Autoantibody appearance and risk for development of childhood diabetes in offspring of parents with type 1 diabetes: the 2-year analysis of the German BABYDIAB Study

The temporal development of autoantibodies was studied in 1,353 offspring of parents with type 1 diabetes. Islet cell antibodies (ICAs) and autoantibodies to insulin (IAAs), glutamic acid decarboxylase, and IA-2 were measured at birth, 9 months, 2 years, and 5 years of age. At birth, no offspring had islet autoimmunity other than maternally acquired antibodies, which were shown to influence antibody prevalence up to age 6 months. Antibodies detected thereafter were likely to represent a true de novo production, since prevalences were the same for offspring from mothers and fathers with diabetes, antibodies detected at 9 months were almost always confirmed in the 2-year sample and were associated with an increased likelihood of having or developing other antibodies. By 2 years of age, autoantibodies appeared in 11% of offspring, 3.5% having more than one autoantibody. IAAs were detected most frequently, and few had autoantibodies in the absence of IAAs. In 23 offspring with multiple islet autoantibodies, IAAs preceded other antibodies in 10 cases and were first detected concurrently with other antibodies in 12 and after detection of other antibodies in 1. Development of additional antibodies and changes in levels, including decline of IAAs at older age, was frequent. Nine children, all with IAAs and ICAs, developed diabetes. Overall cumulative risk for disease by 5 years of age was 1.8% (95% CI 0.2-3.4) and was 50% (95% CI 19-81) for offspring with more than one autoantibody in their 2-year sample. Autoimmunity associated with childhood diabetes is an early event and a dynamic process. Presence of IAAs is a consistent feature of this autoimmunity, and IAA detection can identify children at risk.     

Genetic effects on age-dependent onset and islet cell autoantibody markers in type 1 diabetes

Age-dependent associations between type 1 diabetes risk genes HLA, INS VNTR, and CTLA-4 and autoantibodies to GAD65 (GADAs), ICA512/IA-2, insulin, and islet cells were determined by logistic regression analysis in 971 incident patients with type 1 diabetes and 702 control subjects aged 0-34 years. GADAs were associated with HLA-DQ2 in young but not in older patients (P = 0.009). Autoantibodies to insulin were negatively associated with age (P < 0.0001) but positively associated with DQ8 (P = 0.03) and with INS VNTR (P = 0.04), supporting possible immune tolerance induction. ICA512/IA-2 were negatively associated with age (P < 0.0001) and with DQ2 (P < 0.0001) but positively associated with DQ8 (P = 0.04). Males were more likely than females to be negative for GADA (P < 0.0001), autoantibodies to islet cells (P = 0.04), and all four autoantibody markers (P = 0.004). The CTLA-4 3' end microsatellite marker was not associated with any of the autoantibodies. We conclude that age and genetic factors such as HLA-DQ and INS VNTR need to be combined with islet autoantibody markers when evaluating the risk for type 1 diabetes development.     

Screening for insulitis in adult autoantibody-positive organ donors

Antibodies against islet cell antigens are used as predictive markers of type 1 diabetes, but it is unknown whether they reflect an ongoing autoimmune process in islet tissue. We investigated whether organs from adult donors that are positive for autoantibodies (aAbs) against islet cell antigens exhibit insulitis and/or a reduced beta-cell mass. Serum from 1,507 organ donors (age 25-60 years) was analyzed for islet cell antibodies (ICAs), glutamate decarboxylase aAbs (GADAs), insulinoma-associated protein 2 aAbs (IA-2As), and insulin aAbs. Tissue from the 62 aAb+ donors (4.1%) and from matched controls was examined for the presence of insulitis and for the relative area of insulin+ cells. Insulitis was detected in two cases; it was found in 3 and 9% of the islets and consisted of CD3+/CD8+ T-cells and CD68+ macrophages; in one case, it was associated with insulin+ cells that expressed the proliferation marker Ki67. Both subjects belonged to the subgroup of three donors with positivity for ICA, GADA, and IA-2-Ab and for the susceptible HLA-DQ genotype. Comparison of relative beta-cell area in aAb+ and aAb- donors did not show a significant difference. Insulitis was found in two of the three cases that presented at least three aAbs but in none of the other 59 antibody+ subjects or 62 matched controls. It was only detected in <10% of the islets, some of which presented signs of beta-cell proliferation. No decrease in beta-cell mass was detected in cases with insulitis or in the group of antibody+ subjects.     

Progression to type I diabetes in autoimmune endocrine patients with islet cell antibodies

In an 11-yr screening program carried out on serum samples sent to an autoimmune serology laboratory, 158 patients with clinical or subclinical autoimmune endocrine manifestations and islet cell antibodies (ICAs) in the absence of overt diabetes were identified and followed for the development of insulin-dependent (type I) diabetes. Twenty-two (13.9%) developed type I diabetes in a follow-up of up to 12 yr (mean +/- SE 4.8 +/- 3.2 yr). The probability of being free of type I diabetes was 69.8% at 10 yr after the first detection of ICAs. Progression to disease was influenced by 1) the amount of ICAs represented by high titers (63% of those with ICAs greater than or equal to 20 Juvenile Diabetes Foundation units being free of type I diabetes at 10 yr), ICA persistency (59% being free of type I diabetes; P less than 0.02 vs. nonpersistent ICA), and complement-fixing (CF)-ICAs (63% being free of type I diabetes; P less than 0.05 vs. non-CF-ICA); 2) the coexistence of insulin autoantibodies (IAAs) (25% being free of type I diabetes; P less than 0.005 vs. IAA-); and 3) a positive family history (1st-degree relative) for type I diabetes (32% being free of type I diabetes; P less than 0.005 vs. no family history). There was a trend for diabetes to develop earlier in males of a younger age. No relationships were found with the number, type, or clinical expression of the associated autoimmunities or with a family history of such disorders.(ABSTRACT TRUNCATED AT 250 WORDS)     

Glycotoxin and autoantibodies are additive environmentally determined predictors of type 1 diabetes: a twin and population study

In type 1 diabetes, diabetes-associated autoantibodies, including islet cell antibodies (ICAs), reflect adaptive immunity, while increased serum N(ε)-carboxymethyl-lysine (CML), an advanced glycation end product, is associated with proinflammation. We assessed whether serum CML and autoantibodies predicted type 1 diabetes and to what extent they were determined by genetic or environmental factors. Of 7,287 unselected schoolchildren screened, 115 were ICA(+) and were tested for baseline CML and diabetes autoantibodies and followed (for median 7 years), whereas a random selection (n = 2,102) had CML tested. CML and diabetes autoantibodies were determined in a classic twin study of twin pairs discordant for type 1 diabetes (32 monozygotic, 32 dizygotic pairs). CML was determined by enzyme-linked immunosorbent assay, autoantibodies were determined by radioimmunoprecipitation, ICA was determined by indirect immunofluorescence, and HLA class II genotyping was determined by sequence-specific oligonucleotides. CML was increased in ICA(+) and prediabetic schoolchildren and in diabetic and nondiabetic twins (all P < 0.001). Elevated levels of CML in ICA(+) children were a persistent, independent predictor of diabetes progression, in addition to autoantibodies and HLA risk. In twins model fitting, familial environment explained 75% of CML variance, and nonshared environment explained all autoantibody variance. Serum CML, a glycotoxin, emerged as an environmentally determined diabetes risk factor, in addition to autoimmunity and HLA genetic risk, and a potential therapeutic target.     

Patterns of β-Cell Autoantibody Appearance and Genetic Associations During the First Years of Life

We analyzed demographic and genetic differences between children with various diabetes-associated autoantibodies reflecting the autoimmune process. In a prospective birth cohort comprising children with HLA-conferred susceptibility to type 1 diabetes (T1D), the pattern of autoantibody appearance was analyzed in 520 children with advanced β-cell autoimmunity associated with high risk for disease. In 315 cases, a single biochemical autoantibody could be identified in the first positive sample as insulin (insulin autoantibody [IAA]) in 180, as GAD (GAD antibody [GADA]) in 107, and as IA-2 antigen (IA-2 antibody [IA-2A]) in 28. The age at seroconversion differed significantly between the three groups (P = 0.003). IAA as the first autoantibody showed a peak time of appearance during the second year of life, whereas GADA as the first autoantibody peaked later, between 3 and 5 years of age. The risk-associated insulin gene rs689 A/A genotypes were more frequent in children with IAA as the first autoantibody compared with the other children (P = 0.002). The primary autoantigen in the development of β-cell autoimmunity and T1D seems to strongly correlate with age and genetic factors, indicating heterogeneity in the initiation of the disease process.Immune destruction of the insulin-producing β-cells leading to clinical type 1 diabetes (T1D) is often a long-lasting process. During this preclinical period, antibody responses to several autoantigens can be detected. The number of detectable autoantibodies usually increases with time and correlates with the probability of disease development (1). It is not clear whether a primary autoantigen does exist and immune responses against other molecules represent secondary antigen spreading, or whether multiple molecules can be primary targets (2). Heterogeneities in the preferential age of appearance and in HLA associations have been described for various autoantibodies (3–6). The early appearance and association with younger age at diagnosis of insulin autoantibodies (IAAs) together with the essential role of the insulin molecule in the NOD mouse model have implied (prepro)insulin as the primary antigen (7). Antibody responses to all major antigens nevertheless accumulate with increasing age during the follow-up.Natural history studies of children at high risk who have undergone sequential blood sampling during short intervals provide a unique possibility for analyzing the appearance of autoimmunity in detail and for helping to resolve the question of whether one or multiple primary antigens exist. In the current study, we analyzed the Finnish Type 1 Diabetes Prediction and Prevention (DIPP) study children who developed advanced β-cell autoimmunity, indicating multiple autoantibodies and high risk of disease, and correlated the specificity of the primary autoantibody with demographic and genetic parameters.     

Genetic markers, humoral autoimmunity, and prediction of type 1 diabetes in siblings of affected children. Childhood Diabetes in Finland Study Group

The relationships between genetic markers and disease-associated autoantibodies were studied in an unselected population of 701 siblings of children with type 1 diabetes, and the predictive characteristics of these markers over a period of 9 years were determined. Increased prevalences of all the antibodies were closely associated with HLA identity to the index case, the DR4 and DQB1*0302 alleles, and the DR3/4 phenotype and the DQB1*02/0302 genotype. Antibodies to GAD (GADA) were also associated with the DR3 and DQB1*02 alleles. Siblings carrying the protective DR2 and DQB1*0602-3 alleles were characterized by lower frequencies of islet cell antibodies (ICA), antibodies to IA-2 (IA-2A), and GADA. Higher levels of ICA were related to HLA identity, the DR4 and DQB1*0302 alleles, and the susceptible DQB1 genotypes, while no significant differences were observed in the levels of IA-2A, GADA, or insulin autoantibodies among siblings with different HLA risk markers. The DR2 or DQB1*0602-3 alleles were not related to the levels of any antibody specificity. A combination of the genetic markers and autoantibodies increased the positive predictive values of all autoantibodies substantially, which may have clinical implications when evaluating the risk of developing type 1 diabetes at the individual level or when recruiting high-risk individuals for intervention trials. However, because such combinations also resulted in reduced sensitivity, autoantibodies alone rather than in combination with genetic markers are recommended as the first-line screening in siblings. Finally, not all siblings with a broad humoral autoimmune response or high-risk genetic markers present with type 1 diabetes, while some with a low genetic risk and weak initial signs of humoral autoimmunity may progress to disease.     

Comparison of insulin autoantibodies in diabetes-related and healthy populations by precise displacement ELISA

The second international workshop on insulin autoantibodies (IAAs) demonstrated improved concordance among laboratories with both radioimmunoassay (RIA) and enzyme-linked immunosorbent assay (ELISA) when measurements were based on signals displaceable by preincubation with excess insulin. This feature has been incorporated into our original ELISA for IAAs, and the assay was used to compare IAAs in diabetes-related and healthy populations. The serum from a healthy islet cell antibody (ICA)+ and IAA+ subject was used to construct standard curves with and without preincubation with 1 U/ml human insulin. Reporting results in arbitrary displacement (delta +/- IAA) units derived from the standard curve improved precision and increased the specificity of the assay. Frequency analysis of the results from 200 control adults did not show a normal distribution, and cumulative frequency analysis demonstrated two populations: 10 of 200 (5%) control adults, 8 of 241 (3.3%) healthy schoolchildren, and 18 of 229 (7.9%) non-insulin-dependent diabetes mellitus (NIDDM) patients had IAAs greater than 12 delta +/- IAA units. On the same basis, we tested samples from 89 individuals in the prospective Bart's Windsor Family Study for insulin-dependent diabetes mellitus (IDDM), 31 of whom had ICAs greater than 5 Juvenile Diabetes Foundation (JDF) units. Of those with ICAs greater than 5 JDF units, 12 developed IDDM and 1 developed NIDDM in 10 yr of study. IAAs greater than 12 delta +/- IAA units were found in 6 of 12 (50%) who became diabetic and in 4 of 18 (22%) who remain healthy.(ABSTRACT TRUNCATED AT 250 WORDS)     

Rituximab selectively suppresses specific islet antibodies

OBJECTIVE

The TrialNet Study Group evaluated rituximab, a B-cell–depleting monoclonal antibody, for its effect in new-onset patients with type 1A diabetes. Rituximab decreased the loss of C-peptide over the first year of follow-up and markedly depleted B lymphocytes for 6 months after administration. This article analyzes the specific effect of rituximab on multiple islet autoantibodies.

RESEARCH DESIGN AND METHODS

A total of 87 patients between the ages of 8 and 40 years received either rituximab or a placebo infusion weekly for four doses close to the onset of diabetes. Autoantibodies to insulin (IAAs), GAD65 (GADAs), insulinoma-associated protein 2 (IA2As), and ZnT8 (ZnT8As) were measured with radioimmunoassays. The primary outcome for this autoantibody analysis was the mean level of autoantibodies during follow-up.

RESULTS

Rituximab markedly suppressed IAAs compared with the placebo injection but had a much smaller effect on GADAs, IA2As, and ZnT8As. A total of 40% (19 of 48) of rituximab-treated patients who were IAA positive became IAA negative versus 0 of 29 placebo-treated patients (P < 0.0001). In the subgroup (n = 6) treated within 50 days of diabetes, IAAs were markedly suppressed by rituximab in all patients for 1 year and for four patients as long as 3 years despite continuing insulin therapy. Independent of rituximab treatment, the mean level of IAAs at study entry was markedly lower (P = 0.035) for patients who maintained C-peptide levels during the first year of follow-up in both rituximab-treated and placebo groups.

CONCLUSIONS

A single course of rituximab differentially suppresses IAAs, clearly blocking IAAs for >1 year in insulin-treated patients. For the patients receiving insulin for >2 weeks prior to rituximab administration, we cannot assess whether rituximab not only blocks the acquisition of insulin antibodies induced by insulin administration and/or also suppresses preformed insulin autoantibodies. Studies in prediabetic non–insulin-treated patients will likely be needed to evaluate the specific effects of rituximab on levels of IAAs.Although the anti-CD20 monoclonal antibody rituximab (Rituxan; Genentech, Biogen-IDEC Pharmaceuticals) originally was introduced for therapy of B-cell lymphomas (1), and subsequently applied to a series of antibody-mediated autoimmune disorders, it also has a role in what were thought to be classic T-cell–mediated autoimmune disorders, such as multiple sclerosis (2,3). In several of these diseases, therapeutic responses occur without a change in levels of characteristic autoantibodies. For some immune-mediated disorders, it has been reported that only a subset of autoantibodies decreases following rituximab. For example, it has been reported that rituximab therapy does not decrease the overall thyrotropin receptor–binding antibody, whereas stimulatory thyrotropin receptor–binding antibodies were decreased (4). The etiology of this differential effect is unknown, but it has been hypothesized to relate to the site of autoantibody production, with the observation that although rituximab does not target plasma cells, it does alter tertiary lymphoid structures and short-lived plasma cells that do not reside in the bone marrow (5).The quantitative effect of rituximab on islet autoantibodies in patients with diabetes has not been described. Type 1A, or immune-mediated, diabetes is believed to result from T-cell–mediated destruction of islet β-cells (6). Although T cells are dominant determinants of β-cell destruction in the NOD mouse, and diabetes has been reported in one child lacking B cells (7), multiple studies document a role for both B lymphocytes and autoantibodies in the NOD mouse model (8–11). For both humans and the NOD mouse, anti-CD20 antibodies suppress disease progression (11,12). The study by Pescovitz et al. (12) documented the preservation of C-peptides relative to placebo patients at the 1-year follow-up (see Supplementary Appendix). In this study, we analyzed the effects of rituximab on islet autoantibody levels in both placebo- and rituximab-treated new-onset patients from this trial, using a fluid-phase radioimmunoassay to detect autoantibodies against multiple islet antigens (autoantibodies to insulin [IAAs], GAD65 [GADAs], insulinoma-associated protein 2 [IA-2; IA2As], and ZnT8 [ZnT8As]).     

Predictive Characteristics of Diabetes-Associated Autoantibodies Among Children With HLA-Conferred Disease Susceptibility in the General Population

OBJECTIVE

As data on the predictive characteristics of diabetes-associated autoantibodies for type 1 diabetes in the general population are scarce, we assessed the predictive performance of islet cell autoantibodies (ICAs) in combination with autoantibodies against insulin (IAAs), autoantibodies against GAD, and/or islet antigen 2 for type 1 diabetes in children with HLA-defined disease predisposition recruited from the general population.

RESEARCH DESIGN AND METHODS

We observed 7,410 children from birth (median 9.2 years) for β-cell autoimmunity and diabetes. If a child developed ICA positivity or diabetes, the three other antibodies were measured in all samples available from that individual. Persistent autoantibody positivity was defined as continued positivity in at least two sequential samples including the last available sample.

RESULTS

Pre-diabetic ICA positivity was observed in 1,173 subjects (15.8%), 155 of whom developed type 1 diabetes. With ICA screening, 86% of 180 progressors (median age at diagnosis 5.0 years) were identified. Positivity for four antibodies was associated with the highest disease sensitivity (54.4%) and negative predictive values (98.3%) and the lowest negative likelihood ratio (0.5). The combination of persistent ICA and IAA positivity resulted in the highest positive predictive value (91.7%), positive likelihood ratio (441.8), cumulative disease risk (100%), and specificity (100%). Young age at seroconversion, high ICA level, multipositivity, and persistent positivity for IAA were significant risk markers for type 1 diabetes.

CONCLUSIONS

Within the general population, the combination of HLA and autoantibody screening resulted in disease risks that are likely to be as high as those reported among autoantibody-positive siblings of children with type 1 diabetes.Type 1 diabetes is an immune-mediated disease that leads to the destruction of the pancreatic β-cells and eventually to total dependence on exogenous insulin. The clinical manifestation of the disease is preceded by a preclinical phase, during which diabetes-associated autoantibodies (DAAs) can be detected in the peripheral circulation. The timing and the type of autoantibodies to appear have been used as predictive markers for type 1 diabetes among first-degree relatives of affected individuals (1), but data on the predictive value of DAAs in the background population, from whom ∼90% of new cases are derived, are scarce (2).Today, type 1 diabetes is one of the most common severe chronic ailments of children and adolescents in developed countries (3–5), and its incidence is continuously increasing. In Finland, the incidence is highest in the world, reaching 64 new cases per 100,000 children ages <15 years in 2005 (6). In 1994, a birth cohort study aimed at predicting and preventing type 1 diabetes in the general population was launched. The current work represents data from the first 14 years of this study, assessing the predictive characteristics of DAAs in a population-derived cohort of children with HLA-conferred susceptibility to type 1 diabetes.     

Rising incidence of type 1 diabetes is associated with altered immunophenotype at diagnosis

The incidence of type 1 diabetes has increased rapidly over recent decades, particularly in young children. We aimed to determine whether this rise was associated with changes in patterns of humoral islet autoimmunity at diagnosis. Autoantibodies to insulin (IAA), GAD (GADA), islet antigen-2 (IA-2A), and zinc transporter 8 (ZnT8A) were measured by radioimmunoassay in sera collected from children and young adults with newly diagnosed type 1 diabetes between 1985 and 2002. The influence of date of diagnosis on prevalence and level of autoantibodies was investigated by logistic regression with adjustment for age and HLA class II genetic risk. Prevalence of IA-2A and ZnT8A increased significantly over the period studied, and this was mirrored by raised levels of IA-2A, ZnT8A, and IA-2β autoantibodies (IA-2βA). IAA and GADA prevalence and levels did not change. Increases in IA-2A, ZnT8A, and IA-2βA at diagnosis during a period of rising incidence suggest that the process leading to type 1 diabetes is now characterized by a more intense humoral autoimmune response. Understanding how changes in environment or lifestyle alter the humoral autoimmune response to islet antigens should help explain why the incidence of type 1 diabetes is increasing and may suggest new strategies for preventing disease.     

Antibodies to GAD and tryptic fragments of islet 64K antigen as distinct markers for development of IDDM. Studies with identical twins.

Insulin-dependent diabetes mellitus (IDDM) is associated with antibodies to a 64,000-M(r) islet cell protein, at least part of which is identified as glutamic acid decarboxylase (GAD). These antibodies are detected as two distinct antibody specificities to 50,000-M(r) and 37,000/40,000-M(r) tryptic fragments of the autoantigen (50K and 37K antibodies, respectively). We determined the frequencies of antibodies to intact GAD, tryptic fragments of islet 64,000-M(r) antigen, islet cell antibodies (ICAs), and insulin autoantibodies (IAAs) in sera from 58 nondiabetic identical twins of patients with IDDM, of whom 12 subsequently developed diabetes. ICA, antibodies to intact GAD, and those to tryptic fragments were detected at similar frequencies in prediabetic twins (67-75%), but only 25% had IAA. Of 46 twins who remain nondiabetic, GAD antibodies, 50K antibodies, and ICA were detected in 6 (13%), 7 (15%), and 5 (11%), respectively, whereas only 1 (2%) possessed 37K antibodies and 2 (4%) had IAA. Eight of 9 twins with 37K antibodies and all 6 twins with ICA greater than 20 Juvenile Diabetes Foundation U have developed diabetes. Antibodies to GAD are sensitive markers for diabetes development but may also be present in genetically susceptible individuals who are unlikely to develop disease. Antibodies to 37,000/40,000-M(r) fragments of the 64,000-M(r) antigen or high-titer ICA were the best markers for diabetes development in these twins.     

Novel Association Between Immune-Mediated Susceptibility Loci and Persistent Autoantibody Positivity in Type 1 Diabetes

Islet autoantibodies detected at disease onset in patients with type 1 diabetes are signs of an autoimmune destruction of the insulin-producing β-cells. To further investigate the genetic determinants of autoantibody positivity, we performed dense immune-focused genotyping on the Immunochip array and tested for association with seven disease-specific autoantibodies in a large cross-sectional cohort of 6,160 type 1 diabetes–affected siblings. The genetic association with positivity for GAD autoantibodies (GADAs), IA2 antigen (IA-2A), zinc transporter 8, thyroid peroxidase, gastric parietal cells (PCAs), tissue transglutaminase, and 21-hydroxylase was tested using a linear mixed-model regression approach to simultaneously control for population structure and family relatedness. Four loci were associated with autoantibody positivity at genome-wide significance. Positivity for GADA was associated with 3q28/LPP, for IA-2A with 1q23/FCRL3 and 11q13/RELA, and for PCAs with 2q24/IFIH1. The 3q28 locus showed association after only 3 years duration and might therefore be a marker of persistent GADA positivity. The 1q23, 11q13, and 2q24 loci were associated with autoantibodies close to diabetes onset and constitute candidates for early screening. Major susceptibility loci for islet autoantibodies are separate from type 1 diabetes risk, which may have consequences for intervention strategies to reduce autoimmunity.     

HLA-associated insulin autoantibody formation in newly diagnosed type I diabetic patients

To assess a possible HLA association with anti-insulin autoantibodies (IAAs) in human insulin-dependent (type I) diabetes, 51 newly diagnosed type I diabetic patients (mean age 22 +/- 8 yr) were typed for HLA-DR and HLA-DQ and studied for IAAs before exogenous insulin therapy with a competitive radioimmunoassay (normal range less than or equal to 49 nU/ml). The level of IAAs in 16 patients exceeded our upper limit of normal, and 18 had high-titer islet cell antibodies (ICAs; greater than or equal to 40 Juvenile Diabetes Foundation U). A striking association with HLA-DR4 (DQw3) in both the prevalence and the level of IAAs was found (IAA positivity in patients with DR4/4 vs. DR4 heterozygous vs. non-DR4: 90 vs. 29%, corrected [c] P less than 0.01, vs. 5%, Pc less than 0.0001; IAA positivity in patients with DR4 vs. non-DR4: 50 vs. 5%, Pc less than 0.005; IAA level in patients with DR4/4 vs. DR4 heterozygous vs. non-DR4: 111 vs. 17 nU/ml, Pc less than 0.01, vs. 20 nU/ml, Pc less than 0.0001; IAA level in patients with DR4 vs. non-DR4: 45 vs. 20 nU/ml, Pc less than 0.01). In contrast, none of the DR3+ subjects had IAAs above normal range, except in conjunction with DR4 (DR3 vs. non-DR3: 12 vs. 42%, Pc less than 0.05). However, there was no significant relationship between DR3 and IAAs after correcting for the number of DR4 alleles. No relationship was seen between age of onset, IAA level, and HLA typing in our population, and no relationship was found between ICA positivity and HLA antigens.(ABSTRACT TRUNCATED AT 250 WORDS)     

Prognostically significant heterogeneity of cytoplasmic islet cell antibodies in relatives of patients with type I diabetes.

A significant proportion of relatives of patients with insulin-dependent (type I) diabetes with high titers of cytoplasmic islet cell autoantibodies (ICAs) do not progress to overt diabetes with up to 8 yr of follow-up. This may reflect that follow-up of such relatives has not been long enough to observe diabetes, that despite expression of identical ICAs, some relatives will not progress to diabetes; or that there is heterogeneity in what is identified as ICA. We identified a subset of ICA that was restricted in its species (not reacting with mouse islets) and cell-type reactivity within islets (beta-cell specific). Only one of eight relatives whose sera had the restricted pattern of reactivity progressed to overt diabetes, and on sequential evaluation, all but the one relative who progressed to diabetes have maintained normal first-phase insulin secretion to intravenous glucose. In contrast, by life-table analysis, 70% of relatives expressing nonrestricted ICA became diabetic within 5 yr of follow-up (1 of 8 vs. 16 of 25 diabetic at last follow-up, P less than 0.02). Moreover, preliminary data suggest a significant association of the human leukocyte antigen DQB1*0602 allele of DR2 haplotypes with the restricted ICA pattern (4 of 5 DQB1*0602 restricted vs. 0 nonrestricted ICA, P = 0.006). We propose that expression of a genetically determined restricted ICA pattern confers a markedly lower risk for progression to diabetes.(ABSTRACT TRUNCATED AT 250 WORDS)     

Transmission of maternal islet antibodies and risk of autoimmune diabetes in offspring of mothers with type 1 diabetes

It is suggested that the maternal transmission of islet autoantibodies increases the risk of autoimmune diabetes in mice. The aim of this study was to determine whether fetal exposure to islet autoantibodies modified the risk of type 1 diabetes in humans. Islet autoantibodies were measured at birth in 720 offspring of mothers with type 1 diabetes. Offspring were prospectively followed for the development of multiple islet autoantibodies and diabetes. Offspring who were GAD or IA-2 autoantibody positive at birth (n = 678) had significantly lower risks for developing multiple islet autoantibodies (5-year risk 1.3%) and diabetes (8-year risk 1.1%) than offspring who were islet autoantibody negative at birth (5.3%, P = 0.008; and 3%, P = 0.04, respectively). Risk remained reduced after adjustment for birth weight, gestational age, or maternal diabetes duration (adjusted hazards ratio 0.25, P = 0.007 for multiple islet autoantibodies; 0.25, P = 0.04 for diabetes). Protection in offspring with islet autoantibodies at birth was most striking in offspring without the HLA DRB1*03/DRB1*04-DQB1*0302 genotype. Maternal transmission of antibodies to exogenous insulin did not affect diabetes risk in offspring. These findings suggest that fetal exposure to islet autoantibodies in children born to mothers with type 1 diabetes may be protective against future islet autoimmunity and diabetes.     

Autoantibodies in diabetes

Islet cell autoantibodies are strongly associated with the development of type 1 diabetes. The appearance of autoantibodies to one or several of the autoantigens-GAD65, IA-2, or insulin-signals an autoimmune pathogenesis of beta-cell killing. A beta-cell attack may be best reflected by the emergence of autoantibodies dependent on the genotype risk factors, isotype, and subtype of the autoantibodies as well as their epitope specificity. It is speculated that progression to beta-cell loss and clinical onset of type 1 diabetes is reflected in a developing pattern of epitope-specific autoantibodies. Although the appearance of autoantibodies does not follow a distinct pattern, the presence of multiple autoantibodies has the highest positive predictive value for type 1 diabetes. In the absence of reliable T-cell tests, dissection of autoantibody responses in subjects of genetic risk should prove useful in identifying triggers of islet autoimmunity by examining seroconversion and maturation of the autoantibody response that may mark time to onset of type 1 diabetes. The complexity of the disease process is exemplified by multiple clinical phenotypes, including autoimmune diabetes masquerading as type 2 diabetes in youth and adults. Autoantibodies may also provide prognostic information in clinically heterogeneous patient populations when examined longitudinally.     

Stratification of type 1 diabetes risk on the basis of islet autoantibody characteristics

Family history of type 1 diabetes and autoantibodies to the islet antigens insulin (IAA), glutamate decarboxylase (GADA), and the protein tyrosine phosphatase-like protein IA-2 (IA-2A) are strong predictors of type 1 diabetes, but the rate of progression to diabetes in multiple islet autoantibody-positive relatives varies widely. We asked whether detailed characterization of islet autoantibodies that included determination of titer, epitope specificity, and IgG subclass would improve diabetes prediction in a large cohort of autoantibody-positive relatives. The study shows a strong association between risk and high titer, broad antibody responses to IA-2 and insulin. The highest risks were associated with high-titer IA-2A and IAA, IgG2, IgG3, and/or IgG4 subclass of IA-2A and IAA, and antibodies to the IA-2-related molecule IA-2beta. Using models based on these antibody characteristics, autoantibody-positive relatives can be classified into groups with risks of diabetes ranging from 7 to 89% within 5 years.     

Are insulin autoantibodies markers for insulin-dependent diabetes mellitus?

Recent studies have shown that insulin autoantibodies occur in patients with newly diagnosed insulin-dependent diabetes mellitus (IDDM) before exogenous insulin treatment. Our study was designed to test the hypothesis that insulin autoantibodies, like cytoplasmic islet cell antibodies (ICAs), can identify individuals with ongoing autoimmune beta-cell destruction and increased risk of IDDM development. Insulin autoantibodies detected by use of a radioligand-binding assay were found in 1.4% of normal controls, 4% of first-degree relatives of IDDM patients, and in 37% of newly diagnosed IDDM patients. A strong positive correlation between insulin autoantibodies and ICAs was observed. HLA typing of insulin-autoantibody-positive first-degree relatives of IDDM patients, as well as in the general population, revealed a strong association with HLA-DR3 and/or-DR4, suggesting that insulin autoantibodies are restricted to persons genetically susceptible to IDDM. In an ongoing study of beta-cell function in ICA-positive nondiabetic individuals, the additional presence of insulin autoantibodies significantly increased the likelihood of beta-cell dysfunction. After intravenous glucose stimulation, insulinopenia was present in 70% of ICA and insulin-autoantibody-positive individuals in contrast to only 23% of ICA-positive, insulin-autoantibody-negative persons. These data document a significant association between insulin autoantibodies and ICAs and support the contention that insulin autoantibodies, like ICAs, are markers of ongoing beta-cell destruction.     

Islet cell and thyrogastric antibodies in 633 consecutive 15- to 34-yr-old patients in the diabetes incidence study in Sweden.

The effect of age on ICA and thyrogastric antibodies at diagnosis of IDDM was evaluated in 633 consecutively diagnosed Swedish diabetic patients aged 15-34 yr and in 282 volunteers of the same age. ICAs were present in 61% (383 of 633) of the patients and in 2% (5 of 282) of control subjects. When the initial classification was considered, ICAs were detected in 69% (327 of 473) of patients with IDDM, 23% (19 of 83) of those with NIDDM, 50% (36 of 72) of those with unclassifiable diabetes, and 20% (1 of 5) of those with secondary diabetes. The frequency of ICA fell significantly (P less than 0.001) with age in IDDM patients from 77% (104/135) in those 15-19 yr old to 52% (50 of 96) in 30- to 34-yr-old IDDM patients. The low frequency of ICA in 30- to 34-yr-old IDDM patients was confined to men (42%, 28 of 66). The frequency of gastric (H+, K(+)-ATPase) antibodies was significantly (P less than 0.05) higher in IDDM patients (10%, 47 of 449) than in patients with NIDDM (3%, 3 of 80) and unclassifiable diabetes (4%, 3 of 72). In conclusion, the frequency of ICA at the diagnosis of IDDM in young adult subjects decreases with increasing age, particularly in men. The frequent finding of ICA in patients considered to have NIDDM or unclassifiable diabetes indicates that misclassification of diabetes is frequent in young adult patients recently diagnosed with diabetes.