Pancreatic IL-4 expression results in islet-reactive Th2 cells that inhibit diabetogenic lymphocytes in the nonobese diabetic mouse.

When immunological tolerance breaks down, autoimmune destruction of insulin-producing beta cells in the pancreas can cause insulin-dependent diabetes mellitus. We previously showed that transgenic nonobese diabetic (NOD) mice expressing IL-4 in the pancreas (NOD-IL-4 mice) were protected from insulitis and diabetes. Here we have characterized the avoidance of pathological autoimmunity in these mice. The absence of disease did not result from a lack of T cell priming, because T cells responding to dominant islet Ags were present. These islet Ag-specific T cells displayed a Th2 phenotype, indicating that Th2 responses could account for the observed tolerance. Interestingly, islet Ag-specific Th1 T cells were present and found to be functional, because neutralization of the Th2 effector cytokines IL-4 and IL-10 resulted in diabetes. Histological examination revealed that NOD-IL-4 splenocytes inhibited diabetogenic T cells in cotransfer experiments by limiting insulitis and delaying diabetes. Neutralization of IL-4 in this system abrogated the ability of NOD-IL-4 splenocytes to delay the onset of diabetes. These results indicate that IL-4 expressed in the islets does not prevent the generation of pathogenic islet responses but induces islet Ag-specific Th2 T cells that block the action of diabetogenic T cells in the pancreas.     

Granzyme B is dispensable in the development of diabetes in non-obese diabetic mice

Pancreatic beta cell destruction in type 1 diabetes is mediated by cytotoxic CD8(+) T lymphoctyes (CTL). Granzyme B is an effector molecule used by CTL to kill target cells. We previously showed that granzyme B-deficient allogeneic CTL inefficiently killed pancreatic islets in vitro. We generated granzyme B-deficient non-obese diabetic (NOD) mice to test whether granzyme B is an important effector molecule in spontaneous type 1 diabetes. Granzyme B-deficient islet antigen-specific CD8(+) T cells had impaired homing into islets of young mice. Insulitis was reduced in granzyme B-deficient mice at 70 days of age (insulitis score 0.043±0.019 in granzyme B-deficient versus 0.139±0.034 in wild-type NOD mice p<0.05), but was similar to wild-type at 100 and 150 days of age. We observed a reduced frequency of CD3(+)CD8(+) T cells in the islets and peripheral lymphoid tissues of granzyme B-deficient mice (p<0.005 and p<0.0001 respectively), but there was no difference in cell proportions in the thymus. Antigen-specific CTL developed normally in granzyme B-deficient mice, and were able to kill NOD islet target cells as efficiently as wild-type CTL in vitro. The incidence of spontaneous diabetes in granzyme B-deficient mice was the same as wild-type NOD mice. We observed a delayed onset of diabetes in granzyme B-deficient CD8-dependent NOD8.3 mice (median onset 102.5 days in granzyme B-deficient versus 57.50 days in wild-type NOD8.3 mice), which may be due to the delayed onset of insulitis or inefficient priming at an earlier age in this accelerated model of diabetes. Our data indicate that granzyme B is dispensable for beta cell destruction in type 1 diabetes, but is required for efficient early activation of CTL.     

Comparing the relative role of perforin/granzyme versus Fas/Fas ligand cytotoxic pathways in CD8+ T cell-mediated insulin-dependent diabetes mellitus.

CD8+ cytotoxic T cells play a critical role in initiating insulin-dependent diabetes mellitus. The relative contribution of each of the major cytotoxic pathways, perforin/granzyme and Fas/Fas ligand (FasL), in the induction of autoimmune diabetes remains controversial. To evaluate the role of each lytic pathway in beta cell lysis and induction of diabetes, we have used a transgenic mouse model in which beta cells expressing the influenza virus hemagglutinin (HA) are destroyed by HA-specific CD8+ T cells from clone-4 TCR-transgenic mice. Upon adoptive transfer of CD8+ T cells from perforin-deficient clone-4 TCR mice, there was a 30-fold increase in the number of T cells required to induce diabetes. In contrast, elimination of the Fas/FasL pathway of cytotoxicity had little consequence. When both pathways of cytolysis were eliminated, mice did not become diabetic. Using a model of spontaneous diabetes, which occurs in double transgenic neonates that express both clone-4 TCR and Ins-HA transgenes, mice deficient in either the perforin or FasL/Fas lytic pathway become diabetic soon after birth. This indicates that, in the neonate, large numbers of autoreactive CD8+ T cells can lead to destruction of islet beta cells by either pathway.     

IL-12 administration accelerates autoimmune diabetes in both wild-type and IFN-gamma-deficient nonobese diabetic mice,revealing pathogenic and protective effects of IL-12-induced IFN-gamma

IL-12 administration to nonobese diabetic (NOD) mice induces IFN-gamma-secreting type 1 T cells and high circulating IFN-gamma levels and accelerates insulin-dependent diabetes mellitus (IDDM). Here we show that IL-12-induced IFN-gamma production is dispensable for diabetes acceleration, because exogenous IL-12 could enhance IDDM development in IFN-gamma-deficient as well as in IFN-gamma-sufficient NOD mice. Both in IFN-gamma(+/-) and IFN-gamma(-/-) NOD mice, IL-12 administration generates a massive and destructive insulitis characterized by T cells, macrophages, and CD11c(+) dendritic cells, and increases the number of pancreatic CD4(+) cells secreting IL-2 and TNF-alpha. Surprisingly, IL-12-induced IFN-gamma hinders pancreatic B cell infiltration and inhibits the capacity of APCs to activate T cells. Although pancreatic CD4(+) T cells from IL-12-treated IFN-gamma(-/-) mice fail to up-regulate the P-selectin ligand, suggesting that their entry into the pancreas may be impaired, T cell expansion is favored in these mice compared with IL-12-treated IFN-gamma(+/-) mice because IL-12 administration in the absence of IFN-gamma leads to enhanced cell proliferation and reduced T cell apoptosis. NO, an effector molecule in beta cell destruction, is produced ex vivo in high quantity by pancreas-infiltrating cells through a mechanism involving IL-12-induced IFN-gamma. Conversely, in IL-12-treated IFN-gamma-deficient mice, other pathways of beta cell death appear to be increased, as indicated by the up-regulated expression of Fas ligand on Th1 cells in the absence of IFN-gamma. These data demonstrate that IFN-gamma has a dual role, pathogenic and protective, in IDDM development, and its deletion allows IL-12 to establish alternative pathways leading to diabetes acceleration.     

The countervailing actions of myeloid and plasmacytoid dendritic cells control autoimmune diabetes in the nonobese diabetic mouse

Islet Ag-specific CD4(+) T cells receive antigenic stimulation from MHC class II-expressing APCs. Herein, we delineate the direct in vivo necessity for distinct subsets of macrophages and dendritic cells (DC) in type 1 diabetes mellitus of the NOD mouse by using diphtheria toxin-mediated cell ablation. The ablation of macrophages had no impact on islet Ag presentation or on the induction of insulitis or diabetes in either transfer or spontaneous models. However, the ablation of CD11b(+)CD11c(+) DC led to the loss of T cell activation, insulitis, and diabetes mediated by CD4(+) T cells. When the specific myeloid DC subset was "added-back" to mice lacking total DC, insulitis and diabetes were restored. Interestingly, when NOD mice were allowed to progress to the insulitis phase, the ablation of DC led to accelerated insulitis. This accelerated insulitis was mediated by the loss of plasmacytoid DC (pDC). When pDC were returned to depleted mice, the localized regulation of insulitis was restored. The loss of pDC in the pancreas itself was accompanied by the localized loss of IDO and the acceleration of insulitis. Thus, CD11c(+)CD11b(+) DC and pDC have countervailing actions in NOD diabetes, with myeloid DC providing critical antigenic stimulation to naive CD4(+) T cells and pDC providing regulatory control of CD4(+) T cell function in the target tissue.     

Fas and Fas ligand immunolocalization in pancreatic islets of NOD mice during spontaneous and cyclophosphamide-accelerated diabetes

During insulin-dependent diabetes mellitus, immune cells which infiltrate pancreatic islets mediate beta cell destruction over a prolonged asymptomatic prediabetic period. The molecular mechanisms of beta cell death in vivo remain unresolved. At least two major molecular processes of destruction have been proposed. One involves the Fas–FasL (Fas–Fas ligand) system and the other, the perforin pathway. Here, dual-label immunohistochemistry was employed to examine the intra-islet expression, distribution and cellular sources of Fas and FasL in the NOD mouse, during spontaneous diabetes (days 21, 40 and 90) and following acceleration of diabetes with cyclophosphamide (days 0, 4, 7, 11 and 14 after cyclophosphamide administration). The expression of the proteins was correlated with advancing disease. FasL was expressed constitutively in most beta cells but not in glucagon or somatostatin cells or islet inflammatory cells and paralleled the loss of insulin immunolabelling with advancing disease. It was also expressed in beta cells of non-diabetes prone CD-1 and C57BL/6 mice from a young age (day 21). Strong immunolabelling for Fas was first observed in extra-islet macrophages and those close to the islet in NOD and non-diabetes-prone mice. During spontaneous and cyclophosphamide diabetes, it was observed in a higher proportion of islet infiltrating macrophages than CD4 and CD8 T cells, concomitant with advancing insulitis. In cyclophosphamide-treated mice, the proportion of Fas-positive intra-islet CD4 and CD8 T cells at day 14 (with and without diabetes) was considerably higher than at days 0, 4, 7 and 11. At days 11 and 14, a proportion of Fas-positive intra-islet macrophages co-expressed interleukin-1 and inducible nitric oxide synthase. Fas was not detectable in beta cells and other islet endocrine cells during spontaneous and cyclophosphamide induced diabetes. Our results show constitutive expression of FasL in beta cells in the NOD mouse and predominant expression of Fas in intra-islet macrophages and to a lesser extent in T cells prior to diabetes onset. Interleukin-1 in intra-islet macrophages may induce Fas and inducible nitric oxide synthase expression in an autocrine and paracrine manner and mediate beta cell destruction or even death of some macrophages and T cells. However, other mechanisms of beta cell destruction during spontaneous and cyclophosphamide-accelerated diabetes and independent of Fas–FasL, require examination.     

L-selectin is not required for T cell-mediated autoimmune diabetes

Administration of anti-L-selectin (CD62L) mAb to neonatal nonobese diabetic (NOD) mice mediates long term protection against the development of insulitis and overt diabetes. These results suggested that CD62L has a key role in the general function of beta cell-specific T cells. To further examine the role of CD62L in the development of type 1 diabetes, NOD mice lacking CD62L were established. The onset and frequency of overt diabetes were equivalent among CD62L(+/+), CD62L(+/-), and CD62L(-/-) NOD littermates. Furthermore, patterns of T cell activation, migration, and beta cell-specific reactivity were similar in NOD mice of all three genotypes. Adoptive transfer experiments with CD62L(-/-) CD4(+) T cells prepared from BDC2.5 TCR transgenic mice revealed no apparent defects in migration to pancreatic lymph nodes, proliferation in response to beta cell Ag, or induction of diabetes in NOD.scid recipients. In conclusion, CD62L expression is not essential for the development of type 1 diabetes in NOD mice.     

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.     

降钙素基因相关肽转基因预防小鼠自身免疫性糖尿病发病及其抗氧化应激机制

有证据表明,活性氧(reactive oxygens pecies,ROS)参与了胰岛β细胞自身免疫损伤,是自身免疫性糖尿病发病的重要原因之一。一氧化氮(NO)和过氧化氢(H2O2)介导了致炎性细胞因子对胰岛B细胞的损害,引起脂质过氧化反应,进而损伤胰岛细胞。降钙素基因相关肽(calcitonin gene-related peptide,CGRP)在心肌细胞中可抑制ROS生成而具有细胞保护作用。通过CGRP裸质粒肌肉注射体细胞电针强化转基因方法,使骨骼肌持续表达CGRP,观察其对小剂量多次注射链脲佐菌素(streptozotocin,STZ)造成的小鼠自身免疫性糖尿病发病的影响,进一步测定胰腺局部活性氧含量以及抗氧化酶的改变,探讨其抗氧化应激机制。结果发现,CGRP裸质粒直接注射入小鼠双后肢胫前肌。继以程控电针刺激导入(体内电穿孔法),可使血浆和骨骼肌组织CGRP表达水平显著增高,且持续4周以上;注射STZ同时给予CGRP转基因治疗可减轻胰岛β细胞损伤,显著降低自身免疫性糖尿病的发病率及血糖水平;CGRP转基因可显著抑制自身免疫性糖尿病小鼠胰腺局部活性氧和丙二醛的生成,增加过氧化氢酶(CAT)及超氧化物歧化酶(superoxide dismutase,SOD)的活性。结果提示,CGRP裸质粒直接注射、电针辅助导人转基因可获得CGRF持续高水平的表达,能够预防小鼠自身免疫性糖尿病的发病,其机制之一可能为CGRP抑制了活性氧对胰岛β细胞的损伤。     

The chemokine binding protein M3 prevents diabetes induced by multiple low doses of streptozotocin

Multiple injections of low-dose streptozotocin (MLDS) induce lymphocytic insulitis and diabetes in rodents. To test whether the influx of inflammatory cells was associated with changes in the expression of chemokines, we measured the expression of all known chemokine ligands by real-time quantitative PCR in isolated islets. With the exception of CCL20 and CCL19, chemokines were not significantly expressed in islets from wild-type mice before MLDS treatment. Ten days after treatment, the expression of several chemokines, including CXCL9, CCL1, CXCL10, and CCL21, was dramatically up-regulated. The expression of CCL1, CXCL9, and CCL21 protein was confirmed by immunohistochemistry and was mostly associated with the infiltrating cells. The mouse herpesvirus 68-encoded chemokine decoy receptor M3 can broadly engage these chemokines with high affinity. To test whether a blockade of chemokine function would alter the onset or magnitude of insulitis and diabetes, we used transgenic mice expressing M3 in beta cells (rat insulin promoter (RIP)-M3 mice). RIP-M3 mice were normoglycemic and responded normally to glucose challenge but were remarkably resistant to diabetes induced by MLDS. Islets from MLDS-treated RIP-M3 mice had fewer inflammatory cells and expressed lower levels of chemokines than those from MLDS-treated controls. The role of M3 in chemokine blockade during insulitis was further supported by in vitro experiments demonstrating that multiple chemokines up-regulated during islet inflammation are high-affinity M3 ligands that can be simultaneously sequestered. These results implicate chemokines as key mediators of insulitis and suggest that their blockade may represent a novel strategy to prevent insulitis and islet destruction.     

Histopathological Changes in Insulin,Glucagon and Somatostatin Cells in the Islets of NOD Mice During Cyclophosphamide-accelerated Diabetes: A Combined Immunohistochemical and Histochemical Study

Summary The cyclophosphamide model of accelerated diabetes in the NOD mouse is a useful model of insulin-dependent diabetes mellitus (IDDM). Knowledge on the progressive destruction of beta cells and the fate of other islet endocrine cell-types in this model is sparse. We employed immunohistochemistry and histochemistry, to study temporal changes in islet cell populations, insulitis and glucose transporter-2 expression during cyclophosphamide administration. Cyclophosphamide was administered to day 95 female NOD mice and the pancreas studied at days 0 ( = day 95), 4, 7, 11 and 14 after treatment and in age-matched control mice. At day 0, a majority of the endocrine cells were insulin-positive. Glucagon and somatostatin cells were mostly in the islet periphery and also internally. In the cyclophosphamide group, insulitis was moderate at day 0, declined at day 4 but increased progressively from day 7. The extent of insulitis in treated mice which were diabetes-free at day 14 was comparable to age-matched control mice. From day 11, the marked increase in insulitis correlated with a reciprocal decline in the extent of insulin immunostained islet area. At day 14, the mean insulin area per islet was markedly less in diabetic mice than in age-matched non-diabetic treated and controls. At diabetes, some islets showed co-expression of glucagon and insulin. Our studies suggest that the mean number of glucagon or somatostatin cells per islet does not vary during the study. Glucose transporter-2 immunolabelling was restricted to beta cells but declined in those adjacent to immune cells. We conclude that in the cyclophosphamide model, there is specific and augmented destruction of beta cells immediately prior to diabetes onset. We speculate that the selective loss of glucose transporter-2 shown in this study suggests the existence of a deleterious gradient close to the immune cell and beta cell surface boundary.     

TRPV1+ sensory neurons control beta cell stress and islet inflammation in autoimmune diabetes

In type 1 diabetes, T cell-mediated death of pancreatic beta cells produces insulin deficiency. However, what attracts or restricts broadly autoreactive lymphocyte pools to the pancreas remains unclear. We report that TRPV1(+) pancreatic sensory neurons control islet inflammation and insulin resistance. Eliminating these neurons in diabetes-prone NOD mice prevents insulitis and diabetes, despite systemic persistence of pathogenic T cell pools. Insulin resistance and beta cell stress of prediabetic NOD mice are prevented when TRPV1(+) neurons are eliminated. TRPV1(NOD), localized to the Idd4.1 diabetes-risk locus, is a hypofunctional mutant, mediating depressed neurogenic inflammation. Delivering the neuropeptide substance P by intra-arterial injection into the NOD pancreas reverses abnormal insulin resistance, insulitis, and diabetes for weeks. Concordantly, insulin sensitivity is enhanced in trpv1(-/-) mice, whereas insulitis/diabetes-resistant NODxB6Idd4-congenic mice, carrying wild-type TRPV1, show restored TRPV1 function and insulin sensitivity. Our data uncover a fundamental role for insulin-responsive TRPV1(+) sensory neurons in beta cell function and diabetes pathoetiology.     

Combination therapy with an antioxidant and a corticosteroid prevents autoimmune diabetes in NOD mice.

Oxygen free radicals have been implicated as mediators of pancreatic islet beta cell damage in autoimmune, insulin-dependent diabetes mellitus (IDDM). In this study, we show that the antioxidant, probucol, produced only a small decrease in diabetes incidence in nonobese diabetic (NOD) mice, an animal model for human IDDM. However, combination of probucol with the antiinflammatory corticosteroid, deflazacort, produced an early synergistic effect, delaying diabetes onset by 3 weeks, and a later additive effect, decreasing diabetes incidence from 68% (17 of 25 mice) to 23% (6 of 26 mice, p < 0.005). Protection against diabetes by the combination of probucol and deflazacort was associated with a significant decrease in pancreatic islet infiltration by macrophages/lymphocytes (insulitis) and prevention of islet beta cell loss.     

An Immunohistochemical Study of Macrophage Influx and the Co-localization of Inducible Nitric Oxide Synthase in the Pancreas of Non-obese Diabetic (NOD) Mice During Disease Acceleration with Cyclophosphamide

Cyclophosphamide has been used to accelerate and synchronize diabetes in non-obese diabetic (NOD) mice. It was injected to 70-day-old female NOD mice and its effect on the progression of insulitis studied at days 0, 4, 7, 11 and at onset of diabetes. Pancreatic sections were also examined for the influx of CD4 and CD8 T cells and macrophages following immunofluorescence staining. The kinetics of macrophage immunoreactive cells in the exocrine and intra-islet areas were also investigated. Light and confocal microscopy were employed to examine the expression and co-localization of inducible nitric oxide synthase following dual- and triple-label immunofluorescence histochemistry. After cyclophosphamide administration, the severity of insulitis remained similar from days 0 to 4 but began to rise at day 7 and markedly by day 11 and at onset of diabetes. At these two later stages, the insulitis scores were close to 100% while in age-matched control groups the insulitis scores were considerably lower. Immunohistochemical staining showed increasing numbers of CD4 and CD8 T cell subsets and macrophages within the islets and in exocrine, sinusoidal and peri-vascular regions. At onset of diabetes, several islets contained prominent clusters of macrophage immunoreactive cells. Macrophage influx into the islets increased sharply from day 7 (mean number per islet: 119±54 SEM), peaked at day 11 (mean number per islet: 228±42), and then declined at onset of diabetes (mean number per islet: 148±49). Several cells with immunolabelling for inducible nitric oxide synthase were detectable from day 7 onwards until the onset of diabetes. Dual- and triple-label immunohistochemistry showed that a significant proportion of macrophages and only a few beta cells contained the enzyme. Macrophages positive for the enzyme were located as clusters or occasionally contiguously, in the peri-islet and intra-islet areas but rarely in the exocrine region. Islets with minimal distribution of macrophages in the peri-islet areas were not positive for inducible nitric oxide synthase. Beta cells positive for the enzyme were observed in islets with significant macrophage infiltration in locations close to macrophages. The present results show that cyclophosphamide administration to female NOD mice results in a rapid influx of CD4 and CD8 cells and macrophages. The marked up-regulation of inducible nitric oxide synthase in a selective proportion of macrophages, within the islets, immediately preceding and during the onset of diabetes suggests that nitric oxide released by islet macrophages may be an important molecular mediator of beta cell destruction in this accelerated model of insulin-dependent diabetes mellitus.     

Thymic and postthymic regulation of diabetogenic CD8 T cell development in TCR transgenic nonobese diabetic (NOD) mice

Natural development of diabetes in nonobese diabetic (NOD) mice requires both CD4 and CD8 T cells. Transgenic NOD mice carrying alphabeta TCR genes from a class I MHC (Kd)-restricted, pancreatic beta cell Ag-specific T cell clone develop diabetes significantly faster than nontransgenic NOD mice. In these TCR transgenic mice, a large fraction of T cells express both transgene derived and endogenous TCR beta chains. Only T cells expressing two TCR showed reactivity to the islet Ag. Development of diabetogenic T cells is inhibited in mice with no endogenous TCR expression due to the SCID mutation. These results demonstrate that the expression of two TCRs is necessary for the autoreactive diabetogenic T cells to escape thymic negative selection in the NOD mouse. Further analysis with MHC congenic NOD mice revealed that diabetes development in the class I MHC-restricted islet Ag-specific TCR transgenic mice is still dependent on the presence of the homozygosity of the NOD MHC class II I-Ag7.     

The expression of influenza virus hemagglutinin in the pancreatic beta cells of transgenic mice results in autoimmune diabetes

Insulin-dependent diabetes mellitus results from the autoimmune destruction of the insulin-producing beta cells of the pancreatic islets. The target antigen(s) involved in this immunopathological process has not been identified. Our strategy was to determine whether expression of a novel surface antigen by murine pancreatic beta cells would result in insulin-dependent diabetes mellitus. We have generated lines of transgenic mice (RIP-HA) that express the hemagglutinin of the A/Japan/305/57 strain of influenza virus on their insulin-producing beta cells. Hyperglycemia developed in mice derived from all three founders at a frequency varying from 13% to 27%, and was associated with lymphocytic infiltration of the islets and a humoral response against beta cell antigens, including hemagglutinin. These results suggest that the RIP-HA mice should provide a useful system in which to study the cellular interactions involved in the induction of self-tolerance and autoimmunity.     

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.     

Expression of activated Notch3 in transgenic mice enhances generation of T regulatory cells and protects against experimental autoimmune diabetes

Thymic-derived dysregulated tolerance has been suggested to occur in type 1 diabetes via impaired generation of CD4(+)CD25(+) T regulatory cells, leading to autoimmune beta cell destruction. In this study, we demonstrate that Notch3 expression is a characteristic feature of CD4(+)CD25(+) cells. Furthermore, streptozotocin-induced autoimmune diabetes fails to develop in transgenic mice carrying the constitutively active intracellular domain of Notch3 in thymocytes and T cells. The failure to develop the disease is associated with an increase of CD4(+)CD25(+) T regulatory cells, accumulating in lymphoid organs, in pancreas infiltrates and paralleled by increased expression of IL-4 and IL-10. Accordingly, CD4(+) T cells from Notch3-transgenic mice inhibit the development of hyperglycemia and insulitis when injected into streptozotocin-treated wild-type mice and display in vitro suppressive activity. These observations, therefore, suggest that Notch3-mediated events regulate the expansion and function of T regulatory cells, leading to protection from experimental autoimmune diabetes and identify the Notch pathway as a potential target for therapeutic intervention in type 1 diabetes.     

Preferential costimulation by CD80 results in IL-10-dependent TGF-beta1(+) -adaptive regulatory T cell generation

Costimulatory ligands CD80 and CD86 have different binding preferences and affinities to their receptors, CD28 and CTLA-4. Earlier, we demonstrated that CD80 binds to CTLA-4 with higher affinity and has a role in suppressing T cell response. The current study demonstrates that not only did blockade of CD86 upon Ag presentation by bone marrow-derived dendritic cells (DC) to OVA-specific T cells result in induction of hyporesponsive T cells but also that these T cells could suppress the proliferative response of effector T cells. These T cells showed TGF-beta1 on their surface and secreted TGF-beta1 and IL-10 upon restimulation. Although blockade of CTLA-4 and neutralization of IL-10 profoundly inhibited the induction of these TGF-beta1(+) T cells, their ability to suppress the effector T cell proliferation was abrogated by neutralization of TGF-beta1 alone. Induction of TGF-beta1(+) and IL-10(+) T cells was found to be independent of natural CD4(+)CD25(+) regulatory T cells, demonstrating that preferential ligation of CTLA-4 by CD80 induced IL-10 production by effector T cells, which in turn promoted the secretion of TGF-beta1. Treatment of prediabetic NOD mice with islet beta cell Ag-pulsed CD86(-/-) DCs, but not CD80(-/-) DCs, resulted in the induction of TGF-beta1- and IL-10-producing cells, significant suppression of insulitis, and delay of the onset of hyperglycemia. These observations demonstrate not only that CD80 preferentially binds to CTLA-4 but also that interaction during Ag presentation can result in IL-10-dependent TGF-beta1(+) regulatory T cell induction, reinstating the potential of approaches to preferentially engage CTLA-4 through CD80 during self-Ag presentation in suppressing autoimmunity.     

Cutting edge: CD25+ regulatory T cells prevent expansion and induce apoptosis of B cells specific for tissue autoantigens

To study the role of CD25(+) regulatory T cells (T(regs)) in peripheral B cell tolerance, we generated transgenic rat insulin promoter RIP-OVA/HEL mice expressing the model Ags OVA and HEL in pancreatic islet beta cells (where RIP is rat insulin promoter and HEL is hen egg lysozyme). Adoptively transferred transgenic OVA-specific CD4(+) and CD8(+) T cells proliferated only in the autoantigen-draining pancreatic lymph node (PLN), demonstrating pancreas-specific Ag expression. Transferred HEL-specific transgenic B cells (IgHEL cells) disappeared within 3 wk from transgenic but not from nontransgenic mice immunized with autoantigen. Depletion of CD25(+) FoxP3(+) cells completely restored IgHEL cell numbers. T(reg) exerted an analogous suppressive effect on endogenous HEL-specific autoreactive B cells. T(regs) acted by inhibiting the proliferation of IgHEL cells in the spleen and PLN and by systemic induction of their apoptosis. Furthermore, they reduced BCR and MHC II surface expression on IgHEL cells in the PLN. These findings demonstrate that autoreactive B cells specific for a nonlymphoid tissue autoantigen are controlled by T(regs).