Development of memory-like autoregulatory CD8+ T cells is CD4+ T cell dependent

Progression of spontaneous autoimmune diabetes is associated with development of a disease-countering negative-feedback regulatory loop that involves differentiation of low-avidity autoreactive CD8(+) cells into memory-like autoregulatory T cells. Such T cells blunt diabetes progression by suppressing the presentation of both cognate and noncognate Ags to pathogenic high-avidity autoreactive CD8(+) T cells in the pancreas-draining lymph nodes. In this study, we show that development of autoregulatory CD8(+) T cell memory is CD4(+) T cell dependent. Transgenic (TG) NOD mice expressing a low-affinity autoreactive TCR were completely resistant to autoimmune diabetes, even after systemic treatment of the mice with agonistic anti-CD40 or anti-4-1BB mAbs or autoantigen-pulsed dendritic cells, strategies that dramatically accelerate diabetes development in TG NOD mice expressing a higher affinity TCR for the same autoantigenic specificity. Furthermore, whereas abrogation of RAG-2 expression, hence endogenous CD4(+) T cell and B cell development, decelerated disease progression in high-affinity TCR-TG NOD mice, it converted the low-affinity TCR into a pathogenic one. In agreement with these data, polyclonal CD4(+) T cells from prediabetic NOD mice promoted disease in high-affinity TCR-TG NOD.Rag2(-/-) mice, but inhibited it in low-affinity TCR-TG NOD.Rag2(-/-) mice. Thus, in chronic autoimmune responses, CD4(+) Th cells contribute to both promoting and suppressing pathogenic autoimmunity.     

MHC class I-restricted determinants on the glutamic acid decarboxylase 65 molecule induce spontaneous CTL activity

CD4(+) T cell responses to glutamic acid decarboxylase (GAD65) spontaneously arise in nonobese diabetic (NOD) mice before the onset of insulin-dependent diabetes mellitus (IDDM) and may be critical to the pathogenic process. However, since both CD4(+) and CD8(+) T cells are involved in autoimmune diabetes, we sought to determine whether GAD65-specific CD8(+) T cells were also present in prediabetic NOD mice and contribute to IDDM. To refine the analysis, putative K(d)-binding determinants that were proximal to previously described dominant Th determinants (206-220 and 524-543) were examined for their ability to elicit cytolytic activity in young NOD mice. Naive NOD spleen cells stimulated with GAD65 peptides 206-214 (p206) and 546-554 (p546) produced IFN-gamma and showed Ag-specific CTL responses against targets pulsed with homologous peptide. Conversely, several GAD peptides distal to the Th determinants, and control K(d)-binding peptides did not induce similar responses. Spontaneous CTL responses to p206 and p546 were mediated by CD8(+) T cells that are capable of lysing GAD65-expressing target cells, and p546-specific T cells transferred insulitis to NOD.scid mice. Young NOD mice pretreated with p206 and p546 showed reduced CTL responses to homologous peptides and a delay in the onset of IDDM. Thus, MHC class I-restricted responses to GAD65 may provide an inflammatory focus for the generation of islet-specific pathogenesis and beta cell destruction. This report reveals a potential therapeutic role for MHC class I-restricted peptides in treating autoimmune disease and revisits the notion that the CD4- and CD8-inducing determinants on some molecules may benefit from a proximal relationship.     

Identification of a CD8 T cell that can independently mediate autoimmune diabetes development in the complete absence of CD4 T cell helper functions

Previous work has indicated that an important component for the initiation of autoimmune insulin-dependent diabetes mellitus (IDDM) in the NOD mouse model entails MHC class I-restricted CD8 T cell responses against pancreatic beta cell Ags. However, unless previously activated in vitro, such CD8 T cells have previously been thought to require helper functions provided by MHC class II-restricted CD4 T cells to exert their full diabetogenic effects. In this study, we show that IDDM development is greatly accelerated in a stock of NOD mice expressing TCR transgenes derived from a MHC class I-restricted CD8 T cell clone (designated AI4) previously found to contribute to the earliest preclinical stages of pancreatic beta cell destruction. Importantly, these TCR transgenic NOD mice (designated NOD.AI4alphabeta Tg) continued to develop IDDM at a greatly accelerated rate when residual CD4 helper T cells were eliminated by introduction of the scid mutation or a functionally inactivated CD4 allele. In a previously described stock of NOD mice expressing TCR transgenes derived from another MHC class I-restricted beta cell autoreactive T cell clone, IDDM development was retarded by elimination of residual CD4 T cells. Hence, there is variability in the helper dependence of CD8 T cells contributing to the development of autoimmune IDDM. The AI4 clonotype represents the first CD8 T cell with a demonstrated ability to progress from a naive to functionally activated state and rapidly mediate autoimmune IDDM development in the complete absence of CD4 T cell helper functions.     

Dynamics of pathogenic and suppressor T cells in autoimmune diabetes development

In the nonobese diabetic (NOD) mouse, pathogenic and suppressor CD4(+) T cells can be distinguished by the constitutive expression of CD25. In this study, we demonstrate that the progression of autoimmune diabetes in NOD mice reflects modifications in both T cell subsets. CD4(+)CD25(+) suppressor T cells from 8-, but not 16-wk-old NOD mice delayed the onset of diabetes transferred by 16-wk-old CD25-depleted spleen cells. These results were paralleled by the inhibition of alloantigen-induced proliferation of CD4(+)CD25(-) cells, indicating an age-dependent decrease in suppressive activity. In addition, CD4(+)CD25(-) pathogenic T cells became progressively less sensitive to immunoregulation by CD4(+)CD25(+) T cells during diabetes development. CD4(+)CD25(-) T cells showed a higher proliferation and produced more IFN-gamma, but less IL-4 and IL-10, whereas CD4(+)CD25(+) T suppressor cells produced significantly lower levels of IL-10 in 16- compared with 8-wk-old NOD mice. Consistent with these findings, a higher frequency of Th1 cells was observed in the pancreas of 16-wk-old compared with 8-wk-old NOD mice. An increased percentage of CD4(+)CD25(-) T cells expressing CD54 was present in 16-wk-old and in diabetic NOD, but not in BALB/c mice. Costimulation via CD54 increased the proliferation of CD4(+)CD25(-) T cells from 16-, but not 8-wk-old NOD mice, and blocking CD54 prevented their proliferation, consistent with the role of CD54 in diabetes development. Thus, the pathogenesis of autoimmune diabetes in NOD mice is correlated with both an enhanced pathogenicity of CD4(+)CD25(-) T cells and a decreased suppressive activity of CD4(+)CD25(+) T cells.     

Autoimmunity to both proinsulin and IGRP is required for diabetes in nonobese diabetic 8.3 TCR transgenic mice

T cells specific for proinsulin and islet-specific glucose-6-phosphatase catalytic subunit related protein (IGRP) induce diabetes in nonobese diabetic (NOD) mice. TCR transgenic mice with CD8(+) T cells specific for IGRP(206-214) (NOD8.3 mice) develop accelerated diabetes that requires CD4(+) T cell help. We previously showed that immune responses against proinsulin are necessary for IGRP(206-214)-specific CD8(+) T cells to expand. In this study, we show that diabetes development is dramatically reduced in NOD8.3 mice crossed to NOD mice tolerant to proinsulin (NOD-PI mice). This indicates that immunity to proinsulin is even required in the great majority of NOD8.3 mice that have a pre-existing repertoire of IGRP(206-214)-specific cells. However, protection from diabetes could be overcome by inducing islet inflammation either by a single dose of streptozotocin or anti-CD40 agonist Ab treatment. This suggests that islet inflammation can substitute for proinsulin-specific CD4(+) T cell help to activate IGRP(206-214)-specific T cells.     

Cutting edge: accelerated autoimmune diabetes in the absence of LAG-3

Lymphocyte activation gene-3 (LAG-3; CD223) is a CD4 homolog that is required for maximal regulatory T cell function and for the control of CD4(+) and CD8(+) T cell homeostasis. Lag3(-)(/)(-) NOD mice developed substantially accelerated diabetes with 100% incidence. Adoptive transfer experiments revealed that LAG-3 was primarily responsible for limiting the pathogenic potential of CD4(+) T cells and, to a lesser extent, CD8(+) T cells. Lag3(-)(/)(-) mice exhibited accelerated, invasive insulitis, corresponding to increased CD4(+) and CD8(+) T cell islet infiltration and intraislet proliferation. The frequencies of islet Ag-reactive chromogranin A-specific CD4(+) T cells and islet specific glucose-6-phosphatase-specific CD8(+) T cells were significantly increased in the islets of Lag3(-)(/)(-) mice, suggesting an early expansion of pathogenic clones that is normally restrained by LAG-3. We conclude that LAG-3 is necessary for regulating CD4(+) and CD8(+) T cell function during autoimmune diabetes, and thus may contribute to limiting autoimmunity in disease-prone environments.     

Increased nonobese diabetic Th1:Th2 (IFN-gamma:IL-4) ratio is CD4+ T cell intrinsic and independent of APC genetic background

Autoreactive CD4(+) T cells play a major role in the pathogenesis of autoimmune diabetes in nonobese diabetic (NOD) mice. We recently showed that the non-MHC genetic background controlled enhanced entry into the IFN-gamma pathway by NOD vs B6.G7 T cells. In this study, we demonstrate that increased IFN-gamma, decreased IL-4, and decreased IL-10 production in NOD T cells is CD4 T cell intrinsic. NOD CD4(+) T cells purified and stimulated with anti-CD3/anti-CD28 Abs generated greater IFN-gamma, less IL-4, and less IL-10 than B6.G7 CD4(+) T cells. The same results were obtained in purified NOD.H2(b) vs B6 CD4(+) T cells, demonstrating that the non-MHC NOD genetic background controlled the cytokine phenotype. Moreover, the increased IFN-gamma:IL-4 cytokine ratio was independent of the genetic background of APCs, since NOD CD4(+) T cells generated increased IFN-gamma and decreased IL-4 compared with B6.G7 CD4(+) T cells, regardless of whether they were stimulated with NOD or B6.G7 APCs. Cell cycle analysis showed that the cytokine differences were not due to cycle/proliferative differences between NOD and B6.G7, since stimulated CD4(+) T cells from both strains showed quantitatively identical entry into subsequent cell divisions (shown by CFSE staining), although NOD cells showed greater numbers of IFN-gamma-positive cells with each subsequent cell division. Moreover, 7-aminoactinomycin D and 5-bromo-2'-deoxyuridine analysis showed indistinguishable entry into G(0)/G(1), S, and G(2)/M phases of the cell cycle for both NOD and B6.G7 CD4(+) cells, with both strains generating IFN-gamma predominantly in the S phase. Therefore, the NOD cytokine effector phenotype is CD4(+) T cell intrinsic, genetically controlled, and independent of cell cycle machinery.     

Treatment of experimental autoimmune prostatitis in nonobese diabetic mice by the vitamin D receptor agonist elocalcitol

On the basis of on the marked inhibitory activity of the vitamin D receptor agonist Elocalcitol on basal and growth factor-induced proliferation of human prostate cells and on its potent anti-inflammatory properties, we have tested its capacity to treat experimental autoimmune prostatitis (EAP) induced by injection of prostate homogenate-CFA in nonobese diabetic (NOD) mice. Administration of Elocalcitol, at normocalcemic doses, for 2 wk in already established EAP significantly inhibits the intraprostatic cell infiltrate, leading to a profound reduction in the number of CD4(+) and CD8(+) T cells, B cells, macrophages, dendritic cells, and I-A(g7)-positive cells. Immunohistological analysis demonstrates reduced cell proliferation and increased apoptosis of resident and infiltrating cells. Significantly decreased production of the proinflammatory cytokines IFN-gamma and IL-17 is observed in prostate-draining lymph node T cells from Elocalcitol-treated NOD mice stimulated by TCR ligation. In addition, Elocalcitol treatment reduces IFN-gamma production by prostate-infiltrating CD4(+) T cells and draining lymph node T cells specific for an immunodominant peptide naturally processed from prostate steroid-binding protein, a prostate-specific autoantigen. Finally, CD4(+) splenic T cells from Elocalcitol-treated NOD mice show decreased ability, upon adoptive transfer into NOD.SCID recipients, to induce autoimmune prostatitis, paralleled by a reduced capacity to produce IFN-gamma in response to prostate steroid-binding protein. The results indicate that Elocalcitol is able to interfere with key pathogenic events in already established EAP in the NOD mouse. These data show a novel indication for vitamin D receptor agonists and indicate that treatment with Elocalcitol may inhibit the intraprostatic inflammatory response in chronic prostatitis/chronic pelvic pain syndrome patients.     

Cross-priming of diabetogenic T cells dissociated from CTL-induced shedding of beta cell autoantigens

Cross-presentation of self Ags by APCs is key to the initiation of organ-specific autoimmunity. As MHC class I molecules are essential for the initiation of diabetes in nonobese diabetic (NOD) mice, we sought to determine whether the initial insult that allows cross-presentation of beta cell autoantigens in diabetes is caused by cognate interactions between naive CD8(+) T cells and beta cells. Naive splenic CD8(+) T cells from transgenic NOD mice expressing a diabetogenic TCR killed peptide-pulsed targets in the absence of APCs. To ascertain the role of CD8(+) T cell-induced beta cell lysis in the initiation of diabetes, we expressed a rat insulin promoter (RIP)-driven adenovirus E19 transgene in NOD mice. RIP-E19 expression inhibited MHC class I transport exclusively in beta cells and rendered these cells resistant to lysis by CD8(+) (but not CD4(+)) T cells, both in vitro and in vivo. Surprisingly, RIP-E19 expression impaired the accumulation of CD8(+) T cells in islets and delayed the onset of islet inflammation, without affecting the timing or magnitude of T cell cross-priming in the pancreatic lymph nodes, which is the earliest known event in diabetogenesis. These results suggest that access of beta cell autoantigens to the cross-presentation pathway in diabetes is T cell independent, and reveal a previously unrecognized function of MHC class I molecules on target cells in autoimmunity: local retention of disease-initiating clonotypes.     

Suppressor of cytokine signaling-1 overexpression protects pancreatic beta cells from CD8+ T cell-mediated autoimmune destruction

In type 1 diabetes, cytokine action on beta cells potentially contributes to beta cell destruction by direct cytotoxicity, inducing Fas expression, and up-regulating class I MHC and chemokine expression to increase immune recognition. To simultaneously block beta cell responsiveness to multiple cytokines, we overexpressed suppressor of cytokine signaling-1 (SOCS-1). This completely prevented progression to diabetes in CD8(+) TCR transgenic nonobese diabetic (NOD) 8.3 mice without affecting pancreas infiltration and partially prevented diabetes in nontransgenic NOD mice. SOCS-1 appeared to protect at least in part by inhibiting TNF- and IFN-gamma-induced Fas expression on beta cells. Fas expression was up-regulated on beta cells in vivo in prediabetic NOD8.3 mice, and this was inhibited by SOCS-1. Additionally, IFN-gamma-induced class I MHC up-regulation and TNF- and IFN-gamma-induced IL-15 expression by beta cells were inhibited by SOCS-1, which correlated with suppressed 8.3 T cell proliferation in vitro. Despite this, 8.3 T cell priming in vivo appeared unaffected. Therefore, blocking beta cell responses to cytokines impairs recognition by CD8(+) T cells and blocks multiple mechanisms of beta cell destruction, but does not prevent T cell priming and recruitment to the islets. Our findings suggest that increasing SOCS-1 expression may be useful as a strategy to block CD8(+) T cell-mediated type 1 diabetes as well as to more generally prevent cytokine-dependent tissue destruction in inflammatory diseases.     

Dysregulated B7-1 and B7-2 expression on nonobese diabetic mouse B cells is associated with increased T cell costimulation and the development of insulitis

Little is known about the pathogenic role of B cell dysfunction in T cell-mediated autoimmune disease. We previously reported that B cell hyper-responsiveness, resistance to apoptosis, and accumulation in islets occur during the onset of insulitis, but not in type 1 diabetes (T1D), in NOD mice. In this study we extended these studies to further determine how islet-infiltrated B cells contribute to this inflammatory insulitis. We demonstrate the presence of an increased percentage of B7-1(+) and a decreased percentage of B7-2(+) B cells in the spleen of autoimmune disease-prone NOD and nonobese diabetes-resistant mice compared with the spleen of nonautoimmune disease-prone C57BL/6 and BALB/c mice. An age-dependent differential expression of B7-1 and B7-2 was associated with the development of insulitis and CD4(+)CD25(+) T cell deficiency in autoimmune disease-prone mice. Whereas BCR and LPS stimulation increased B7-2 expression on B cells from autoimmune disease-prone and nonautoimmune disease-prone mice, LPS-induced B7-1 expression was higher on NOD than C57BL/6 B cells. Interestingly, increased expression of B7-1 and B7-2 was found on islet-infiltrated B cells, and this increase was associated with enhanced T cell costimulation. Islet-infiltrated B cells were shown to be a source of TNF-alpha production in islets. B7 blockade of BCR-stimulated NOD B cells by anti-B7-1 and anti-B7-2 mAbs during coadoptive transfer with diabetogenic T cells into NOD.scid mice protected these recipients from T1D. These results suggest that increased B7-1 and B7-2 expression on islet-infiltrated NOD B cells is associated with increased T cell costimulation and the development of inflammatory insulitis in NOD mice.     

Perturbed homeostasis of peripheral T cells elicits decreased susceptibility to anti-CD3-induced apoptosis in prediabetic nonobese diabetic mice

Activation-induced cell death (AICD) plays a key role in the homeostasis of the immune system. Autoreactive T cells are eliminated through AICD both from the thymus and periphery. In this study, we show that NOD peripheral T cells, especially CD8(+) T cells, display a decreased susceptibility to anti-CD3-induced AICD in vivo compared with T cells from diabetes-resistant B6, nonobese diabetes-resistant, and NOD.B6Idd4 mice. The susceptibility of NOD CD8(+) T cells to AICD varies in an age- and dose-dependent manner upon stimulation in vivo with either a mitogenic or nonmitogenic anti-CD3. NOD T cells preactivated by anti-CD3 in vivo are less susceptible than B6 T cells to TCR-induced AICD. Treatment of NOD mice with a mitogenic anti-CD3 depletes CD4(+)CD25(-)CD62L(+) but not CD4(+)CD25(+)CD62L(+) T cells, thereby resulting in an increase of the latter subset in the spleen. Treatment with a nonmitogenic anti-CD3 mAb delays the onset of T1D in 8.3 TCR transgenic NOD mice. These results demonstrate that the capacity of anti-CD3 to protect NOD mice from T1D correlates with its ability to perturb T cell homeostasis by inducing CD8(+) T cell AICD and increasing the number of CD4(+)CD25(+)CD62L(+) T cells in the periphery.     

Activated NKT cells inhibit autoimmune diabetes through tolerogenic recruitment of dendritic cells to pancreatic lymph nodes

NKT cell activation by alpha-galactosylceramide (alpha-GalCer) inhibits autoimmune diabetes in NOD mice, in part by inducing recruitment to pancreatic lymph nodes (PLNs) of mature dendritic cells (DCs) with disease-protective effects. However, how activated NKT cells promote DC maturation, and what downstream effect this has on diabetogenic T cells was unknown. Activated NKT cells were found to produce a soluble factor(s) inducing DC maturation. Initially, there was a preferential accumulation of mature DCs in the PLNs of alpha-GalCer-treated NOD mice, followed by a substantial increase in T cells. Adoptive transfer of a diabetogenic CD8 T cell population (AI4) induced a high rate of disease (75%) in PBS-treated NOD recipients, but not in those pretreated with alpha-GalCer (8%). Significantly, more AI4 T cells accumulated in PLNs of alpha-GalCer than PBS-treated recipients, while no differences were found in mesenteric lymph nodes from each group. Compared with those in mesenteric lymph nodes, AI4 T cells entering PLNs underwent greater levels of apoptosis, and the survivors became functionally anergic. NKT cell activation enhanced this process. Hence, activated NKT cells elicit diabetes protection in NOD mice by producing a soluble factor(s) that induces DC maturation and accumulation in PLNs, where they subsequently recruit and tolerize pathogenic T cells.     

TNF receptor 1-dependent beta cell toxicity as an effector pathway in autoimmune diabetes

Autoimmune diabetes is characterized by a chronic progressive inflammatory autoimmune reaction that ultimately causes the selective elimination of pancreatic beta cells. To address the question of whether the cell death-inducing cytokines TNF and lymphotoxin alpha are involved in this process, we generated nonobese diabetic (NOD) mice that are deficient for TNF receptor 1 (TNFR1 or TNFRp55). Insulitis developed in these mice similarly to that in normal control NOD mice, but progression to diabetes was completely abrogated. Since this was probably due to the complex immunomodulatory effects of TNF and lymphotoxin alpha signaled via TNFR1 on lymphohemopoietic cells, adoptive transfer experiments with spleen cells from diabetic NOD mice were conducted. It was found that the absence of TNFR1 in recipients delayed diabetes induced by normal control and precluded diabetes induced by perforin-deficient spleen cells. In a CD8+ T cell-mediated model of diabetes, however, diabetes induced by adoptive transfer of TCR transgenic lymphocytic choriomeningitis virus glycoprotein-specific CD8+ T cells was not delayed by the absence of TNFR1 in recipient mice. Together with the described expression patterns of perforin and TNF in the mononuclear islet infiltrates of NOD mice, these results indicate that two diabetogenic effector mechanisms are delivered by distinct cell populations: CD8+ T cells lyse beta cells via perforin-dependent cytotoxicity, whereas CD4+ T cells, macrophages, and dendritic cells contribute to diabetes development via TNFR1-dependent beta cell toxicity.     

TNF receptor 1 deficiency increases regulatory T cell function in nonobese diabetic mice

TNF has been implicated in the pathogenesis of type 1 diabetes. When administered early in life, TNF accelerates and increases diabetes in NOD mice. However, when administered late, TNF decreases diabetes incidence and delays onset. TNFR1-deficient NOD mice were fully protected from diabetes and only showed mild peri-insulitis. To further dissect how TNFR1 deficiency affects type 1 diabetes, these mice were crossed to β cell-specific, highly diabetogenic TCR transgenic I-A(g7)-restricted NOD4.1 mice and Kd-restricted NOD8.3 mice. TNFR1-deficient NOD4.1 and NOD8.3 mice were protected from diabetes and had significantly less insulitis compared with wild type NOD4.1 and NOD8.3 controls. Diabetic NOD4.1 mice rejected TNFR1-deficient islet grafts as efficiently as control islets, confirming that TNFR1 signaling is not directly required for β cell destruction. Flow cytometric analysis showed a significant increase in the number of CD4(+)CD25(+)Foxp3(+) T regulatory cells in TNFR1-deficient mice. TNFR1-deficient T regulatory cells were functionally better at suppressing effector cells than were wild type T regulatory cells both in vitro and in vivo. This study suggests that blocking TNF signaling may be beneficial in increasing the function of T regulatory cells and suppression of type 1 diabetes.     

Manipulation of CD98 resolves type 1 diabetes in nonobese diabetic mice

The interplay of CD4(+) and CD8(+) T cells targeting autoantigens is responsible for the progression of a number of autoimmune diseases, including type 1 diabetes mellitus (T1D). Understanding the molecular mechanisms that regulate T cell activation is crucial for designing effective therapies for autoimmune diseases. We probed a panel of Abs with T cell-modulating activity and identified a mAb specific for the H chain of CD98 (CD98hc) that was able to suppress T cell proliferation. The anti-CD98hc mAb also inhibited Ag-specific proliferation and the acquisition of effector function by CD4(+) and CD8(+) T cells in vitro and in vivo. Injection of the anti-CD98hc mAb completely prevented the onset of cyclophosphamide-induced diabetes in NOD mice. Treatment of diabetic NOD mice with anti-CD98hc reversed the diabetic state to normal levels, coincident with decreased proliferation of CD4(+) T cells. Furthermore, treatment of diabetic NOD mice with CD98hc small interfering RNA resolved T1D. These data indicate that strategies targeting CD98hc might have clinical application for treating T1D and other T cell-mediated autoimmune diseases.     

Regulatory and effector CD4 T cells in nonobese diabetic mice recognize overlapping determinants on glutamic acid decarboxylase and use distinct V beta genes

The 524--543 region of glutamic acid decarboxylase (GAD65), GAD65(524--543), is one of the first fragments of this islet Ag to induce proliferative T cell responses in the nonobese diabetic (NOD) mouse model of spontaneous autoimmune diabetes. Furthermore, NOD mice given tolerogenic doses of GAD65(524--543) are protected from spontaneous and cyclophosphamide-induced diabetes. In this study, we report that there are at least two I-A(g7)-restricted determinants present in the GAD65(524--543) sequence, each capable of recruiting unique T cell repertoires characterized by distinct TCR V beta gene use. CD4(+) T cells arise spontaneously in young NOD mice to an apparently dominant determinant found within the GAD65 peptide 530--543 (p530); however, T cells to the overlapping determinant 524-538 (p524) dominate the response only after immunization with GAD65(524--543). All p530-responsive T cells used the V beta 4 gene, whereas the V beta 12 gene is preferentially used to encode the TCR of p524-responsive T cell populations. T cell clones and hybridomas from both of these T cell groups were responsive to APC pulsed with GAD65(524--543) or whole rGAD65. p524-reactive cells appeared to be regulatory upon adoptive transfer into young NOD mice and could inhibit insulin-dependent diabetes mellitus development, although they were unable to produce IL-4, IL-10, or TGF beta upon antigenic challenge. Furthermore, we found that i.p. injection with p524/IFA was very effective in providing protection from cyclophosphamide-induced insulin-dependent diabetes mellitus. These data demonstrate that the regulatory T cells elicited by immunizing with GAD65(524--543) are unique and distinct from those that arise from spontaneous endogenous priming, and that T cells to this limited region of GAD65 may be either regulatory or pathogenic.     

Rotavirus infection accelerates type 1 diabetes in mice with established insulitis

Infection modulates type 1 diabetes, a common autoimmune disease characterized by the destruction of insulin-producing islet beta cells in the pancreas. Childhood rotavirus infections have been associated with exacerbations in islet autoimmunity. Nonobese diabetic (NOD) mice develop lymphocytic islet infiltration (insulitis) and then clinical diabetes, whereas NOD8.3 TCR mice, transgenic for a T-cell receptor (TCR) specific for an important islet autoantigen, show more rapid diabetes onset. Oral infection of infant NOD mice with the monkey rotavirus strain RRV delays diabetes development. Here, the effect of RRV infection on diabetes development once insulitis is established was determined. NOD and NOD8.3 TCR mice were inoculated with RRV aged > or = 12 and 5 weeks, respectively. Diabetes onset was significantly accelerated in both models (P < 0.024), although RRV infection was asymptomatic and confined to the intestine. The degree of diabetes acceleration was related to the serum antibody titer to RRV. RRV-infected NOD mice showed a possible trend toward increased insulitis development. Infected males showed increased CD8(+) T-cell proportions in islets. Levels of beta-cell major histocompatibility complex class I expression and islet tumor necrosis factor alpha mRNA were elevated in at least one model. NOD mouse exposure to mouse rotavirus in a natural experiment also accelerated diabetes. Thus, rotavirus infection after beta-cell autoimmunity is established affects insulitis and exacerbates diabetes. A possible mechanism involves increased exposure of beta cells to immune recognition and activation of autoreactive T cells by proinflammatory cytokines. The timing of infection relative to mouse age and degree of insulitis determines whether diabetes onset is delayed, unaltered, or accelerated.     

Quetiapine, an Atypical Antipsychotic, Is Protective against Autoimmune-Mediated Demyelination by Inhibiting Effector T Cell Proliferation

Quetiapine (Que), a commonly used atypical antipsychotic drug (APD), can prevent myelin from breakdown without immune attack. Multiple sclerosisis (MS), an autoimmune reactive inflammation demyelinating disease, is triggered by activated myelin-specific T lymphocytes (T cells). In this study, we investigated the potential efficacy of Que as an immune-modulating therapeutic agent for experimental autoimmune encephalomyelitis (EAE), a mouse model for MS. Que treatment was initiated on the onset of MOG(35-55) peptide induced EAE mice and the efficacy of Que on modulating the immune response was determined by Flow Cytometry through analyzing CD4(+)/CD8(+) populations and the proliferation of effector T cells (CD4(+)CD25(-)) in peripheral immune organs. Our results show that Que dramatically attenuates the severity of EAE symptoms. Que treatment decreases the extent of CD4(+)/CD8(+) T cell infiltration into the spinal cord and suppresses local glial activation, thereby diminishing the loss of mature oligodendrocytes and myelin breakdown in the spinal cord of EAE mice. Our results further demonstrate that Que treatment decreases the CD4(+)/CD8(+) T cell populations in lymph nodes and spleens of EAE mice and inhibits either MOG(35-55) or anti-CD3 induced proliferation as well as IL-2 production of effector T cells (CD4(+)CD25(-)) isolated from EAE mice spleen. Together, these findings suggest that Que displays an immune-modulating role during the course of EAE, and thus may be a promising candidate for treatment of MS.