Spontaneous autoimmune diabetes in monoclonal T cell nonobese diabetic mice

It has been established that insulin-dependent diabetes mellitus (IDDM) in nonobese diabetic (NOD) mice results from a CD4+ and CD8+ T cell-dependent autoimmune process directed against the pancreatic beta cells. The precise roles that beta cell-reactive CD8+ and CD4+ T cells play in the disease process, however, remain ill defined. Here we have investigated whether naive beta cell-specific CD8+ and CD4+ T cells can spontaneously accumulate in pancreatic islets, differentiate into effector cells, and destroy beta cells in the absence of other T cell specificities. This was done by introducing Kd- or I-Ag7-restricted beta cell-specific T cell receptor (TCR) transgenes that are highly diabetogenic in NOD mice (8.3- and 4.1-TCR, respectively), into recombination-activating gene (RAG)-2-deficient NOD mice, which cannot rearrange endogenous TCR genes and thus bear monoclonal TCR repertoires. We show that while RAG-2(-/-) 4.1-NOD mice, which only bear beta cell-specific CD4+ T cells, develop diabetes as early and as frequently as RAG-2+ 4.1-NOD mice, RAG-2(-/-) 8.3-NOD mice, which only bear beta cell-specific CD8+ T cells, develop diabetes less frequently and significantly later than RAG-2(+) 8.3-NOD mice. The monoclonal CD8+ T cells of RAG-2(-/-) 8.3-NOD mice mature properly, proliferate vigorously in response to antigenic stimulation in vitro, and can differentiate into beta cell-cytotoxic T cells in vivo, but do not efficiently accumulate in islets in the absence of a CD4+ T cell-derived signal, which can be provided by splenic CD4+ T cells from nontransgenic NOD mice. These results demonstrate that naive beta cell- specific CD8+ and CD4+ T cells can trigger diabetes in the absence of other T or B cell specificities, but suggest that efficient recruitment of naive diabetogenic beta cell-reactive CD8+ T cells to islets requires the assistance of beta cell-reactive CD4+ T cells.     

B lymphocytes are critical antigen-presenting cells for the initiation of T cell-mediated autoimmune diabetes in nonobese diabetic mice

Nonobese diabetic (NOD) mice genetically deficient in B lymphocytes (NODJg mu(null)) are resistant to T cell-mediated autoimmune insulin-dependent diabetes mellitus (IDDM). Ig infusions from diabetic NOD donors did not abrogate IDDM resistance in NODJg mu(null) mice. However, T cell responses to the candidate pancreatic beta cell autoantigen glutamic acid decarboxylase (GAD), but not the control Ag keyhole limpet hemocyanin, were eliminated in NODJg mu(null) mice. To initially test whether they contribute to IDDM as APC, NOD B lymphocytes were transferred into NODJg mu(null) recipients. B lymphocytes transferred into unmanipulated NODJg mu(null) recipients were rejected by MHC class I-restricted T cells. Stable T and B lymphocyte repopulation was achieved in irradiated NODJg mu(null) mice reconstituted with syngeneic bone marrow admixed with NOD B lymphocytes. IDDM susceptibility was restored in NODJg mu(null) mice reconstituted with syngeneic marrow plus B lymphocytes, but not with syngeneic marrow only. T cell responses to GAD were restored only in NODJg mu(null) mice reconstituted with syngeneic marrow plus B lymphocytes. Hence, B lymphocytes appear to contribute to IDDM in NOD mice as APC with a preferential ability to present certain beta cell Ags such as GAD to autoreactive T cells.     

Immunosuppression preventing concordant xenogeneic islet graft rejection is not sufficient to prevent recurrence of autoimmune diabetes in nonobese diabetic mice

BACKGROUND: We and others have reported previously that the immunosuppressant, leflunomide (Lef), can prevent allogeneic and xenogeneic islet graft rejection in streptozocin (STZ)-induced diabetic animals. However, whether Lef required to prevent islet graft rejection is sufficient to prevent the recurrence of autoimmune diabetes has not been addressed. METHODS: The effect of Lef on concordant xenogeneic islet graft in STZ-induced diabetic mice and autoimmune nonobese diabetic (NOD) mice were studied. Then, whether Lef prevents the onset of spontaneous diabetes in young NOD mice and the recurrence of diabetes after major histocompatibility complex (MHC)-matched islet transplantation in diabetic NOD mice were investigated. RESULTS: In STZ-induced diabetic BALB/c mice, Lef treatment significantly prolonged rat islet graft survival. However, Lef could not significantly prolong rat islet graft survival in autoimmune diabetic NOD mice. For prevention studies, treatment with Lef at 30 mg/ kg/day from 4 weeks to 20 weeks of age significantly reduced the incidence of spontaneous diabetes in NOD mice. However, when the NOD mice were treated from 8 to 24 weeks of age, the incidence of spontaneous diabetes was not significantly reduced as compared to the incidence of diabetes in the untreated female NOD mice at 28 weeks of age. Finally, in the MHC-matched islet transplant model, Lef could not significantly prolong MHC-matched nonobese diabetes-resistant mice islet graft survival in NOD mice. CONCLUSIONS: Lef preventing concordant xenogeneic islet graft rejection is not sufficient to prevent the recurrence of autoimmune diabetes in NOD mice. We believe that controlling autoimmunity after islet transplantation will lead the way to promote successful clinical islet transplantation in the future.     

Evidence that macrophages are required for T-cell infiltration and rejection of fetal pig pancreas xenografts in nonobese diabetic mice

BACKGROUND: Host macrophages are abundant within fetal pig pancreas xenografts undergoing rejection, but their role is unknown. Therefore, we examined the effect of host macrophage depletion on xenograft rejection. METHODS: Nonobese diabetic (NOD) mice were given clodronate-loaded liposomes intravenously to deplete macrophages. Controls received phosphate-buffered saline (PBS) or PBS-liposomes. General immune status was assessed after 2, 3, and 7 days by (1) fluorescence-activated cell sorter analysis of peripheral blood, spleen, and lymph node cells, (2) immunohistochemistry on spleens, and (3) mixed lymphocyte reaction. Organ-cultured fetal pig pancreas was transplanted under the kidney capsule of NOD mice 3 days after clodronate or PBS injection. Grafts were assessed histologically at 4, 5, 6, and 8 days after transplantation. RESULTS: Splenic macrophages and peripheral blood monocytes were depleted 2 days after clodronate treatment but had recovered within 11 days. T cell, B cell, and dendritic cell numbers were normal in spleen, peripheral blood, and lymph nodes of clodronate-treated mice, and T cells and antigen-presenting cells from these mice functioned normally in mixed lymphocyte reaction. Clodronate treatment markedly reduced graft infiltration by macrophages, T cells, and eosinophils at 4, 5, and 6 days after transplantation, and was associated with maintenance of endocrine cell viability and insulin expression. However, all grafts were rejected 8 days after transplantation, concordant with reappearance of splenic macrophages. CONCLUSIONS: Short-term, specific depletion of macrophages markedly delayed cellular infiltration and rejection of xenografts. The results provide the first evidence that macrophages promote T-cell infiltration and rejection of fetal pig pancreas xenografts in NOD mice.     

Major histocompatibility complex class I-restricted T cells are required for all but the end stages of diabetes development in nonobese diabetic mice and use a prevalent T cell receptor alpha chain gene rearrangement

Nonobese diabetic (NOD) mice develop insulin-dependent diabetes mellitus due to autoimmune T lymphocyte-mediated destruction of pancreatic beta cells. Although both major histocompatibility complex class I-restricted CD8(+) and class II-restricted CD4(+) T cell subsets are required, the specific role each subset plays in the pathogenic process is still unclear. Here we show that class I-dependent T cells are required for all but the terminal stages of autoimmune diabetes development. To characterize the diabetogenic CD8(+) T cells responsible, we isolated and propagated in vitro CD8(+) T cells from the earliest insulitic lesions of NOD mice. They were cytotoxic to NOD islet cells, restricted to H-2Kd, and showed a diverse T cell receptor beta chain repertoire. In contrast, their alpha chain repertoire was more restricted, with a recurrent amino acid sequence motif in the complementarity-determining region 3 loop and a prevalence of Valpha17 family members frequently joined to the Jalpha42 gene segment. These results suggest that a number of the CD8(+) T cells participating in the initial phase of autoimmune beta cell destruction recognize a common structural component of Kd/peptide complexes on pancreatic beta cells, possibly a single peptide.     

Protection of nonobese diabetic mice from autoimmune diabetes by reduction of islet mass before insulitis

Nonobese diabetic mice spontaneously develop diabetes that is caused by autoimmune cell-mediated destruction of pancreatic beta cells. Here we report that surgical removal of 90% of pancreatic tissue before onset of insulitis induced a long-term diabetes-free condition in nonobese diabetic mice. Pancreatectomy after development of moderate insulitis had no effect on the course of diabetes. The effect of pancreatectomy was abrogated with subsequent development of diabetes by infusion of islet-cell-specific T lymphocytes and by transplantation of pancreatic islets. Lymphocytes from pancreatectomized diabetes-free mice exhibited low response to islet cells but responded normally to alloantigens. These results suggest that the islet cell mass plays a critical role in development of autoimmune diabetes.     

Amelioration of diabetes in nonobese diabetic mice with advanced disease by linomide-induced immunoregulation combined with Reg protein treatment

Oral linomide, (quinoline-3-carboxamide), has been shown to prevent autoimmune insulitis, islet destruction, and diabetes in NOD mice treated at an early stage of the disease, but confers only partial protection in animals with advanced disease. Reg protein, the gene product of a complementary DNA isolated from a regenerating rat islet library, has been previously shown to induce expansion of beta-cell mass in pancreatectomized rats. To determine the effect of treatment combining immunomodulation and Reg protein on advanced autoimmune diabetes, we treated female NOD mice with oral linomide and i.p. Reg protein injections. In 14-week-old animals with less severe disease (glucose tolerant), treatment with each agent alone resulted in amelioration of diabetes, as did treatment with Reg alone in 5-week-old prediabetic mice. In 14-week-old animals with more severe disease (glucose intolerant), only treatment with the combination of both agents, but not that with each separately, resulted in amelioration of diabetes. Our study suggests that treatment aimed at abrogation of autoimmunity combined with expansion of beta-cell mass constitutes a potential therapeutic approach for treatment of insulin-dependent diabetes mellitus.     

Tolerance to IDDM induced by CD4 antibodies in nonobese diabetic mice is reversed by cyclophosphamide

IDDM can be induced in nonobese diabetic (NOD) mice in several ways, including high doses of cyclophosphamide and transfer of diabetic spleen cells to sublethally irradiated recipients. It has previously been established that transferred diabetes can be prevented by treatment with a nondepleting CD4 monoclonal antibody; however, we report herein that cyclophosphamide-induced diabetes also can be prevented using this antibody. The protection induced by CD4 monoclonal antibody to transferred diabetes is maintained for a long period after cessation of antibody treatment. However, cyclophosphamide can abrogate this induced tolerance and we report that this abrogation does not require new T-cells. During the course of the experimental work described, we observed that the thymus had a suppressive effect on the expression of transferred disease. Mice that were depleted of their peripheral T-cells showed a doubling of the time for disease expression if they were euthymic, compared with thymectomized mice.     

Systemic delivery of interleukin 10 by intramuscular injection of expression plasmid DNA prevents autoimmune diabetes in nonobese diabetic mice

We previously demonstrated that intramuscular plasmid injection serves as a useful method of long-term systemic delivery of cytokines. In the present study, we assess intramuscular DNA injection as a means of systemically delivering interleukin 10 (IL-10), a cytokine with immunosuppressive properties, and preventing the progression of autoimmune diabetes in the nonobese diabetic (NOD) mouse, an excellent model for human insulin-dependent diabetes mellitus (IDDM). We injected IL-10 expression plasmid (pCAGGS-IL10) or a control pCAGGS plasmid into the muscles of NOD mice twice at 3 and 5 weeks of age. IL-10 was detectable by ELISA in the sera of mice injected with pCAGGS-IL10 for more than 2 weeks after the injection. Although the severity of insulitis at 13 weeks of age was not improved by the intramuscular injection of pCAGGS-IL10, the incidence of diabetes was markedly reduced in NOD mice injected with pCAGGS-IL10 as compared with those injected with pCAGGS or as compared with nontreated NOD mice. These results show that the progression of autoimmune diseases in mice can effectively be suppressed by intramuscular DNA injection, and suggest that this method is potentially applicable to the treatment of human autoimmune diseases.     

Prevention of autoimmune diabetes by linomide in nonobese diabetic (NOD) mice is associated with up-regulation of the TCR-mediated activation of p21(ras)

Oral therapy with linomide protects prediabetic nonobese diabetic (NOD) mice from insulin-dependent diabetes mellitus. The mechanisms by which linomide exerts its protective effect are not fully understood. A decreased TCR-mediated activity of the GTP-GDP binding p21(ras) proto-oncogene is associated with prediabetes in NOD mice. However, the role of this signal transduction defect in the pathogenesis of autoimmune diabetes is not known. The TCR-mediated and protein kinase C-induced activations of p21(ras) were determined in mononuclear cells from lymph nodes of linomide-treated and untreated prediabetic NOD mice. TCR cross-linking by Con A induced an increase of 13 +/- 6.8% and a decrease of 0.8 +/- 1.8% in p21(ras) activity in the linomide-treated group and the untreated controls, respectively. Cell stimulation with PMA resulted in a 15 +/- 2% increase in p21(ras) activity in the linomide-treated mice and a 10 +/- 11.4% decrease in the untreated mice. Protein levels of p21(ras) and its regulatory elements, the GTPase-activating protein and the guanine nucleotide-releasing factor, mSOS, were comparable in both groups. We, therefore, conclude that prevention of autoimmune diabetes by linomide is associated with up-regulation of the p21(ras) T cell signal transduction defect in NOD mice.     

Overexpression of natural killer T cells protects Valpha14- Jalpha281 transgenic nonobese diabetic mice against diabetes

Progression to destructive insulitis in nonobese diabetic (NOD) mice is linked to the failure of regulatory cells, possibly involving T helper type 2 (Th2) cells. Natural killer (NK) T cells might be involved in diabetes, given their deficiency in NOD mice and the prevention of diabetes by adoptive transfer of alpha/beta double-negative thymocytes. Here, we evaluated the role of NK T cells in diabetes by using transgenic NOD mice expressing the T cell antigen receptor (TCR) alpha chain Valpha14-Jalpha281 characteristic of NK T cells. Precise identification of NK1.1(+) T cells was based on out-cross with congenic NK1.1 NOD mice. All six transgenic lines showed, to various degrees, elevated numbers of NK1.1(+) T cells, enhanced production of interleukin (IL)-4, and increased levels of serum immunoglobulin E. Only the transgenic lines with the largest numbers of NK T cells and the most vigorous burst of IL-4 production were protected from diabetes. Transfer and cotransfer experiments with transgenic splenocytes demonstrated that Valpha14-Jalpha281 transgenic NOD mice, although protected from overt diabetes, developed a diabetogenic T cell repertoire, and that NK T cells actively inhibited the pathogenic action of T cells. These results indicate that the number of NK T cells strongly influences the development of diabetes.     

Local expression of transgene encoded TNF alpha in islets prevents autoimmune diabetes in nonobese diabetic (NOD) mice by preventing the development of auto-reactive islet-specific T cells

Lately, TNF alpha has been the focus of studies of autoimmunity; its role in the progression of autoimmune diabetes is, however, still unclear. To analyze the effects of TNF alpha in insulin-dependent diabetes mellitus (IDDM), we have generated nonobese diabetic (NOD) transgenic mice expressing TNF alpha under the control of the rat insulin II promoter (RIP). In transgenic mice, TNF alpha expression on the islets resulted in massive insulitis, composed of CD4+ T cells, CD8+ T cells, and B cells. Despite infiltration of considerable number of lymphoid cells in islets, expression of TNF alpha protected NOD mice from IDDM. To determine the mechanism of TNF alpha action, splenic cells from control NOD and RIP-TNF alpha mice were adoptively transferred to NOD-SCID recipients. In contrast to the induction of diabetes by splenic cells from control NOD mice, splenic cells from RIP-TNF alpha transgenic mice did not induce diabetes in NOD-SCID recipients. Diabetes was induced however, in the RIP-TNF alpha transgenic mice when CD8+ diabetogenic cloned T cells or splenic cells from diabetic NOD mice were adoptively transferred to these mice. Furthermore, expression of TNF alpha in islets also downregulated splenic cell responses to autoantigens. These data establish a mechanism of TNF alpha action and provide evidence that local expression of TNF alpha protects NOD mice from autoimmune diabetes by preventing the development of autoreactive islet-specific T cells.     

Quantitative immunohistochemical changes in the endocrine pancreas of nonobese diabetic (NOD) mice

Two-centimeter nerve allografts were transplanted across a major histocompatibility barrier from donor ACI rats into a 0.5-cm gap in the sciatic nerve of recipient Lewis rats and immunosuppressed with FK506, 2 mg/kg per day for 3 months. One group of animals continued to receive intermittent immunosuppression with FK506, 2 mg/kg twice a week for another 2 months, whereas the second group of animals received no further immunosuppression in order to determine whether rejection of nerve allografts can still occur after immunosuppression is withdrawn, even after the axons have regenerated through the nerve graft. The sciatic function index improved from -76.3 at 3 months to -46.6 at 5 months in those animals continuing to receive intermittent immunosuppression, but only improved to -66.8 at 5 months when immunosuppression was discontinued. Similarly, somatosensory evoked potentials demonstrated an improvement in relative latency from 2.3 msec at 3 months to 0.34 msec at 5 months in animals continuing to receive intermittent immunosuppression, but only improved to 1.29 msec at 5 months when immunosuppression was discontinued. Nerve allografts continuing to receive intermittent immunosuppression showed no signs of rejection by light or electron microscopy and no significant difference compared with isografts, whereas nerve allografts whose immunosuppression had been stopped at 3 months showed mild signs of rejection, less regeneration, and a smaller number of nerve fibers.(ABSTRACT TRUNCATED AT 250 WORDS)     

Maternal IL-11Ralpha function is required for normal decidua and fetoplacental development in mice

In eutherian mammals, implantation and establishment of the chorioallantoic placenta are essential for embryo development and survival. As a maternal response to implantation, uterine stromal cells proliferate, differentiate, and generate the decidua, which encapsulates the conceptus and forms the maternal part of the placenta. Little is known about decidual functions and the molecular interactions that regulate its development and maintenance. Here we show that the receptor for the cytokine interleukin-11 (IL-11Ralpha) is required specifically for normal establishment of the decidua. Females homozygous for a hypomorphic IL-11Ralpha allele are fertile and their blastocysts implant and elicit the decidual response. Because of reduced cell proliferation, however, only small deciduae form. Mutant deciduae degenerate progressively, and consequently embryo-derived trophoblast cells generate a network of trophoblast giant cells but fail to form a chorioallantoic placenta, indicating that the decidua is essential for normal fetoplacentation. IL-11Ralpha is expressed in the decidua as well as in numerous other tissues and cell types, including the ovary and lymphocytes. The differentiation state and proliferative responses of B and T-lymphocytes in mutant females were normal, and wild-type females carrying IL-11Ralpha mutant ovaries had normal deciduae, suggesting that the decidualization defects do not arise secondarily as a consequence of perturbed IL-11Ralpha signaling defects in lymphoid organs or in the ovary. Therefore, IL-11Ralpha signaling at the implantation site appears to be required for decidua development.     

Anti-CD3 antibody induces long-term remission of overt autoimmunity in nonobese diabetic mice

We examined the axotomy-induced expression of the immediate-early gene (proto-oncogene) c-jun in the Ola mouse mutant (which exhibits a dramatic delay in Wallerian degeneration) using immunocytochemistry to c-JUN (the protein product of the protooncogene c-jun). c-JUN-like protein immunoreactivity was present in a similar proportion (ca. 60%) of L4 dorsal root ganglion (DRG) neuronal cell bodies from normal (C57/6J/BL) and Ola mice at 1 week following a sciatic nerve crush (axotomy). In normal mice, the intensity and extent of staining declined at 3 weeks, correlating with regeneration. In contrast, Ola mice exhibited a marked reduction (by 77%) in the extent of staining at 2 weeks. At 3 weeks (coinciding to the onset of extensive axonal degeneration in this mutant), staining levels were increased to 1 week levels. Taken together, these findings suggest that multiple signals (both independent and dependent on axonal degeneration) regulate c-jun expression in DRG neuronal cell bodies.     

Beta-cell destruction may be a late consequence of the autoimmune process in nonobese diabetic mice

The NOD mouse is an animal model of IDDM that shows many of the characteristics of human IDDM. It has been proposed that beta-cell destruction in IDDM progresses over time in a linear manner. Recently, we and others have demonstrated that T helper type 1 (Th1) cells have pathogenic roles in the NOD model and proposed that cytokine balances change as the disease progresses. However, it has not been demonstrated how or when the cytokine balances change or how the beta-cell destruction progresses. We have recently demonstrated that the cytokine profiles of CD45RB(low) CD4+ cells correlate either with their pathogenic or with their protective roles in the NOD mouse. To further analyze this apparent correlation between the shift in cytokine level and IDDM, we examined the anti-CD3-induced cytokine profiles of this subset from NOD mice of various ages compared with that from age-matched I-Ak transgenic NOD and BALB/c mice as controls. A significantly higher ratio of anti-CD3-induced interferon-gamma/interleukin-4 was found in diabetic NOD mice (P < 0.0001) but not in age-matched nondiabetic NOD mice. This cytokine ratio did not change significantly until the onset of diabetes in NOD mice. Based upon these results, we propose that IDDM in the NOD mouse progresses as a predominant inflammatory beta-cell dysfunction without actual beta-cell destruction until late in the disease process. This supports the possibility that late-stage immunotherapy may preserve islet beta-cell mass.     

BDNF is required for the normal development of taste neurons in vivo

The vallate gustatory epithelium of neonatal trkB null mutant mice (-/-) lacked innervation. This prompted the evaluation of null mutant mice corresponding to the three neurotrophin ligands for tyrosine kinase receptor B (TrkB): brain-derived neurotrophic factor (BDNF), neurotrophin (NT)3, NT4. The vallate gustatory epithelium of nt3-/- mice and of nt4-/- mice appeared normal. Only bdnf-/- mice had a vallate papilla that was stunted, sparsely innervated, and lacked up to 98% of its taste buds. All three defects persisted. For example, the vallate papilla of 12-day-old bdnf-/- mice remained markedly less well innervated than the vallate of 7-day-old or newborn bdnf+/+ mice. The foliate taste papillae of neonatal bdnf-/- mice had similar defects. We conclude that the normal development of taste neurons requires BDNF.     

Autoreactivity of T cells from nonobese diabetic mice: an I-Ag7-dependent reaction

Mice bearing the I-Ag7 class II major histocompatibility complex molecules contain a high number of spontaneous autoreactive T cells, as estimated by limiting-dilution assays. We found this autoreactivity in various strains that bear the I-Ag7 molecule, such as the nonobese diabetic (NOD) mouse strain, which spontaneously develops autoimmune diabetes. However, NOD mice strains that do not express the I-Ag7 molecule, but instead express I-Ab, do not have a high incidence of autoreactive T cells. About 15% of the autoreactive T cells also recognize the I-Ag7 molecule expressed in the T2 line, which is defective in the processing of protein antigens. We interpret this to mean that some of the T cells may interact with class II molecules that are either devoid of peptides or contain a limited peptide content. We also find a high component of autoreactivity among antigen-specific T cell clones. These T cell clones proliferate specifically to protein antigens but also have a high level of reactivity to antigen-presenting cells not pulsed with antigen. Thus, the library of T cell receptors in NOD mice is skewed to autoreactivity, which we speculate is based on the weak peptide-binding properties of I-Ag7 molecules.     

TNF-alpha down-regulates type 1 cytokines and prolongs survival of syngeneic islet grafts in nonobese diabetic mice

Administration of TNF-alpha to autoimmune diabetes-prone nonobese diabetic mice and biobreeding rats inhibits diabetes development; however, the mechanism(s) of diabetes prevention by TNF-alpha has not been established. We used the model of syngeneic islet transplantation into diabetic nonobese diabetic mice to study the effects of TNF-alpha administration on the types of mononuclear cells and cytokines expressed in the islet grafts and on autoimmune diabetes recurrence. Twice daily i.p. injections of TNF-alpha (20 microg/day) from day 1 to day 30 after islet transplantation significantly prolonged islet graft survival; thus, 70% (16 of 23) of mice treated with TNF-alpha were normoglycemic at 30 days after islet transplantation compared with none (0 of 14) of vehicle-treated control mice. Islet grafts and spleens from TNF-alpha-treated mice at 10 days after islet transplantation contained significantly fewer CD4+ and CD8+ T cells, and significantly decreased mRNA levels of type 1 cytokines (IFN-gamma, IL-2, and TNF-beta) than islet grafts and spleens from control mice. Regarding type 2 cytokines, IL-4 mRNA levels were not changed significantly in islet grafts or spleens of TNF-alpha-treated mice, whereas IL-10 mRNA levels were decreased significantly in islet grafts of TNF-alpha-treated mice and not significantly changed in spleens. TGF-beta mRNA levels in islet grafts and spleens were similar in TNF-alpha-treated and control mice. These results suggest that TNF-alpha partially protects beta cells in syngeneic islet grafts from recurrent autoimmune destruction by reducing CD4+ and CD8+ T cells and down-regulating type 1 cytokines, both systemically and locally in the islet graft.     

Alpha-interferon inhibits the development of diabetes in NOD mice

The NOD mouse is a model of human IDDM, which is characterized by a cell-mediated autoimmune process resulting in spontaneous diabetes. Alpha-interferon (IFN-alpha) is thought to play a pathogenic role in this autoimmune process. We report that recombinant alpha-interferon (rIFN-alpha) administration decreases the development of spontaneous diabetes and the passive transfer of diabetes in NOD mice. Spontaneous diabetes was inhibited by IFN-alpha in a dose-dependent fashion. A dose of as little as 20 x 10(3) U inhibited diabetes development, while a dose of 100 x 10(3) U potently prevented diabetes (14% incidence vs. 70% incidence in control mice). Even at the termination of the experiment, nondiabetic mice administered rIFN-alpha maintained normal glucose tolerance. Islet inflammation was 65% lower in the pancreases of rIFN-alpha mice. rIFN-alpha administration decreased anti-islet effector cell bioactivity of spleen cells without inducing generalized immunosuppression. Passive transfer experiments demonstrated that the decreased anti-islet effector cell activity was not a direct action of rIFN-alpha on these cells. In conclusion, rIFN-alpha potently and paradoxically prevents diabetes by indirectly decreasing anti-islet effector cell activity and in turn the development of insulitis without inducing generalized immunosuppression. This work, which goes against our current understanding of the role of rIFN-alpha in autoimmunity, may have significant implications to further our understanding of the pathogenesis of IDDM and to further the development of novel modes to prevent the disease.