Type 1 Diabetes Resistance Research Articles

Nfkbid Overexpression in Nonobese Diabetic Mice Elicits Complete Type 1 Diabetes Resistance in Part Associated with Enhanced Thymic Deletion of Pathogenic CD8 T Cells and Increased Numbers and Activity of Regulatory T Cells.

Type 1 diabetes (T1D) in both humans and NOD mice is caused by T cell-mediated autoimmune destruction of pancreatic β cells. Increased frequency or activity of autoreactive T cells and failures of regulatory T cells (Tregs) to control these pathogenic effectors have both been implicated in T1D etiology. Due to the expression of MHC class I molecules on β cells, CD8 T cells represent the ultimate effector population mediating T1D. Developing autoreactive CD8 T cells normally undergo extensive thymic negative selection, but this process is impaired in NOD mice and also likely T1D patients. Previous studies identified an allelic variant of Nfkbid, a NF-κB signal modulator, as a gene strongly contributing to defective thymic deletion of autoreactive CD8 T cells in NOD mice. These previous studies found ablation of Nfkbid in NOD mice using the clustered regularly interspaced short palindromic repeats system resulted in greater thymic deletion of pathogenic CD8 AI4 and NY8.3 TCR transgenic T cells but an unexpected acceleration of T1D onset. This acceleration was associated with reductions in the frequency of peripheral Tregs. In this article, we report transgenic overexpression of Nfkbid in NOD mice also paradoxically results in enhanced thymic deletion of autoreactive CD8 AI4 T cells. However, transgenic elevation of Nfkbid expression also increased the frequency and functional capacity of peripheral Tregs, in part contributing to the induction of complete T1D resistance. Thus, future identification of a pharmaceutical means to enhance Nfkbid expression might ultimately provide an effective T1D intervention approach.

Next-Generation HLA Sequence Analysis Uncovers Seven HLA-DQ Amino Acid Residues and Six Motifs Resistant to Childhood Type 1 Diabetes.

HLA-DQA1 and -DQB1 genes have significant and potentially causal associations with autoimmune type 1 diabetes (T1D). To follow up on the earlier analysis on high-risk HLA-DQ2.5 and DQ8.1, the current analysis uncovers seven residues (αa1, α157, α196, β9, β30, β57, and β70) that are resistant to T1D among subjects with DQ4-, 5-, 6-, and 7-resistant DQ haplotypes. These 7 residues form 13 common motifs: 6 motifs are significantly resistant, 6 motifs have modest or no associations (P values >0.05), and 1 motif has 7 copies observed among control subjects only. The motifs "DAAFYDG," "DAAYHDG," and "DAAYYDR" have significant resistance to T1D (odds ratios [ORs] 0.03, 0.25, and 0.18; P = 6.11 × 10-24, 3.54 × 10-15, and 1.03 × 10-21, respectively). Remarkably, a change of a single residue from the motif "DAAYHDG" to "DAAYHSG" (D to S at β57) alters the resistance potential, from resistant motif (OR 0.15; P = 3.54 × 10-15) to a neutral motif (P = 0.183), the change of which was significant (Fisher P value = 0.0065). The extended set of linked residues associated with T1D resistance and unique to each cluster of HLA-DQ haplotypes represents facets of all known features and functions of these molecules: antigenic peptide binding, peptide-MHC class II complex stability, β167-169 RGD loop, T-cell receptor binding, formation of homodimer of α-β heterodimers, and cholesterol binding in the cell membrane rafts. Identification of these residues is a novel understanding of resistant DQ associations with T1D. Our analyses endow potential molecular approaches to identify immunological mechanisms that control disease susceptibility or resistance to provide novel targets for immunotherapeutic strategies.

The CD137 Ligand Is Important for Type 1 Diabetes Development but Dispensable for the Homeostasis of Disease-Suppressive CD137+ FOXP3+ Regulatory CD4 T Cells.

CD137 modulates type 1 diabetes (T1D) progression in NOD mice. We previously showed that CD137 expression in CD4 T cells inhibits T1D, but its expression in CD8 T cells promotes disease development by intrinsically enhancing the accumulation of β-cell-autoreactive CD8 T cells. CD137 is expressed on a subset of FOXP3+ regulatory CD4 T cells (Tregs), and CD137+ Tregs are the main source of soluble CD137. Soluble CD137 suppresses T cells in vitro by binding to the CD137 ligand (CD137L) upregulated on activated T cells. To further study how the opposing functions of CD137 are regulated, we successfully targeted Tnfsf9 (encoding CD137L) in NOD mice using the CRISPR/Cas9 system (designated NOD.Tnfsf9 -/-). Relative to wild-type NOD mice, T1D development in the NOD.Tnfsf9 -/- strain was significantly delayed, and mice developed less insulitis and had reduced frequencies of β-cell-autoreactive CD8 T cells. Bone marrow chimera experiments showed that CD137L-deficient hematopoietic cells were able to confer T1D resistance. Adoptive T cell transfer experiments showed that CD137L deficiency on myeloid APCs was associated with T1D suppression. Conversely, lack of CD137L on T cells enhanced their diabetogenic activity. Furthermore, neither CD137 nor CD137L was required for the development and homeostasis of FOXP3+ Tregs. However, CD137 was critical for the in vivo T1D-suppressive activity of FOXP3+ Tregs, suggesting that the interaction between CD137 and CD137L regulates their function. Collectively, our results provide new insights into the complex roles of CD137-CD137L interaction in T1D.

Gut bacteria modulate dendritic cell priming of diabetogenic T cell effector functions in a mouse model of autoimmune diabetes

Abstract Increasing evidence implicates a contribution of the microbiome, within the gastrointestinal tract, in the initiation and progression of type 1 diabetes (T1D). Notably, our understanding of mechanisms whereby gut flora interaction with the host immune system can influence T1D pathogenesis remain poorly understood. Comparison of stool samples from the non-obese diabetic (NOD) mouse model of spontaneous T1D and non-obese resistant (NOR) mice revealed distinct bacterial flora communities present within the two strains correlated to a Th17 bias. Given that dendritic cells (DC) are critical in sampling luminal antigens and priming naïve T lymphocyte effector functions, we next interrogated the populations of CD11c+ DC within the lamina propria (LP) of NOD and NOR mice. Phenotypic characterization of LP DC revealed that NOR mice possessed more mature DC denoted by a higher frequency of CD11c+ MHCII+ cells and CD103+ CD86+ cells. We have previously shown that the oral administration of a gut bacterium Lactobaccillus johnsonii (LjN6.2), present in diabetes resistant rodents, was capable of conferring diabetes resistance to diabetes prone rodents while another strain Lactobacillus reuterii (LrTD1) had no effect. Notably, T1D resistance was correlated to a Th17 bias. Hence, we sought to investigate the influence of LjN6.2 on NOD and NOR DC in comparison to LrTD1 in vitro. We found that LjN6.2, but not LrTD1 mediated an increase in IL6 and IL10 cytokine production by DC. Together, these data suggest that gut bacteria have the important ability to shape the maturation and priming abilities of DC. These results could have critical implications regarding the ability of bacterial flora to regulate the generation of a diabetogenic immune repertoire.

HLA-DR*0401 expression in the NOD mice prevents the development of autoimmune diabetes by multiple alterations in the T-cell compartment

Several human HLA alleles have been found associated with type 1 diabetes (T1D), but their precise role is not clearly defined. Herein, we report that a human MHC class II (HLA-DR*0401) allele transgene that has been expressed into NOD (H-2g7I-Enull) mice prone to T1D rendered the mice resistant to the disease. T1D resistance occurred in the context of multi-point T-cell alterations such as: (i) skewed CD4/CD8 T-cell ratio, (ii) decreased size of CD4+CD44high T memory pool, (iii) aberrant TCR Vβ repertoire, (iv) increased neonatal number of Foxp3+ and TR-1+ regulatory cells, and (v) reduced IFN-γ inflammatory response vs. enhanced IL-10 suppressogenic response of T-cells upon polyclonal and antigen-specific stimulation. The T-cells from NOD/DR4 Tg mice were unable to induce or suppress diabetes in NOD/RAG deficient mice. This study describes a multifaceted regulatory function of the HLA-DR*0401 allele strongly associated with the lack of T1D development in NOD mice.

The non-obese diabetic mouse sequence, annotation and variation resource: an aid for investigating type 1 diabetes

Model organisms are becoming increasingly important for the study of complex diseases such as type 1 diabetes (T1D). The non-obese diabetic (NOD) mouse is an experimental model for T1D having been bred to develop the disease spontaneously in a process that is similar to humans. Genetic analysis of the NOD mouse has identified around 50 disease loci, which have the nomenclature Idd for insulin-dependent diabetes, distributed across at least 11 different chromosomes. In total, 21 Idd regions across 6 chromosomes, that are major contributors to T1D susceptibility or resistance, were selected for finished sequencing and annotation at the Wellcome Trust Sanger Institute. Here we describe the generation of 40.4 mega base-pairs of finished sequence from 289 bacterial artificial chromosomes for the NOD mouse. Manual annotation has identified 738 genes in the diabetes sensitive NOD mouse and 765 genes in homologous regions of the diabetes resistant C57BL/6J reference mouse across 19 candidate Idd regions. This has allowed us to call variation consequences between homologous exonic sequences for all annotated regions in the two mouse strains. We demonstrate the importance of this resource further by illustrating the technical difficulties that regions of inter-strain structural variation between the NOD mouse and the C57BL/6J reference mouse can cause for current next generation sequencing and assembly techniques. Furthermore, we have established that the variation rate in the Idd regions is 2.3 times higher than the mean found for the whole genome assembly for the NOD/ShiLtJ genome, which we suggest reflects the fact that positive selection for functional variation in immune genes is beneficial in regard to host defence. In summary, we provide an important resource, which aids the analysis of potential causative genes involved in T1D susceptibility.Database URLs: http://www.sanger.ac.uk/resources/mouse/nod/; http://vega-previous.sanger.ac.uk/info/data/mouse_regions.html

Subcongenic Analyses Reveal Complex Interactions between Distal Chromosome 4 Genes Controlling Diabetogenic B Cells and CD4 T Cells in Nonobese Diabetic Mice

Autoimmune type 1 diabetes (T1D) in humans and NOD mice results from interactions between multiple susceptibility genes (termed Idd) located within and outside the MHC. Despite sharing ∼88% of their genome with NOD mice, including the H2(g7) MHC haplotype and other important Idd genes, the closely related nonobese resistant (NOR) strain fails to develop T1D because of resistance alleles in residual genomic regions derived from C57BLKS mice mapping to chromosomes (Chr.) 1, 2, and 4. We previously produced a NOD background strain with a greatly decreased incidence of T1D as the result of a NOR-derived 44.31-Mb congenic region on distal Chr. 4 containing disease-resistance alleles that decrease the pathogenic activity of autoreactive B and CD4 T cells. In this study, a series of subcongenic strains for the NOR-derived Chr. 4 region was used to significantly refine genetic loci regulating diabetogenic B and CD4 T cell activity. Analyses of these subcongenic strains revealed the presence of at least two NOR-origin T1D resistance genes within this region. A 6.22-Mb region between rs13477999 and D4Mit32, not previously known to contain a locus affecting T1D susceptibility and now designated Idd25, was found to contain the main NOR gene(s) dampening diabetogenic B cell activity, with Ephb2 and/or Padi2 being strong candidates as the causal variants. Penetrance of this Idd25 effect was influenced by genes in surrounding regions controlling B cell responsiveness and anergy induction. Conversely, the gene(s) controlling pathogenic CD4 T cell activity was mapped to a more proximal 24.26-Mb region between the rs3674285 and D4Mit203 markers.

Gene expression and sub-congenic analyses of the Idd9/11 locus that regulates the diabetogenic activity of CD4 T-cells in NOD mice (171.43)

Abstract Despite sharing the H2g7 MHC, the closely NOD-related NOR strain remains type 1 diabetes (T1D) resistant due to the presence of protective Idd5.2, Idd9/11, and Idd13 loci. We previously showed that CD4-T cells isolated from the Idd9/11 congenic strain (NOD.Chr4NOR) were less diabetogenic than those from standard NOD mice. To further determine the underlying mechanism, we asked if CD4-T cells from the NOD.Chr4NOR strain have enhanced suppressive activity compared to those from NOD mice. We used a co-transfer system to show that CD4-T cells isolated from NOD.Chr4NOR but not standard NOD mice (both expressing CD45.1) could actively suppress the diabetogenic activity of those from CD45.2 congenic NOD mice. We further demonstrated that the T1D suppressive activity of the NOR-derived Idd9/11 region was completely lost in the CD28-deficient mice that had greatly reduced numbers of Foxp3+ regulatory T-cells (Tregs). These results suggest that an enhanced T1D suppressive Treg activity contributes to NOR Idd9/11-mediated disease resistance. We have also generated two subcongenic lines carrying distinct intervals of the NOR-derived Idd9/11 region. T1D incidence studies indicated that more than one gene within the NOR-derived Idd9/11 region conferred T1D resistance. The region within the Idd9/11 interval suppressing the diabetogenic activity of CD4 T-cells was further refined from 44.3Mb to 27.1Mb. Microarray gene expression analysis was used to identify Idd9/11 candidate genes.

Role of genetics in resistance to type 1 diabetes

A single nucleotide polymorphism in the mitochondrial gene encoding NADH dehydrogenase subunit 2 (mt-ND2) has been associated with reduced incidence of human type 1 diabetes (T1D). We identified the orthologue of this mitochondrial single nucleotide polymorphism in mouse and using NOD mouse models linked this genetic polymorphism to T1D resistance. The mechanism how this single nucleotide polymorphism affects the development of diabetes is studied using mouse models and beta cell lines. The impact of this single nucleotide polymorphism on mitochondrial function and resistance to reactive oxygen species was assessed. For these studies we measured oxygen consumption by isolated mitochondria under different doses of nitric oxide. In addition, alloxan sensitivity of beta cell lines was tested using the MTT method to measure cell survival. mt-Nd2a is associated with protection against mouse T1D and alloxan-induced diabetes. Mice with mt-Nd2a exhibited resistance to transfer of diabetes by single clone of diabetogenic CD4+ or CD8+ T cells. Beta cell line with mt-Nd2a resist in vitro attack of diabetogenic CD8+ cytotoxic T cells, as well as free radicals generated by alloxan; isolated mitochondria with mt-Nd2a showed lower reactive oxygen species production and were more resistant to nitric oxide. mt-Nd2a protects against T1D in mouse models. The protection is at beta cell level and is associated with resistance against reactive oxygen species-mediated damage and death.

Testing the Role of P2X7 Receptors in the Development of Type 1 Diabetes in Nonobese Diabetic Mice

Abstract Although P2rx7 has been proposed as a type 1 diabetes (T1D) susceptibility gene in NOD mice, its potential pathogenic role has not been directly determined. To test this possibility, we generated a new NOD stock deficient in P2X7 receptors. T1D development was not altered by P2X7 ablation. Previous studies found CD38 knockout (KO) NOD mice developed accelerated T1D partly because of a loss of CD4+ invariant NKT (iNKT) cells and Foxp3+ regulatory T cells (Tregs). These immunoregulatory T cell populations are highly sensitive to NAD-induced cell death activated by ADP ribosyltransferase-2 (ART2)-mediated ADP ribosylation of P2X7 receptors. Therefore, we asked whether T1D acceleration was suppressed in a double-KO NOD stock lacking both P2X7 and CD38 by rescuing CD4+ iNKT cells and Tregs from NAD-induced cell death. We demonstrated that P2X7 was required for T1D acceleration induced by CD38 deficiency. The CD38 KO-induced defects in homeostasis of CD4+ iNKT cells and Tregs were corrected by coablation of P2X7. T1D acceleration in CD38-deficient NOD mice also requires ART2 expression. If increased ADP ribosylation of P2X7 in CD38-deficient NOD mice underlies disease acceleration, then a comparable T1D incidence should be induced by coablation of both CD38 and ART2, or CD38 and P2X7. However, a previously established NOD stock deficient in both CD38 and ART2 expression is T1D resistant. This study demonstrated the presence of a T1D resistance gene closely linked to the ablated Cd38 allele in the previously reported NOD stock also lacking ART2, but not in the newly generated CD38/P2X7 double-KO line.

Implications of gut bacteria/dendritic cells interactions in development of Th17 lymphocytes and Type 1 Diabetes resistance (167.12)

Abstract Recent literature has suggested that Type 1 Diabetes (T1D) onset is negatively correlated to the presence of TH17 cells. Consistent with this notion, we observed that total lymph nodes isolated from NOD mice (which spontaneously develop T1D) produced lower levels of IL17 in vitro than from diabetes resistant NOR or C57BL/6 mice. Significantly, increasing evidence shows that gut bacteria are vital in the proper development of TH17 cells. Oral feedings of Lactobacillus johnsonii (LjN6.2), a strain isolated from the gut, has been shown to mediate T1D resistance and a TH17 bias. We used LjN6.2 to stimulate diabetes prone and resistant strains, measuring cytokine production and cell populations via flow cytometry. When equal numbers of T cells and antigen presenting cells (APCs) were incubated with LjN6.2, it was observed that NOD T cells were capable of producing abundant IL17. Because APCs in NOD mice are reduced in number and defective, we next analyzed whether this IL17 production was due to restored APC function by LjN6.2. APCs responded to LjN6.2 by producing extensive IL6 and upregulated MHCI, CD86, and CD80. We next tested if a footpad injected vaccine of LjN6.2 pulsed BMDCs could cause a TH17 bias in vitro. Indeed, splenocytes isolated from treated NOD mice showed increased production of IL6 and IL17. These studies present a possible role for gut flora in biasing T lymphocyte effector functions away from autoimmune diseases like T1D through dendritic cell modulation.

Inhibition of Type 1 Diabetes Correlated to a Lactobacillus johnsonii N6.2-Mediated Th17 Bias

Although it is known that resident gut flora contribute to immune system function and homeostasis, their role in the progression of the autoimmune disease type 1 diabetes (T1D) is poorly understood. Comparison of stool samples isolated from Bio-Breeding rats, a classic model of T1D, shows that distinct bacterial populations reside in spontaneous Bio-Breeding diabetes-prone (BBDP) and Bio-Breeding diabetes-resistant animals. We have previously shown that the oral transfer of Lactobacillus johnsonii strain N6.2 (LjN6.2) from Bio-Breeding diabetes-resistant to BBDP rodents conferred T1D resistance to BBDP rodents, whereas Lactobacillus reuteri strain TD1 did not. In this study, we show that diabetes resistance in LjN6.2-fed BBDP rodents was correlated to a Th17 cell bias within the mesenteric lymph nodes. The Th17 bias was not observed in the non-gut-draining axillary lymph nodes, suggesting that the Th17 bias was because of immune system interactions with LjN6.2 within the mesenteric lymph node. LjN6.2 interactions with the immune system were observed in the spleens of diabetes-resistant, LjN6.2-fed BBDP rats, as they also possessed a Th17 bias in comparison with control or Lactobacillus reuteri strain TD1-fed rats. Using C57BL/6 mouse in vitro assays, we show that LjN6.2 directly mediated enhanced Th17 differentiation of lymphocytes in the presence of TCR stimulation, which required APCs. Finally, we show that footpad vaccination of NOD mice with LjN6.2-pulsed dendritic cells was sufficient to mediate a Th17 bias in vivo. Together, these data suggest an interesting paradigm whereby T1D induction can be circumvented by gut flora-mediated Th17 differentiation.

Evidence for linkage of Type 1 Diabetes (T1D) resistance and upregulation of eotaxin (CCL11) in pancreatic beta cells to a chromosome 12 locus in the Biobreeding rat (49.2)

Abstract The Biobreeding (BB) rat spontaneously develops autoimmune Type 1 Diabetes (T1D). We tested the hypothesis that the recently reported upregulation of CCL11 in BB rat βcells prior to insulitis is genetically determined and linked to T1D. This time-dependent upregulation of CCL11 transcription was not observed in T1D resistant ACI rats. Therefore linkage analysis for T1D and pancreatic CCL11 was performed in a conditioned cross/intercross between BB and ACI rats where all animals (n=574) carried T1D susceptibility alleles at the two known BB rat T1D genes. Eight T1D loci (chr 1, 2, 3, 2 in 6, 12, 14 and 17) were mapped establishing the polygenic nature of T1D in the BB rat and at three of these (chr 1, 3 and 12) the BB allele confers T1D resistance. Strikingly, upregulation of pancreatic CCL11 transcription mapped to the T1D locus on chromosome 12 (LOD=3.65) and the peak of linkage (D12rat51) was the same for the two traits. At D12rat51, homozygosity for the BB allele confers high levels of pancreatic eotaxin expression and T1D resistance, raising the possibility that upregulation of the Th2 chemokine CCL11 in the target tissue of the anti-pancreatic autoimmune process is protective. Research supported by Genome Canada and Banting and Best Diabetes Centre.

Commonalities of genetic resistance to spontaneous autoimmune and free radical-mediated diabetes

ALR/Lt, a NOD-related mouse strain, was selected for resistance to alloxan free radical-mediated diabetes (ALD). Despite extensive genomic identity with NOD (> 70%), ALR mice display strong resistance to autoimmune type 1 diabetes (T1D) due to both an unusual elevation in systemic antioxidant defenses and a reduction in cellular ROS production that extends to the beta cell level. Reciprocal backcross to NOD previously linked the ALR-derived T1D resistance to Chr. 3, 8, and 17 as well as to the ALR mt-Nd2 a allele encoded by the mitochondrial genome (mtDNA). To determine whether any of the ALR-derived loci protecting against T1D also protected against ALD, 296 six-week-old F2 mice from reciprocal outcrosses were alloxan-treated and assessed for diabetes onset, and a genome-wide scan (GWS) was conducted. GWS linked mt-Nd2 as well as three nuclear loci with alloxan-induced diabetes. A dominant ALR-derived ALD resistance locus on Chr. 8 colocalized with the ALR-derived T1D resistance locus identified in the previous backcross analysis. In contrast, whereas ALR contributed a novel T1D resistance locus on Chr. 3 marked by Susp, a more proximal ALR-derived region marked by Il-2 contributed ALD susceptibility, not resistance. In addition, a locus was mapped on Chr. 2, where heterozygosity provided heightened susceptibility. Tests for alloxan sensitivity in ALR conplastic mice encoding the NOD mt-Nd2 c allele and NOD mice congenic for the protective Chr. 8 locus supported our mapping results. Alloxan sensitivity was increased in ALR.mt NOD mice, whereas it was decreased by congenic introduction of ALR genome on Chr. 8 into NOD. These data demonstrate both similarities and differences in the genetic control of T1D versus ROS-induced diabetes.

Genes within the Idd5 and Idd9/11 Diabetes Susceptibility Loci Affect the Pathogenic Activity of B Cells in Nonobese Diabetic Mice

Autoreactive T cells clearly mediate the pancreatic beta cell destruction causing type 1 diabetes (T1D). However, studies in NOD mice indicate that B cells also contribute to pathogenesis because their ablation by introduction of an Igmunull mutation elicits T1D resistance. T1D susceptibility is restored in NOD.Igmunull mice that are irradiated and reconstituted with syngeneic bone marrow plus NOD B cells, but not syngeneic bone marrow alone. Thus, we hypothesized some non-MHC T1D susceptibility (Idd) genes contribute to disease by allowing development of pathogenic B cells. Supporting this hypothesis was the finding that unlike those from NOD donors, engraftment with B cells from H2g7 MHC-matched, but T1D-resistant, nonobese-resistant (NOR) mice failed to restore full disease susceptibility in NOD.Igmunull recipients. T1D resistance in NOR mice is mainly encoded within the Idd13, Idd5.2, and Idd9/11 loci. B cells from NOD congenic stocks containing Idd9/11 or Idd5.1/5.2-resistance loci, respectively, derived from the NOR or C57BL/10 strains were characterized by suppressed diabetogenic activity. Immature autoreactive B cells in NOD mice have an impaired ability to be rendered anergic upon Ag engagement. Interestingly, both Idd5.1/5.2 and Idd9/11-resistance loci were found to normalize this B cell tolerogenic process, which may represent a mechanism contributing to the inhibition of T1D.

Partial versus Full Allogeneic Hemopoietic Chimerization Is a Preferential Means to Inhibit Type 1 Diabetes as the Latter Induces Generalized Immunosuppression

In both humans and NOD mice, particular combinations of MHC genes provide the primary risk factor for development of the autoreactive T cell responses causing type 1 diabetes (T1D). Conversely, other MHC variants can confer dominant T1D resistance, and previous studies in NOD mice have shown their expression on hemopoietically derived APC is sufficient to induce disease protection. Although allogeneic hemopoietic chimerization can clearly provide a means for blocking T1D development, its clinical use for this purpose has been obviated by a requirement to precondition the host with what would be a lethal irradiation dose if bone marrow engraftment is not successful. There have been reports in which T1D-protective allogeneic hemopoietic chimerization was established in NOD mice that were preconditioned by protocols not including a lethal dose of irradiation. In most of these studies, virtually all the hemopoietic cells in the NOD recipients eventually converted to donor type. We now report that a concern about such full allogeneic chimeras is that they are severely immunocompromised potentially because their T cells are positively selected in the thymus by MHC molecules differing from those expressed by the APC available in the periphery to activate T cell effector functions. However, this undesirable side effect of generalized immunosuppression is obviated by a new protocol that establishes without a lethal preconditioning component, a stable state of mixed allogeneic hemopoietic chimerism sufficient to inhibit T1D development and also induce donor-specific tolerance in NOD recipients.

Molecular Genetic Analysis of the Idd4 Locus Implicates the IFN Response in Type 1 Diabetes Susceptibility in Nonobese Diabetic Mice

High-resolution mapping and identification of the genes responsible for type 1 diabetes (T1D) has proved difficult because of the multigenic etiology and low penetrance of the disease phenotype in linkage studies. Mouse congenic strains have been useful in refining Idd susceptibility loci in the NOD mouse model and providing a framework for identification of genes underlying complex autoimmune syndromes. Previously, we used NOD and a nonobese diabetes-resistant strain to map the susceptibility to T1D to the Idd4 locus on chromosome 11. Here, we report high-resolution mapping of this locus to 1.4 megabases. The NOD Idd4 locus was fully sequenced, permitting a detailed comparison with C57BL/6 and DBA/2J strains, the progenitors of T1D resistance alleles found in the nonobese diabetes-resistant strain. Gene expression arrays and quantitative real-time PCR were used to prioritize Idd4 candidate genes by comparing macrophages/dendritic cells from congenic strains where allelic variation was confined to the Idd4 interval. The differentially expressed genes either were mapped to Idd4 or were components of the IFN response pathway regulated in trans by Idd4. Reflecting central roles of Idd4 genes in Ag presentation, arachidonic acid metabolism and inflammation, phagocytosis, and lymphocyte trafficking, our combined analyses identified Alox15, Alox12e, Psmb6, Pld2, and Cxcl16 as excellent candidate genes for the effects of the Idd4 locus.