Interactions between Idd5.1/Ctla4 and other type 1 diabetes genes

Two loci, Idd5.1 and Idd5.2, that determine susceptibility to type 1 diabetes (T1D) in the NOD mouse are on chromosome 1. Idd5.1 is likely accounted for by a synonymous single nucleotide polymorphism in exon 2 of Ctla4: the B10-derived T1D-resistant allele increases the expression of the ligand-independent isoform of CTLA-4 (liCTLA-4), a molecule that mediates negative signaling in T cells. Idd5.2 is probably Nramp1 (Slc11a1), which encodes a phagosomal membrane protein that is a metal efflux pump and is important for host defense and Ag presentation. In this study, two additional loci, Idd5.3 and Idd5.4, have been defined to 3.553 and 78 Mb regions, respectively, on linked regions of chromosome 1. The most striking findings, however, concern the evidence we have obtained for strong interactions between these four disease loci that help explain the association of human CTLA4 with T1D. In the presence of a susceptibility allele at Idd5.4, the CTLA-4 resistance allele causes an 80% reduction in T1D, whereas in the presence of a protective allele at Idd5.4, the effects of the resistance allele at Ctla4 are modest or, as in the case in which resistance alleles at Idd5.2 and Idd5.3 are present, completely masked. This masking of CTLA-4 alleles by different genetic backgrounds provides an explanation for our observation that the human CTLA-4 gene is only associated with T1D in the subgroup of human T1D patients with anti-thyroid autoimmunity.     

Fine mapping, gene content, comparative sequencing, and expression analyses support Ctla4 and Nramp1 as candidates for Idd5.1 and Idd5.2 in the nonobese diabetic mouse

At least two loci that determine susceptibility to type 1 diabetes in the NOD mouse have been mapped to chromosome 1, Idd5.1 (insulin-dependent diabetes 5.1) and Idd5.2. In this study, using a series of novel NOD.B10 congenic strains, Idd5.1 has been defined to a 2.1-Mb region containing only four genes, Ctla4, Icos, Als2cr19, and Nrp2 (neuropilin-2), thereby excluding a major candidate gene, Cd28. Genomic sequence comparison of the two functional candidate genes, Ctla4 and Icos, from the B6 (resistant at Idd5.1) and the NOD (susceptible at Idd5.1) strains revealed 62 single nucleotide polymorphisms (SNPs), only two of which were in coding regions. One of these coding SNPs, base 77 of Ctla4 exon 2, is a synonymous SNP and has been correlated previously with type 1 diabetes susceptibility and differential expression of a CTLA-4 isoform. Additional expression studies in this work support the hypothesis that this SNP in exon 2 is the genetic variation causing the biological effects of Idd5.1. Analysis of additional congenic strains has also localized Idd5.2 to a small region (1.52 Mb) of chromosome 1, but in contrast to the Idd5.1 interval, Idd5.2 contains at least 45 genes. Notably, the Idd5.2 region still includes the functionally polymorphic Nramp1 gene. Future experiments to test the identity of Idd5.1 and Idd5.2 as Ctla4 and Nramp1, respectively, can now be justified using approaches to specifically alter or mimic the candidate causative SNPs.     

Sex-specific effect of insulin-dependent diabetes 4 on regulation of diabetes pathogenesis in the nonobese diabetic mouse

Many human autoimmune diseases are more frequent in females than males, and their clinical severity is affected by sex hormone levels. A strong female bias is also observed in the NOD mouse model of type I diabetes (T1D). In both NOD mice and humans, T1D displays complex polygenic inheritance and T cell-mediated autoimmune pathogenesis. The identities of many of the insulin-dependent diabetes (Idd) loci, their influence on specific stages of autoimmune pathogenesis, and sex-specific effects of Idd loci in the NOD model are not well understood. To address these questions, we analyzed cyclophosphamide-accelerated T1D (CY-T1D) that causes disease with high and similar frequencies in male and female NOD mice, but not in diabetes-resistant animals, including the nonobese diabetes-resistant (NOR) strain. In this study we show by genetic linkage analysis of (NOD x NOR) x NOD backcross mice that progression to severe islet inflammation after CY treatment was controlled by the Idd4 and Idd9 loci. Congenic strains on both the NOD and NOR backgrounds confirmed the roles of Idd4 and Idd9 in CY-T1D susceptibility and revealed the contribution of a third locus, Idd5. Importantly, we show that the three loci acted at distinct stages of islet inflammation and disease progression. Among these three loci, Idd4 alleles alone displayed striking sex-specific behavior in CY-accelerated disease. Additional studies will be required to address the question of whether a sex-specific effect of Idd4, observed in this study, is also present in the spontaneous model of the disease with striking female bias.     

The diabetes susceptibility locus Idd5.1 on mouse chromosome 1 regulates ICOS expression and modulates murine experimental autoimmune encephalomyelitis

Linkage analysis and congenic mapping in NOD mice have identified a susceptibility locus for type 1 diabetes, Idd5.1 on mouse chromosome 1, which includes the Ctla4 and Icos genes. Besides type 1 diabetes, numerous autoimmune diseases have been mapped to a syntenic region on human chromosome 2q33. In this study we determined how the costimulatory molecules encoded by these genes contribute to the immunopathogenesis of experimental autoimmune encephalomyelitis (EAE). When we compared levels of expression of costimulatory molecules on T cells, we found higher ICOS and lower full-length CTLA-4 expression on activated NOD T cells compared with C57BL/6 (B6) and C57BL/10 (B10) T cells. Using NOD.B10 Idd5 congenic strains, we determined that a 2.1-Mb region controls the observed expression differences of ICOS. Although Idd5.1 congenic mice are resistant to diabetes, we found them more susceptible to myelin oligodendrocyte glycoprotein 35-55-induced EAE compared with NOD mice. Our data demonstrate that higher ICOS expression correlates with more IL-10 production by NOD-derived T cells, and this may be responsible for the less severe EAE in NOD mice compared with Idd5.1 congenic mice. Paradoxically, alleles at the Idd5.1 locus have opposite effects on two autoimmune diseases, diabetes and EAE. This may reflect differential roles for costimulatory pathways in inducing autoimmune responses depending upon the origin (tissue) of the target Ag.     

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.     

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.     

The enlarged population of marginal zone/CD1d(high) B lymphocytes in nonobese diabetic mice maps to diabetes susceptibility region Idd11

The NOD mouse is an important experimental model for human type 1 diabetes. T cells are central to NOD pathogenesis, and their function in the autoimmune process of diabetes has been well studied. In contrast, although recognized as important players in disease induction, the role of B cells is not clearly understood. In this study we characterize different subpopulations of B cells and demonstrate that marginal zone (MZ) B cells are expanded 2- to 3-fold in NOD mice compared with nondiabetic C57BL/6 (B6) mice. The NOD MZ B cells displayed a normal surface marker profile and localized to the MZ region in the NOD spleen. Moreover, the MZ B cell population developed early during the ontogeny of NOD mice. By 3 wk of age, around the time when autoreactive T cells are first activated, a significant MZ B cell population of adult phenotype was found in NOD, but not B6, mice. Using an F2(B6 x NOD) cross in a genome-wide scan, we map the control of this trait to a region on chromosome 4 (logarithm of odds score, 4.4) which includes the Idd11 and Idd9 diabetes susceptibility loci, supporting the hypothesis that this B cell trait is related to the development of diabetes in the NOD mouse.     

Subcongenic analysis of genetic basis for impaired development of invariant NKT cells in NOD mice

Reduced numbers and function of invariant NKT (iNKT) cells partially contribute to type 1 diabetes (T1D) development in NOD mice. Previous linkage analysis identified a genetic locus on chromosome 2 controlling numbers of thymic iNKT cells. Interestingly, this locus resides within the Idd13 region that distinguishes NOD mice from the closely genetically related, but strongly T1D-resistant NOR strain. Thus, we tested if a genetic variant that confers T1D resistance in NOR mice may do so by enhancing iNKT cell numbers. iNKT cells were enumerated by an α-GalCer analog loaded CD1d tetramer in NOD and NOR mice as well as in NOD stocks carrying NOR-derived congenic regions on chromosome 1, 2, or 4. Significantly, more thymic and splenic iNKT cells were present in NOR than NOD mice. The NOR-derived Idd13 region on chromosome 2 contributed the most significant effect on increasing iNKT cell numbers. Subcongenic analyses indicated that at least two genes within the Idd13 region regulate iNKT cell numbers. These results further define the genetic basis for numerical iNKT cell defects contributing to T1D development in NOD mice.     

Through regulation of TCR expression levels, an Idd7 region gene(s) interactively contributes to the impaired thymic deletion of autoreactive diabetogenic CD8+ T cells in nonobese diabetic mice

When expressed in NOD, but not C57BL/6 (B6) genetic background mice, the common class I variants encoded by the H2g7 MHC haplotype aberrantly lose the ability to mediate the thymic deletion of autoreactive CD8+ T cells contributing to type 1 diabetes (T1D). This indicated some subset of the T1D susceptibility (Idd) genes located outside the MHC of NOD mice interactively impair the negative selection of diabetogenic CD8+ T cells. In this study, using both linkage and congenic strain analyses, we demonstrate contributions from a polymorphic gene(s) in the previously described Idd7 locus on the proximal portion of Chromosome 7 predominantly, but not exclusively, determines the extent to which H2g7 class I molecules can mediate the thymic deletion of diabetogenic CD8+ T cells as illustrated using the AI4 TCR transgenic system. The polymorphic Idd7 region gene(s) appears to control events that respectively result in high vs low expression of the AI4 clonotypic TCR alpha-chain on developing thymocytes in B6.H2g7 and NOD background mice. This expression difference likely lowers levels of the clonotypic AI4 TCR in NOD, but not B6.H2g7 thymocytes, below the threshold presumably necessary to induce a signaling response sufficient to trigger negative selection upon Ag engagement. These findings provide further insight to how susceptibility genes, both within and outside the MHC, may interact to elicit autoreactive T cell responses mediating T1D development in both NOD mice and human patients.     

Truncated pStat5B is associated with the Idd4 locus in NOD mice

We investigate JAK-STAT5 activation and its relationship to full-length Stat5B (FL-Stat5) and constitutive phosphorylated carboxy-truncated Stat5B (ct-pStat5) in four different strains of mouse. Our electrophoresis mobility shift assays data indicate constitutive phosphorylation of full-length-Stat5 (p<0.001) and DNA binding in NOD but not in B6 mice. Our data suggest that the relative ratio of FL-Stat5: ct-Stat5 in NOD is 5- to 8-fold lower (p<0.0001) when compared with normal B6 mice. Additionally, EMSAs data from B6.NOD/c11 suggest contribution of Idd4 susceptibility locus on chromosome 11 in constitutive phosphorylation of Stat5 in NOD mice. The presence of ct-pStat5 in regulatory T cells of NOD mice suggests this form of Stat5 is associated with impaired function of Tregs in NOD mouse. In agreement with our previous report the JAK-Stat5B defective pathway in NOD mice along with other defective factors is associated with the pathogenesis of autoimmune type 1 diabetes in NOD mice.     

The autoimmune diabetes locus Idd9 regulates development of type 1 diabetes by affecting the homing of islet-specific T cells

Several genetic insulin-dependent diabetes (Idd) intervals that confer resistance to autoimmune diabetes have been identified in mice and humans, but the mechanisms by which they protect against development of diabetes have not been elucidated. To determine the effect of Idd9 on the function of islet-specific T cells, we established novel BDC-Idd9 mice that harbor BDC2.5 TCR transgenic T cells containing the Idd9 of diabetes-resistant B10 mice. We show that the development and functional responses of islet-specific T cells from BDC-Idd9 mice are not defective compared with those from BDC mice, which contain the Idd9 of diabetes-susceptible NOD mice. Upon transfer, BDC T cells rapidly induced severe insulitis and diabetes in NOD.scid mice, whereas those from BDC-Idd9 mice mediated a milder insulitis and induced diabetes with a significantly delayed onset. BDC and BDC-Idd9 T cells expanded comparably in recipient mice. However, BDC-Idd9 T cells accumulated in splenic periarteriolar lymphatic sheaths, whereas BDC T cells were mainly found in pancreatic lymph nodes and pancreata of recipients, indicating that the transferred T cells differed in their homing. We provide evidence that the migration pattern of transferred BDC and BDC-Idd9 T cells at least partly depends on their differential chemotaxis toward the CCR7 ligand CCL19. Taken together, our data show that the Idd9 locus regulates development of type 1 diabetes by affecting the homing of islet-specific T cells.     

Localization of Idd11 using NOD congenic mouse strains: elimination of Slc9a1 as a candidate gene

 Type 1 diabetes is a multigenic autoimmune disease, the genetic basis for which is perhaps best characterized in the nonobese diabetic (NOD) mouse model. We previously located a NOD diabetes susceptibility locus, designated Idd11, on mouse Chromosome (Chr) 4 by analyzing diabetic backcross mice produced after crossing NOD/Lt with the nondiabetic resistant strain C57BL/6 (B6) strain. In order to confirm Idd11 and further refine its location, three NOD congenic mouse strains with different B6 derived intervals within Chr 4 were generated. Two of the congenic strains had a significant decrease in the cumulative incidence of diabetes compared with NOD/Lt control mice. The third NOD congenic strain, containing a B6 interval surrounding the Slc9a1 locus, was not protected against diabetes. These results define a new distal boundary for Idd11 and eliminate the Slc9a1 gene as a candidate. The Idd11 locus has now been definitively mapped to a 13cM interval on mouse Chr 4. Received: 15 May 1999 / Revised: 25 September 1999     

A 20-Mb region of chromosome 4 controls TNF-alpha-mediated CD8+ T cell aggression toward beta cells in type 1 diabetes

Identification of candidate genes and their immunological mechanisms that control autoaggressive T cells in inflamed environments, may lead to novel therapies for autoimmune diseases, like type 1 diabetes (T1D). In this study, we used transgenic NOD mice that constitutively express TNF-alpha in their islets from neonatal life (TNF-alpha-NOD) to identify protective alleles that control T1D in the presence of a proinflammatory environment. We show that TNF-alpha-mediated breakdown in T cell tolerance requires recessive NOD alleles. To identify some of these recessive alleles, we crossed TNF-alpha-NOD mice to diabetes-resistant congenic NOD mice having protective alleles at insulin-dependent diabetes (Idd) loci that control spontaneous T1D at either the preinsulitis (Idd3.Idd5) or postinsulitis (Idd9) phases. No protection from TNF-alpha-accelerated T1D was afforded by resistance alleles at Idd3.Idd5. Lack of protection was not at the level of T cell priming, the efficacy of islet-infiltrating APCs to present islet peptides, nor the ability of high levels of CD4+ Foxp3+ T cells to accumulate in the islets. In contrast, protective alleles at Idd9 significantly increased the age at which TNF-alpha-NOD mice developed T1D. Disease delay was associated with a decreased ability of CD8+ T cells to respond to islet Ags presented by islet-infiltrating APCs. Finally, we demonstrate that the protective region on chromosome 4 that controls T1D in TNF-alpha-Idd9 mice is restricted to the Idd9.1 region. These data provide new evidence of the mechanisms by which selective genetic loci control autoimmune diseases in the presence of a strong inflammatory assault.     

Fine mapping of type 1 diabetes regions Idd9.1 and Idd9.2 reveals genetic complexity

Nonobese diabetic (NOD) mice congenic for C57BL/10 (B10)-derived genes in the Idd9 region of chromosome 4 are highly protected from type 1 diabetes (T1D). Idd9 has been divided into three protective subregions (Idd9.1, 9.2, and 9.3), each of which partially prevents disease. In this study we have fine-mapped the Idd9.1 and Idd9.2 regions, revealing further genetic complexity with at least two additional subregions contributing to protection from T1D. Using the NOD sequence from bacterial artificial chromosome clones of the Idd9.1 and Idd9.2 regions as well as whole-genome sequence data recently made available, sequence polymorphisms within the regions highlight a high degree of polymorphism between the NOD and B10 strains in the Idd9 regions. Among numerous candidate genes are several with immunological importance. The Idd9.1 region has been separated into Idd9.1 and Idd9.4, with Lck remaining a candidate gene within Idd9.1. One of the Idd9.2 regions contains the candidate genes Masp2 (encoding mannan-binding lectin serine peptidase 2) and Mtor (encoding mammalian target of rapamycin). From mRNA expression analyses, we have also identified several other differentially expressed candidate genes within the Idd9.1 and Idd9.2 regions. These findings highlight that multiple, relatively small genetic effects combine and interact to produce significant changes in immune tolerance and diabetes onset.     

Genetic control of anti-Sm autoantibody production in NOD congenic mice narrowed to the Idd9.3 region

Anti-Smith (anti-Sm) autoantibodies are directed to proteins in the small-nuclear ribonucleoprotein (snRNP) family and are considered specific for systemic lupus erythematosus (SLE) in both humans and mice. We previously established that NOD.c3c4 mice, carrying B6 and B10 congenic segments from chromosomes 3 to 4 on an nonobese diabetic (NOD) background, and NOD.Idd9R28 mice, carrying a B10 segment on c4 alone, developed significant penetrance of anti-Sm antibody production. Here we determine autoantibody incidence in additional NOD.Idd9 congenic strains and use a congenic mapping approach to narrow the interval necessary for enhanced autoantibody production to a ∼5.6-Mb region containing insulin-dependent diabetes (Idd)9.3. The Idd9.3 interval contains the candidate molecule cluster of differentiation (CD)137, which is a member of the tumor necrosis factor (TNF) receptor superfamily, functions as an inducible costimulator of T cells, and controls T–B interactions. The NOD and B10 CD137 alleles have sequence polymorphisms and different functional effects on T cells; the NOD CD137 allele mediates weaker T cell proliferative responses and decreased interleukin (IL)-2 production after CD137-mediated costimulation. Our work establishes CD137 as a candidate gene for control of autoantibody production in NOD.Idd9.3 congenic mice.     

Enhanced early expansion and maturation of semi-invariant NK T cells inhibited autoimmune pathogenesis in congenic nonobese diabetic mice

Semi-invariant NK T cell (iNKT) deficiency has long been associated with the pathogenesis of type 1 diabetes (T1D), but the linkage between this the deficiency and T1D susceptibility gene(s) remains unclear. We analyzed NOD mice subcongenic for resistant alleles of Idd9 locus in search for protective mechanisms against T1D, and found that iNKT cell development was significantly enhanced with a more advanced mature phenotype and function in mice containing Idd9.1 sublocus of B10 origin. The enhanced iNKT cell development and function suppressed effector function of diabetogenic T cells. Elimination of iNKT cells by CD1d deficiency almost abolished T1D protection in these mice. Interestingly, although the iNKT cells were responsible for a Th2 orientated cytokine profile that is often regarded as a mechanism of T1D prevention, our data suggests that the Th2 bias played little if any role for the protection. In addition, dendritic cells from the congenic NOD mice showed increased abilities to engage and potentiate iNKT cells, suggesting that a mechanism mediated by dendritic cells or other APCs may be critical for the enhanced development and maturation of iNKT cells. The products of T1D susceptibility gene(s) in Idd9.1 locus may be a key factor for this mechanism.     

Diabetes resistance/susceptibility in T cells of nonobese diabetic mice conferred by MHC and MHC-linked genes

Polymorphism of MHC and MHC-linked genes is tightly associated with susceptibility to type 1 diabetes (T1D) in human and animal models. Despite the extensive studies, however, the role of MHC and MHC-linked genes expressed by T cells on T1D susceptibility remains unclear. Because T cells develop from TCR(-) thymic precursor (pre-T) cells that undergo MHC restriction mediated by thymic stroma cells, we reconstituted the T cell compartment of NOD.scid-RIP-B7.1 mice using pre-T cells isolated from NOD, NOR, AKR, and C57BL/6 (B6) mice. T1D developed rapidly in the mice reconstituted with pre-T cells derived from NOD or NOR donors. In contrast, most of the NOD.scid-RIP-B7.1 mice reconstituted with pre-T cells from AKR or B6 donors were free of T1D. Further analysis revealed that genes within MHC locus of AKR or B6 origin reduced incidence of T1D in the reconstituted NOD.scid-RIP-B7.1 mice. The expression of MHC class I genes of k, but not b haplotype, in T cells conferred T1D resistance. Replacement of an interval near the distal end of the D region in T cells of B6 origin with an identical allele of 129.S6 origin resulted in T1D development in the reconstituted mice. These results provide evidence that the expression of MHC class I and MHC-linked genes in T cells of NOD mice indeed contributes to T1D susceptibility, while expression of specific resistance alleles of MHC or MHC-linked genes in T cells alone would effectively reduce or even prevent T1D.     

Impact of protective IL-2 allelic variants on CD4+ Foxp3+ regulatory T cell function in situ and resistance to autoimmune diabetes in NOD mice

Type I diabetes (T1D) susceptibility is inherited through multiple insulin-dependent diabetes (Idd) genes. NOD.B6 Idd3 congenic mice, introgressed with an Idd3 allele from T1D-resistant C57BL/6 mice (Idd3(B6)), show a marked resistance to T1D compared with control NOD mice. The protective function of the Idd3 locus is confined to the Il2 gene, whose expression is critical for naturally occurring CD4(+)Foxp3(+) regulatory T (nT(reg)) cell development and function. In this study, we asked whether Idd3(B6) protective alleles in the NOD mouse model confer T1D resistance by promoting the cellular frequency, function, or homeostasis of nT(reg) cells in vivo. We show that resistance to T1D in NOD.B6 Idd3 congenic mice correlates with increased levels of IL-2 mRNA and protein production in Ag-activated diabetogenic CD4(+) T cells. We also observe that protective IL2 allelic variants (Idd3(B6) resistance allele) also favor the expansion and suppressive functions of CD4(+)Foxp3(+) nT(reg) cells in vitro, as well as restrain the proliferation, IL-17 production, and pathogenicity of diabetogenic CD4(+) T cells in vivo more efficiently than control do nT(reg) cells. Lastly, the resistance to T1D in Idd3 congenic mice does not correlate with an augmented systemic frequency of CD4(+)Foxp3(+) nT(reg) cells but more so with the ability of protective IL2 allelic variants to promote the expansion of CD4(+)Foxp3(+) nT(reg) cells directly in the target organ undergoing autoimmune attack. Thus, protective, IL2 allelic variants impinge the development of organ-specific autoimmunity by bolstering the IL-2 producing capacity of self-reactive CD4(+) T cells and, in turn, favor the function and homeostasis of CD4(+)Foxp3(+) nT(reg) cells in vivo.     

Increased generation of dendritic cells from myeloid progenitors in autoimmune-prone nonobese diabetic mice

Aberrant dendritic cell (DC) development and function may contribute to autoimmune disease susceptibility. To address this hypothesis at the level of myeloid lineage-derived DC we compared the development of DC from bone marrow progenitors in vitro and DC populations in vivo in autoimmune diabetes-prone nonobese diabetic (NOD) mice, recombinant congenic nonobese diabetes-resistant (NOR) mice, and unrelated BALB/c and C57BL/6 (BL/6) mice. In GM-CSF/IL-4-supplemented bone marrow cultures, DC developed in significantly greater numbers from NOD than from NOR, BALB/c, and BL/6 mice. Likewise, DC developed in greater numbers from sorted (lineage(-)IL-7Ralpha(-)SCA-1(-)c-kit(+)) NOD myeloid progenitors in either GM-CSF/IL-4 or GM-CSF/stem cell factor (SCF)/TNF-alpha. [(3)H]TdR incorporation indicated that the increased generation of NOD DC was due to higher levels of myeloid progenitor proliferation. Generation of DC with the early-acting hematopoietic growth factor, flt3 ligand, revealed that while the increased DC-generative capacity of myeloid-committed progenitors was restricted to NOD cells, early lineage-uncommitted progenitors from both NOD and NOR had increased DC-generative capacity relative to BALB/c and BL/6. Consistent with these findings, NOD and NOR mice had increased numbers of DC in blood and thymus and NOD had an increased proportion of the putative myeloid DC (CD11c(+)CD11b(+)) subset within spleen. These findings demonstrate that diabetes-prone NOD mice exhibit a myeloid lineage-specific increase in DC generative capacity relative to diabetes-resistant recombinant congenic NOR mice. We propose that an imbalance favoring development of DC from myeloid-committed progenitors predisposes to autoimmune disease in NOD mice.