Histological study of pancreatic beta-cell loss in relation to the insulitis process in the non-obese diabetic mouse

Tracking Ca2+ Dynamics in NOD Mouse Islets During Spontaneous Diabetes Development

The mechanisms accounting for the functional changes of α- and β-cells over the course of type 1 diabetes (T1D) development are largely unknown. Permitted by our established technology of high spatiotemporal resolution imaging of cytosolic Ca2+ ([Ca2+]c) dynamics on fresh pancreas tissue slices, we tracked the [Ca2+]c dynamic changes, as the assessment of function, in islet α- and β-cells of female nonobese diabetic (NOD) mice during the development of spontaneous diabetes. We showed that, during the phases of islet inflammation, 8 mmol/L glucose-induced synchronized short [Ca2+]c events in β-cells were diminished, whereas long [Ca2+]c events were gradually more triggerable at substimulatory 4 and 6 mmol/L glucose. In the islet destruction phase, the synchronized short [Ca2+]c events in a subset of β-cells resumed at high glucose condition, while the long [Ca2+]c events were significantly elevated already at substimulatory glucose concentrations. In the α-cells, the glucose sensitivity of the [Ca2+]c events persisted throughout the course of T1D development. At the late islet destruction phase, the α-cell [Ca2+]c events exhibited patterns of synchronicity. Our work has uncovered windows of functional recovery in β-cells and potential α-cells functional synchronization in NOD mice over the course of T1D development.

ARTICLE HIGHLIGHTS

In NOD mice β-cells, 8 mmol/L glucose-induced synchronized short [Ca2+]c events diminish in the early phases of islet inflammation, and long Ca2+ events became more sensitive to substimulatory 4 and 6 mmol/L glucose. In the late islet destruction phase, the synchronized short [Ca2+]c events in a subset of β-cells resumed at 8 mmol/L glucose, while the long Ca2+ events were significantly elevated at substimulatory glucose concentrations. In the α-cells, the glucose sensitivity of the [Ca2+]c events persisted throughout the course of type 1 diabetes development. α-Cell [Ca2+]c events occasionally synchronize in the islets with severe β-cell destruction.

Exposure to perfluoroundecanoic acid (PFUnDA) accelerates insulitis development in a mouse model of type 1 diabetes

Perfluoralkylated substances (PFAS) are classified as persistent, bioaccumulative and toxic substances and are widespread environmental contaminants. Humans are exposed through food, drinking water and air. We have previously reported that bisphenol A accelerates spontaneous diabetes development in non-obese diabetic (NOD) mice and observed in the present study that perfluoroundecanoic acid, PFUnDA, increased insulitis development, a prerequisite for diabetes development in NOD mice. We exposed NOD mice to PFUnDA in drinking water (3, 30 and 300 μg/l) at mating, during gestation and lactation and until 30 weeks of age. After 300 μg/l PFUnDA exposure, we report (i) increased pancreatic insulitis, (ii) increased number of apoptotic cells in pancreatic islets prior to insulitis and (iii) decreased phagocytosis in peritoneal macrophages. There was also a trend of decreased number of tissue resident macrophages in pancreatic islets prior to insulitis after exposure to 300 μg/l, and altered cytokine secretion in activated splenocytes after exposure to 3 μg/l PFUnDA. Although insulitis is a prerequisite for autoimmune diabetes, the accelerated insulitis was not associated with accelerated diabetes development. Instead, the incidence of diabetes tended to be reduced in the animals exposed to 3 and 30 μg/l PFUnDA, suggesting a non-monotonic dose response. The effects of PFUnDA exposure on increased apoptosis in pancreas and reduced macrophage function as well as accelerated insulitis development in NOD mice, may also be relevant for human insulitis. Further observational autoimmune diabetes clinical cohort studies and animal experiments for PFUnDA as well as other PFASs are therefore encouraged.

Immunomodulation with SA-FasL protein as an effective means of preventing islet allograft rejection in chemically diabetic NOD mice

Allogeneic islet grafts are subject to rejection by both auto- and alloimmune responses when transplanted into diabetic individuals. T cells play a critical role in the initiation and perpetuation of both autoimmunity and allograft rejection. T cells up-regulate Fas and become sensitive to FasL-mediated killing following antigenic stimulation. Therefore, we tested if immunomodulation with an apoptotic form of FasL chimeric with streptavidin (SA-FasL) is effective in preventing the rejection of allogeneic C57BL/6 islet grafts in chemically diabetic NOD mice. C57BL/6 splenocytes and pancreatic islets were biotinylated and engineered to display the SA-FasL protein on their surface. Female NOD mice (6-7 weeks old) were treated with streptozotocin to induce diabetes and transplanted 5 days later with C57BL/6 islets engineered with SA-FasL in conjunction with transient treatment with rapamycin (3.0 mg/kg daily for days 0-19). Graft recipients were also systemically immunomodulated by intraperitoneal injection of 5 × 10(6) donor SA-FasL-engineered splenocytes on days 1, 3, and 5 after islet transplantation. This regimen resulted in the survival of all allogeneic islet grafts for the 250-day observation period, compared with a mean survival time (MST) of 14.2 ± 3.9 days for the control group. The survival effect was SA-FasL specific, with all NOD mice transplanted with control streptavidin protein-engineered islet grafts and treated with SA-engineered splenocytes under transient cover of rapamycin rejecting their grafts with an MST of 39.8 ± 8.5 days (P < .01). Taken together, these data demonstrate that immunomodulation with SA-FasL-engineered allogeneic islet grafts and splenocytes is effective in overcoming rejection in female NOD mice with preexisting autoimmunity with important clinical implications.

Polymeric delivery of therapeutic RAE-1 plasmid to the pancreatic islets for the prevention of type 1 diabetes

The activating receptor NKG2D plays an important role in the development of type-1 diabetes. Exploiting a natural phenomenon observed in tumors, plasmid DNA encoding for a soluble ligand to NKG2D (sRAE-1γ) was isolated and engineered into a plasmid expression system. A polymeric gene delivery system was developed to deliver the soluble RAE-1 plasmid to the pancreatic islets. The bioreducible cationic polymer poly(cystamine bisacrylamide-diamino hexane) (p(CBA-DAH)) was modified with poly(ethylene glycol) (PEG) and the targeting peptide CHVLWSTRC, known to target the EphA2 and EphA4 receptors. We observed a higher uptake of the targeting polymer Eph-PEG-p(CBA-DAH) in the pancreas of NOD mice compared to non-targeting controls. To evaluate the efficacy of preventing diabetes, the Eph-PEG-p(CBA-DAH)/RAE-1 complex (polyplex) was intravenously injected into 6-week-old female NOD mice. Within 17 weeks blood glucose levels were stabilized in animals injected with polyplex, while those treated without therapeutic plasmid developed progressive hyperglycemia. Additionally, the degree of insulitis and the infiltration of CD8⁺ T-cells in the polyplex treated group were improved over the targeting polymer only treated group. The current study suggests that the therapy of the Eph-PEG-p (CBA-DAH) delivering therapeutic sRAE-1 gene may be used to protect β-cells from autoimmune destruction and prevent type-1 diabetes.

The IL-2 diphtheria toxin fusion protein denileukin diftitox modulates the onset of diabetes in female nonobese diabetic animals in a time-dependent manner and breaks tolerance in male nonobese diabetic animals

Denileukin diftitox, also known as DAB(389)IL-2 or Ontak, is a fusion protein toxin consisting of the full-length sequence of the IL-2 protein and as toxophore the truncated diphtheria toxin. As a consequence, it delivers the toxic agent to CD25-bearing cells, whereby CD25 represents the high-affinity α-subunit of the IL-2 receptor. Initially it was developed for the treatment of patients with cutaneous T cell lymphoma. Meanwhile, denileukin diftitox is also used as an adjuvant in other tumor therapies and neoplastic disorders. In this study, to our knowledge we report for the first time that denileukin diftitox has also dramatic effects regarding the pathology of type 1 diabetes using the NOD mouse model. Repeated injections of denileukin diftitox into female NOD mice at 12 wk of age led to a clear acceleration of disease onset, whereas injection at 7 wk of age did not. Using male NOD mice, which are much less susceptible to diabetes, we demonstrate that the injection of denileukin diftitox leads to a dramatic development of type 1 diabetes within days after injection, thereby obviously breaking pre-existing tolerance mechanisms. This is accompanied by an increased IFN-γ production of autoreactive splenic cells and a decreased presence of regulatory CD4(+)CD25(+)Foxp3(+) T cells. In contrast, transfer of CD4(+)CD25(+)Foxp3(+) T cells could correct the defect after denileukin diftitox treatment. Furthermore, whereas IFN-γ production was increased in the pancreata of treated animals, insulin expression was strongly reduced. These finding should be considered when denileukin diftitox is used for the treatment of patients suffering from tumors and/or autoimmune disorders.

Three-dimensional analysis of the islet vasculature

The pancreatic islets of Langerhans are highly vascularized structures scattered throughout the pancreas that contain a capillary network 5-10 times denser than that of the exocrine pancreas. A simple method for three-dimensional (3D) analysis of this intricate intraislet vasculature has been difficult because of the intrinsic opacity of the pancreas. We developed a whole-mount imaging technique that allows relatively easy visualization of the islet vasculature. In combination with confocal microscopy and the use of 3D imaging software, we were able to readily reconstruct the 3D architecture of an islet, allowing delineation of the islet volume, length of the intraislet vessels, and the number of vessel branch-points. This technique allows for straightforward 3D image analysis that may help toward understanding islet function.

In vivo islet protection by a nuclear import inhibitor in a mouse model of type 1 diabetes

Background

Insulin-dependent Type 1 diabetes (T1D) is a devastating autoimmune disease that destroys beta cells within the pancreatic islets and afflicts over 10 million people worldwide. These patients face life-long risks for blindness, cardiovascular and renal diseases, and complications of insulin treatment. New therapies that protect islets from autoimmune destruction and allow continuing insulin production are needed. Increasing evidence regarding the pathomechanism of T1D indicates that islets are destroyed by the relentless attack by autoreactive immune cells evolving from an aberrant action of the innate, in addition to adaptive, immune system that produces islet-toxic cytokines, chemokines, and other effectors of islet inflammation. We tested the hypothesis that targeting nuclear import of stress-responsive transcription factors evoked by agonist-stimulated innate and adaptive immunity receptors would protect islets from autoimmune destruction.

Principal Findings

Here we show that a first-in-class inhibitor of nuclear import, cSN50 peptide, affords in vivo islet protection following a 2-day course of intense treatment in NOD mice, which resulted in a diabetes-free state for one year without apparent toxicity. This nuclear import inhibitor precipitously reduces the accumulation of islet-destructive autoreactive lymphocytes while enhancing activation-induced cell death of T and B lymphocytes derived from autoimmune diabetes-prone, non-obese diabetic (NOD) mice that develop T1D. Moreover, in this widely used model of human T1D we noted attenuation of pro-inflammatory cytokine and chemokine production in immune cells.

Conclusions

These results indicate that a novel form of immunotherapy that targets nuclear import can arrest inflammation-driven destruction of insulin-producing beta cells at the site of autoimmune attack within pancreatic islets during the progression of T1D.

Exendin-4 modulates diabetes onset in nonobese diabetic mice

Activation of the glucagon-like peptide-1 receptor (GLP-1R) is associated with expansion of beta-cell mass due to stimulation of cell proliferation and induction of antiapoptotic pathways coupled to beta-cell survival. Although the GLP-1R agonist Exenatide (exendin-4) is currently being evaluated in subjects with type 1 diabetes, there is little information available about the efficacy of GLP-1R activation for prevention of experimental type 1 diabetes. We examined the consequences of exendin-4 (Ex-4) administration (100 ng once daily and 2 microg twice daily) on diabetes onset in nonobese diabetic mice beginning at either 4 or 9 wk of age prior to the onset of diabetes. Ex-4 treatment for 26 wk (2 microg twice daily) initiated at 4 wk of age delayed the onset of diabetes (P = 0.007). Ex-4-treated mice also exhibited a significant reduction in insulitis scores, enhanced beta-cell mass, and improved glucose tolerance. Although GLP-1R mRNA transcripts were detected in spleen, thymus, and lymph nodes from nonobese diabetic mice, Ex-4 treatment was not associated with significant changes in the numbers of CD4+ or CD8+ T cells or B cells in the spleen. However, Ex-4 treatment resulted in an increase in the number of CD4+ and CD8+ T cells in the lymph nodes and a reduction in the numbers of CD4+CD25+Foxp3+ regulatory T cells in the thymus but not in lymph nodes. These findings demonstrate that sustained GLP-1R activation in the absence of concomitant immune intervention may be associated with modest but significant delay in diabetes onset in a murine model of type 1 diabetes.

Regulatory and Effector T Cell Activation Levels Are Prime Determinants of In Vivo Immune Regulation

Little is known about the in vivo conditions in which CD4+CD25+ regulatory T cells (T(reg)) exert their suppressive effect in nonlymphopenic mice. To this end, we analyzed T(reg)-mediated suppression of expansion and cytokine production at different levels of Ag-specific CD4+CD25- T cell activation. Using Ab-mediated depletion of endogenous T(reg), we show that basal immunosuppression is dependent on effector T cell activation. These polyclonal T(reg), which were poorly activated in our immunization conditions, were effective in weak but not high T cell activation context. In contrast, the same immunization conditions led to proliferation of cotransferred Ag-specific T(reg). Those efficiently inhibited T cell proliferation and cytokine production even in strong T cell activation context. Interestingly, T(reg) selectively suppressed expansion or cytokine production depending on the experimental approach. The importance of the immune context for efficient suppression is further supported by the observation that T(reg) depletion exacerbated diabetes of NOD mice only at the early stage of the disease. Overall, our study suggests that T(reg)-mediated suppression depends on the relative activation of T(reg) and effector T cells in vivo. This balance may be a critical factor in the regulation of immune responses.

An autoradiographic study of [(18)F]FDG uptake to islets of Langerhans in NOD mouse

To evaluate the potential of in vivo imaging of accumulation of lymphocytes to islets of Langerhans (insulitis), we compared 2-[(18)F]fluoro-2-deoxy-d-glucose ([(18)F]FDG) uptake in the pancreas and pancreatic islets of healthy BALB/c mice, phenotypically healthy NOD mice with insulitis and diabetic NOD mice. [(18)F]FDG was injected i.v. to 14 female BALB/c mice (age 13+/-3 weeks, plasma glucose 8+/-2 mmol/l) and 21 age-matched female NOD mice (plasma glucose 8+/-4 mmol/l, p=0.06). The mice were killed 90-min post injection and distribution of radioactivity was analysed using digital autoradiography. There was no correlation of plasma glucose concentration with the [(18)F]FDG uptake values. Uptake of radioactivity in NOD mice to the islets affected by insulitis was up to 2.3 times higher (p=0.001) than that to unaffected islets in the same pancreas. Uptake to NOD islets with insulitis was also clearly enhanced (1.0-2.3 times higher) compared to the islets in the BALB/c mice. In conclusion, NOD mouse islets with insulitis accumulate [(18)F]FDG markedly more than islets without insulitis or BALB/c islets. However, the relatively small difference in the [(18)F]FDG intensity between healthy and diseased islets, combined with the limited resolution ability of the positron emission tomography (PET), probably prevent the use of [(18)F]FDG in PET studies aiming at in vivo documentation of onset and progression of insulitis and prediabetes in mouse and man.

Prevention of autoimmune insulitis by delivery of a chimeric plasmid encoding interleukin-4 and interleukin-10

The combined administration of interleukin-4 (IL-4) and interleukin-10 (IL-10) expression plasmids has demonstrated synergistic effects on the prevention of autoimmune diabetes. To this end, we constructed a co-expression 'chimeric' plasmid, pCMV-IL4-IL10, in which the expression of IL-4 and IL-10 was driven by two separate CMV immediate early promoters by using the biodegradable polymer, poly[alpha-(4-aminobutyl)-L-glycolic acid] (PAGA) as a gene carrier to optimize gene delivery. In vitro transfection assays of the chimeric plasmid in 293T cells showed higher expression levels as well as dose dependence than the single gene expression plasmids. To evaluate the in vivo efficacy of the chimeric plasmid, the pCMV-IL4-IL10/PAGA complex was intravenously injected into 4-week-old non-obese diabetic (NOD) mice and compared to the co-administration group. While both groups had persistent gene expression longer than 5 weeks, the IL-4 and IL-10 serum levels of the chimeric group were higher than those in the co-administration group. Furthermore, the degree of insulitis in the chimeric group was improved over both the co-administration and non-injected control groups. These results suggest that the chimeric IL-4 and IL-10 expression plasmid can effectively reduce the incidence of autoimmune insulitis.

Prevention of autoimmune insulitis by delivery of interleukin-4 plasmid using a soluble and biodegradable polymeric carrier

PURPOSE

We delivered interleukin-4 (IL-4) plasmid (pCAGGS-IL-4) using the biodegradable polymer, poly[alpha-(4-aminobutyl)-L-glycolic acid] (PAGA), to prevent autoimmune insulitis in NOD mice.

METHODS

The pCAGGS-IL-4/PAGA complex was transfected to 293T cells. The expression level of IL-4 was measured by ELISA. The pCAGGS IL-4/PAGA complex was injected once to NOD mice intravenously at the age of 4 weeks. RT-PCR was performed to evaluate the level of the IL-4 mRNA in the liver. At 6 weeks after the injection, the grade of insulitis of the mice was evaluated by double blind methods.

RESULTS

In vitro transfecton assays showed that PAGA enhanced the expression of IL-4 in 293T cells. RT-PCR of the liver showed that IL-4 was expressed highest in the complex injected group. In the plasmid/PAGA complex injected group, the prevalence of severe insulitis in NOD mice was markedly improved, suggesting that PAGA enhanced the delivery of IL-4 plasmid.

CONCLUSION

The pCAGGS-IL-4/PAGA complex is an effective system to prevent autoimmune insulitis in NOD mice and applicable for the prevention of autoimmune diabetes.

Degradable polymeric carrier for the delivery of IL-10 plasmid DNA to prevent autoimmune insulitis of NOD mice

Recently, we have reported that biodegradable poly [alpha-(4-aminobutyl)-L-glycolic acid] (PAGA) can condense and protect plasmid DNA from DNase I. In this study, we investigated whether the systemic administration of pCAGGS mouse IL-10 (mIL-10) expression plasmid complexed with PAGA can reduce the development of insulitis in non-obese diabetic (NOD) mice. PAGA/mIL-10 plasmid complexes were stable for more than 60 min, but the naked DNA was destroyed within 10 min by DNase I. The PAGA/DNA complexes were injected into the tail vein of 3-week-old NOD mice. Serum mIL-10 level peaked at 5 days after injection, and could be detected for more than 9 weeks. The prevalence of severe insulitis on 12-week-old NOD mice was markedly reduced by the intravenous injection of PAGA/DNA complex (15.7%) compared with that of naked DNA injection (34.5%) and non-treated controls (90.9%). In conclusion, systemic administration of pCAGGS mIL-10 plasmid/PAGA complexes can reduce the severity of insulitis in NOD mice. This study shows that the PAGA/DNA complex has the potential for the prevention of autoimmune diabetes mellitus. Gene Therapy (2000) 7, 2099-2104.

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.

Beta cell destruction in the development of autoimmune diabetes in the non-obese diabetic (NOD) mouse

In the non-obese diabetic (NOD) mouse model of Type 1 (insulin-dependent) diabetes, evidence suggests that pancreatic beta cells are destroyed in part by apoptotic mechanisms. The precise mechanisms of beta cell destruction leading to diabetes remain unclear. The NOD mouse has been studied to gain insight into the cellular and molecular mediators of beta cell death, which are discussed in this review. Perforin, secreted by CD8(+) T cells, remains one of the only molecules confirmed to be implicated in beta cell death in the NOD mouse. There are many other molecules, including Fas ligand and cytokines such as interferon-gamma, interleukin-1 and tumor necrosis factor-alpha, which may lead to beta cell destruction either directly or indirectly via regulation of toxic molecules such as nitric oxide. As beta cell death can occur in the absence of perforin, these other factors, in addition to other as yet unidentified factors, may be important in the development of diabetes. Effective protection of NOD mice from beta cell destruction may therefore require inhibition of multiple effector mechanisms.

Two genetic loci regulate T cell-dependent islet inflammation and drive autoimmune diabetes pathogenesis

Insulin-dependent diabetes mellitus (IDDM) is a polygenic disease caused by progressive autoimmune infiltration (insulitis) of the pancreatic islets of Langerhan, culminating in the destruction of insulin-producing beta cells. Genome scans of families with diabetes suggest that multiple loci make incremental contributions to disease susceptibility. However, only the IDDM1 locus is well characterized, at a molecular and functional level, as alleleic variants of the major histocompatibility complex (MHC) class II HLA-DQB1, DRB1, and DPB1 genes that mediate antigen presentation to T cells. In the nonobese diabetic (NOD) mouse model, the Idd1 locus was shown to be the orthologous MHC gene I-Ab. Inheritance of susceptibility alleles at IDDM1/Idd1 is insufficient for disease development in humans and NOD mice. However, the identities and functions of the remaining diabetes loci (Idd2-Idd19 in NOD mice) are largely undefined. A crucial limitation in previous genetic linkage studies of this disease has been reliance on a single complex phenotype-diabetes that displays low penetrance and is of limited utility for high-resolution genetic mapping. Using the NOD model, we have identified an early step in diabetes pathogenesis that behaves as a highly penetrant trait. We report that NOD-derived alleles at both the Idd5 and Idd13 loci regulate a T lymphocyte-dependent progression from a benign to a destructive stage of insulitis. Human chromosomal regions orthologous to the Idd5 and -13 intervals are also linked to diabetes risk, suggesting that conserved genes encoded at these loci are central regulators of disease pathogenesis. These data are the first to reveal a role for individual non-MHC Idd loci in a specific, critical step in diabetes pathogenesis-T cell recruitment to islet lesions driving destructive inflammation. Importantly, identification of intermediate phenotypes in complex disease pathogenesis provides the tools required to progress toward gene identification at these loci.

Troglitazone prevents insulin dependent diabetes in the non-obese diabetic mouse

Troglitazone has recently been introduced in the treatment of Type 2 diabetes. In addition to its anti-diabetic effects it acts as a perixosome proliferator activated receptor-gamma (PPAR-gamma) agonist and has anti-inflammatory properties by inhibiting macrophage tumour necrosis factor-alpha (TNF-alpha) secretion. It also inhibits the production of endothelial selectin (e-selectin). Troglitazone also reduces interleukin-1alpha induced nitric oxide production in pancreatic beta-cells, which may be relevant in preventing nitric oxide mediated damage to these cells in the Type 1 diabetes process. We tested troglitazone in the spontaneous model of autoimmune diabetes, the non-obese diabetic (NOD) mouse, to determine its effect on the disease process. When administered by gavage from weaning at a dose of 400 mg/kg body weight (n = 32), troglitazone reduced the incidence of diabetes by 16 weeks compared to controls (n = 32) in a pattern that was maintained up to the conclusion of the experiment at 31 weeks of age (p < 0.05). Insulitis was unaltered (index = 1.05 +/- 0.71 vs. 1.13 +/- 0.82, treated vs. controls, p = 0.78). The study was repeated using troglitazone in the diet of NOD mice (n = 24) to give a dose of approximately 200 mg/kg body weight in order to provide a more consistent level of troglitazone during the time course of the experiment. There was a reduction of diabetes incidence in this group but it did not reach significance. Insulin levels were reduced in gavage treated mice although such reduction did not reach significance (p < 0.07). We conclude that, in view of its effect on this model of autoimmune diabetes and because of its known function as an insulin sensitiser, troglitazone might be considered for potential use in those patients with Type 1 masquerading as Type 2 diabetes.

Specific reg II gene overexpression in the non-obese diabetic mouse pancreas during active diabetogenesis

The reg gene, previously described in islets of 90% pancreatectomized and nicotinamide-treated rats, has been shown to be expressed in many pharmacological or surgical animal models of beta cell regeneration. We have studied the non-obese diabetic (NOD) mouse, which represents a good model of spontaneous autoimmune diabetes in which regenerative processes have recently been demonstrated. Two reg genes have been described in the mouse genome, both recognized by the human reg cDNA. In a previous work, using the human probe, we have demonstrated a strong correlation between pancreatic reg gene expression and the likelihood of developing diabetes. In the present study, we have examined the respective levels of both mouse reg I and reg II mRNA in the NOD mouse pancreas using their specific cDNA probes. We found that reg II expression was specifically prevalent compared to reg I, irrespective of sex or state of the disease. Reg II mRNA was particularly increased in overtly diabetic female mice and in cyclophosphamide-treated male mice. These data underline the need to study separately the reg genes using specific probes and show that both reg genes are subjected to various regulations, strongly suggesting that their physiological functions may be different.

Diabetes results from a late change in the autoimmune response of NOD mice

IDDM in the NOD mouse is the result of a chronic autoimmune process. NOD mice are shown to express benign autoimmunity that converts to a state of malignant autoimmunity and the development of IDDM. Young disease-prone NOD mice are in a state of benign autoimmunity that is correlated with a non-destructive response to islet tissue and the preservation of insulin-containing beta-cells. A proportion of mice with benign autoimmunity convert to having malignant autoimmunity. Clinical diabetes is diagnosed approximately 3 weeks from the development of malignant autoimmunity which is correlated with a destructive response to grafted islet tissue and extensive beta-cell destruction. We conclude that the development of clinical disease is correlated with a change in the state of autoimmunity, that is, from benign to malignant autoimmunity.

Systemic production of interferon-gamma inducing factor (IGIF) versus local IFN-gamma expression involved in the development of Th1 insulitis in NOD mice

We report that the onset of Th1 insulitis is preceded by a rise of interferon-gamma inducing factor (IGIF) mRNA expression in the spleen. This systemic shift towards Th1 reactivities was underlined by a close correlation of IGIF and IL-12p40 mRNA levels in the spleen, as determined by semi-quantitative RT-PCR. Cyclophosphamide-induced IGIF expression was also observed in MHC congenic NOR mice, but not in MHC class II-incompatible NON mice. The systemic rise of IGIF was followed by the development of destructive Th1-associated intra-insulitis. Interestingly, immunohistochemistry showed IL-4-positive cells evenly dispersed throughout the infiltrate, while IFN-gamma-positive cells were restricted to the vicinity of beta-cells. We conclude that cyclophosphamide induces a systemic shift in antigen presenting cells towards favouring Th1 responses, in an MHC dependent manner. Despite this general bias in immune reactivity, activation of Th1 cells in insulitis occurs only close to beta-cells, indicating a crucial role of antigen presentation by beta-cells or in their immediate vicinity.

Active stage of autoimmune diabetes is associated with the expression of a novel cytokine, IGIF, which is located near Idd2

Recently, interferon-gamma-inducing-factor (IGIF) has been described as a novel monokine that is a more potent interferon-gamma (IFN-gamma) inducer than IL-12. By cloning IGIF from affected tissue and studying IGIF gene expression, we describe for the first time a close association of this cytokine with an autoimmune disease. The non-obese diabetic (NOD) mouse spontaneously develops autoimmune insulitis and diabetes which can be accelerated and synchronized by a single injection of cyclophosphamide. IGIF mRNA was demonstrated by reverse transcriptase PCR in NOD mouse pancreas during early stages of insulitis. Levels of IGIF mRNA increased rapidly after cyclophosphamide treatment and preceded a rise in IFN-gamma mRNA, and subsequently diabetes. Interestingly, these kinetics mimick that of IL-12p40 mRNA, resulting in a close correlation of individual mRNA levels. Cloning of the IGIF cDNA from pancreas RNA followed by sequencing revealed identity with the IGIF sequence cloned from Kupffer cells and in vivo preactivated macrophages. When extending our study to macrophages of the spleen we observed that NOD mouse macrophages responded to cyclophosphamide with IGIF gene expression while macrophages from Balb/c mice treated in parallel did not. The IGIF gene position is located within the Idd2 interval on mouse chromosome 9 and therefore it is a candidate for the Idd2 susceptible gene. We conclude that IGIF expression is abnormally regulated in autoimmune NOD mice and closely associated with diabetes development.

Tolerance: a case of self/not-self discrimination maintained by clonal deletion?

The clonal selection theory of immune reactivity is based on a metaphor of self/not-self discrimination and considers self-tolerance to result from clonal deletion. There is evidence that a deletional mechanism is responsible for negative selection of self MHC-reactive T-cells in the thymus. Bretscher/Cohn theory builds on this concept and provides a model which allows self/not-self discrimination to occur at any time throughout the life of the individual. However, modern concepts of antigen presentation in which MHC-peptide co-presentation is the unit recognised by the T-cell receptor have abandoned the Bretscher/Cohn requirement for associative recognition of antigen. For this reason, such models of APC function cannot use Bretscher/Cohn theory to explain self/not-self discrimination. Matzinger's 'danger' metaphor for the immune system provides a theoretical way forward by moving the emphasis away from an immune system based on self/not-self discrimination. These theoretical developments lead to a novel approach to the control of autoimmunity that is based on the strengthening of immune regulation by the use of adjuvant therapy.

Temporal discontinuities in progression of NOD autoimmune diabetes

Consideration of the pathophysiology of insulin-dependent diabetes mellitus in the nonobese diabetic (NOD) mouse can be viewed from a temporal perspective. We argue that there are discontinuous phases and each phase may reflect a phenotype educed by a particular set of genetic and epigenetic events. Therefore, temporal dissection may be a useful platform for causal dissection and we have set out this article as follows: 1. Introduction. 2. "Pre-time." a. Genetics. b. Parental effects. 3. Development of insulitis. a. Development of autoimmunity vs waning of or failure to establish tolerance. b. Importance of beta cell mass. c. Homing. 4. Onset of beta cell destruction. 5. Further Discussion.

Autoimmune diabetes: caught in the causality trap?

The lack of concordance between genotype and clinical diabetes has prompted a search for the infectious agent that precipitates this autoimmune disease. However, this approach may be misleading. It assumes that the disease-prone individuals that do not develop diabetes do not have autoimmunity. In the non-obese diabetic (NOD) mouse, the genotype is a primary determinant of autoimmunity. Not all animals of the disease-prone genotype develop clinical disease; however, all have autoimmunity. This is expressed as a destructive or non-destructive process. Multiple pathways are open to the immune system and whether or not the immune response is destructive and leads to the development of clinical disease, appears to be a random process. If this is the case, the most important questions relating to autoimmune disease are not those concerning the 'causative' agents. Instead we should be asking what are the differences between pathways open to the immune system and what factors affect the probability that one or another pathway is finally selected?