Management status and its predictive factors in patients with type 2 diabetes in China: A Nationwide Multicenter Study: A Nationwide Multicenter Study.

BACKGROUND: The prevalence of type 2 diabetes in China is increasing rapidly. Appropriate management of glycemia, blood pressure and dyslipidemia in this population is a major public health concern. OBJECTIVE: The aim of this study was to assess metabolic control including glycated hemoglobin A1c (HbA1c ), blood pressure (BP) and low density lipoprotein cholesterol (LDL-c), in a large sample of patients with type 2 diabetes in China and to identify factors that correlated with the achievement of HbA1c, BP and LDL-c goals (ABCs). METHOD: A nationwide survey was conducted in 50 medical centres across China from April to July of 2010. Baseline information on demographics, medical history, HbA1c , BP and LDL-c levels were measured in 5961 patients with type 2 diabetes. RESULTS: Mean age, body mass index (BMI) and HbA1c were 59.5 ± 1.3 years, 24.5 ± 4.1 kg/m(2) and 8.3 ± 2.2%, respectively. With respect to generally accepted ABC treatment goals, 35.2% of participants had HbA1c <7%; 35.5% had BP < 140/80 mmHg, and 45.1% had LDL-c < 100 mg/dl. The proportion of patients who met all three targets was only 5.4%. Logistic regression revealed that smoking (P=0.000), higher BMI (P=0.001) and insulin use (P=0.000) were statistically significant predictors of failing to meet ABC targets. CONCLUSION: The percentage of Chinese patients with type 2 diabetes who met recommended targets for HbA1c , BP and LDL-c in 2010 was low. Smoking, higher BMI and insulin use were the strongest determinants of failing to meet ABC targets.

Evaluation, Medical Therapy, and Course of Adult Persistent Hyperinsulinemic Hypoglycemia After Roux-en-Y Gastric Bypass Surgery: A Case Series.

OBJECTIVE: To describe the evaluation and treatment of hyperinsulinemic hypoglycemia in adults who had undergone gastric bypass surgery. A small number of patients who undergo Roux-en-Y bypass surgery develop postprandial hypoglycemia in the absence of dumping. In some cases, such patients have been treated with pancreatectomy. METHODS: We report the demographics, diagnostic results, response to medical therapy, and subsequent course of 6 referral patients with post-Roux-en-Y gastric bypass hypoglycemia. RESULTS: Characteristic clinical and metabolic parameters consistent with hyperinsulinemic hypoglycemia were identified. Parameters were similar for both spontaneous and glucose-challenge-induced hypoglycemia. In the context of exclusively postprandial symptoms, simultaneous glucose ≤55 mg/dL, insulin ≥17 µU/mL, C peptide ≥3.0 ng/mL, and insulin to glucose ratio >0.3 were associated with Roux-en-Y gastric bypass hyperinsulinemic hypoglycemia. Five of 6 patients improved on therapy consisting of dietary modification plus either calcium channel blockade, acarbose, or both. Two patients have remained on therapy for 12 to 15 months. The nonresponder was atypical and had had hypoglycemic events for several decades. Three treated patients were subsequently observed to have undergone partial or complete remission from hypoglycemic episodes after 2 to 37 months of therapy. None of the 6 have undergone pancreatectomy, and none have evidence of insulinoma. Invasive diagnostic procedures were of limited utility. CONCLUSION: In a subset of patients with post-Roux-en-Y gastric bypass hyperinsulinemic hypoglycemia, medical management can be efficacious and an alternative to partial pancreatectomy. In some cases, the disorder remits spontaneously.

T Cell Receptor Genotype and Ubash3a Determine Susceptibility to Rat Autoimmune Diabetes.

Genetic analyses of human type 1 diabetes (T1D) have yet to reveal a complete pathophysiologic mechanism. Inbred rats with a high-risk class II major histocompatibility complex (MHC) haplotype (RT1B/Du) can illuminate such mechanisms. Using T1D-susceptible LEW.1WR1 rats that express RT1B/Du and a susceptible allele of the Ubd promoter, we demonstrate that germline knockout of Tcrb-V13S1A1, which encodes the Vß13a T cell receptor ß chain, completely prevents diabetes. Using the RT1B/Du-identical LEW.1W rat, which does not develop T1D despite also having the same Tcrb-V13S1A1 ß chain gene but a different allele at the Ubd locus, we show that knockout of the Ubash3a regulatory gene renders these resistant rats relatively susceptible to diabetes. In silico structural modeling of the susceptible allele of the Vß13a TCR and its class II RT1u ligand suggests a mechanism by which a germline TCR ß chain gene could promote susceptibility to T1D in the absence of downstream immunoregulation like that provided by UBASH3A. Together these data demonstrate the critical contribution of the Vß13a TCR to the autoimmune synapse in T1D and the regulation of the response by UBASH3A. These experiments dissect the mechanisms by which MHC class II heterodimers, TCR and regulatory element interact to induce autoimmunity.

The Vbeta13 T Cell Receptor Monoclonal Antibody Reduces Hyaluronan and CD68+, CD3+, and CD8+ Cell Infiltrations to Delay Diabetes in Congenic BB DRLyp/Lyp Rats.

The depleting Vß13a T cell receptor monoclonal antibody (mAb) 17D5 prevents both induced and spontaneous autoimmune diabetes in BB rats. Here it was tested in congenic DRLyp/Lyp rats, all of which spontaneously developed diabetes. Starting at 40 days of age, rats were injected once weekly with either saline, His42 Vß16 mAb, or 17D5 mAb and monitored for hyperglycemia. Diabetes occurred in 100% (n = 5/5) of saline-treated rats (median age, 66 days; range 55-73), and in 100% (n = 6/6) of His42-treated rats (median age, 69 days; range 59-69). Diabetes occurred in fewer (n = 8/11, 73%) 17D5-treated rats at a later age (median 76 days, range 60-92). Three (27%) of the 17D5-treated rats were killed at 101-103 days of age without diabetes (17D5 no-diabetes rats). Survival analysis demonstrated that 17D5 mAb delayed diabetes onset. Saline- and His42-treated rats had severely distorted islets with substantial loss of insulin-positive cells. These rats exhibited prominent hyaluronan (HA) staining, with the intra-islet HA+ accumulations measuring 5,000 ± 2,400 µm2 and occupying 36 ± 12% of islet area, and severe (grade 4) insulitis with abundant infiltration by CD68+, CD3+, and CD8+ cells. The 17D5 mAb-treated rats with delayed diabetes onset exhibited less severe insulitis (predominantly grade 3). In contrast, the 17D5 no-diabetes rats had mostly normal islets, with insulin+ cells representing 76 ± 3% of islet cells. In these rats, the islet HA deposits were significantly smaller than in the diabetic rats; the intra-islet HA+ areas were 1,200 ± 300 µm2 and accounted for 8 ± 1% of islet area. Also, islet-associated CD68+ and CD3+ cells occurred less frequently (on average in 60 and 3% of the islets, respectively) than in the diabetes rats (present in >95% of the islets). No CD8+ cells were detected in islets in all 17D5 no-diabetes rats. We conclude that mAb 17D5 delayed diabetes in DRLyp/Lyp rats and markedly reduced expression of HA and concomitant infiltration of CD68+, CD3+, and CD8+ cells. Our findings underscore the importance of refining immune suppression in prevention or intervention clinical trials to use mAb reagents that are directed against specific T cell receptors.

Analysis of the rat Iddm14 diabetes susceptibility locus in multiple rat strains: identification of a susceptibility haplotype in the Tcrb-V locus.

Iddm14 (formerly Iddm4) is a non-MHC-linked genetic locus associated with autoimmune diabetes. Its effects have been well-documented in BB-derived rats in which diabetes is either induced by immunologic perturbation or occurs spontaneously. The role of Iddm14 in non-BB rat strains is unknown. Our goal was to extend the analysis of Iddm14 in new diabetes-susceptible strains and to identify candidate genes in the rat Iddm14 diabetes susceptibility locus that are common to these multiple diabetic strains. To determine if Iddm14 is important in strains other than BB, we first genotyped a (LEW.1WR1 x WF)F2 cohort in which diabetes was induced by perturbation with polyinosinic:polycytidylic acid. We found that Iddm14 is a major determinant of diabetes susceptibility in LEW.1WR1 rats. We then used nucleotide sequencing to establish a strain distribution pattern of polymorphisms (insertions, deletions, and single nucleotide polymorphisms [SNPs]) that predicts susceptibility to diabetes in a panel of inbred and congenic rats. Using the positional information from the congenic strains and the new linkage data, we identified a susceptibility haplotype in the T-cell receptor Vbeta chain (Tcrb-V) locus. This haplotype includes Tcrb-V13, which is identical in five susceptible strains but different in resistant WF and F344 rats. We conclude that Iddm14 is a powerful determinant of both spontaneous and induced autoimmune diabetes in multiple rat strains, and that Tcrb-V13 SNPs constitute a haplotype of gene elements that may be critical for autoimmune diabetes in rats.

Depletion of the programmed death-1 receptor completely reverses established clonal anergy in CD4(+) T lymphocytes via an interleukin-2-dependent mechanism.

Recent studies have implicated the cell surface receptor Programmed Death-1 (PD-1) in numerous models of T cell anergy, though the specific mechanisms by which the PD-1 signal maintains tolerance is not clear. We demonstrate that the depletion of PD-1 with siRNA results in a complete reversal of clonal anergy in the A.E7 T cell model, suggesting that the mechanism by which PD-1 maintains the anergic phenotype is a T-cell-intrinsic phenomenon, and not one dependent on other cell populations in vivo. We have also shown that the neutralization of IL-2 during restimulation abrogates the effect of PD-1 depletion, suggesting that tolerance mediated by PD-1 is wholly IL-2 dependent, and likewise intrinsic to the tolerized cells.

Failure of alpha-galactosylceramide to prevent diabetes in virus-inducible models of type 1 diabetes in the rat.

BACKGROUND: Alpha-galactosylceramide (alpha-GalCer) is an invariant natural killer T (iNKT) cell ligand that prevents type 1 diabetes in NOD mice. However, alpha-GalCer can activate or suppress immune responses, raising concern about its potential use in human diabetes. MATERIALS AND METHODS: To evaluate this therapeutic issue further, BBDR and LEW.1WR1 rats were treated with Kilham rat virus (KRV) plus polyinosinic-polycytidylic acid, with or without alpha-GalCer, and followed for onset of diabetes. RESULTS: alpha-GalCer did not prevent diabetes in inducible rat models. To investigate this discrepancy, we analyzed iNKT cell function. Splenocytes stimulated with alpha-GalCer produced similar levels of IFNgamma in all rat strains, but less than mouse splenocytes. Rat splenocytes stimulated with alpha-GalCer preferentially produced IL-12, whereas mouse splenocytes preferentially produced IL-4. CONCLUSION: alpha-GalCer elicits species-specific cytokine responses in iNKT cells. In humans with type 1 diabetes, differences in iNKT cell responses to stimulation with alpha-GalCer due to age, genetic variability and other factors may influence its therapeutic potential.

Genetic Variation Within the HLA-DRA1 Gene Modulates Susceptibility to Type 1 Diabetes in HLA-DR3 Homozygotes.

Type 1 diabetes (T1D) involves the interaction of multiple gene variants, environmental factors, and immunoregulatory dysfunction. Major T1D genetic risk loci encode HLA-DR and -DQ. Genetic heterogeneity and linkage disequilibrium in the highly polymorphic HLA region confound attempts to identify additional T1D susceptibility loci. To minimize HLA heterogeneity, T1D patients (N = 365) and control subjects (N = 668) homozygous for the HLA-DR3 high-risk haplotype were selected from multiple large T1D studies and examined to identify new T1D susceptibility loci using molecular inversion probe sequencing technology. We report that risk for T1D in HLA-DR3 homozygotes is increased significantly by a previously unreported haplotype of three single nucleotide polymorphisms (SNPs) within the first intron of HLA-DRA1. The homozygous risk haplotype has an odds ratio of 4.65 relative to the protective homozygous haplotype in our sample. Individually, these SNPs reportedly function as "expression quantitative trait loci," modulating HLA-DR and -DQ expression. From our analysis of available data, we conclude that the tri-SNP haplotype within HLA-DRA1 may modulate class II expression, suggesting that increased T1D risk could be attributable to regulated expression of class II genes. These findings could help clarify the role of HLA in T1D susceptibility and improve diabetes risk assessment, particularly in high-risk HLA-DR3 homozygous individuals.

Protein kinase C signaling during T cell activation induces the endoplasmic reticulum stress response.

T cell receptor (TCR) ligation (signal one) in the presence of co-stimulation (signal two) results in downstream signals that increase protein production enabling naïve T cells to fully activate and gain effector function. Enhanced production of proteins by a cell requires an increase in endoplasmic reticulum (ER) chaperone expression, which is accomplished through activation of a cellular mechanism known as the ER stress response. The ER stress response is initiated during the cascade of events that occur for the activation of many cells; however, this process has not been comprehensively studied for T cell function. In this study, we used primary T cells and mice circulating TCR transgenic CD8(+) T cells to investigate ER chaperone expression in which TCR signaling was initiated in the presence or absence of co-stimulation. In the presence of both signals, in vitro and in vivo analyses demonstrated induction of the ER stress response, as evidenced by elevated expression of GRP78 and other ER chaperones. Unexpectedly, ER chaperones were also increased in T cells exposed only to signal one, a treatment known to cause T cells to enter the 'nonresponsive' states of anergy and tolerance. Treatment of T cells with an inhibitor to protein kinase C (PKC), a serine/threonine protein kinase found downstream of TCR signaling, indicated PKC is involved in the induction of the ER stress response during the T cell activation process, thus revealing a previously unknown role for this signaling protein in T cells. Collectively, these data suggest that induction of the ER stress response through PKC signaling is an important component for the preparation of a T cell response to antigen.

Hematopoietic chimerism and central tolerance created by peripheral-tolerance induction without myeloablative conditioning.

Allogeneic hematopoietic chimerism leading to central tolerance has significant therapeutic potential. Realization of that potential has been impeded by the need for myeloablative conditioning of the host and development of graft-versus-host disease (GVHD). To surmount these impediments, we have adapted a costimulation blockade-based protocol developed for solid organ transplantation for use in stem cell transplantation. The protocol combines donor-specific transfusion (DST) with anti-CD154 mAb. When applied to stem cell transplantation, administration of DST, anti-CD154 mAb, and allogeneic bone marrow leads to hematopoietic chimerism and central tolerance with no myeloablation and no GVHD. Tolerance in this system results from deletion of both peripheral host alloreactive CD8+ T cells and nascent intrathymic alloreactive CD8+ T cells. In the absence of large numbers of host alloreactive CD8+ T cells, the transfusion that precedes transplantation need not be of donor origin, suggesting that both allospecific and non-allospecific mechanisms regulate engraftment. Agents that interfere with peripheral transplantation tolerance impair establishment of chimerism. We conclude that robust allogeneic hematopoietic chimerism and central tolerance can be established in the absence of host myeloablative conditioning using a peripheral transplantation tolerance protocol.

Refinement of the Iddm4 diabetes susceptibility locus reveals TCRVbeta4 as a candidate gene.

Iddm4 is a dominant non-major histocompatibility complex (MHC) determinant of diabetes susceptibility in BBDR rats treated with poly I:C, plus depletion of regulatory T cells. In congenic MHC-identical normal WF rats, Iddm4(d) sensitively and specifically predicts induced diabetes. We report a new diabetes-susceptible subcongenic line that carries Iddm4 in a < 2.6 megabase interval. Candidate genes include the T cell receptor beta chain variable (TCRVbeta) family. We found that TCRVbeta4 in WF rats contains a stop codon, whereas 5/5 diabetes-susceptible rat strains express TCRVbeta4. We conclude that Iddm4-mediated diabetes resistance in rats may be due to a recessive protective mutation in TCRVbeta4.

Development of new-generation HU-PBMC-NOD/SCID mice to study human islet alloreactivity.

The use of "humanized" mice represents an appealing translational model for studies of the pathogenesis of immune-mediated diseases and for the evaluation of potential therapeutics. The utility of humanized mice depends on their ability to model the human immune system with high fidelity, and, in this respect, previous models have fallen short. The recently developed NOD-scid Il2rgamma(null) mouse, however, exhibits greatly enhanced ability to support the engraftment of human peripheral blood mononuclear cells. Herein, we describe the challenges of recapitulating human immunity in humanized mice and features of NOD-scid Il2rgamma(null) mice that help overcome them.

A Critical Role for the Type I Interferon Receptor in Virus-Induced Autoimmune Diabetes in Rats.

The pathogenesis of human type 1 diabetes, characterized by immune-mediated damage of insulin-producing ß-cells of pancreatic islets, may involve viral infection. Essential components of the innate immune antiviral response, including type I interferon (IFN) and IFN receptor-mediated signaling pathways, are candidates for determining susceptibility to human type 1 diabetes. Numerous aspects of human type 1 diabetes pathogenesis are recapitulated in the LEW.1WR1 rat model. Diabetes can be induced in LEW.1WR1 weanling rats challenged with virus or with the viral mimetic polyinosinic:polycytidylic acid (poly I:C). We hypothesized that disrupting the cognate type I IFN receptor (type I IFN α/ß receptor [IFNAR]) to interrupt IFN signaling would prevent or delay the development of virus-induced diabetes. We generated IFNAR1 subunit-deficient LEW.1WR1 rats using CRISPR-Cas9 (clustered regularly interspaced short palindromic repeats-associated protein 9) genome editing and confirmed functional disruption of the Ifnar1 gene. IFNAR1 deficiency significantly delayed the onset and frequency of diabetes and greatly reduced the intensity of insulitis after poly I:C treatment. The occurrence of Kilham rat virus-induced diabetes was also diminished in IFNAR1-deficient animals. These findings firmly establish that alterations in innate immunity influence the course of autoimmune diabetes and support the use of targeted strategies to limit or prevent the development of type 1 diabetes.

The rat diabetes susceptibility locus Iddm4 and at least one additional gene are required for autoimmune diabetes induced by viral infection.

BBDR rats develop autoimmune diabetes only after challenge with environmental perturbants. These perturbants include polyinosinic:polycytidylic acid (poly I:C, a ligand of toll-like receptor 3), agents that deplete regulatory T-cell (Treg) populations, and a non-beta-cell cytopathic parvovirus (Kilham rat virus [KRV]). The dominant diabetes susceptibility locus Iddm4 is required for diabetes induced by treatment with poly I:C plus Treg depletion. Iddm4 is penetrant in congenic heterozygous rats on the resistant WF background and is 79% sensitive and 80% specific as a predictor of induced diabetes. Surprisingly, an analysis of 190 (BBDR x WF)F2 rats treated with KRV after brief exposure to poly I:C revealed that the BBDR-origin allele of Iddm4 is necessary but not entirely sufficient for diabetes expression. A genome scan identified a locus on chromosome 17, designated Iddm20, that is also required for susceptibility to diabetes after exposure to KRV and poly I:C (logarithm of odds score 3.7). These data suggest that the expression of autoimmune diabetes is a complex process that requires both major histocompatibility complex genes that confer susceptibility and additional genes such as Iddm4 and Iddm20 that operate only in the context of specific environmental perturbants, amplifying the immune response and the rate of disease progression.

LEW.1WR1 rats develop autoimmune diabetes spontaneously and in response to environmental perturbation.

We describe a new rat model of autoimmune diabetes that arose in a major histocompatibility complex congenic LEW rat. Spontaneous diabetes in LEW.1WR1 rats (RT1(u/u/a)) occurs with a cumulative frequency of approximately 2% at a median age of 59 days. The disease is characterized by hyperglycemia, glycosuria, ketonuria, and polyuria. Both sexes are affected, and islets of acutely diabetic rats are devoid of beta-cells, whereas alpha- and delta-cell populations are spared. The peripheral lymphoid phenotype is normal, including the fraction of ART2(+) regulatory T-cells. We tested the hypothesis that the expression of diabetes would be increased by immunological perturbation of innate or adaptive immunity. Treatment of young rats with depleting anti-ART2.1 monoclonal antibody increased the frequency of diabetes to 50%. Treatment with the toll-like receptor 3 ligand polyinosinic:polycytidylic acid increased the frequency of diabetes to 100%. All diabetic rats exhibited end-stage islets. The LEW.1WR1 rat is also susceptible to collagen-induced arthritis but is free of spontaneous thyroiditis. The LEW.1WR1 rat provides a new model for studying autoimmune diabetes and arthritis in an animal with a genetic predisposition to both disorders that can be amplified by environmental perturbation.

Autoimmune diabetes and resistance to xenograft transplantation tolerance in NOD mice.

Costimulation blockade induces prolonged rat islet and skin xenograft survival in C57BL/6 mice. Nonobese diabetic (NOD) mice, which are used to model human autoimmune diabetes, are resistant to costimulation blockade-induced allograft tolerance. We tested the hypothesis that NOD mice would also be resistant to costimulation blockade-induced rat xenograft tolerance. We report that rat islet xenograft survival is short in spontaneously diabetic NOD mice treated with a tolerizing regimen of donor-specific transfusion and anti-CD154 antibody. Rat islet xenograft survival is only marginally longer in chemically diabetic NOD mice treated with costimulation blockade but is prolonged further in NOD Idd congenic mice bearing C57-derived chromosome 3 loci. Reciprocally, the presence of NOD-derived chromosome 3 loci shortens islet xenograft survival in tolerized C57BL/6 mice. Islet xenograft survival is longer in tolerized NOD.CD4a(-/-) and (NOD x C57BL/6)F1 mice than in NOD mice but still much shorter than in C57BL/6 mice. Skin xenograft survival in (NOD x C57BL/6)F1 mice treated with costimulation blockade is short, suggesting a strong genetic resistance to skin xenograft tolerance induction. We conclude that the resistance of NOD mice to xenograft tolerance induction involves some mechanisms that also participate in the expression of autoimmunity and other mechanisms that are distinct.

Costimulatory blockade induces hyporesponsiveness in T cells that recognize alloantigen via indirect antigen presentation.

BACKGROUND: Blockade of T cell costimulation by treatment with donor-specific transfusion (DST) and anti-CD154 monoclonal antibody (mAb) induces prolonged allograft survival in mice. This effect is due in part to deletion of host CD8 and CD4 T cells that recognize alloantigen by direct presentation. The fate of host CD4 T cells that recognize alloantigen by indirect presentation, however, is unclear. METHODS: We studied Tg361 TCR transgenic CD4 T cells that recognize alloantigen by indirect presentation. Carboxyfluorescein diacetate, succinimidyl ester-labeled Tg361 cells were adoptively transferred into syngeneic nontransgenic recipients and their fate in the peripheral blood, spleen, and lymph nodes following treatment with DST and anti-CD154 was analyzed. RESULTS: Treatment of mice with DST plus anti-CD154 mAb does not delete Tg361 CD4 T cells, but instead renders them hyporesponsive to rechallenge with alloantigen. Mice circulating hyporesponsive CD4 T cells also fail to reject skin allografts. The hyporesponsive state of the T cells is not reversed by the addition of interleukin-2, anti-CD28 mAb, or an agonistic anti-CD134 mAb in the presence of antigen. These T cells are capable of activation, however, as evidenced by in vitro proliferation in response to anti-CD3 mAb. CONCLUSIONS: These results demonstrate that costimulation blockade can induce hyporesponsiveness of host CD4 T cells recognizing alloantigens by indirect presentation, thus prolonging graft survival by a mechanism that does not involve deletion of alloreactive T cells.

The iddm4 locus segregates with diabetes susceptibility in congenic WF.iddm4 rats.

Viral antibody-free BBDR and WF rats never develop spontaneous diabetes. BBDR rats, however, develop autoimmune diabetes after perturbation of the immune system, e.g., by viral infection. We previously identified a disease-susceptibility locus in the BBDR rat, iddm4, which is associated with the development of autoimmune diabetes after treatment with polyinosinic:polycytidylic acid and an antibody that depletes ART2(+) regulatory cells. We have now developed lines of congenic WF.iddm4 rats and report that in an intercross of N5 generation WF.iddm4 rats, approximately 70% of animals either homozygous or heterozygous for the BBDR origin allele of iddm4 became hyperglycemic after treatment to induce diabetes. Fewer than 20% of rats expressing the WF origin allele of iddm4 became diabetic. Testing the progeny of various recombinant N5 WF.iddm4 congenic rats for susceptibility to diabetes suggests that iddm4 is centered on a small segment of chromosome 4 bounded by the proximal marker D4Rat135 and the distal marker D4Got51, an interval of <2.8 cM. The allele at iddm4 has 79% sensitivity and 80% specificity in prediction of diabetes in rats that are segregating for this locus. These characteristics suggest that iddm4 is one of the most powerful non-major histocompatibility complex determinants of susceptibility to autoimmune diabetes described to date.

NOD congenic mice genetically protected from autoimmune diabetes remain resistant to transplantation tolerance induction.

The loss of self-tolerance leading to autoimmune type 1 diabetes in the NOD mouse model involves at least 19 genetic loci. In addition to their genetic defects in self-tolerance, NOD mice resist peripheral transplantation tolerance induced by costimulation blockade using donor-specific transfusion and anti-CD154 antibody. Hypothesizing that these two abnormalities might be related, we investigated whether they could be uncoupled through a genetic approach. Diabetes-resistant NOD and C57BL/6 stocks congenic for various reciprocally introduced Idd loci were assessed for their ability to be tolerized. Surprisingly, in NOD congenic mice that are almost completely protected from diabetes, costimulation blockade failed to prolong skin allograft survival. In reciprocal C57BL/6 congenic mice with NOD-derived Idd loci, skin allograft survival was readily prolonged by costimulation blockade. These data indicate that single or multiple combinations of evaluated Idd loci that dramatically reduce diabetes frequency do not correct resistance to peripheral transplantation tolerance induced by costimulation blockade. We suggest that mechanisms controlling autoimmunity and transplantation tolerance in NOD mice are not completely overlapping and are potentially distinct, or that the genetic threshold for normalizing the transplantation tolerance defect is higher than that for preventing autoimmune diabetes.

Islet allograft survival induced by costimulation blockade in NOD mice is controlled by allelic variants of Idd3.

NOD mice develop type 1 autoimmune diabetes and exhibit genetically dominant resistance to transplantation tolerance induction. These two phenotypes are genetically separable. Costimulation blockade fails to prolong skin allograft survival in (NOD x C57BL/6)F1 mice and in NOD-related strains made diabetes-resistant by congenic introduction of protective major histocompatibility complex (MHC) or non-MHC Idd region genes. Here, we tested the hypothesis that the genetic basis for the resistance of NOD mice to skin allograft tolerance also applies to islet allografts. Surprisingly, costimulation blockade induced permanent islet allograft survival in (NOD x C57BL/6)F1 mice but not in NOD mice. After costimulation blockade, islet allograft survival was prolonged in diabetes-resistant NOD.B6 Idd3 mice and shortened in diabetes-free C57BL/6 mice congenic for the NOD Idd3 variant. Islet allograft tolerance could not be induced in diabetes-resistant NOD.B10 Idd5 and NOD.B10 Idd9 mice. The data demonstrate that 1) NOD mice resist islet allograft tolerance induction; 2) unlike skin allografts, resistance to islet allograft tolerance is a genetically recessive trait; 3) an Idd3 region gene(s) is an important determinant of islet allograft tolerance induction; and 4) there may be overlap in the mechanism by which the Idd3 resistance locus improves self-tolerance and the induction of allotolerance.