Molecular targeting of islet autoantigens.

Type 1 diabetes of man and animal models results from immune-mediated specific beta cell destruction. Multiple islet antigens are targets of autoimmunity and most of these are not beta cell specific. Immune responses to insulin appear to be essential for the development of diabetes of the NOD mouse. In this review, we will emphasize the unusual manner in which selected autoantigenic peptides (particularly the recently discovered target of BDC2.5 T cells [chromagranin A]) are presented and recognized by autoreactive CD4(+) T cell receptors. We hypothesize that "unusual" structural interactions of specific trimolecular complexes (MHC class II, peptide, and T cell receptors) are fundamental to the escape from the thymus of autoreactive T cells able to cause type 1 diabetes.

Risk of pediatric celiac disease according to HLA haplotype and country.

BACKGROUND: The presence of HLA haplotype DR3-DQ2 or DR4-DQ8 is associated with an increased risk of celiac disease. In addition, nearly all children with celiac disease have serum antibodies against tissue transglutaminase (tTG). METHODS: We studied 6403 children with HLA haplotype DR3-DQ2 or DR4-DQ8 prospectively from birth in the United States, Finland, Germany, and Sweden. The primary end point was the development of celiac disease autoimmunity, which was defined as the presence of tTG antibodies on two consecutive tests at least 3 months apart. The secondary end point was the development of celiac disease, which was defined for the purpose of this study as either a diagnosis on biopsy or persistently high levels of tTG antibodies. RESULTS: The median follow-up was 60 months (interquartile range, 46 to 77). Celiac disease autoimmunity developed in 786 children (12%). Of the 350 children who underwent biopsy, 291 had confirmed celiac disease; an additional 21 children who did not undergo biopsy had persistently high levels of tTG antibodies. The risks of celiac disease autoimmunity and celiac disease by the age of 5 years were 11% and 3%, respectively, among children with a single DR3-DQ2 haplotype, and 26% and 11%, respectively, among those with two copies (DR3-DQ2 homozygosity). In the adjusted model, the hazard ratios for celiac disease autoimmunity were 2.09 (95% confidence interval [CI], 1.70 to 2.56) among heterozygotes and 5.70 (95% CI, 4.66 to 6.97) among homozygotes, as compared with children who had the lowest-risk genotypes (DR4-DQ8 heterozygotes or homozygotes). Residence in Sweden was also independently associated with an increased risk of celiac disease autoimmunity (hazard ratio, 1.90; 95% CI, 1.61 to 2.25). CONCLUSIONS: Children with the HLA haplotype DR3-DQ2, especially homozygotes, were found to be at high risk for celiac disease autoimmunity and celiac disease early in childhood. The higher risk in Sweden than in other countries highlights the importance of studying environmental factors associated with celiac disease. (Funded by the National Institute of Diabetes and Digestive and Kidney Diseases and others.).

Monoclonal antibody blocking the recognition of an insulin peptide-MHC complex modulates type 1 diabetes.

The primary autoantigen triggering spontaneous type 1 diabetes mellitus in nonobese diabetic (NOD) mice is insulin. The major T-cell insulin epitope lies within the amino acid 9-23 peptide of the ß-chain (B:9-23). This peptide can bind within the peptide binding groove of the NOD MHC class II molecule (MHCII), IA(g7), in multiple positions or "registers." However, the majority of pathogenic CD4 T cells recognize this complex only when the insulin peptide is bound in register 3 (R3). We hypothesized that antibodies reacting specifically with R3 insulin-IA(g7) complexes would inhibit autoimmune diabetes specifically without interfering with recognition of other IA(g7)-presented antigens. To test this hypothesis, we generated a monoclonal antibody (mAb287), which selectively binds to B:9-23 and related variants when presented by IA(g7) in R3, but not other registers. The monoclonal antibody blocks binding of IA(g7)-B:10-23 R3 tetramers to cognate T cells and inhibits T-cell responses to soluble B:9-23 peptides and NOD islets. However, mAb287 has no effect on recognition of other peptides bound to IA(g7) or other MHCII molecules. Intervention with mAb287, but not irrelevant isotype matched antibody, at either early or late stages of disease development, significantly delayed diabetes onset by inhibiting infiltration by not only insulin-specific CD4 T cells, but also by CD4 and CD8 T cells of other specificities. We propose that peptide-MHC-specific monoclonal antibodies can modulate autoimmune disease without the pleiotropic effects of nonselective reagents and, thus, could be applicable to the treatment of multiple T-cell mediated autoimmune disorders.

Type 1 diabetes.

Over the past decade, knowledge of the pathogenesis and natural history of type 1 diabetes has grown substantially, particularly with regard to disease prediction and heterogeneity, pancreatic pathology, and epidemiology. Technological improvements in insulin pumps and continuous glucose monitors help patients with type 1 diabetes manage the challenge of lifelong insulin administration. Agents that show promise for averting debilitating disease-associated complications have also been identified. However, despite broad organisational, intellectual, and fiscal investments, no means for preventing or curing type 1 diabetes exists, and, globally, the quality of diabetes management remains uneven. This Seminar discusses current progress in epidemiology, pathology, diagnosis, and treatment of type 1 diabetes, and prospects for an improved future for individuals with this disease.

Immune intervention in type 1 diabetes.

Type 1 diabetes (T1D) is a chronic autoimmune disease that results in the specific immune destruction of insulin producing beta cells. Currently there is no cure for T1D and treatment for the disease consists of lifelong administration of insulin. Immunotherapies aimed at preventing beta cell destruction in T1D patients with residual c-peptide or in individuals developing T1D are being evaluated. Networks of researchers such as TrialNet and the Immune Tolerance Network in the U.S. and similar networks in Europe have been established to evaluate such immunotherapies. This review focuses on immune intervention for the prevention and amelioration of human T1D with a focus on potential immune suppressive, antigen specific and environmental therapies.

Structure-based selection of small molecules to alter allele-specific MHC class II antigen presentation.

Class II major histocompatibility molecules are the primary susceptibility locus for many autoimmune disorders, including type 1 diabetes. Human DQ8 and I-A(g7), in the NOD mouse model of spontaneous autoimmune diabetes, confers diabetes risk by modulating presentation of specific islet peptides in the thymus and periphery. We used an in silico molecular docking program to screen a large "druglike" chemical library to define small molecules capable of occupying specific structural pockets along the I-A(g7) binding groove, with the objective of influencing presentation to T cells of the autoantigen insulin B chain peptide consisting of amino acids 9-23. In this study we show, using both murine and human cells, that small molecules can enhance or inhibit specific TCR signaling in the presence of cognate target peptides, based upon the structural pocket targeted. The influence of compounds on the TCR response was pocket dependent, with pocket 1 and 6 compounds inhibiting responses and molecules directed at pocket 9 enhancing responses to peptide. At nanomolar concentrations, the inhibitory molecules block the insulin B chain peptide consisting of amino acids 9-23, endogenous insulin, and islet-stimulated T cell responses. Glyphosine, a pocket 9 compound, enhances insulin peptide presentation to T cells at concentrations as low as 10 nM, upregulates IL-10 secretion, and prevents diabetes in NOD mice. These studies present a novel method for identifying small molecules capable of both stimulating and inhibiting T cell responses, with potentially therapeutic applications.

Diabetogenic T cells recognize insulin bound to IAg7 in an unexpected, weakly binding register.

A peptide derived from the insulin B chain contains a major epitope for diabetogenic CD4(+) T cells in the NOD mouse model of type 1 diabetes (T1D). This peptide can fill the binding groove of the NOD MHCII molecule, IA(g7), in a number of ways or "registers." We show here that a diverse set of NOD anti-insulin T cells all recognize this peptide bound in the same register. Surprisingly, this register results in the poorest binding of peptide to IA(g7). The poor binding is due to an incompatibility between the p9 amino acid of the peptide and the unique IA(g7) p9 pocket polymorphisms that are strongly associated with susceptibility to T1D. Our findings suggest that the association of autoimmunity with particular MHCII alleles may be do to poorer, rather than more favorable, binding of the critical self-epitopes, allowing T-cell escape from thymic deletion.

Seroconversion to multiple islet autoantibodies and risk of progression to diabetes in children.

IMPORTANCE: Type 1 diabetes usually has a preclinical phase identified by circulating islet autoantibodies, but the rate of progression to diabetes after seroconversion to islet autoantibodies is uncertain. OBJECTIVE: To determine the rate of progression to diabetes after islet autoantibody seroconversion. DESIGN, SETTING, AND PARTICIPANTS: Data were pooled from prospective cohort studies performed in Colorado (recruitment, 1993-2006), Finland (recruitment, 1994-2009), and Germany (recruitment, 1989-2006) examining children genetically at risk for type 1 diabetes for the development of insulin autoantibodies, glutamic acid decarboxylase 65 (GAD65) autoantibodies, insulinoma antigen 2 (IA2) autoantibodies, and diabetes. Participants were all children recruited and followed up in the 3 studies (Colorado, 1962; Finland, 8597; Germany, 2818). Follow-up assessment in each study was concluded by July 2012. MAIN OUTCOMES AND MEASURES: The primary analysis was the diagnosis of type 1 diabetes in children with 2 or more autoantibodies. The secondary analysis was the diagnosis of type 1 diabetes in children with 1 autoantibody or no autoantibodies. RESULTS: Progression to type 1 diabetes at 10-year follow-up after islet autoantibody seroconversion in 585 children with multiple islet autoantibodies was 69.7% (95% CI, 65.1%-74.3%), and in 474 children with a single islet autoantibody was 14.5% (95% CI, 10.3%-18.7%). Risk of diabetes in children who had no islet autoantibodies was 0.4% (95% CI, 0.2%-0.6%) by the age of 15 years. Progression to type 1 diabetes in the children with multiple islet autoantibodies was faster for children who had islet autoantibody seroconversion younger than age 3 years (hazard ratio [HR], 1.65 [95% CI, 1.30-2.09; P < .001]; 10-year risk, 74.9% [95% CI, 69.7%-80.1%]) vs children 3 years or older (60.9% [95% CI, 51.5%-70.3%]); for children with the human leukocyte antigen (HLA) genotype DR3/DR4-DQ8 (HR, 1.35 [95% CI, 1.09-1.68; P = .007]; 10-year risk, 76.6% [95% CI, 69.2%-84%]) vs other HLA genotypes (66.2% [95% CI, 60.2%-72.2%]); and for girls (HR, 1.28 [95% CI, 1.04-1.58; P = .02];10-year risk, 74.8% [95% CI, 68.0%-81.6%]) vs boys (65.7% [95% CI, 59.3%-72.1%]). CONCLUSIONS AND RELEVANCE: The majority of children at risk of type 1 diabetes who had multiple islet autoantibody seroconversion progressed to diabetes over the next 15 years. Future prevention studies should focus on this high-risk population.

A functional variant of lymphoid tyrosine phosphatase is associated with type I diabetes.

We report that a single-nucleotide polymorphism (SNP) in the gene (PTPN22) encoding the lymphoid protein tyrosine phosphatase (LYP), a suppressor of T-cell activation, is associated with type 1 diabetes mellitus (T1D). The variants encoded by the two alleles, 1858C and 1858T, differ in a crucial amino acid residue involved in association of LYP with the negative regulatory kinase Csk. Unlike the variant encoded by the more common allele 1858C, the variant associated with T1D does not bind Csk.

Congruence as a measurement of extended haplotype structure across the genome.

BACKGROUND: Historically, extended haplotypes have been defined using only a few data points, such as alleles for several HLA genes in the MHC. High-density SNP data, and the increasing affordability of whole genome SNP typing, creates the opportunity to define higher resolution extended haplotypes. This drives the need for new tools that support quantification and visualization of extended haplotypes as defined by as many as 2000 SNPs. Confronted with high-density SNP data across the major histocompatibility complex (MHC) for 2,300 complete families, compiled by the Type 1 Diabetes Genetics Consortium (T1DGC), we developed software for studying extended haplotypes. METHODS: The software, called ExHap (Extended Haplotype), uses a similarity measurement we term congruence to identify and quantify long-range allele identity. Using ExHap, we analyzed congruence in both the T1DGC data and family-phased data from the International HapMap Project. RESULTS: Congruent chromosomes from the T1DGC data have between 96.5% and 99.9% allele identity over 1,818 SNPs spanning 2.64 megabases of the MHC (HLA-DRB1 to HLA-A). Thirty-three of 132 DQ-DR-B-A defined haplotype groups have > 50% congruent chromosomes in this region. For example, 92% of chromosomes within the DR3-B8-A1 haplotype are congruent from HLA-DRB1 to HLA-A (99.8% allele identity). We also applied ExHap to all 22 autosomes for both CEU and YRI cohorts from the International HapMap Project, identifying multiple candidate extended haplotypes. CONCLUSIONS: Long-range congruence is not unique to the MHC region. Patterns of allele identity on phased chromosomes provide a simple, straightforward approach to visually and quantitatively inspect complex long-range structural patterns in the genome. Such patterns aid the biologist in appreciating genetic similarities and differences across cohorts, and can lead to hypothesis generation for subsequent studies.

Predicting the onset of Addison's disease: ACTH, renin, cortisol and 21-hydroxylase autoantibodies.

CONTEXT: Autoantibodies to 21-hydroxylase (21OH-AA) precede onset of autoimmune Addison's disease (AD). Progression to AD can take months to years, and early detection of metabolic decompensation may prevent morbidity and mortality. OBJECTIVE: To define optimal methods of predicting progression to overt AD (defined by subnormal peak cortisol response to Cosyntropin) in 21OH-AA+ individuals. DESIGN, SETTING AND PARTICIPANTS: Individuals were screened for 21OH-AA at the Barbara Davis Center from 1993 to 2011. Subjects positive for 21OH-AA (n = 87) were tested, and the majority prospectively followed for the development of Addison's disease, including seven diagnosed with AD upon 21OH-AA discovery (discovered), seven who progressed to AD (progressors) and 73 nonprogressors. MAIN OUTCOME MEASURED: Plasma renin activity (PRA), ACTH, baseline cortisol, peak cortisol and 21OH-AA were measured at various time points relative to diagnosis of AD or last AD-free follow-up. RESULTS: Compared with nonprogressors, in the time period 2 months-2 years prior to the onset of AD, progressors were significantly more likely to have elevated ACTH (11-22 pM, P < 1E-4), with no significant differences in mean PRA (P = 0·07) or baseline cortisol (P = 0·08), and significant but less distinct differences seen with 21OH-AA levels (P < 1E-4) and poststimulation cortisol levels (P = 6E-3). CONCLUSION: Moderately elevated ACTH is a more useful early indicator of impending AD than 21OH-AA, PRA or peak cortisol, in the 2 months-2 years preceding the onset of AD.

Central nervous system destruction mediated by glutamic acid decarboxylase-specific CD4+ T cells.

High titers of autoantibodies against glutamic acid decarboxylase (GAD) 65 are commonly observed in patients suffering from type 1 diabetes as well as stiff-person syndrome (SPS), a disorder that affects the CNS, and a variant of SPS, progressive encephalomyelitis with rigidity and myoclonus. Although there is a considerable amount of data focusing on the role of GAD65-specific CD4(+) T cells in type 1 diabetes, little is known about their role in SPS. In this study, we show that mice possessing a monoclonal GAD65-specific CD4(+) T cell population (4B5, PA19.9G11, or PA17.9G7) develop a lethal encephalomyelitis-like disease in the absence of any other T cells or B cells. GAD65-reactive CD4(+) T cells were found throughout the CNS in direct concordance with GAD65 expression and activated microglia: proximal to the circumventricular organs at the interface between the brain parenchyma and the blood-brain barrier. In the presence of B cells, high titer anti-GAD65 autoantibodies were generated, but these had no effect on the incidence or severity of disease. In addition, GAD65-specific CD4(+) T cells isolated from the brain were activated and produced IFN-gamma. These findings suggest that GAD65-reactive CD4(+) T cells alone mediate a lethal encephalomyelitis-like disease that may serve as a useful model to study GAD65-mediated diseases of the CNS.

Measuring adrenal autoantibody response: interlaboratory concordance in the first international serum exchange for the determination of 21-hydroxylase autoantibodies.

21-hydroxylase autoantibodies (21OHAb) are the gold standard immune marker to identify patients with clinical or subclinical autoimmune Addison's disease (AAD). No assessment of interlaboratory concordance has been made for 21OHAb measurement. Serum samples from 267 patients with primary adrenal insufficiency and from 83 healthy control subjects were distributed to four independent laboratories that determined presence and titer of 21OHAb, by using radiobinding assays with either in vitro translated 35S-radiolabelled or 125I-radiolabelled autoantigen. Cohen's κ of inter-rater agreement ranged from 0.857 to 0.983, showing a very good concordance of the positive/negative score among the four laboratories. Passing-Bablok regression showed a good agreement of 21OHAb titers arranged by ranks, but important discrepancies emerged at the Bland-Altman plot, as the repeatability coefficient was much higher than the laboratory cut-offs, which indicates that results from different laboratories cannot be used interchangeably. A standardization international program for 21OHAb measurement is strongly needed.

Insulin as an autoantigen in NOD/human diabetes.

Although multiple islet autoantigens are recognized by T lymphocytes and autoantibodies before the development of type 1A (immune-mediated diabetes), there is increasing evidence that autoimmunity to insulin may be central to disease pathogenesis. Evidence is strongest for the NOD mouse model where blocking immune responses to insulin prevents diabetes, and insulin peptides can be utilized to induce diabetes. In man insulin gene polymorphisms are associated with disease risk, and autoantibodies and T cells reacting with multiple insulin/proinsulin epitopes are present. It is not currently clear why insulin autoimmunity is so prominent and frequent, and though insulin can be used to immunologically prevent diabetes of NOD mice, insulin-based preventive immunoregulation of diabetes in man is not yet possible.

Immunization with an insulin peptide-MHC complex to prevent type 1 diabetes of NOD mice.

BACKGROUND: Mutating the insulin B:9-23 peptide prevents diabetes in NOD mice. Thus, the trimolecular complex of I-Ag7-insulin B:9-23 peptide-TCR may be essential for the development of spontaneous diabetes. Pathogenic T cells recognize the B:9-23 peptide presented by I-Ag7 in what is termed register 3, with the B22 basic amino acid (arginine) of the peptide bound in pocket 9 of I-Ag7. Our hypothesis is that immunization with an insulin B:12-22 peptide linked to I-Ag7 in register 3 (I-Ag7-B:RE#3 complex) can induce specific antibodies to the complex, block pathogenic TCRs, and thus prevent diabetes. METHODS: We immunized young NOD mice with recombinant I-Ag7-B:RE#3 protein, in which two amino acids of the peptide were mutated to fix the peptide in register 3, and investigated the induced antibodies targeted to the peptide in register 3. RESULTS: Specific antibodies targeting I-Ag7-B:RE#3 but not I-Ag7-HEL were identified in the sera of I-Ag7-B:RE#3 immunized mice. The sera inhibited B:9-23-induced T-cell responses in vitro. I-Ag7-B:RE#3 immunization delayed progression to diabetes (versus PBS, p=0.0005), while immunization with I-Ag7-HEL control complex did not. CONCLUSIONS: Immunization with I-Ag7-B:RE#3 complex significantly delays the development of insulin autoantibodies and the onset of diabetes in NOD mice, which is associated with the induction of I-Ag7-B:RE#3 antibodies.

Erythrocyte membrane omega-3 fatty acid levels and omega-3 fatty acid intake are not associated with conversion to type 1 diabetes in children with islet autoimmunity: the Diabetes Autoimmunity Study in the Young (DAISY).

AIM: We investigated whether omega-3 fatty acid intake and erythrocyte membrane omega-3 fatty acid levels are associated with conversion to type 1 diabetes in children with islet autoimmunity (IA). METHODS: The Diabetes Autoimmunity Study in the Young is following children at increased genetic risk for type 1 diabetes for the development of persistent IA, as defined as being positive for glutamic acid decarboxylase 65, i, or insulin autoantibodies on two consecutive visits, and then for the development of type 1 diabetes, as diagnosed by a physician. One hundred and sixty-seven children with persistent IA were followed for a mean of 4.8 yr, and 45 of these developed type 1 diabetes at a mean age of 8.7 yr. Erythrocyte membrane fatty acids (as a percent of total lipid) and dietary fatty acid intake (estimated via food frequency questionnaire) were analyzed as time-varying covariates in proportional hazards survival analysis, with follow-up time starting at detection of the first autoantibody. RESULTS: Neither dietary intake of omega-3 fatty acids nor omega-6 fatty acids were associated with conversion to type 1 diabetes, adjusting for human leukocyte antigen (HLA)-DR, family history of type 1 diabetes, age at first IA positivity, maternal age, maternal education, and maternal ethnicity. Adjusting for HLA-DR, family history of type 1 diabetes and age at first IA positivity, omega-3 and omega-6 fatty acid levels of erythrocyte membranes were not associated with conversion to type 1 diabetes. CONCLUSIONS: In this observational study, omega-3 fatty acid intake and status are not associated with conversion to type 1 diabetes in children with IA.

Persistently autoantibody negative (PAN) type 1 diabetes mellitus in children.

BACKGROUND: Autoantibody-negative children diagnosed with type 1 diabetes might have unrecognized monogenic or type 2 diabetes. RESEARCH DESIGN AND METHODS: At diagnosis of type 1 diabetes (between ages 0.5 and 16.3 yr, n = 470), autoantibodies [glutamic acid decarboxylase (GAD), insulinoma-associated protein 2 (IA2), insulin autoantibodies (IAA), and/or islet cell antibody (ICA)] were positive (ab+) in 330 and negative in 37 (unknown in 103). Autoantibody-negative patients were retested at median diabetes duration of 3.2 yr (range 0.9-16.2) for autoantibodies (GAD, IA2, ZnT8), human leukocyte antigen (HLA) typing, non-fasting C-peptide, and sequencing of HNF4A, HNF1A, KCNJ11, and INS. RESULTS: Nineteen (5% of 367) remained persistently autoantibody negative (PAN), 17 were positive on repeat testing (PORT), and 1 refused retesting. No mutations were found in PORT. One PAN was heterozygous for P112L mutation in HNF1A and transferred from insulin to oral gliclazide. Another PAN transferred to metformin and the diagnosis was revised to type 2 diabetes. The remaining 17 PAN were indistinguishable from the ab+ group by clinical characteristics. HLA genotype was at high risk for type 1 diabetes in 82% of remaining PAN and 100% of PORT. After excluding patients with diabetes duration <1 yr, C-peptide was detectable more frequently in the remaining PAN (7/16) and PORT (6/17) than in a random selection of ab+ (3/28, p = 0.03). CONCLUSIONS: The diagnosis of type 1 diabetes should be reevaluated in PAN patients, because a subset has monogenic or type 2 diabetes. The remaining PAN have relatively preserved C-peptide compared with ab+, suggesting slower ß-cell destruction, but a very high frequency of diabetogenic HLA, implying that type 1B (idiopathic) diabetes is rare.

Elimination of maternally transmitted autoantibodies prevents diabetes in nonobese diabetic mice.

The influence of maternally transmitted immunoglobulins on the development of autoimmune diabetes mellitus in genetically susceptible human progeny remains unknown. Given the presence of islet beta cell-reactive autoantibodies in prediabetic nonobese diabetic (NOD) mice, we abrogated the maternal transmission of such antibodies in order to assess their influence on the susceptibility of progeny to diabetes. First, we used B cell-deficient NOD mothers to eliminate the transmission of maternal immunoglobulins. In a complementary approach, we used immunoglobulin transgenic NOD mothers to exclude autoreactive specificities from the maternal B-cell repertoire. Finally, we implanted NOD embryos in pseudopregnant mothers of a non-autoimmune strain. The NOD progeny in all three groups were protected from spontaneous diabetes. These findings demonstrate that the maternal transmission of antibodies is a critical environmental parameter influencing the ontogeny of T cell-mediated destruction of islet beta cells in NOD mice. It will be important to definitively determine whether the transmission of maternal autoantibodies in humans affects diabetes progression in susceptible offspring.

Prime role for an insulin epitope in the development of type 1 diabetes in NOD mice.

A fundamental question about the pathogenesis of spontaneous autoimmune diabetes is whether there are primary autoantigens. For type 1 diabetes it is clear that multiple islet molecules are the target of autoimmunity in man and animal models. It is not clear whether any of the target molecules are essential for the destruction of islet beta cells. Here we show that the proinsulin/insulin molecules have a sequence that is a primary target of the autoimmunity that causes diabetes of the non-obese diabetic (NOD) mouse. We created insulin 1 and insulin 2 gene knockouts combined with a mutated proinsulin transgene (in which residue 16 on the B chain was changed to alanine) in NOD mice. This mutation abrogated the T-cell stimulation of a series of the major insulin autoreactive NOD T-cell clones. Female mice with only the altered insulin did not develop insulin autoantibodies, insulitis or autoimmune diabetes, in contrast with mice containing at least one copy of the native insulin gene. We suggest that proinsulin is a primary autoantigen of the NOD mouse, and speculate that organ-restricted autoimmune disorders with marked major histocompatibility complex (MHC) restriction of disease are likely to have specific primary autoantigens.

Conserved T cell receptor alpha-chain induces insulin autoantibodies.

A fundamental question is what are the molecular determinants that lead to spontaneous preferential targeting of specific autoantigens in autoimmune diseases, such as the insulin B:9-23 peptide sequence in type 1 diabetes. Anti-insulin B:9-23 T cell clones isolated from prediabetic NOD islets have a conserved Valpha-segment/Jalpha-segment, but no conservation of the alpha-chain N region and no conservation of the Vbeta-chain. Here, we show that the conserved T cell receptor alpha-chain generates insulin autoantibodies when transgenically or retrogenically introduced into mice without its corresponding Vbeta. We suggest that a major part of the mystery as to why islet autoimmunity develops relates to recognition of a primary insulin peptide by a conserved alpha chain T cell receptor.