The NOD mouse

Rodent models of cholestatic liver disease: A practical guide for translational research

Cholestatic liver disease denotes any situation associated with impaired bile flow concomitant with a noxious bile acid accumulation in the liver and/or systemic circulation. Cholestatic liver disease can be subdivided into different types according to its clinical phenotype, such as biliary atresia, drug-induced cholestasis, gallstone liver disease, intrahepatic cholestasis of pregnancy, primary biliary cholangitis and primary sclerosing cholangitis. Considerable effort has been devoted to elucidating underlying mechanisms of cholestatic liver injuries and explore novel therapeutic and diagnostic strategies using animal models. Animal models employed according to their appropriate applicability domain herein play a crucial role. This review provides an overview of currently available in vivo animal models, fit-for-purpose in modelling different types of cholestatic liver diseases. Moreover, a practical guide and workflow is provided which can be used for translational research purposes, including all advantages and disadvantages of currently available in vivo animal models.

The Inhibitory G Protein α-Subunit, Gαz, Promotes Type 1 Diabetes-Like Pathophysiology in NOD Mice

The α-subunit of the heterotrimeric Gz protein, Gαz, promotes β-cell death and inhibits β-cell replication when pancreatic islets are challenged by stressors. Thus, we hypothesized that loss of Gαz protein would preserve functional β-cell mass in the nonobese diabetic (NOD) model, protecting from overt diabetes. We saw that protection from diabetes was robust and durable up to 35 weeks of age in Gαz knockout mice. By 17 weeks of age, Gαz-null NOD mice had significantly higher diabetes-free survival than wild-type littermates. Islets from these mice had reduced markers of proinflammatory immune cell infiltration on both the histological and transcript levels and secreted more insulin in response to glucose. Further analyses of pancreas sections revealed significantly fewer terminal deoxynucleotidyltransferase-mediated dUTP nick end labeling (TUNEL)-positive β-cells in Gαz-null islets despite similar immune infiltration in control mice. Islets from Gαz-null mice also exhibited a higher percentage of Ki-67-positive β-cells, a measure of proliferation, even in the presence of immune infiltration. Finally, β-cell-specific Gαz-null mice phenocopy whole-body Gαz-null mice in their protection from developing hyperglycemia after streptozotocin administration, supporting a β-cell-centric role for Gαz in diabetes pathophysiology. We propose that Gαz plays a key role in β-cell signaling that becomes dysfunctional in the type 1 diabetes setting, accelerating the death of β-cells, which promotes further accumulation of immune cells in the pancreatic islets, and inhibiting a restorative proliferative response.

The H1-receptor antagonist cetirizine ameliorates high-fat diet-induced glucose intolerance in male C57BL/6 mice, but not diabetes outcome in female non-obese diabetic (NOD) mice

BACKGROUND

It has been proposed that the histamine 1-receptor (H1-receptor) not only promotes allergic reactions, but also modulates innate immunity and autoimmune reactions. In line with this, we have recently reported that the H1-receptor antagonist cetirizine partially counteracts cytokine-induced beta-cell signaling and destruction. Therefore, the aim of this study was to determine whether cetirizine affects diabetes in NOD mice, a model for human type 1 diabetes, and glucose intolerance in high-fat diet C57BL/6 mice, a model for human glucose intolerance.

METHODS

Female NOD mice were treated with cetirizine in the drinking water (25 mg/kg body weight) from 9 until 30 weeks of age during which precipitation of diabetes was followed. Male C57BL/6 mice were given a high-fat diet from 5 weeks of age. When the mice were 12 weeks of age cetirizine was given for 2 weeks in the drinking water. The effects of cetirizine were analyzed by blood glucose determinations, glucose tolerance tests, and insulin sensitivity tests.

RESULTS

Cetirizine did not affect diabetes development in NOD mice. On the other hand, cetirizine treatment for 1 week protected against high-fat diet-induced hyperglycemia. The glucose tolerance after 2 weeks of cetirizine treatment was improved in high-fat diet mice. We observed no effect of cetirizine on the insulin sensitivity of high-fat diet mice.

CONCLUSION

Our results suggest a protective effect of cetirizine against high-fat diet-induced beta-cell dysfunction, but not against autoimmune beta-cell destruction.

The potential role of dendritic cells in the therapy of Type 1 diabetes

Type 1 diabetes (T1D) is the result of T-cell mediated autoimmune destruction of pancreatic islet β-cells. The two current treatments for T1D are based on insulin or islet-cell replacement rather than the pathogenesis of T1D and remain problematic. Islet/pancreas transplantation does not cater for the majority of sufferers due to the lack of supply of organs and the need for continuous immunosuppression regimens. The mainstay treatment is insulin replacement, but this is disruptive to lifestyle and does not protect against severe long-term complications. An early vaccination and long-term restoration of immune tolerance to self-antigens in T1D patients (reversing the immunopathogenesis of the disease) would be preferable. Dendritic cells (DCs) are potent APCs and play an important role in inducing and maintaining immune tolerance. Targeting DCs through different DC surface molecules shows effective modulation of immune responses. Their feasibility for immunotherapy to prolong transplant survival and cancer immunotherapy has been demonstrated. Therefore, DCs could potentially be used in the treatment of autoimmune diseases. This review summarizes new insights into DCs as a potential therapeutic target for the treatment of T1D.

Intrapatient variations in type 1 diabetes-specific iPS cell differentiation into insulin-producing cells

Nuclear reprogramming of adult somatic tissue enables embryo-independent generation of autologous, patient-specific induced pluripotent stem (iPS) cells. Exploiting this emergent regenerative platform for individualized medicine applications requires the establishment of bioequivalence criteria across derived pluripotent lines and lineage-specified derivatives. Here, from individual patients with type 1 diabetes (T1D) multiple human iPS clones were produced and prospectively screened using a battery of developmental markers to assess respective differentiation propensity and proficiency in yielding functional insulin (INS)-producing progeny. Global gene expression profiles, pluripotency expression patterns, and the capacity to differentiate into SOX17- and FOXA2-positive definitive endoderm (DE)-like cells were comparable among individual iPS clones. However, notable intrapatient variation was evident upon further guided differentiation into HNF4α- and HNF1β-expressing primitive gut tube, and INS- and glucagon (GCG)-expressing islet-like cells. Differential dynamics of pluripotency-associated genes and pancreatic lineage-specifying genes underlined clonal variance. Successful generation of glucose-responsive INS-producing cells required silencing of stemness programs as well as the induction of stage-specific pancreatic transcription factors. Thus, comprehensive fingerprinting of individual clones is mandatory to secure homogenous pools amenable for diagnostic and therapeutic applications of iPS cells from patients with T1D.

Approaches to the pathogenesis of primary biliary cirrhosis through animal models

Primary biliary cirrhosis (PBC) is a chronic and progressive cholestatic liver disease of unknown etiopathogenesis that mainly affects middle-aged women. Patients show non-suppurative cholangitis with damage and destruction of the small- and medium-sized intrahepatic bile ducts. Characteristically, the disease is strongly associated with autoimmune phenomena such as the appearance of serum antimitochondrial autoantibodies (AMA) and portal infiltrating T cells against the inner lipoyl domain in the E2 component of the pyruvate dehydrogenase complex (PDC-E2). Here we review the major characteristics of a series of inducible and genetically modified animal models of PBC and analyze the similarities and differences to PBC features in humans.

Manipulation of CD98 resolves type 1 diabetes in nonobese diabetic mice

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

A subset of interleukin-21+ chemokine receptor CCR9+ T helper cells target accessory organs of the digestive system in autoimmunity

This study describes a CD4+ T helper (Th) cell subset marked by coexpression of the cytokine interleukin 21 (IL-21) and the gut-homing chemokine receptor CCR9. Although CCR9+ Th cells were observed in healthy mice and humans, they were enriched in the inflamed pancreas and salivary glands of NOD mice and in the circulation of Sjögren's syndrome patients. CCR9+ Th cells expressed large amounts of IL-21, inducible T cell costimulator (ICOS), and the transcription factors Bcl6 and Maf, and also supported antibody production from B cells, thereby resembling T follicular B helper (Tfh) cells. However, in contrast to Tfh cells, CCR9+ Th cells displayed limited expression of CXCR5 and the targets of CCR9+ Th cells were CD8+ T cells whose responsiveness to IL-21 was necessary for the development of diabetes. Thus, CCR9+ Th cells are a subset of IL-21-producing T helper cells that influence regional specification of autoimmune diseases that affect accessory organs of the digestive system.

Interleukin-21 is critically required in autoimmune and allogeneic responses to islet tissue in murine models

OBJECTIVE

Type 1 diabetes is an incurable chronic autoimmune disease. Although transplantation of pancreatic islets may serve as a surrogate source of insulin, recipients are subjected to a life of immunosuppression. Interleukin (IL)-21 is necessary for type 1 diabetes in NOD mice. We examined the efficacy of an IL-21-targeted therapy on prevention of diabetes in NOD mice, in combination with syngeneic islet transplantation. In addition, we assessed the role of IL-21 responsiveness in islet allograft rejection in mouse animal models.

RESEARCH DESIGN AND METHODS

NOD mice were treated with IL-21R/Fc, an IL-21-neutralizing chimeric protein. This procedure was combined with syngeneic islet transplantation to treat diabetic NOD mice. Survival of allogeneic islet grafts in IL-21R-deficient mice was also assessed.

RESULTS

Evidence is provided that IL-21 is continually required by the autoimmune infiltrate, such that insulitis was reduced and reversed and diabetes inhibited by neutralization of IL-21 at a late preclinical stage. Recovery from autoimmune diabetes was achieved by combining neutralization of IL-21 with islet transplantation. Furthermore, IL-21-responsiveness by CD8+ T-cells was sufficient to mediate islet allograft rejection.

CONCLUSIONS

Neutralization of IL-21 in NOD mice can inhibit diabetes, and when paired with islet transplantation, this therapeutic approach restored normoglycemia. The influence of IL-21 on a graft-mounted immune response was robust, since the absence of IL-21 signaling prevented islet allograft rejection. These findings suggest that therapeutic manipulation of IL-21 may serve as a suitable treatment for patients with type 1 diabetes.

Mitochondria mediated cell death in diabetes

Mitochondrial dysfunction plays a role in the pathogenesis of a wide range of diseases that involve disordered cellular fuel metabolism and survival/death pathways, including neurodegenerative diseases, cancer and diabetes. Cytokine, virus recognition and cellular stress pathways converging on mitochondria cause apoptotic and/or necrotic cell death of beta-cells in type-1 diabetes. Moreover, since mitochondria generate crucial metabolic signals for glucose stimulated insulin secretion (GSIS), mitochondrial dysfunction underlies both the functional derangement of GSIS and (over-nutrition) stress-induced apoptotic/necrotic beta-cell death, hallmarks of type-2 diabetes. The apparently distinct mechanisms governing beta-cell life/death decisions during the development of diabetes provide a remarkable example where remote metabolic, immune and stress signalling meet with mitochondria mediated apoptotic/necrotic death pathways to determine the fate of the beta-cell. We summarize the main findings supporting such a pivotal role of mitochondria in beta-cell death in the context of current trends in diabetes research.

Metastable pluripotent states in NOD-mouse-derived ESCs

Embryonic stem cells (ESCs) are isolated from the inner cell mass (ICM) of blastocysts, whereas epiblast stem cells (EpiSCs) are derived from the postimplantation epiblast and display a restricted developmental potential. Here we characterize pluripotent states in the nonobese diabetic (NOD) mouse strain, which prior to this study was considered "nonpermissive" for ESC derivation. We find that NOD stem cells can be stabilized by providing constitutive expression of Klf4 or c-Myc or small molecules that can replace these factors during in vitro reprogramming. The NOD ESCs and iPSCs appear to be "metastable," as they acquire an alternative EpiSC-like identity after removal of the exogenous factors, while their reintroduction converts the cells back to ICM-like pluripotency. Our findings suggest that stem cells from different genetic backgrounds can assume distinct states of pluripotency in vitro, the stability of which is regulated by endogenous genetic determinants and can be modified by exogenous factors.

Ectopic PDX-1 expression in liver ameliorates type 1 diabetes

Type 1 diabetes mellitus (T1DM) results from a specific autoimmune mediated destruction of the pancreatic beta-cells. PDX-1 induced developmentally redirected liver cells were suggested to restore the ablated pancreatic function in chemically induced diabetes. However, developmentally redirected liver cells, may have acquired along with the desired beta-cell characteristics and functions, also undesired sensitivity to autoimmune attack and therefore may be inefficient in ameliorating T1DM. This study analyzes whether subjects with beta-cell autoimmunity could benefit from Ad-CMV-PDX-1 gene therapy. Using the model of cyclophosphamide-accelerated diabetes in non-obese diabetic (CAD-NOD) mice, we report that recombinant adenovirus mediated PDX-1 gene therapy, ameliorates hyperglycemia in CAD-NOD mice. Our data demonstrate that 43% of the overtly diabetic CAD-NOD mice treated with Ad-CMV-PDX-1 became normoglycemic and maintained a stable body weight. Ectopic PDX-1 expression induced pancreatic gene expression and insulin production in the mice livers. The amelioration of hyperglycemia, in PDX-1 treated diabetic mice was associated with an immune modulation manifested by Th1 to Th2 shift in the autoimmune T-cell response to antigens associated with NOD diabetes. Thus, liver-to-pancreas transdifferentiation ameliorates T1DM in a process which is associated with a concomitant modulation of the autoimmune attack. Our findings suggest a beneficial therapeutic effect of the PDX-1 gene therapy for treating autoimmune type 1 diabetes mellitus (T1DM).

Recruitment and activation of naive T cells in the islets by lymphotoxin beta receptor-dependent tertiary lymphoid structure

The development of spontaneous insulin-dependent diabetes mellitus is preceded by the organization of tertiary lymphoid organ (TLO) in situ, but its role in the development of tissue destruction and the cytokines that control such structures have not been fully defined. We have now observed that TNF superfamily 14 (TNFSF14) is upregulated in aged nonobese diabetic (NOD) pancreas with the appearance of TLO. Blockade of TNFSF14 signaling caused a substantial reduction in the expression of lymphotoxin beta receptor (LTbetaR)-controlled migration factors within the islets and disrupts organization of tertiary structures, leading to prevention of diabetes. Consistently, enhancing LTbetaR signaling by transgenic expression of TNFSF14 in the islets of NOD mice rapidly promoted de novo formation of local TLO, resulting in diabetes, even in the absence of draining lymph nodes (LN). Thus, the TNFSF14-LTbetaR pathway appears to be critical in the development and maintenance of TLO for the onset of diabetes.

NOD.c3c4 congenic mice develop autoimmune biliary disease that serologically and pathogenetically models human primary biliary cirrhosis

Primary biliary cirrhosis (PBC) is an autoimmune disease with a strong genetic component characterized by biliary ductular inflammation with eventual liver cirrhosis. The serologic hallmark of PBC is antimitochondrial antibodies that react with the pyruvate dehydrogenase complex, targeting the inner lipoyl domain of the E2 subunit (anti-PDC-E2). Herein we demonstrate that NOD.c3c4 mice congenically derived from the nonobese diabetic strain develop an autoimmune biliary disease (ABD) that models human PBC. NOD.c3c4 (at 9-10 wk, before significant biliary pathology) develop antibodies to PDC-E2 that are specific for the inner lipoyl domain. Affected areas of biliary epithelium are infiltrated with CD3+, CD4+, and CD8+ T cells, and treatment of NOD.c3c4 mice with monoclonal antibody to CD3 protects from ABD. Furthermore, NOD.c3c4-scid mice develop disease after adoptive transfer of splenocytes or CD4+ T cells, demonstrating a central role for T cells in pathogenesis. Histological analysis reveals destructive cholangitis, granuloma formation, and eosinophilic infiltration as seen in PBC, although, unlike PBC, the extrahepatic biliary ducts are also affected. Using a congenic mapping approach, we define the first ABD (Abd) locus, Abd1. These results identify the NOD.c3c4 mouse as the first spontaneous mouse model of PBC.

How defects in central tolerance impinge on a deficiency in regulatory T cells

Both central (thymic) and peripheral (nonthymic) mechanisms are important for the induction and maintenance of T cell tolerance. Mice with a defect in Foxp3, required for the generation and activity of CD4(+)CD25(+) regulatory T cells, exhibit massive lymphoproliferation and severe inflammatory infiltration of multiple organs, in particular the lungs, liver, and skin. We have explored how this phenotype is influenced by an additional defect in central tolerance induction, generated by either crossing in a null mutation of the Aire gene or substituting the nonobese diabetic (NOD) genetic background. The double-deficient mice had fulminant autoimmunity in very early life and a gravely shortened lifespan vis-à-vis single-deficient littermates. They showed massive lymphoproliferation and exacerbated inflammatory damage, particularly in the lungs and liver. Yet, the range of affected sites was not noticeably extended, and, surprisingly, many organs, or regions of organs, remained untouched, suggesting additional important mechanisms to enforce immunological self-tolerance.

Prevention of diabetes in NOD mice at a late stage by targeting OX40/OX40 ligand interactions

Autoreactive T cells play a major role in the development of insulin-dependent diabetes mellitus, suggesting that costimulatory molecules that regulate T cell responses might be essential for disease progression. In NOD mice, CD28/B7 and CD40/CD40 ligand (L) interactions control the onset of diabetes from 2 to 4 weeks of age, but blocking these molecules has little effect after this time. Hence, it is possible that other ligand/receptor pairs control a later phase of disease. We now show that OX40 is expressed on CD4 and CD8 T cells several weeks prior to islet destruction, which is initiated around weeks 12-14, and that OX40L is present on dendritic cells in both secondary lymphoid organs and the pancreas from 11 to 13 weeks of age. Blocking OX40L at 6, 9, or 15 weeks after birth had little effect on disease; however, inhibiting OX40/OX40L interactions at week 12, or continuous treatment from week 12 onwards, significantly reduced the incidence of diabetes. Histological examination showed that islet destruction was prevented and insulitis reduced by targeting OX40L. These studies show that OX40/OX40L interactions form a late checkpoint in diabetes development and suggest that these molecules are realistic targets for therapeutic intervention.

Site-specific regulation of tissue dendritic cell function by granulocyte-macrophage colony-stimulating-factor

Tissue dendritic cells (DC) are usually associated with phagocytic function but poor T-cell immunostimulatory capacity. Following activation, dendritic cells are stimulated to leave tissue sites and migrate to lymphoid tissue, acquiring immunostimulatory capacity during the process. We provide evidence that the immunostimulatory capacity of tissue DC, but not spleen cells, can be affected in situ by granulocyte-macrophage colony-stimulating-factor (GM-CSF). Initially it was found that islet cells from non-obese diabetic and BALB/c mice, which produce GM-CSF, showed significantly higher immunostimulatory capacity than islets from C3H and C57BL/6 mice, which do not produce GM-CSF. Second, pretreatment of nonobese diabetic mice with anti-GM-CSF antibody significantly reduced the immunostimulatory capacity of islet cells, but not spleen cells, although it had no effect on the numbers of cells expressing DC-associated antigens. Therefore the immunostimulatory function of islet DC is partially dependent on GM-CSF. By contrast, spleen DC immunostimulatory function does not show the same dependence on GM-CSF. This may affect the ability of dendritic cells to stimulate autoimmune responses or tolerance.

CXC Chemokine Ligand 10 Neutralization Suppresses the Occurrence of Diabetes in Nonobese Diabetic Mice through Enhanced β Cell Proliferation without Affecting Insulitis

We have shown that neutralization of IFN-inducible protein 10/CXCL10, a chemokine for Th1 cells, breaks Th1 retention in the draining lymph nodes, resulting in exacerbation in Th1-dominant autoimmune disease models induced by immunization with external Ags. However, there have been no studies on the role of CXCL10 neutralization in Th1-dominant disease models induced by constitutive intrinsic self Ags. So, we have examined the effect of CXCL10 neutralization using a type 1 diabetes model initiated by developmentally regulated presentation of beta cell Ags. CXCL10 neutralization suppressed the occurrence of diabetes after administration with cyclophosphamide in NOD mice, although CXCL10 neutralization did not significantly inhibit insulitis and gave no influence on the trafficking of effector T cells into the islets. Because both CXCL10 and CXCR3 were, unexpectedly, coexpressed on insulin-producing cells, CXCL10 was considered to affect mature and premature beta cells in an autocrine and/or paracrine fashion. In fact, CXCL10 neutralization enhanced proliferative response of beta cells and resultantly increased beta cell mass without inhibiting insulitis. Thus, CXCL10 neutralization can be a new therapeutic target for beta cell survival, not only during the early stage of type 1 diabetes, but also after islet transplantation.

Gamma-aminobutyric acid inhibits T cell autoimmunity and the development of inflammatory responses in a mouse type 1 diabetes model

Gamma-aminobutyric acid (GABA) is both a major inhibitory neurotransmitter in the CNS and a product of beta cells of the peripheral islets. Our previous studies, and those of others, have shown that T cells express functional GABAA receptors. However, their subunit composition and physiological relevance are unknown. In this study, we show that a subset of GABAA receptor subunits are expressed by CD4+ T cells, including the delta subunit that confers high affinity for GABA and sensitivity to alcohol. GABA at relatively low concentrations down-regulated effector T cell responses to beta cell Ags ex vivo, and administration of GABA retarded the adoptive transfer of type 1 diabetes (T1D) in NOD/scid mice. Furthermore, treatment with low dose of GABA (600 microg daily) dramatically inhibited the development of proinflammatory T cell responses and disease progression in T1D-prone NOD mice that already had established autoimmunity. Finally, GABA inhibited TCR-mediated T cell cycle progression in vitro, which may underlie GABA's therapeutic effects. The immunoinhibitory effects of GABA on T cells may contribute to the long prodomal period preceding the development of T1D, the immunological privilege of the CNS, and the regulatory effects of alcohol on immune responses. Potentially, pharmacological modulation of GABAA receptors on T cells may provide a new class of therapies for human T1D as well as other inflammatory diseases.

Functional immunomics: microarray analysis of IgG autoantibody repertoires predicts the future response of mice to induced diabetes

One's present repertoire of antibodies encodes the history of one's past immunological experience. Can the present autoantibody repertoire be consulted to predict resistance or susceptibility to the future development of an autoimmune disease? Here, we developed an antigen microarray chip and used bioinformatic analysis to study a model of type 1 diabetes developing in nonobese diabetic male mice in which the disease was accelerated and synchronized by exposing the mice to cyclophosphamide at 4 weeks of age. We obtained sera from 19 individual mice, treated the mice to induce cyclophosphamide-accelerated diabetes (CAD), and found, as expected, that 9 mice became severely diabetic, whereas 10 mice permanently resisted diabetes. We again obtained serum from each mouse after CAD induction. We then analyzed, by using rank-order and superparamagnetic clustering, the patterns of antibodies in individual mice to 266 different antigens spotted on the chip. A selected panel of 27 different antigens (10% of the array) revealed a pattern of IgG antibody reactivity in the pre-CAD sera that discriminated between the mice resistant or susceptible to CAD with 100% sensitivity and 82% specificity (P = 0.017). Surprisingly, the set of IgG antibodies that was informative before CAD induction did not separate the resistant and susceptible groups after the onset of CAD; new antigens became critical for post-CAD repertoire discrimination. Thus, at least for a model disease, present antibody repertoires can predict future disease, predictive and diagnostic repertoires can differ, and decisive information about immune system behavior can be mined by bioinformatic technology. Repertoires matter.

Genetic Control of Autoimmunity: Protection from Diabetes, but Spontaneous Autoimmune Biliary Disease in a Nonobese Diabetic Congenic Strain

At least 20 insulin-dependent diabetes (Idd) loci modify the progression of autoimmune diabetes in the NOD mouse, an animal model of human type 1 diabetes. The NOD.c3c4 congenic mouse, which has multiple B6- and B10-derived Idd-resistant alleles on chromosomes 3 and 4, respectively, is completely protected from autoimmune diabetes. We demonstrate in this study, however, that NOD.c3c4 mice develop a novel spontaneous and fatal autoimmune polycystic biliary tract disease, with lymphocytic peribiliary infiltrates and autoantibodies. Strains having a subset of the Idd-resistant alleles present in the NOD.c3c4 strain show component phenotypes of the liver disease: NOD mice with B6 resistance alleles only on chromosome 3 have lymphocytic liver infiltration without autoantibody formation, while NOD mice with B10 resistance alleles only on chromosome 4 show autoantibody formation without liver infiltration. The liver disease is transferable to naive NOD.c3c4 recipients using splenocytes from affected NOD.c3c4 mice, demonstrating an autoimmune etiology. Thus, substitution of non-NOD genetic intervals into the NOD strain can prevent diabetes, but in turn cause an entirely different autoimmune syndrome, a finding consistent with a generalized failure of self-tolerance in the NOD genetic background. The complex clinical phenotypes in human autoimmune conditions may be similarly resolved into largely overlapping biochemical pathways that are then modified, potentially by alleles at a few key chromosomal regions, to produce specific autoimmune syndromes.

Effective destruction of Fas-deficient insulin-producing beta cells in type 1 diabetes

In type 1 diabetes, autoimmune T cells cause destruction of pancreatic β cells by largely unknown mechanism. Previous analyses have shown that β cell destruction is delayed but can occur in perforin-deficient nonobese diabetic (NOD) mice and that Fas-deficient NOD mice do not develop diabetes. However, because of possible pleiotropic functions of Fas, it was not clear whether the Fas receptor was an essential mediator of β cell death in type 1 diabetes. To directly test this hypothesis, we have generated a β cell–specific knockout of the Fas gene in a transgenic model of type 1 autoimmune diabetes in which CD4⁺ T cells with a transgenic TCR specific for influenza hemagglutinin (HA) are causing diabetes in mice that express HA under control of the rat insulin promoter. Here we show that the Fas-deficient mice develop autoimmune diabetes with slightly accelerated kinetics indicating that Fas-dependent apoptosis of β cells is a dispensable mode of cell death in this disease.

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

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

The natural killer cell -- friend or foe in autoimmune disease?

Autoimmune diseases are chronic conditions resulting from a loss of immunological tolerance to self-antigens. Recent observations have supported an ever-broader role for innate immune responses in directing and regulating adaptive immunity, including responses to self. This review summarizes recent findings supporting important functions of natural killer (NK) cells in regulating autoimmunity. A close survey of the current literature reveals multiple steps where NK cells can regulate inflammation and intervene in loss of self-tolerance. Importantly, the findings also caution against inferring a similar role for NK cells in all autoimmune phenomena or during separate stages of the same disease. Indeed, NK cells may have different influences during the priming and the effector phases of disease. Hence, an increased understanding of the involvement of NK cells in inflammation and infection should provide new insights into the pathogenesis of autoimmune disease.

Target cell defense prevents the development of diabetes after viral infection

The mechanisms that regulate susceptibility to virus-induced autoimmunity remain undefined. We establish here a fundamental link between the responsiveness of target pancreatic beta cells to interferons (IFNs) and prevention of coxsackievirus B4 (CVB4)-induced diabetes. We found that an intact beta cell response to IFNs was critical in preventing disease in infected hosts. The antiviral defense, raised by beta cells in response to IFNs, resulted in a reduced permissiveness to infection and subsequent natural killer (NK) cell-dependent death. These results show that beta cell defenses are critical for beta cell survival during CVB4 infection and suggest an important role for IFNs in preserving NK cell tolerance to beta cells during viral infection. Thus, alterations in target cell defenses can critically influence susceptibility to disease.

Impaired activation of islet-reactive CD4 T cells in pancreatic lymph nodes of B cell-deficient nonobese diabetic mice

Despite the impressive protection of B cell-deficient (muMT(-/-)) nonobese diabetic (NOD) mice from spontaneous diabetes, existence of mild pancreatic islet inflammation in these mice indicates that initial autoimmune targeting of beta cells has occurred. Furthermore, muMT(-/-) NOD mice are shown to harbor a latent repertoire of diabetogenic T cells, as evidenced by their susceptibility to cyclophosphamide-induced diabetes. The quiescence of this pool of islet-reactive T cells may be a consequence of impaired activation of T lymphocytes in B cell-deficient NOD mice. In this regard, in vitro anti-CD3-mediated stimulation demonstrates impaired activation of lymph node CD4 T cells in muMT(-/-) NOD mice as compared with that of wild-type counterparts, a deficiency that is correlated with an exaggerated CD4 T cell:APC ratio in lymph nodes of muMT(-/-) NOD mice. This feature points to an insufficient availability of APC costimulation on a per T cell basis, resulting in impaired CD4 T cell activation in lymph nodes of muMT(-/-) NOD mice. In accordance with these findings, an islet-reactive CD4 T cell clonotype undergoes suboptimal activation in pancreatic lymph nodes of muMT(-/-) NOD recipients. Overall, the present study indicates that B cells in the pancreatic lymph node microenvironment are critical in overcoming a checkpoint involving the provision of optimal costimulation to islet-reactive NOD CD4 T cells.

Increased entry into the IFN-gamma effector pathway by CD4+ T cells selected by I-Ag7 on a nonobese diabetic versus C57BL/6 genetic background

IFN-gamma-mediated Th1 effects play a major role in the pathogenesis of autoimmune diabetes in nonobese diabetic (NOD) mice. We analyzed functional responses of CD4(+) T cells from NOD and B6.G7 MHC congenic mice, which share the H2(g7) MHC region but differ in their non-MHC genetic background. T cells from each strain proliferated equally to panstimulation with T cell lectins as well as to stimulation with glutamic acid decarboxylase 524-543 (self) and hen egg lysozyme 11-23 (foreign) I-A(g7)-binding peptide epitopes. Despite comparable proliferative responses, NOD CD4(+) T cells had significantly increased IFN-gamma intracellular/extracellular protein and mRNA responses compared with B6.G7 T cells as measured by intracellular cytokine analysis, time resolved fluorometry, and RNase protection assays. The increased IFN-gamma production was not due to an increase in the amount of IFN-gamma produced per cell but to an increase in the number of NOD CD4(+) T cells entering the IFN-gamma-producing pathway. The increased IFN-gamma response in NOD mice was not due to increased numbers of activated precursors as measured by activation/memory markers. B6.G7 lymphoid cells demonstrated an absolute decrease in IFN-gamma mRNA, an increase in IL-4 mRNA production, and a significantly decreased IFN-gamma:IL-4 mRNA transcript ratio compared with NOD cells. CD4(+) T cells from C57BL6 mice also showed significantly decreased IFN-gamma production compared with CD4(+) T cells from NOD.H2(b) MHC-congenic mice (which have an H2(b) MHC region introgressed onto an NOD non-MHC background). Therefore, the NOD non-MHC background predisposes to a quantitatively increased IFN-gamma response, independent of MHC class II-mediated T cell repertoire selection, even when compared with a prototypical Th1 strain.

Reversal of spontaneous autoimmune insulitis in nonobese diabetic mice by soluble lymphotoxin receptor

One striking feature of spontaneous autoimmune diabetes is the prototypic formation of lymphoid follicular structures within the pancreas. Lymphotoxin (LT) has been shown to play an important role in the formation of lymphoid follicles in the spleen. To explore the potential role of LT-mediated microenvironment in the pathogenesis of insulin-dependent diabetes mellitus (IDDM), an LTbeta receptor-immunoglobulin fusion protein (LTbetaR-Ig) was administered to nonobese diabetic mice. Early treatment with LTbetaR-Ig prevented insulitis and IDDM, suggesting that LT plays a critical role in the insulitis development. LTbetaR-Ig treatment at a late stage of the disease also dramatically reversed insulitis and prevented diabetes. Moreover, LTbetaR-Ig treatment prevented the development of IDDM by diabetogenic T cells in an adoptive transfer model. Thus, LTbetaR-Ig can disassemble the well established lymphoid microenvironment in the islets, which is required for the development and progression of IDDM.

Oral administration of insulin to neonates suppresses spontaneous and cyclophosphamide induced diabetes in the NOD mouse

Oral administration of autoantigens to adult mice is an effective means of suppressing experimental autoimmune diseases including diabetes and experimental allergic encephalomyelitis (EAE). Different mechanisms are involved in induction of oral tolerance including active suppression, anergy and deletion. Oral tolerance is generally not inducible in the neonatal period and we previously found that EAE development in Lewis rats is enhanced when animals are fed myelin antigens as neonates. Here we report the unexpected finding that oral administration of either human insulin or the insulin B-chain peptide (10-24) in the neonatal period suppresses the development of diabetes in the non-obese diabetic (NOD) mouse. Furthermore, suppression of diabetes by neonatal oral human insulin was more effective than oral human insulin given to NOD mice (3-4 weeks of age). No protection against EAE was observed in NOD mice neonatally fed PLP (48-70) or MOG (35-55) peptide prior to EAE induction, whereas adult NOD mice orally tolerized to these peptides were protected against EAE. Neonatal administration of insulin B-chain peptide also suppressed cyclophosphamide induced diabetes in the NOD whereas oral insulin administration to 4-week-old NOD mice had no effect, suggesting that the mechanism of disease suppression in the neonate involved anergy or deletion. Our findings that neonatal feeding of human insulin or insulin B-chain peptide is effective in inhibiting diabetes when given to the NOD mouse may have applications in preventing diabetes in high risk human populations.

Detection of glutamic acid decarboxylase-activated T cells with I-Ag7 tetramers

CD4(+) T cells selected by the type 1 diabetes associated class II MHC I-A(g7) molecules play a critical role in the disease process. Multivalent MHC/peptide tetramers have been used to directly detect antigen-specific T cells. Detection of autoantigen-activated CD4(+) T cells with tetramers should be very helpful in the study of the roles of these cells in diabetes. We report here the generation of tetramers of I-A(g7) covalently linked to two glutamic acid decarboxylase (GAD) peptides and the detection of GAD peptide-activated T cells from nonobese diabetic (NOD) mice. The I-A(g7) heterodimers can form stable complexes with a covalently bound GAD peptide and can stimulate antigen specific T cells. Furthermore, I-A(g7)/GAD peptide tetramer can detect most if not all of the antigen-specific CD4(+) T cells from immunized NOD mice. Antigen-specific T cells detected by the tetramers can up-regulate their CD4 expression on the cell surface after being restimulated with the GAD peptides in vitro. In contrast, the tetramers can detect a percentage of T cells in lymph nodes and spleens and T cells infiltrating islets from nonimmunized mice that is not significantly above the background. Therefore, T cells specific for the GAD peptides are present in NOD mice at a frequency too low to be detected, but immunization of NOD mice can facilitate their detection by tetramers.

Impaired CD4 T cell activation due to reliance upon B cell-mediated costimulation in nonobese diabetic (NOD) mice

Diabetes in nonobese diabetic (NOD) mice results from the activation of I-A(g7)-restricted, islet-reactive T cells. This study delineates several characteristics of NOD CD4 T cell activation, which, independent of I-A(g7), are likely to promote a dysregulated state of peripheral T cell tolerance. NOD CD4 T cell activation was found to be resistant to antigenic stimulation via the TCR complex, using the progression of cell division as a measure. The extent of NOD CD4 T cell division was highly sensitive to changes in Ag ligand density. Moreover, even upon maximal TCR complex-mediated stimulation, NOD CD4 T cell division prematurely terminated. Maximally stimulated NOD CD4 T cells failed to achieve the threshold number of division cycles required for optimal susceptibility to activation-induced death, a critical mechanism for the regulation of peripheral T cell tolerance. Importantly, these aberrant activation characteristics were not T cell-intrinsic but resulted from reliance on B cell costimulatory function in NOD mice. Costimulation delivered by nonautoimmune strain APCs normalized NOD CD4 T cell division and the extent of activation-induced death. Thus, by disrupting the progression of CD4 T cell division, polarization of APC costimulatory function to the B cell compartment could allow the persistence and activation of diabetogenic cells in NOD mice.

Regulation of TCR-induced IFN-gamma release from islet-reactive non-obese diabetic CD8(+) T cells by prostaglandin E(2) receptor signaling

Prostaglandins (PG) are released during tissue injury and inflammation, and inhibit immune responses at many points. PG may be one of several factors that protect not only against injury-induced, but also spontaneous, organ-specific autoimmune disease. Here we show that the production of PGE(2), normally produced at a very low rate in islets of Langerhans, is significantly increased in inflamed islets of non-obese diabetic (NOD) mice. We investigated a possible role of PGE(2) in controlling TCR-dependent release of IFN-gamma from islet-reactive NOD CD8(+) T cells. PGE(2) inhibited anti-TCR antibody-triggered release of IFN-gamma from CD8(+) T cell clone 8D8 and from polyclonal cytotoxic T lymphocytes (CTL). Using receptor subtype selective agonists, we present evidence that the effect of PGE(2) is mediated by EP(2) and EP(4) receptors, both of which are coupled to an increase in intracellular cAMP production. The cAMP analogs 8-Br-cAMP and Sp-cAMPS mimic the effect of EP(2)/EP(4) receptor agonists, inhibiting TCR-triggered IFN-gamma release from NOD CD8(+) T cells in a dose-dependent manner. The inhibitory effect of PGE(2) was largely reversed by IL-2 added at the time of culture initiation and decreased with increasing strength of stimulation through the TCR. Resting CTL were more sensitive to PGE(2) than recently expanded CTL and NOD CD8(+) T cells remained insensitive to PGE(2) for a longer time than BALB/c cells. Our study suggests that PGE(2) may be part of a regulatory network that controls local activation of T cells and may play a role in the balance between the development of islet autoimmunity or maintenance of tolerance.

Insulin in Oral Immune “Tolerance”: A One-Amino Acid Change in the B Chain Makes the Difference

Oral administration of self-Ags can dampen or prevent autoimmune processes by induction of bystander suppression. Based on encouraging results from experiments in nonobese diabetic (NOD) mice, clinical trials have been initiated in type 1 diabetes using human insulin as an oral Ag. However, neither the precise antigenic requirements nor the mechanism of bystander suppression are currently understood in detail. Here we report that 1) a 1-aa difference in position 30 of the insulin B chain abrogated the ability of insulin to confer protection in both NOD as well as a virus-induced transgenic mouse model for type 1 diabetes. In the latter model transgenic mice express the nucleoprotein (NP) of lymphocytic choriomeningitis virus (LCMV) under the control of the rat insulin promotor (RIP) in the pancreatic β cells and develop diabetes only following LCMV infection; and 2) protection could be transferred with insulin B chain-restimulated but not LCMV-restimulated splenocytes from RIP-NP transgenic mice, demonstrating that the mechanism of diabetes prevention in the RIP-NP model is mediated by insulin B chain-specific, IL-4-producing regulatory cells acting as bystander suppressors.

Initiation of autoimmune diabetes by developmentally regulated presentation of islet cell antigens in the pancreatic lymph nodes

Little is known about the events triggering lymphocyte invasion of the pancreatic islets in prelude to autoimmune diabetes. For example, where islet-reactive T cells first encounter antigen has not been identified. We addressed this issue using BDC2.5 T cell receptor transgenic mice, which express a receptor recognizing a natural islet beta cell antigen. In BDC2.5 animals, activated T cells were found only in the islets and the lymph nodes draining them, and there was a close temporal correlation between lymph node T cell activation and islet infiltration. When naive BDC2.5 T cells were transferred into nontransgenic recipients, proliferating cells were observed only in pancreatic lymph nodes, and this occurred significantly before insulitis was detectable. Surprisingly, proliferation was not seen in 10-day-old recipients. This age-dependent dichotomy was reproduced in a second transfer system based on an unrelated antigen artificially expressed on beta cells. We conclude that beta cell antigens are transported specifically to pancreatic lymph nodes, where they trigger reactive T cells to invade the islets. Systemic or extrapancreatic T cell priming, indicative of activation via molecular mimicry or superantigens, was not seen. Compromised presentation of beta cell antigens in the pancreatic lymph nodes of juvenile animals may be the root of a first "checkpoint" in diabetes progression.