Pertussigen treatment retards, but fails to prevent, the development of type I, insulin-dependent diabetes mellitus (IDDM) in NOD mice

Current evidence supports an autoimmune etiopathogenesis for Type I, insulin-dependent diabetes mellitus (IDDM) in which the pancreatic beta (beta) cell is the specific target tissue. Recently, the NOD (non-obese diabetic) mouse has become an important model for IDDM, exhibiting many of the pathological features observed in man, including a progressive pancreatic islet leukocytic inflammation referred to as insulitis. The present study was carried out to determine the efficacy of the bacterial-derived bio-product, pertussigen, to retard the progression of insulitis and thereby prevent overt diabetes. Results revealed that (1) the rapid onset of IDDM in female NOD mice is absent if the mothers are treated with pertussigen prior to mating, (2) treatment of young prediabetic NOD mice with repeated injections of pertussigen results in the retardation of onset of IDDM when compared to untreated control NOD mice, and (3) the severity of insulitis in pertussigen-treated NOD mice not developing IDDM was noticeably less severe than age and sex-matched untreated control mice. Since earlier work had shown that pertussis vaccine, which contains pertussigen, could prevent development of IDDM in mice treated with streptozotocin, the present results may indicate basic differences in the inflammatory responses in the genetically-predisposed NOD mice and IDDM-nonsusceptible mice with streptozotocin-induced diabetes.     

Genetic and immunological basis of autoimmune diabetes in the NOD mouse

The non-obese diabetic (NOD) mouse is an animal model of human insulin-dependent diabetes mellitus (IDDM). Most NOD mice show insulitis at several weeks of age, and 60-90% of the female mice develop overt diabetes after 20-30 weeks of age. NOD mice share many features of human IDDM. As in human IDDM, the disease development in NOD mice is controlled by a number of disease susceptibility or resistant genes (Idds), including the major histocompatibility complex locus. Cumulative evidence suggests that Thl CD4+ T cells play a critical role in the autoimmune process leading to beta cell destruction. In addition to CD4+ T cells, CD8+ cells and B cells also participate in the pathogenesis. There are several candidate antigens recognized by autoreactive T cells such as glutamic acid decarboxylase (GAD), insulin and heat shock protein (HSP) 60. Treatment by these antigens suppresses IDDM development in NOD mice, suggesting that they may initiate the autoimmune process of NOD mice.     

Intradermal administration of GAD & evaluation of diabetes incidence in mice: possible relevance for skin tests in humans

In vitro cell mediated reactivity to Glutamic Acid Decarboxylase (GAD) has been reported in man and in the non-obese diabetic (NOD) mouse. The demonstration of such reactivity in vivo using GAD in a simple intradermal skin test would be useful for mass screening of subjects at risk of Type 1 diabetes. Such a skin test could be simply applied to the forearm, then signs of local reaction would indicate patients at risk. However, in order to safely apply a skin test of this type it must be certain that administration of the antigen does not itself provoke or start the process leading to diabetes in susceptible individuals. In the present study the NOD mouse model was used. GAD and two peptides of GAD, which may have relevance to the disease process, were applied intradermally to these mice to determine whether a local reaction could be seen and to see if the diabetes rate was altered. Moreover, Balb/c mice, which can be considered to be at zero risk of developing the disease, were also injected with the same GAD and GAD peptides. No significant differences were seen in the diabetes incidence of the treatment groups compared to the control groups in either the NOD or Balb/c mice although a local swelling was seen in female NOD mice susceptible to diabetes after GAD administration in the footpad. We conclude that the administration of GAD and/or GAD peptides does not provoke or accelerate diabetes incidence in the NOD mouse and that an intradermal skin-test with GAD may be suitable for preliminary trials aimed at large scale screening of humans for their potential to develop type 1 diabetes.     

Transfer of dendritic cells (DC) ex vivo stimulated with interferon-gamma (IFN-gamma) down-modulates autoimmune diabetes in non-obese diabetic (NOD) mice.

The NOD mouse has been used to explore the many features of insulin-dependent diabetes mellitus (IDDM) that is caused by the destruction of insulin-producing beta cells in the islets of Langerhans of the pancreas. Self-reactive T cells have been considered to mediate IDDM in the NOD mouse, and antigen-presenting cells like DC and macrophages are expected to be involved in the processes from their role in generating regulatory or effector T cells. The present study shows that transfer of IFN-gamma-stimulated DC of the NOD or ICR mouse into the NOD mouse did not accelerate IDDM onset but afforded long-lasting protection against clinical and histological signs of IDDM in the recipient mice. The anti-diabetogenic ability was unique to IFN-gamma-stimulated DC when compared with unstimulated DC. A considerable proportion of the injected IFN-gamma-stimulated DC was demonstrated to migrate into the pancreas and its associated lymphoid tissues, suggesting the DC exert their anti-diabetogenic effects there. These findings suggest that development of autoimmune diabetes in the NOD mouse is under the control of DC, and that IDDM onset could be controlled by appropriately manipulating DC systems in vivo, which may open the gate for the therapeutic application of ex vivo-conditioned DC to human IDDM.     

Intradermal Administration of GAD & Evaluation of Diabetes Incidence in Mice: Possible Relevance for Skin Tests in Humans

In vitro cell mediated reactivity to Glutamic Acid Decarboxylase (GAD) has been reported in man and in the non-obese diabetic (NOD) mouse. The demonstration of such reactivity in vivo using GAD in a simple intradermal skin test would be useful for mass screening of subjects at risk of Type 1 diabetes. Such a skin test could be simply applied to the forearm, then signs of local reaction would indicate patients at risk. However, in order to safely apply a skin test of this type it must be certain that administration of the antigen does not itself provoke or start the process leading to diabetes in susceptible individuals.

In the present study the NOD mouse model was used. GAD and two peptides of GAD, which may have relevance to the disease process, were applied intradermally to these mice to determine whether a local reaction could be seen and to see if the diabetes rate was altered. Moreover, Balb/c mice, which can be considered to be at zero risk of developing the disease, were also injected with the same GAD and GAD peptides.

No significant differences were seen in the diabetes incidence of the treatment groups compared to the control groups in either the NOD or Balb/c mice although a local swelling was seen in female NOD mice susceptible to diabetes after GAD administration in the footpad.

We conclude that the administration of GAD and/or GAD peptides does not provoke or accelerate diabetes incidence in the NOD mouse and that an intradermal skin-test with GAD may be suitable for preliminary trials aimed at large scale screening of humans for their potential to develop type 1 diabetes     

Effects of sodium fusidate in animal models of insulin-dependent diabetes mellitus and septic shock.

We have evaluated the effects of the novel immunosuppressant sodium fusidate (fusidin) in the non-obese diabetic (NOD) mouse and in D-galactosamine (D-Gal)-presensitized BALB/c mice challenged with the bacterial superantigen, Staphylococcus aureus enterotoxin B (SEB) or with the endotoxin, Escherichia coli lipopolysaccharide (LPS). The NOD mouse model has clinical and histoimmunological features similar to those of human insulin-dependent diabetes mellitus (IDDM). The SEB- and LPS-treated BALB/c mouse models exhibit pathogenic similarities with human septic shock conditions. In the NOD mouse, fusidin suppressed the spontaneous development of insulitis (mean inhibition 73%) and hyperglycaemia (IDDM incidence 25% versus 0%) when administered at 40 mg/kg five times weekly for 8 consecutive weeks from the fourth week of age; concurrently treated animals exhibited reduced percentages of splenic T lymphocytes. This anti-diabetogenic effect was confirmed in the accelerated model of diabetes induced in the NOD mouse with cyclophosphamide (CY) (IDDM incidence 55% versus 21-6% using dosages of fusidin from 40 to 80 mg/kg five times weekly); protection from IDDM development was achieved even when the drug (80 mg/kg/day) was first administered 7 days after CY challenge. In contrast, fusidin did not reverse hyperglycaemia when administered to CY-treated animals within 3 days of IDDM development. In the two models of septic shock, prophylactic treatment with fusidin, 80 mg/kg given three times for 2 days prior to D-Gal/SEB or D-Gal/LPS challenge, drastically reduced the lethality compared with D-Gal/buffer-treated mice. This effect may depend on the inhibitory action of fusidin on the secretion of cytokines such as interferon-gamma and tumour necrosis factor-alpha, the serum levels of which were greatly diminished in the fusidin-treated mice (mean inhibition 50-90%). These results demonstrate that fusidin may have a role in the treatment of cell-mediated autoimmune diseases and cytokine-mediated infectious diseases in humans.     

Both central and peripheral tolerance mechanisms play roles in diabetes prevention in NOD-E transgenic mice

The non-obese diabetic (NOD) mouse spontaneously develops diabetes and is a widely used model of Type 1 Diabetes in humans. The major histocompatibility complex class II plays an important role in governing disease susceptibility in NOD mice. NOD mice express a rare I-A allele, I-A(g7), and do not express I-E molecules. Interestingly, transgenic NOD mice which express I-E (NOD-E) fail to develop diabetes although, the protective mechanism(s) are incompletely understood. Initially, we explored whether diabetes prevention was due to deletion of autoreactive T cells. Through adoptive transfer with depletion of CD25+ T cells, we demonstrated that autoreactive T cells were present in the periphery of NOD-E mice. Although, BDC2.5NOD T cells proliferated less in the pancreatic lymph nodes of NOD-E mice, we found that they transferred disease with a similar kinetic in NOD.scid and NOD-E.scid recipients suggesting that there was little difference in peripheral antigen presentation in NOD-E mice. We also found that there were no proportional or functional differences between NOD and NOD-E T regs. Our studies indicate that autoreactive T cells are present within the periphery of NOD-E mice but that these cells are present in low numbers suggesting that peripheral tolerogenic mechanisms are able to prevent them from inducing diabetes.     

The functional state of the beta cells in the pathogenesis of insulin-dependent diabetes mellitus.

Besides the thymus-dependent immune system, growing evidence suggests that the functional state of the beta cell plays a role in the pathogenesis of Type 1 (insulin-dependent) diabetes. Increased incidence of diabetes has been described after increased insulin production and vice versa, and actual hyperinsulinemia has been observed in relation to the diabetogenesis. Prophylactic insulin treatment and intensive insulin therapy at diagnosis are discussed. The studies referred to are mostly animal model investigations of BB rats and NOD mice and-to a lesser degree- of streptozotocin- and encephalomyocarditis-virus-induced diabetes. Also human evidence exists, but naturally of a more sporadic character. Three possible mechanisms behind the beta cell sensitivity as a function of their activity are suggested: increased antigen expression (including both gangliosides and proteins) in beta cells with high activity which could activate the destruction caused by the immune system, and increased susceptibility to the toxicity of interleukins and to diabetogenic agents. With respect to developing preventive treatment the described research area may turn out to be very important. Further studies both in animal models and in humans are awaited.     

The unique nucleotide sequence of the A beta gene in the NOD mouse is shared with its nondiabetic sister strains, the ILI and the CTS mouse

It is generally held that one of the recessive genes controlling diabetes in the NOD mouse is linked to the major histocompatibility complex (MHC). Unique substitution of Asp57 with Ser in the A beta chain is considered to make the A beta gene the MHC-linked susceptibility gene. We therefore analysed the nucleotide sequences of the A beta second exon in ILI, CTS, and NON mice, which are nondiabetic inbred strains but are derived from the same Jcl-ICR mice as the NOD mouse. The DNA sequence analyses revealed that the A beta second exon sequences in the ILI and CTS mice, but not in the NON mouse, are identical to that of the NOD mouse. Possible roles of Ser57 of the A beta chain in the nondiabetic sister strains are discussed.     

Islet-infiltrating T cell clones from non-obese diabetic mice that promote or prevent accelerated onset diabetes

In humans and non-obese diabetic mice (NOD), insulin-dependent diabetes mellitus (IDDM) results from a spontaneous T cell-dependent autoimmune destruction of the insulin-producing pancreatic beta cells. Previous data suggest that a delicate balance between autoaggressive T cells and suppressor-type immune phenomena determine whether expression of autoimmunity is limited to insulitis or progresses to IDDM. To resolve the cellular basis of this intricate network of pathogenic CD4+ and CD8+ T cells and the role of T cells in suppressive immune phenomena. T cell clones were propagated directly from islets of NOD mice at the onset of insulitis. Insofar as insulitis, but not IDDM, is universal in NOD mice, we have screened for the in vivo effects of the islet-infiltrating T cell clones upon expression of IDDM, not insulitis. A CD4+ T cell clone, IS-3S7D, proliferates in response to islet antigen(s) and its transfer into prediabetic NOD mice promotes the rapid onset of IDDM. An interleukin 2 (IL 2)-dependent noncytolytic, V beta 11+ CD8+. T cell clones IS-2.15, prevents an accelerated onset diabetes in two distinct models. The present study, which documents the presence of CD4+ diabetogenic T cell clones and CD8+ T cell clones that dampen autoimmunity, gives tangible evidence that opposing autoimmune processes may determine whether an autoimmune-prone host develops frank disease.     

Lymphocyte vaccination prevents spontaneous diabetes in the non-obese diabetic mouse.

The aim of this study was to investigate whether lymphocyte vaccination can prevent diabetes occurring in the non-obese diabetic (NOD) mouse, an animal model of human insulin-dependent diabetes mellitus (IDDM). The lymphocyte vaccine was composed of lymphocytes isolated from the spleens of diabetic NOD mice, activated in vitro using concanavalin A (Con A) and rendered immunogenic using glutaraldehyde treatment. These cells were used to vaccinate mice at 6 weeks with boosters at weeks 10, 14 and 18. The animals were then monitored for signs of diabetes until week 30. Twenty-eight NOD mice (11 male, 17 female) were T-lymphocyte vaccinated while 35 littermates (14 male, 21 female) were sham vaccinated with the vaccine carrier, as control mice. The percentage of mice remaining non-diabetic was 50% in the T-lymphocyte-vaccinated group compared with 20% in control mice (P < 0.05). When the results were divided according to sex of the mouse the percentage of female NOD mice remaining non-diabetic was 47.1% in the T-lymphocyte-vaccinated group compared to only 9.4% in the controls (P < 0.01), while in the males there was no significant difference between the groups. These results suggest that T-lymphocyte vaccination can prevent diabetes in NOD mice and that it has its greatest effect in females. The therapy is apparently safe and its efficacy indicates that it may be of value in prediabetes in man.     

Protection of IFN-gamma signaling-deficient NOD mice from diabetes by cyclophosphamide

Non-obese diabetic (NOD) mice that are genetically deficient in either IFN-gamma or beta chain of the IFN-gammaR develop diabetes with similar kinetics to wild-type NOD mice. In the current study, we demonstrated that treatment of IFN-gamma signaling-deficient NOD mice with cyclophosphamide (CY) not only fails to induce acute diabetes but also confers permanent protection from diabetes. Protection was mediated by the preferential generation of regulatory T cells (Treg cells) that are capable of suppressing the diabetogenic process, with no change in the total number and function of Treg cells. Moreover, CY treatment of IFN-gamma signaling-deficient NOD mice reversed the ongoing pathogenic process and eliminated cellular infiltrates of pancreatic islets. While these results have been derived using a genetically modified mouse model of diabetes, they indicate that knowledge of host genetic factors and environmental factors influencing the development of Type I diabetes mellitus may provide a rational approach to develop a means to reverse the development of Type I diabetes in human.     

The effect of bone marrow and thymus chimerism between non-obese diabetic (NOD) and NOD-E transgenic mice,on the expression and prevention of diabetes

The non-obese diabetic (NOD) mouse is an established animal model of the autoimmune disease, insulin-dependent diabetes mellitus (IDDM). The NOD-E mouse is a transgenic mouse which expresses the I-E molecule (absent in NOD mice). Expression of I-E protects these mice from both insulitis and IDDM.We have investigated the possible mechanisms of this protection by constructing bone marrow, and combined bone marrow and thymus chimeras between NOD and NOD-E mice. Our data suggest that thymic epithelium may play no direct role in either protection against, or promotion of, IDDM. Protection from diabetes is provided either by NOD-E donor bone marrow or NOD-E recipient non-thymic radioresistant cells. The means by which protection may be achieved in this system are discussed.     

Susceptibility to type I diabetes in women is associated with the CD3 epsilon locus on chromosome 11.

Type I diabetes is associated with the DQ loci of the MHC and to a lesser extent with the T cell antigen receptor (TcR) beta chain genes. The non-obese diabetic (NOD) mouse is an animal model of human diabetes, in which up to 90% of female mice develop overt insulin-dependent diabetes. Genetic studies in the NOD mouse suggest that there are at least three diabetogenic genes; one that maps to the MHC, another that may map to the mouse Thy-I locus, and a third that has still to be identified. We have investigated loci in the vicinity of the human Thy-I locus on chromosome 11q23 and report here the results of restriction fragment length polymorphism (RFLP) analysis of the CD3 epsilon locus of 168 Caucasoid patients with type I diabetes. While no association was found between this locus and type I diabetes, a significant difference in the frequency of the CD3 epsilon 8-kb allele was found between male and female patients (0.268 versus 0.430; P less than 0.0025, Pc = 0.02) and between female patients and healthy female controls (0.430 versus 0.267; P less than 0.015). These results suggest that a gene residing on chromosome 11q23 may confer susceptibility to type I diabetes in women.     

IL－2对NOD鼠糖尿病的影响

ＮＯＤ鼠是人类胰岛素依赖型糖尿病的动物模型，其发病与自身免疫有关。环磷酰胺（ＣＰ）可以加速这一过程，使ＮＯＤ鼠糖尿病的发病率提高或提前。一些研究表明：ＮＯＤ鼠的淋巴细胞在淋巴细胞混合反应中（ＭＬＲ），在有或无刺激物的存在下，白细胞介素２（ＩＬ－２）的产量均明显低于正常鼠的淋巴细胞。该实验对注射了一次大剂量的ＣＰ（３００ｍｇ／ｋｇ体重）后的ＮＯＤ鼠试用了ＩＬ－２治疗。结果显示：对于年幼的ＮＯＤ鼠ＩＬ－２治疗１４无可以明显减轻注射ＣＰ后的胰岛破坏加速。病理检查显示三组胰岛炎严重程度积分分别为２９；８１；８８。ＩＬ－２处理组明显低于ＣｏｎＡ处理组与对照组。这个研究还显示，对于１２周龄的ＮＯＤ鼠，经１４天的ＩＬ－２治疗，可以完全预防ＣＰ诱导的糖尿病的发生。糖尿病发病率在ＩＬ－２组为０／１２；对照组为７／１２。但对已发病的ＮＯＤ鼠自发性糖尿病ＩＬ－２不能使其缓解。     

Adrenalitis in the non-obese diabetic mouse

The non-obese diabetic (NOD) mouse is a model of spontaneous type-1 diabetes used in the field of diabetes research. This study looked at the adrenal glands of NOD and control mice both indirectly in vivo for hormone secretion, and directly in vitro for histological examination. Adrenal glands were taken from NOD mice, of both sexes, at different ages and corticosterone and adrenocorticotropic hormone (ACTH) plasma levels evaluated by radioimmunoassay. There was evidence of lymphocytic infiltration of the adrenal glands, which however, was not accompanied by changes in corticosterone levels. There was a reduction in ACTH levels with age (R2 = 0.98). Mice from other strains (TFW, CBA and Balb/c) showed no lymphocytic infiltration in the adrenal glands and had lower levels of corticosterone than NOD mice of similar ages, but the differences were not significant. In conclusion, since the NOD mouse shows histological signs of adrenalitis, thyroiditis, sialitis and parathyroiditis, this animal can be regarded as a model to investigate mechanisms involved in diffuse lymphocytic infiltration of peripheral endocrine glands (polyendocrine autoimmunity). In addition, if diabetes in the NOD mouse is the result of a polyendocrine disorder rather than a process specific for diabetes, then this finding may have implications for attempts to prevent type-1 diabetes in humans.     

Inhibition of autoimmune diabetes in NOD mice with serum from streptococcal preparation (OK-432)-injected mice.

We have recently reported that systemic and chronic administration of recombinant tumour necrosis factor alpha (TNF-alpha), as well as streptococcal preparation (OK-432), inhibits development of insulin-dependent diabetes mellitus (IDDM) in NOD mice and BB rats, models of IDDM. In this study we examined whether serum containing endogenous TNF induced by OK-432 injection could inhibit IDDM in NOD mice. Treatment twice a week from 4 weeks of age with OK-432-injected mouse serum, which contained endogenous TNF (75U), but not IL-1, IL-2 and interferon-gamma (IFN-gamma) activity, reduced the intensity of insulitis and significantly inhibited the cumulative incidence of diabetes by 28 weeks of age in NOD mice, as compared with the incidence in non-treated mice (P less than 0.01) and in mice treated with control serum (P less than 0.02). This inhibitory effect of the serum was diminished, although not significantly, by neutralization of serum TNF activity with anti-mouse TNF antibody. In the mice treated with the serum from OK-432-injected mice, Thy-1.2+ or CD8+ spleen cells decreased (P less than 0.01) and surface-Ig+ (S-Ig+) cells increased (P less than 0.05), whereas the proliferative response of spleen cells to concanavalin A (P less than 0.01) and lipopolysaccharide (P less than 0.05) increased. The results indicate that the inhibition by OK-432 treatment of IDDM in NOD mice was partially mediated by serum factors including endogenous TNF.     

Anti-alpha/beta T cell receptor monoclonal antibody provides an efficient therapy for autoimmune diabetes in nonobese diabetic (NOD) mice.

The nonobese diabetic (NOD) mouse is a relevant model for studying human insulin-dependent diabetes mellitus (IDDM). The selective destruction of insulin-secreting cells in this model is subsequent to an autoimmune reaction directed towards the beta cells inside the islets of Langerhans of the pancreas. Given the key role played by T cells in the development of IDDM, we investigated a model of IDDM prevention in NOD mice by administration of a monoclonal antibody to the alpha/beta dimer of the T cell receptor for antigen. Our data provide evidence that aiming at the T cell receptor protects against both spontaneous and cyclophosphamide-induced diabetes in the NOD mouse. Interestingly, potential clinical application is suggested by the efficient and durable reversal of recent onset diabetes in mice treated with anti-alpha/beta monoclonal antibody within 1 week following the clinical discovery of IDDM.     

Circulating lymphocyte populations and autoantibodies in non-obese diabetic (NOD) mice: a longitudinal study.

Several previous observations indicate a role for the immune system in the pathogenesis of insulin-dependent diabetes mellitus (IDDM) in non-obese diabetic (NOD) mice. In order to assess the status of the immune system in this model of spontaneous diabetes we studied the phenotype of circulating lymphocytes and the humoral autoimmunity to islet cells in non-diabetic NOD mice at various ages. Lymphocyte numbers were low in young NOD mice (age less than 160 days) as compared with other strains of mice and increased later to reach values in or above the range of controls. The percentages of circulating T lymphocytes and their L3T4+ and Lyt2+ subsets were higher in NOD mice of all ages and both sexes than in controls; however, no imbalance of the L3T4+ and Lyt2+ subpopulations was found. Anti-insulin autoantibodies were detected by an ELISA assay in all the NOD mice studied throughout the entire period of observation. Autoantibodies reacting with the cytoplasm of islet cells in Bouin's fixed pancreas sections, likely to be anti-insulin antibodies, were found in 47 to 58% of the samples from NOD mice aged 75 to 150 days. Antibodies to surface antigens of rat insulinoma cells were virtually absent in young NOD mice (75-100 days) and appeared in 33 to 43% of the samples from 150 to 185 days old NOD mice. The autoantibodies and the quantitative lymphocyte abnormalities reported here, although not predictive of the appearance of overt diabetes, are likely to be involved in the pathogenesis of the disease and therefore may indicate directions for future investigations.     

Autoimmunity in HLA-DQ8 transgenic mice expressing granulocyte/macrophage-colony stimulating factor in the beta cells of islets of Langerhans

Type 1 diabetes (T1D) is a polygenic autoimmune disease with a strong HLA association particularly, HLA-DQ8. We investigated whether islet-specific expression of granulocyte/macrophage colony-stimulating factor (Ins.GM-CSF) in A Beta degrees.NOD.DQ8 mice (HLA-DQ8 transgenic mice on a NOD background lacking endogenous mouse MHC class II molecules) would predispose to development of spontaneous autoimmune diabetes. A Beta degrees.NOD.DQ8 mice expressing GM-CSF in the pancreatic ss cells (8+ G+) as well as litter mates lacking either HLA-DQ8 (8 - G+) or GM-CSF (8+ G -) or both (8 - G -) exhibited insulitis and sialadenitis of varying degrees. But none of the mice progressed to develop T1D. Other than the marked mononuclear cell infiltration in livers of mice expressing GM-CSF irrespective of HLA-DQ8 expression (8+ G+ or 8 - G+), no other changes were observed in the animals. Thus, we have shown for the first time that expression of HLA-DQ8 in the diabetes-predisposing mileu of NOD genetic background is not sufficient to predispose to development of autoimmune diabetes even when the potent immunostimulatory cytokine, GM-CSF is expressed in the pancreatic islets.