 peptide in vitro and in vivo in a class II restricted fashion. Interestingly, the CD8+ tetramer(-) T cells that are expressing endogenous TCR can delay diabetes induction in a transfer model, as we previously showed for CD4+ tetramer+ T cells in these mice. The MHC mismatched CD8+ cells appear to be positively selected in an atypical fashion, in that they do not upregulate CD69 or reexpress CD44, and they escape negative selection. We find that production of these CD8+ cells is not dependent on NOD thymus or high affinity of the TCR, but is dependent on the atypical TCR transgenic thymic environment.

The T cell response to glutamic acid decarboxylase 65 in T cell receptor transgenic NOD mice.

Using BW 5147 T cell hybridomas isolated by fusion with spleen and lymph node cells from NOD female mice, two T cell receptor transgenic NOD mouse lines were produced. Both TCR transgenics respond to their cognate peptide/MHC (GAD65 206-220 and 286-300) and produce IL-2, IFN-gamma, and small amounts of IL-10. Unexpectedly, the transgenic mice do not develop diabetes and have no insulitis. Analysis with a GAD65 286-300/I-A(g7) tetramer reveals that transgenic T cells are negatively selected in the thymus and further negatively selected in the periphery. When crossed to the C(alpha)(-/-) NOD line, CD4 T cells were reduced by 90% in the thymus and periphery. Further, the tetramer positive GAD65 286-300 specific T cells were capable of delaying the onset of diabetes in a standard transfer system. Thus, GAD65 specific TCR transgenic T cells (1) must express a second a chain to survive negative selection, (2) produce IL-2 and IFN-gamma, and (3) have a mildly protective effect on transfer of diabetes with diabetogenic spleen cells.

Nonobese diabetic mice express aspects of both type 1 and type 2 diabetes.

Before the onset of autoimmune destruction, type 1 diabetic patients and an animal model, the nonobese diabetic (NOD) mouse, show morphological and functional abnormalities in target organs, which may act as inciting events for leukocyte infiltration. To better understand these abnormalities, but without the complications associated with lymphocytic infiltrates, we examined genes expressed in autoimmune target tissues of NOD/severe combined immunodeficient (scid) mice and of autoimmune-resistant C57BL/6/scid mice. Our results suggest that the NOD genetic background may predispose them to diabetic complications, including insulin resistance in the absence of high circulating glucose levels and without autoimmune destruction of their beta cells. Several of these genes lie within known type 1 and 2 diabetes loci. These data suggest that the NOD mouse may be a good candidate to study an interface between type 1 and type 2 diabetes.

DRB1*0401-restricted human T cell clone specific for the major proinsulin73-90 epitope expresses a down-regulatory T helper 2 phenotype.

Recently, we have identified proinsulin (P-Ins)(73-90) as an immunodominant T cell epitope of HLA-DRB1*0401 (DR4) subjects with beta-islet cell autoimmunity and of HLA-DR4/CD4 double-transgenic mice immunized with human P-Ins. We have compared the fine specificities of one human CD4 T cell clone and two mouse T cell hybridoma clones recognizing this epitope, and, although these three clones all recognized the same core region (LALEGSLQK), there were major differences in how they interacted with the peptide (p)/HLA complex, reflecting the fact that human P-Ins is a foreign antigen in the mouse and an autoantigen in the type 1 diabetes patient. The human T cell clone was forkhead transcription factor 3 (Foxp3)-positive, a marker for regulatory T cell lineages, and secreted predominantly IL-5, IL-10, and low levels of IFNgamma in response to P-Ins(73-90). This finding is compatible with the previously detected regulatory cytokine pattern in subjects with beta-cell autoimmunity. However, added N- or C-terminal amino acids drastically changed HLA and tetramer binding capacity as well as T cell reactivity and the cytokine phenotype of the P-Ins(73-90)-specific human CD4 T cell clone, suggesting a potential for this P-Ins epitope as a target for therapeutic intervention in HLA-DR4-positive humans with beta-islet cell autoimmunity or recent-onset type 1 diabetes.

The role of TNF-alpha in the pathogenesis of type 1 diabetes in the nonobese diabetic mouse: analysis of dendritic cell maturation.

TNF-alpha has been linked to the development of type 1 diabetes (T1D). We previously reported that neonatal treatment of nonobese diabetic (NOD) mice with TNF-alpha accelerated the onset of T1D, whereas TNF-alpha blockade in the same time period resulted in a complete absence of diabetes. The mechanisms by which TNF-alpha modulates development of T1D in NOD mice remain unclear. Here we tested the effects of TNF-alpha on the maturation of dendritic cells (DCs) in the NOD mouse. We found that neonatal treatment with TNF-alpha caused an increase in expression of maturation markers on CD11c(+)CD11b(+) DC subpopulations, whereas treatment with anti-TNF-alpha resulted in a decrease in expression of maturation markers in the CD11c(+)CD11b(+) subset. Moreover, neonatal treatment with TNF-alpha resulted in skewed development of a CD8alpha(+)CD11b(-)CD11c(+) DC subset such that TNF-alpha decreases the CD8alpha(+)CD11c(+) DC subset, increases the CD11c(+)CD11b(+) subset, and causes an increase in the expression of CD40 and CD54 on mature DCs capable of inducing immunity. Anti-TNF-alpha-treated mice had an increase in the CD8alpha(+)CD11c(+) DCs. Notably, adoptively transferred naïve CD4(+) T cells from BDC2.5 T cell receptor transgenic mice proliferated in the pancreatic lymph nodes in TNF-alpha-treated NOD mice but not in anti-TNF-alpha-treated mice. Finally, we show that anti-TNF-alpha-treated mice showed immunological tolerance to islet cell proteins. We conclude that TNF-alpha plays an important role in the initiation of T1D in the NOD mouse by regulating the maturation of DCs and, thus, the activation of islet-specific pancreatic lymph node T cells.

Expansion of functional endogenous antigen-specific CD4+CD25+ regulatory T cells from nonobese diabetic mice.

CD4+CD25+Foxp3+ regulatory T cells (T(reg)) are critical for controlling autoimmunity. Evidence suggests that T(reg) development, peripheral maintenance, and suppressive function are dependent on Ag specificity. However, there is little direct evidence that the T(reg) responsible for controlling autoimmunity in NOD mice or other natural settings are Ag specific. In fact, some investigators have argued that polyclonal Ag-nonspecific T(reg) are efficient regulators of immunity. Thus, the goal of this study was to identify, expand, and characterize islet Ag-specific T(reg) in NOD mice. Ag-specific T(reg) from NOD mice were efficiently expanded in vitro using IL-2 and beads coated with recombinant islet peptide mimic-MHC class II and anti-CD28 mAb. The expanded Ag-specific T(reg) expressed prototypic surface markers and cytokines. Although activated in an Ag-specific fashion, the expanded T(reg) were capable of bystander suppression both in vitro and in vivo. Importantly, the islet peptide mimic-specific T(reg) were more efficient than polyclonal T(reg) in suppressing autoimmune diabetes. These results provide a direct demonstration of the presence of autoantigen-specific T(reg) in the natural setting that can be applied as therapeutics for organ-specific autoimmunity.

Immunopathogenic role of TH1 cells in autoimmune diabetes: evidence from a T1 and T2 doubly transgenic non-obese diabetic mouse model.

To improve the feasibility of in vivo monitoring of autoreactive T cells in the diabetogenic process, we generated T1 and T2 doubly transgenic non-obese diabetic (NOD) mice in which transgenic human CD90 (hCD90) is simultaneously expressed on IFN-gamma-producing cells or murine CD90.1 (mCD90.1) is expressed on IL-4-producing cells. These transgenic NOD mice develop diabetes with the same kinetics and incidence as wild type NOD mice, permitting the physiological characterization of CD4(+)hCD90(+) cells, which represent T(H)1 cells in lymphoid organs and at the site of insulitis. CD4(+)hCD90(+) cells had a higher capacity to secret IFN-gamma than CD4(+)hCD90(-) cells in an autoantigen-specific manner. Transgenic mice treated with GAD65 plasmid were protected from autoimmune diabetes, and had a lower number of CD4(+)hCD90(+) cells, confirming the pathogenic role of CD4(+)hCD90(+) cells in autoimmune diabetes. To further investigate the effect of IL-12 on the development of T(H)1 cells in autoimmune diabetes, we crossed these doubly transgenic mice to IL-12p35-deficient NOD mice. Despite severe disturbance of diabetes in p35(-/-) mice, the frequency of T(H)1 cells in these mice was slightly lower than in wild type mice. These data support the pathological role of IL-12 in autoimmune diabetes and suggest the existence an IL-12-independent pathway of T(H)1 development.

Specific antigen vaccination to treat autoimmune disease.

Specific antigen vaccination by administration of the target antigen in aqueous solution has resulted in significant decreases of disease severity in animal models of experimental allergic encephalomyelitis, type I diabetes, and several forms of antigen-induced arthritis, even if administered after the initiation of symptoms. However, in experimental autoimmune encephalomyelitis (EAE) and type I diabetes in nonobese diabetic (NOD) mice, repeated administration of peptide fragments of target antigens in incomplete Freund's adjuvant has resulted in severe anaphylactic reactions. Although these methods of administration are known to potentiate CD4 T helper 2 (Th2) responses, which is the goal of specific antigen vaccination, the risk of anaphylaxis raises a red flag concerning use of this therapy for diseases such as type I diabetes, where the survival time after onset is quite long. It is clear that specific antigen vaccination is effective in preventing several animal models of autoimmune disease, and in treating these diseases once the symptoms are overt. However, the risks of this therapy require serious consideration of alternative methods for down-regulation of the autoimmune process.

The discovery of linkage between the MHC and genetic control of the immune response.

Immunization of rabbits, and inbred strains of mice with branched, multichain, synthetic polypeptides, such as (T, G) - A--L and (H, G) - A--L, revealed striking differences in the ability of different strains of mice to produce specific antibody. F1 and F1 x parental backcross mice revealed clear genetic control. Initial attempts to link this genetic control to known genetic markers were unsuccessful. The second approach, which attempted to transfer response from high or immediate responders into low responder recipients, initially encountered graft vs. host and host vs. graft reactions. The transfer of F1 spleen cells into the low responder parent demonstrated that ability to respond was a property of immunocompetent cells (spleen cells), not of the recipient's background genes. Mapping studies with recombinant H2 haplotype congenic strains, and a classic 4-point mapping cross were concordant in placing the gene controlling this trait within the H2 complex, between the K and Ss loci. Subsequent studies mapped the genes for stimulation in the mixed lymphocyte culture reaction to the same position, suggesting cell surface expression. Production of antisera to 'I-region' products defined 'Ia' antigens, the 2-chain alpha/beta MHC class II molecules.

Multiple roles for tumor necrosis factor-alpha and lymphotoxin alpha/beta in immunity and autoimmunity.

Tumor necrosis factor (TNF)-alpha and lymphotoxin (LT) alpha/beta play multiple roles in the development and function of the immune system. This article focuses on three important aspects of the effects of these cytokines on the immune response and on autoimmunity. In several experimental systems (Jurkat T cells, murine T-cell hybridomas), TNF-alpha appears to cause a downregulation of signaling through the TCR, revealed by changes in calcium flux, activation of p21, p23 and ZAP70, and a decrease in nuclear activation of NF-kappaB. Previous and present results suggest that TNF-alpha interferes in some manner with signaling through the TCR, at a locus yet to be delineated. Transgenic expression of LTbetaR-Fc in nonobese diabetic (NOD) transgenic mice results in prevention of type 1 diabetes in NOD mice as long as the level of expression of the fusion protein (under the control of the cytomegalovirus promoter) remains above a level of 2-3 microg/ml. Once the expression levels of the fusion protein have dropped below this critical level, the diabetic process resumes and the animals become diabetic at 40-50 weeks of age, whereas nontransgenic littermates develop diabetes by 25-30 weeks of age. The paradoxical effects of neonatal TNF-alpha administration in NOD mice in increasing incidence of and hastening onset of type 1 diabetes, while neonatal anti-TNF administration completely prevents all signs of islet cell autoimmunity, are due partly to the low levels of CD4+CD25+ T cells in NOD mice. These low levels are reduced by a further 50% on neonatal administration of nontoxic levels of TNF-alpha. In contrast, neonatal administration of anti-TNF-alpha results in a dramatic increase in the levels of CD4+CD25+ regulatory T cells, to levels beyond those seen in wild-type untreated NOD mice. TNF-alpha and LTalpha/beta thus have pleomorphic regulatory effects on the development and expression of autoimmunity.

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

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

Prevention of type I diabetes transfer by glutamic acid decarboxylase 65 peptide 206-220-specific T cells.

Glutamic acid decarboxylase (GAD) 65 is one of the major pancreatic antigens targeted by self-reactive T cells in type I diabetes mellitus. T cells specific for GAD65 are among the first to enter inflamed islets and may be important for the initiation of autoimmune diabetes. However, we previously reported that nonobese diabetic (NOD) mice transgenic for a T cell antigen receptor (TCR) specific for one of the immunodominant epitopes of GAD65, peptide 286-300 (G286), are protected from insulitis and diabetes. To examine whether other GAD65-reactive T cells share this phenotype, we have generated TCR transgenic NOD mice for a second immunodominant epitope of GAD65, peptide 206-220 (G206). As in G286 mice, G206 mice do not develop islet inflammation or diabetes. When adoptively transferred along with diabetogenic T cells, activated G206 T cells significantly delayed the onset of diabetes in NOD.scid recipients. Both G206 and G286 T cells produce immunoregulatory cytokines IFN-gamma and IL-10 at low levels when activated by cognate antigens. These data suggest that GAD65-specific T cells may play a protective role in diabetes pathogenesis by regulating pathogenic T cell responses. A better understanding of the functions of autoreactive T cells in type I diabetes will be necessary for choosing desirable targets for immunotherapy.