Nonobese diabetic mouse congenic analysis reveals chromosome 11 locus contributing to diabetes susceptibility, macrophage STAT5 dysfunction, and granulocyte-macrophage colony-stimulating factor overproduction

Elucidating the Role of Ezh2 in Tolerogenic Function of NOD Bone Marrow-Derived Dendritic Cells Expressing Constitutively Active Stat5b

Tolerogenic dendritic cells (toDCs) are crucial to controlling the development of autoreactive T cell responses and the prevention of autoimmunity. We have reported that NOD.CD11c^Stat5b-CA transgenic mice expressing a constitutively active (CA) form of Stat5b under the control of a CD11c promoter are protected from diabetes and that Stat5b-CA-expressing DCs are tolerogenic and halt ongoing diabetes in NOD mice. However, the molecular mechanisms by which Stat5b-CA modulates DC tolerogenic function are not fully understood. Here, we used bone marrow-derived DCs (BMDCs) from NOD.CD11c^Stat5b-CA transgenic mice (Stat5b-CA.BMDCs) and found that Stat5b-CA.BMDCs displayed high levels of MHC class II, CD80, CD86, PD-L1, and PD-L2 and produced elevated amounts of TGFβ but low amounts of TNFα and IL-23. Stat5b-CA.BMDCs upregulated Irf4 and downregulated Irf8 genes and protein expression and promoted CD11c⁺CD11b⁺ DC2 subset differentiation. Interestingly, we found that the histone methyltransferase Ezh2 and Stat5b-CA bound gamma-interferon activated site (GAS) sequences in the Irf8 enhancer IRF8 transcription, whereas Stat5b but not Ezh2 bound GAS sequences in the Irf4 promoter to enhance IRF4 transcription. Injection of Stat5b-CA.BMDCs into prediabetic NOD mice halted progression of islet inflammation and protected against diabetes. Importantly, inhibition of Ezh2 in tolerogenic Stat5b-CA.BMDCs reduced their ability to prevent diabetes development in NOD recipient mice. Taken together, our data suggest that the active form of Stat5b induces tolerogenic DC function by modulating IRF4 and IRF8 expression through recruitment of Ezh2 and highlight the fundamental role of Ezh2 in Stat5b-mediated induction of tolerogenic DC function.

Csf2 and Ptgs2 Epigenetic Dysregulation in Diabetes-prone Bicongenic B6.NODC11bxC1tb Mice

In Type 1 diabetic (T1D) human monocytes, STAT5 aberrantly binds to epigenetic regulatory sites of two proinflammatory genes, CSF2 (encoding granulocyte-macrophage colony-stimulating factor) and PTGS2 (encoding prostaglandin synthase 2/cyclooxygenase 2). Bicongenic B6.NOD C11bxC1tb mice re-create this phenotype of T1D monocytes with only two nonobese diabetic (NOD) Idd subloci (130.8 Mb-149.7 Mb, of Idd5 on Chr 1 and 32.08-53.85 Mb of Idd4.3 on Chr11) on C57BL/6 genetic background. These two Idd loci interact through STAT5 binding at upstream regulatory regions affecting Csf2 (Chr 11) and Ptgs2 (Chr 1) expression. B6.NODC11bxC1tb mice exhibited hyperglycemia and immune destruction of pancreatic islets between 8 and 30 weeks of age, with 12%-22% penetrance. Thus, B6.NODC11bxC1tb mice embody NOD epigenetic dysregulation of gene expression in myeloid cells, and this defect appears to be sufficient to impart genetic susceptibility to diabetes in an otherwise genetically nonautoimmune mouse.

Identification of the inflammasome Nlrp1b as the candidate gene conferring diabetes risk at the Idd4.1 locus in the nonobese diabetic mouse

Type 1 diabetes in the NOD mouse model has been linked to >30 insulin-dependent diabetes (Idd) susceptibility loci. Idd4 on chromosome 11 consists of two subloci, Idd4.1 and Idd4.2. Using congenic analysis of alleles in NOD and NOD-resistant (NOR) mice, we previously defined Idd4.1 as an interval containing >50 genes that controlled expression of genes in the type 1 IFN pathway. In this study, we report refined mapping of Idd4.1 to a 1.1-Mb chromosomal region and provide genomic sequence analysis and mechanistic evidence supporting its role in innate immune regulation of islet-directed autoimmunity. Genetic variation at Idd4.1 was mediated by radiation-sensitive hematopoietic cells, and type 1 diabetes protection conferred by the NOR allele was abrogated in mice treated with exogenous type 1 IFN-β. Next generation sequence analysis of the full Idd4.1 genomic interval in NOD and NOR strains supported Nlrp1b as a strong candidate gene for Idd4.1. Nlrp1b belongs to the Nod-like receptor (NLR) gene family and contributes to inflammasome assembly, caspase-1 recruitment, and release of IL-1β. The Nlrp1b of NOR was expressed as an alternative spliced isoform that skips exon 9, resulting in a premature stop codon predicted to encode a truncated protein. Functional analysis of the truncated NOR Nlrp1b protein demonstrated that it was unable to recruit caspase-1 and process IL-1β. Our data suggest that Idd4.1-dependent protection from islet autoimmunity is mediated by differences in type 1 IFN- and IL-1β-dependent immune responses resulting from genetic variation in Nlrp1b.

Persistent STAT5 phosphorylation and epigenetic dysregulation of GM-CSF and PGS2/COX2 expression in Type 1 diabetic human monocytes

STAT5 proteins are adaptor proteins for histone acetylation enzymes. Histone acetylation at promoter and enhancer chromosomal regions opens the chromatin and allows access of transcription enzymes to specific genes in rapid response cell signals, such as in inflammation. Histone acetylation-mediated gene regulation is involved in expression of 2 key inflammatory response genes: CSF2, encoding granulocyte-macrophage colony stimulating factor (GM-CSF), and PTGS2, encoding prostaglandin synthase 2/cyclooxygenase 2 (PGS2/COX2). Prolonged CSF2 expression, high GM-CSF production, and GM-CSF activation of PTGS2 gene expression all are seen in type 1 diabetes (T1D) monocytes. Persistent phosphorylation activation of monocyte STAT5 (STAT5Ptyr) is also found in individuals with or at-risk for T1D. To examine whether elevated T1D monocyte STAT5Ptyr may be associated with aberrant inflammatory gene expression in T1D, blood monocytes from non-autoimmune controls and T1D patients were analyzed by flow cytometry for STAT5Ptyr activation, and by chromatin immuno-precipitation (ChIP) analyses for STAT5Ptyr’s ability to bind at CSF2 and PTGS2 regulatory sites in association with histone acetylation. In unstimulated monocytes, STAT5Ptyr was elevated in 59.65% of T1D, but only 2.44% of control subjects (p<0.0001). Increased STAT5Ptyr correlated with T1D disease duration (p = 0.0030, r² = 0.0784). Unstimulated (p = 0.140) and GM-CSF-stimulated (p = 0.0485) T1D monocytes, had greater STAT5Ptyr binding to epigenetic regulatory sites upstream of CSF2 than control monocytes. Increased STAT5Ptyr binding in T1D monocytes was concurrent with binding at these sites of STAT6Ptyr (p = 0.0283), CBP/P300 histone acetylase, acetylated histones H3, SMRT/NCoR histone deacetylase (p = 0.0040), and RNA Polymerase II (p = 0.0040). Our study indicates that in T1D monocytes, STAT5Ptyr activation is significantly higher and that STAT5Ptyr is found bound to CSF2 promoter and PTGS2 enhancer regions coincident with histone acetylation and RNA polymerase II. These findings suggest that the persistent activation of STAT5 by GM-CSF may be involved in altering the epigenetic regulation of these inflammatory response genes in T1D monocytes.

Enhanced T cell lymphoma in NOD.Stat5b transgenic mice is caused by hyperactivation of Stat5b in CD8+ thymocytes

Activation of signal transducers and activators of transcription (STAT) proteins may be critical to their oncogenic functions as demonstrated by the development of B-cell lymphoma/leukemia in transgenic (TG) mice overexpressing a constitutively activated form of Stat5b. However, low incidence of CD8⁺ T cell lymphoma was observed in B6 transgenic mice overexpressing a wild-type Stat5b (B6.Stat5b^Tg) despite of undetectable Stat5b phosphorylation and the rate of lymphomagenesis was markedly enhanced by immunization or the introduction of TCR transgenes [1]. Here, we report that the wild-type Stat5b transgene leads to the acceleration and high incidence (74%) of CD8⁺ T cell lymphoblastic lymphomas in the non-obese-diabetic (NOD) background. In contrast to the B6.Stat5b^Tg mice, Stat5b in transgenic NOD (NOD.Stat5b^Tg) mice is selectively and progressively phosphorylated in CD8⁺ thymocytes. Stat5 phosphorylation also leads to up-regulation of many genes putatively relevant to tumorigenesis. Treatment of NOD.Stat5b^Tg mice with cancer chemopreventive agents Apigenin and Xanthohumol efficiently blocked lymphomagenesis through reduction of Stat5 phosphorylation and genes up-regulated in the NOD.Stat5b^Tg mice. These results suggest that NOD genetic background is critical to the Stat5b-mediated lymphomagenesis through regulation of Stat5 hyperactivation. NOD.Stat5b^Tg mouse is an excellent model for studying the molecular mechanisms underlying lymphomagenesis and testing novel chemoprevention strategies.

Comparative genetics: synergizing human and NOD mouse studies for identifying genetic causation of type 1 diabetes

Although once widely anticipated to unlock how human type 1 diabetes (T1D) develops, extensive study of the nonobese diabetic (NOD) mouse has failed to yield effective treatments for patients with the disease. This has led many to question the usefulness of this animal model. While criticism about the differences between NOD and human T1D is legitimate, in many cases disease in both species results from perturbations modulated by the same genes or different genes that function within the same biological pathways. Like in humans, unusual polymorphisms within an MHC class II molecule contributes the most T1D risk in NOD mice. This insight supports the validity of this model and suggests the NOD has been improperly utilized to study how to cure or prevent disease in patients. Indeed, clinical trials are far from administering T1D therapeutics to humans at the same concentration ranges and pathological states that inhibit disease in NOD mice. Until these obstacles are overcome it is premature to label the NOD mouse a poor surrogate to test agents that cure or prevent T1D. An additional criticism of the NOD mouse is the past difficulty in identifying genes underlying T1D using conventional mapping studies. However, most of the few diabetogenic alleles identified to date appear relevant to the human disorder. This suggests that rather than abandoning genetic studies in NOD mice, future efforts should focus on improving the efficiency with which diabetes susceptibility genes are detected. The current review highlights why the NOD mouse remains a relevant and valuable tool to understand the genes and their interactions that promote autoimmune diabetes and therapeutics that inhibit this disease. It also describes a new range of technologies that will likely transform how the NOD mouse is used to uncover the genetic causes of T1D for years to come.

Over-expression of Stat5b confers protection against diabetes in the non-obese diabetic (NOD) mice via up-regulation of CD4(+)CD25(+) regulatory T cells

The signal transducers and activators of transcription (STAT) family of proteins play a critical role in cytokine signaling required for fine tuning of immune regulation. Previous reports showed that a mutation (L327M) in the Stat5b protein leads to aberrant cytokine signaling in the NOD mice. To further elaborate the role of Stat5b in diabetes, we established a NOD transgenic mouse that over-expresses the wild type Stat5b gene. The incidences of spontaneous diabetes as well as cyclophosphamide-induced diabetes were significantly reduced and delayed in the Stat5b transgenic NOD mice compared to their littermate controls. The total cell numbers of CD4(+) T cells and especially CD8(+) T cells in the spleen and pancreatic lymph node were increased in the Stat5b transgenic NOD mice. Consistent with these findings, CD4(+) and CD8(+) T cells from the Stat5b transgenic NOD mice showed a higher proliferation capacity and up-regulation of multiple cytokines including IL-2, IFN-γ, TNF-α and IL-10 as well as anti-apoptotic gene Bcl-xl. Furthermore, the number and proportion of CD4(+)CD25(+) regulatory T cells were significantly increased in transgenic mice although in vitro suppression ability of the regulatory T-cells was not affected by the transgene. Our results suggest that Stat5b confers protection against diabetes in the NOD mice by regulating the numbers and function of multiple immune cell types, especially by up-regulating CD4(+)CD25(+) regulatory T cells.

Linking chronic infection and autoimmune diseases: Mycobacterium avium subspecies paratuberculosis, SLC11A1 polymorphisms and type-1 diabetes mellitus

BACKGROUND

The etiology of type 1 diabetes mellitus (T1DM) is still unknown; numerous studies are performed to unravel the environmental factors involved in triggering the disease. SLC11A1 is a membrane transporter that is expressed in late endosomes of antigen presenting cells involved in the immunopathogenic events leading to T1DM. Mycobacterium avium subsp. paratuberculosis (MAP) has been reported to be a possible trigger in the development of T1DM.

METHODOLOGY/PRINCIPAL FINDINGS

Fifty nine T1DM patients and 79 healthy controls were genotyped for 9 polymorphisms of SLC11A1 gene, and screened for the presence of MAP by PCR. Differences in genotype frequency were evaluated for both T1DM patients and controls. We found a polymorphism in the SLC11A1 gene (274C/T) associated to type 1 diabetic patients and not to controls. The presence of MAP DNA was also significantly associated with T1DM patients and not with controls.

CONCLUSIONS/SIGNIFICANCE

The 274C/T SCL11A1 polymorphism was found to be associated with T1DM as well as the presence of MAP DNA in blood. Since MAP persists within macrophages and it is also processed by dendritic cells, further studies are necessary to evaluate if mutant forms of SLC11A1 alter the processing or presentation of MAP antigens triggering thereby an autoimmune response in T1DM patients.

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

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

NOD x 129.H2(g7) backcross delineates 129S1/SvImJ-derived genomic regions modulating type 1 diabetes development in mice

OBJECTIVE

Introduction of genes targeted in 129/Sv embryonic stem (ES) cells into NOD mice brings about linked genes that may modulate type 1 diabetes. Our objective was to identify 129S1/SvJ non-MHC regions contributing type 1 diabetes resistance or susceptibility in backcross to NOD/LtJ.

RESEARCH DESIGN AND METHODS

After congenic transfer of the NOD H2(g7) haplotype onto 129S1/Sv, 310 females were produced by NOD x (NOD x 129.H2(g7))F1 backcross (N2). A genome scan for quantitative trait locus (QTL) affecting clinical diabetes, age of diabetes onset, and insulitis severity was performed using subphenotype characteristics to improve power and resolution for detection of diabetes susceptibility loci.

RESULTS

Thirty-six of 310 (11.6%) N2 females developed type 1 diabetes between 14 and 40 weeks. Significant evidence of linkage for only a single previously reported Idd complex locus (Idd10/17/18, chromosome [Chr] 3) was indicated for clinical diabetes. The quantitative traits of insulitis either alone or combined with age at type 1 diabetes onset were significantly linked to known Idd regions on Chr 1 (Idd5 region), Chr 4 (Idd9 region), Chr 8 (Idd22), Chr 11 (Idd4.3), and proximal Chr 17 (Idd16 region). Significant 129S1/Sv resistance contributions were identified on Chr 1, 15 (two loci), and 19, with suggestive evidence for additional novel 129/Sv resistance QTL on Chr 5 and 17 and susceptibility on Chr 2.

CONCLUSIONS

The 129S1/SvJ genome harbors collections of both known and potentially novel non-MHC Idd loci. Investigators targeting 129/Sv genes mapping within chromosomal regions reported herein or elsewhere in the genome need to exclude potential contributions from linked Idd loci by generating a NOD.129 control strain expressing the nontargeted allele.

M-CSF and GM-CSF regulation of STAT5 activation and DNA binding in myeloid cell differentiation is disrupted in nonobese diabetic mice

Defects in macrophage colony-stimulating factor (M-CSF) signaling disrupt myeloid cell differentiation in nonobese diabetic (NOD) mice, blocking myeloid maturation into tolerogenic antigen-presenting cells (APCs). In the absence of M-CSF signaling, NOD myeloid cells have abnormally high granulocyte macrophage colony-stimulating factor (GM-CSF) expression, and as a result, persistent activation of signal transducer/activator of transcription 5 (STAT5). Persistent STAT5 phosphorylation found in NOD macrophages is not affected by inhibiting GM-CSF. However, STAT5 phosphorylation in NOD bone marrow cells is diminished if GM-CSF signaling is blocked. Moreover, if M-CSF signaling is inhibited, GM-CSF stimulation in vitro can promote STAT5 phosphorylation in nonautoimmune C57BL/6 mouse bone marrow cultures to levels seen in the NOD. These findings suggest that excessive GM-CSF production in the NOD bone marrow may interfere with the temporal sequence of GM-CSF and M-CSF signaling needed to mediate normal STAT5 function in myeloid cell differentiation gene regulation.

Gene-gene interactions in the NOD mouse model of type 1 diabetes

Human genome wide association studies (GWAS) have recently identified at least four new, non-MHC-linked candidate genes or gene regions causing type one diabetes (T1D), highlighting the need for functional models to investigate how susceptibility alleles at multiple common genes interact to mediate disease. Progress in localizing genes in congenic strains of the nonobese diabetic (NOD) mouse has allowed the reproducible testing of gene functions and gene-gene interactions that can be reflected biologically as intrapathway interactions, for example, IL-2 and its receptor CD25, pathway-pathway interactions such as two signaling pathways within a cell, or cell-cell interactions. Recent studies have identified likely causal genes in two congenic intervals associated with T1D, Idd3, and Idd5, and have documented the occurrence of gene-gene interactions, including "genetic masking", involving the genes encoding the critical immune molecules IL-2 and CTLA-4. The demonstration of gene-gene interactions in congenic mouse models of T1D has major implications for the understanding of human T1D since such biological interactions are highly likely to exist for human T1D genes. Although it is difficult to detect most gene-gene interactions in a population in which susceptibility and protective alleles at many loci are randomly segregating, their existence as revealed in congenic mice reinforces the hypothesis that T1D alleles can have strong biological effects and that such genes highlight pathways to consider as targets for immune intervention.

Slc11a1 enhances the autoimmune diabetogenic T-cell response by altering processing and presentation of pancreatic islet antigens

OBJECTIVE

Efforts to map non-major histocompatibility complex (MHC) genes causing type 1 diabetes in NOD mice identified Slc11a1, formerly Nramp1, as the leading candidate gene in the Idd5.2 region. Slc11a1 is a membrane transporter of bivalent cations that is expressed in late endosomes and lysosomes of macrophages and dendritic cells (DCs). Because DCs are antigen-presenting cells (APCs) known to be critically involved in the immunopathogenic events leading to type 1 diabetes, we hypothesized that Slc11a1 alters the processing or presentation of islet-derived antigens to T-cells.

RESEARCH DESIGN AND METHODS

NOD mice having wild-type (WT) or mutant Slc11a1 molecules and 129 mice having WT or null Slc11a1 alleles were examined for parameters associated with antigen presentation.

RESULTS

We found that Slc11a1 enhanced the presentation of a diabetes-related T-cell determinant of GAD65, and its function contributed to the activation of a pathogenic T-cell clone, BDC2.5. An enhanced generation of interferon (IFN)-gamma-producing T-cells was also associated with functional Slc11a1. The alteration of immune responsiveness by Slc11a1 genotype did not correlate with altered MHC class II expression in DCs; however, functional Slc11a1 was associated with accelerated phagocytosis and phagosomal acidification in DCs.

CONCLUSIONS

The association of variants encoding Slc11a1 with type 1 diabetes may reflect its function in processing and presentation of islet self-antigens in DCs. Thus, non-MHC genes could affect the MHC-restricted T-cell response through altered antigen processing and presentation.

GM-CSF induces STAT5 binding at epigenetic regulatory sites within the Csf2 promoter of non-obese diabetic (NOD) mouse myeloid cells

Myeloid cells from non-obese diabetic (NOD) mouse and human type 1 diabetic (T1D) patients overexpress granulocyte-macrophage colony stimulation factor (GM-CSF). This overproduction prolongs the activation of signal transduction and activator of transcription 5 (STAT5) proteins, involved in GM-CSF-induced control of myeloid cell gene expression. We found that GM-CSF can regulate the binding of STAT5 on the promoter of its own gene, Csf2, within regions previously identified as sites of chromatin epigenetic modification important to the regulation of GM-CSF during myeloid differentiation and inflammation. We found multiple sequence polymorphisms within NOD mouse chromosome 11 Idd4.3 diabetes susceptibility region that alter STAT5 GAS binding sequences within the Csf2 promoter. STAT5 binding at these sites in vivo is increased significantly in GM-CSF-stimulated-bone marrow cells and in unactivated, high GM-CSF-producing macrophages from NOD mice as compared to non-autoimmune C57BL/6 mouse myeloid cells. Thus, GM-CSF overproduction by NOD myeloid cells may be perpetuating a positive epigenetic regulatory feedback on its own gene expression through its induction of STAT5 binding to its promoter. These findings suggest that aberrant STAT5 binding at epigenetic regulatory sites may contribute directly to immunopathology through cytokine-induced gene expression dysregulation that can derail myeloid differentiation and increase inflammatory responsiveness.

Differential contributions of APC subsets to T cell activation in nonobese diabetic mice

Despite the pivotal role of dendritic cells (DC) in shaping immunity, little is known about their functionality in type 1 diabetes. Moreover, due to the paucity of DC in vivo, functional studies have relied largely upon in vitro-expanded cells to elucidate type 1 diabetes-associated functional abnormalities. In this study, we provide a comprehensive analysis of the functional capabilities of in vivo-derived DC subsets from NOD mice by comparing DC to other NOD APC types and to DC from autoimmune-resistant strains. NOD DC closely resemble those from nonautoimmune strains with respect to costimulation and cytokine production. The exception is the CD8alpha(+)CD11b(-)DC subset which is numerically reduced in NOD spleens, but not in the pancreatic lymph nodes, while DC from both tissues produce little IL-12 in this strain. This defect results in unusual deferral toward macrophage-derived IL-12 in NOD mice; NOD macrophages produce aberrantly high IL-12 levels that can overcompensate for the DC defect in Th1 polarization. APC subset use for autoantigen presentation also differs in NOD mice. NOD B cells overshadow DC at activating islet-reactive T cells, whereas DC and B cells in NOD-resistant mice are functionally comparable. Differential involvement of APC subsets in T cell activation and tolerance induction may prove to be a crucial factor in the selection and expansion of autoreactive T cells.

Nonobese diabetic (NOD) mice congenic for a targeted deletion of 12/15-lipoxygenase are protected from autoimmune diabetes

OBJECTIVE

12/15-lipoxygenase (12/15-LO), one of a family of fatty acid oxidoreductase enzymes, reacts with polyenoic fatty acids to produce proinflammatory lipids. 12/15-LO is expressed in macrophages and pancreatic beta-cells. It enhances interleukin 12 production by macrophages, and several of its products induce apoptosis of beta-cells at nanomolar concentrations in vitro. We had previously demonstrated a role for 12/15-LO in beta-cell damage in the streptozotocin model of diabetes. Since the gene encoding 12/15-LO (gene designation Alox15) lies within the Idd4 diabetes susceptibility interval in NOD mice, we hypothesized that 12/15-LO is also a key regulator of diabetes susceptibility in the NOD mouse.

RESEARCH DESIGN AND METHODS

We developed NOD mice carrying an inactivated 12/15-LO locus (NOD-Alox15(null)) using a "speed congenic" protocol, and the mice were monitored for development of insulitis and diabetes.

RESULTS

NOD mice deficient in 12/15-LO develop diabetes at a markedly reduced rate compared with NOD mice (2.5 vs. >60% in females by 30 weeks). Nondiabetic female NOD-Alox15(null) mice demonstrate improved glucose tolerance, as well as significantly reduced severity of insulitis and improved beta-cell mass, when compared with age-matched nondiabetic NOD females. Disease resistance is associated with decreased numbers of islet-infiltrating activated macrophages at 4 weeks of age in NOD-Alox15(null) mice, preceding the development of insulitis. Subsequently, islet-associated infiltrates are characterized by decreased numbers of CD4(+) T cells and increased Foxp3(+) cells.

CONCLUSIONS

These results suggest an important role for 12/15-LO in conferring susceptibility to autoimmune diabetes in NOD mice through its effects on macrophage recruitment or activation.

Functional deficiencies of granulocyte-macrophage colony stimulating factor and interleukin-3 contribute to insulitis and destruction of beta cells

The pathogenesis of type 1 diabetes (T1D) involves the immune-mediated destruction of insulin-producing beta cells in the pancreatic islets of Langerhans. Genetic analysis of families with a high incidence of T1D and nonobese diabetic (NOD) mice, a prototypical model of the disorder, uncovered multiple susceptibility loci, although most of the underlying immune defects remain to be delineated. Here we report that aged mice doubly deficient in granulocyte-macrophage colony-stimulating factor (GM-CSF) and interleukin-3 (IL-3) manifest insulitis, destruction of insulin-producing beta cells, and compromised glucose homeostasis. Macrophages from mutant mice produce increased levels of p40 after LPS stimulation, whereas concurrent ablation of interferon-gamma (IFN-gamma) ameliorates the disease. The administration of antibodies that block cytotoxic T lymphocyte associated antigen-4 (CTLA-4) to young mutant mice precipitates the onset of insulitis and hyperglycemia. These results, together with previous reports of impaired hematopoietic responses to GM-CSF and IL-3 in patients with T1D and in NOD mice, indicate that functional deficiencies of these cytokines contribute to diabetes.

No alterations in the frequency of FOXP3+ regulatory T-cells in type 1 diabetes

Regulatory T-cells (Tregs) play a critical role in maintaining dominant peripheral tolerance. Previous characterizations of Tregs in type 1 diabetes have used antibodies against CD4 and alpha-chain of the interleukin-2 receptor complex (CD25). This report extends those investigations by the addition of a more lineage-specific marker for Tregs, transcription factor forkhead box P3 (FOXP3), in subjects with type 1 diabetes, their first-degree relatives, and healthy control subjects. With inclusion of this marker, two predominant populations of CD4(+)CD25(+) T-cells were identified: CD4(+)CD25(+)FOXP3(+) as well as CD4(+)FOXP3(-) T-cells expressing low levels of CD25 (CD4(+)CD25(LOW)FOXP3(-)). In all study groups, the frequency of CD4(+)CD25(+)FOXP3(+) cells was age independent, whereas CD4(+)CD25(LOW)FOXP3(-) cell frequencies strongly associated with age. In terms of additional markers for delineating cells of Treg lineage, FOXP3(+) cells were CD127(-) to CD127(LOW) whereas CD25(+) cells were less restricted in their expression of this marker, with CD127 expressed across a continuum of levels. Importantly, no differences were observed in the frequency of CD4(+)CD25(+)FOXP3(+) T-cells in individuals with or at varying degrees of risk for type 1 diabetes. These investigations suggest that altered peripheral blood frequencies of Tregs, as defined by the expression of FOXP3, are not specifically associated with type 1 diabetes and continue to highlight age as an important variable in analysis of immune regulation.