Prevalence, characteristics and diabetes risk associated with transient maternally acquired islet antibodies and persistent islet antibodies in offspring of parents with type 1 diabetes

Accurate assessment of type 1 diabetes risk in young children requires discrimination between antibodies that are produced by the child and antibodies acquired through the placenta from an islet antibody-positive mother. We studied 682 offspring from mothers with type 1 diabetes and 329 offspring from fathers with type 1 diabetes and nondiabetic mothers for insulin (auto)antibodies, glutamic acid decarboxylase antibodies, and tyrosine phosphatase IA-2 antibodies before age 1 yr and again at age 2 yr to ascertain transience or persistence. Antibodies were detected at age 9 months in 5 (1.5%) offspring from fathers with type 1 diabetes; all were insulin (auto)antibodies only, all persisted and developed multiple antibodies, and 1 developed type 1 diabetes. In contrast, 31 (4.5%) offspring from mothers with type 1 diabetes had antibodies at 9 months; 12 (1.8%) persisted at age 2 yr, and 19 (2.8%) did not persist, suggestive of transient residual maternal antibodies. Multiple antibodies at 9 months were usually persistent (3 of 4 offspring), as were single insulin (auto)antibodies in offspring from mothers with type 1 diabetes (8 of 13 offspring), whereas persistent glutamic acid decarboxylase antibodies (1 of 12) and tyrosine phosphatase IA-2 antibodies (0 of 2) were rare. Offspring with persistent antibodies at age 9 months had a high type 1 diabetes risk (100% by age 5 yr for those with multiple antibodies and 27% for single antibodies at 9 months), whereas offspring with transient antibodies had 0% type 1 diabetes risk (P < 0.01). Transience was associated with very high antibody levels at birth. For insulin (auto)antibodies, the measurement of subclass was also informative. Residual maternal antibody was indicated by similar insulin (auto)antibodies subclasses at 9 months and at birth, whereas different subclasses were indicative of nonmaternal antibody. Moreover, the presence of IgG1-insulin (auto)antibodies was associated with antibody persistence and type 1 diabetes risk. These strategies are helpful in discriminating high and low risk antibodies before age 1 yr and should be important for prognosis and reducing unnecessary parent anxiety.

Risk of type 1 diabetes development in children with incidental hyperglycemia: A multicenter Italian study

OBJECTIVE

The aim of our study was to determine whether children with incidental hyperglycemia are at an increased risk of developing type 1 diabetes.

RESEARCH DESIGN AND METHODS

A total of 748 subjects, 1-18 years of age (9.04 +/- 3.62, mean +/- SD), without family history of type 1 diabetes, without obesity, and not receiving drugs were studied and found to have incidental elevated glycemia defined as fasting plasma glucose >5.6 mmol/l confirmed on two occasions. Subjects were tested for immunological, metabolic, and immunogenetic markers.

RESULTS

Islet cell antibodies >5 Juvenile Diabetes Foundation units were found in 10% of subjects, elevated insulin autoantibody levels in 4.6%, GAD antibody in 4.9%, and anti-tyrosine phosphatase-like protein autoantibodies in 3.9%. First-phase insulin response (FPIR) was <1st centile in 25.6% of subjects. The HLA-DR3/DR3 and HLA-DR4/other alleles were more frequent in hyperglycemic children than in normal control subjects (P = 0.012 and P = 0.005, respectively), and the HLA-DR other/other allele was less frequent than in normal control subjects (P = 0.000027). After a median follow-up of 42 months (range 1 month to 7 years), 16 (2.1%) subjects (11 males and 5 females), 4.1-13.9 years of age, became insulin dependent. All had one or more islet autoantibodies, and the majority had impaired insulin response and genetic susceptibility to type 1 diabetes. Diabetes symptoms were recorded in 11 patients and ketonuria only in 4 patients. The cumulative risk of type 1 diabetes was similar in males and females, and it was also similar in subjects under or over 10 years, whereas the cumulative risk of type 1 diabetes was increased in subjects with one or more autoantibodies and in those with FPIR <1st centile.

CONCLUSIONS

Children with incidental hyperglycemia have a higher-than-normal frequency of immunological, metabolic, or genetic markers for type 1 diabetes and have an increased risk of developing type 1 diabetes.

T cell responses to type 1 diabetes related peptides sharing homologous regions

Glutamic acid decarboxylase (GAD) 65 is a major autoantigen in type 1 diabetes. Regions of homology exist between GAD65 (residues 250-273) and the Coxsackie P2-C protein (residues 28-50) and between GAD65 (residues 506-518) and proinsulin (residues 24-36), and each of these has been reported to be a diabetes-associated T cell target. The aim of this study was to determine whether the homologous regions are shared targets of T lymphocyte reactivity in individual patients with type 1 diabetes. T cell proliferation against the corresponding peptide pairs, GAD254-276 and Coxsackie P2-C32-54 and GAD506-518 and proinsulin24-36, were measured in peripheral blood mononuclear cells from 26 patients with newly diagnosed type 1 diabetes and 24 control subjects. Responses with stimulation indices higher than 3 were found against each of the antigens tested in both patients and control subjects, and no differences were observed between groups. A strong positive correlation was found between responses to the corresponding peptide pairs GAD254-276 and Coxsackie P2-C32-54 (r=0.77, P<0.0001), and between responses to the corresponding peptide pairs GAD506-518 and proinsulin24-36 (r=0.66, P<0.0001). However, a similar correlation was also observed between responses to the noncorresponding pairs Coxsackie P2-C32-54 and proinsulin24-36 (r=0.82, P<0.0001), Coxsackie P2-C32-54 and GAD506-518 (r=0.82, P<0.0001), and GAD254-276 and proinsulin24-36 (r=0.83, P<0.0001). Strikingly, increased responses to peptides were found almost exclusively in subjects with high stimulation indices against the recall antigen tetanus toxoid, further suggesting that peripheral blood T cell responses are related to a general subject hyperreactivity. These data suggest that proliferative T cell responses to peptides containing putative autoreactive epitopes of GAD65 and proinsulin are not specific for type 1 diabetes, that correlation between T cell reactivity to peptides is not restricted to those containing homologous regions, and that non-antigen-specific factors are important determinants of in vitro measurements of T cell reactivity.

Islet cell and thyroid antibody prevalence in patients with hepatitis C virus infection: effect of treatment with interferon

An increased prevalence of hepatitis C virus (HCV) infection in patients with diabetes and a higher prevalence of diabetes in HCV-infected patients have been reported. However, the relationship between these two conditions remains controversial. In addition, although the effect of interferon treatment on thyroid autoimmunity has been extensively reported, its influence on beta-cell autoantibodies has not been investigated. The aims of the study were (1) to evaluate whether autoimmune beta-cell damage could be involved in the development of diabetes mellitus in HCV-infected patients and (2) to determine whether interferon treatment influences the appearance of beta-cell and thyroid autoantibodies. The prevalence of islet cell autoantibodies (glutamic acid decarboxylase antibodies [GADAs], tyrosine phosphatase antibodies [IA-2s], islet cell antibodies [ICAs]) was assessed in 303 non-selected HCV-infected patients (277 non-diabetic and 26 type 2 diabetic patients) and in 273 sex- and age-matched control subjects. ICAs and thyroid autoantibodies were also determined before and 6 and 12 months after treatment with interferon for 24 weeks in a subgroup of 46 HCV-infected patients. GADAs were detected in 4 of 277 (1.4%) HCV-infected non-diabetic patients, 1 of 273 (0.3%) control subjects, and 0 of 26 (0%) HCV-infected patients with diabetes. Anti-IA2s and ICAs were negative in all subjects. Both GADAs and anti-IA2s were negative in all HCV-infected patients treated with interferon. After therapy, only thyroid antibodies became positive in 5 of 46 (10.9%) treated patients, disappearing in all but 1 of these at the 12-month follow-up. Our results suggest that beta-cell autoimmunity is not associated with HCV infection, thus making it unlikely that the increased diabetes mellitus prevalence among HCV-infected patients could be mediated by autoimmune mechanisms. In addition, interferon treatment induces a transient increase in thyroid autoantibodies but does not influence the appearance of beta-cell autoantibodies.

Human monoclonal antibodies isolated from type I diabetes patients define multiple epitopes in the protein tyrosine phosphatase-like IA-2 antigen

Protein tyrosine phosphatase-like IA-2 autoantigen is one of the major targets of humoral autoimmunity in patients with insulin-dependant diabetes mellitus (IDDM). In an effort to define the epitopes recognized by autoantibodies against IA-2, we generated five human mAbs (hAbs) from peripheral B lymphocytes isolated from patients most of whom had been recently diagnosed for IDDM. Determination and fine mapping of the critical regions for autoantibody binding was performed by RIA using mutant and chimeric constructs of IA-2- and IA-2beta-regions. Four of the five IgG autoantibodies recognized distinct epitopes within the protein tyrosine phosphatase (PTP)-like domain of IA-2. The minimal region required for binding by three of the PTP-like domain-specific hAbs could be located to aa 777-979. Two of these hAbs cross-reacted with the related IA-2beta PTP-like domain (IA-2beta aa 741-1033). A further PTP-like domain specific hAb required the entire PTP-like domain (aa 687-979) for binding, but critical amino acids clustered in the N-terminal region 687-777. An additional epitope could be localized within the juxtamembrane domain (aa 603-779). In competition experiments, the epitope recognized by one of the hAbs was shown to be targeted by 10 of 14 anti-IA-2-positive sera. Nucleotide sequence analysis of this hAb revealed that it used a V(H) germline gene (DP-71) preferably expressed in autoantibodies associated with IDDM. The presence of somatic mutations in both heavy and light chain genes and the high affinity or this Ab suggest that the immune response to IA-2 is Ag driven.

Development of celiac disease-associated antibodies in offspring of parents with type I diabetes

AIMS/HYPOTHESIS

The aim of this study was to determine the frequency and temporal development of antibodies related to celiac disease in offspring of parents with Type I (insulin-dependent) diabetes mellitus.

METHODS

Sera from 913 offspring of parents with Type I diabetes prospectively followed from birth to the age of 8 years were tested for IgG-transglutaminase antibodies (IgG-tTGCAs), endomysial IgA antibodies (EMA) and gliadin antibodies.

RESULTS

We found tTGCAs in 32 (3.5%) of the 913 relatives. Prevalence was related to age and reached 6.5% at age 8 years. Endomysial IgA antibodies were detected in 44% of the relatives with tTGCAs and 0.6% of tTGCA negative relatives and were also most prevalent (5 %) in those aged 8 years. Both tTGCAs and EMAs were more frequent in relatives with the HLA DRB1*03 DQA1*0501 DQB1*02 haplotype (7.1% and 7.2%, respectively; p < 0.005). Antigliadin antibodies were common in both tTGCA positive (42%) and negative (23%) relatives, did not show a relation with age and were less prevalent in relatives with HLA DR3 (p < 0.05). There was no association between the presence of antibodies associated with celiac disease and islet autoantibodies in these relatives. Of the relatives 15 (1.6%) had tTGCAs plus EMAs. In two of these, anti-gliadin antibodies were detected before the detection of tTGCAs and EMAs at the age of 9 months whereas none of the remainder had any antibodies associated with celiac disease before age 2 years. In three there were no detectable antigliadin antibodies in any of the samples tested. Celiac disease without clinical symptoms was diagnosed in 9 of 12 by intestinal biopsy. CONCLUSION/INTERPRETATION. A statistically significant proportion of relatives of patients with Type I diabetes have celiac disease-associated autoimmunity and the silent form of celiac disease early in life. These relatives should, therefore, be considered for celiac antibody screening.

Exposure to exogenous insulin promotes IgG1 and the T-helper 2-associated IgG4 responses to insulin but not to other islet autoantigens

Insulin immunization in animal models induces T-helper (Th) 2-like antibody subclass responses to insulin and other beta-cell antigens. The aim of this study was to determine whether exposure to insulin in humans resulted in a similar subclass bias of the humoral immune response. Levels of IgG subclass antibodies to insulin (IAs), GAD, and IA-2 were measured before and after treatment with insulin in the following groups of patients: 29 patients with newly diagnosed type 1 diabetes treated with intravenous and/or subcutaneous insulin; 10 newly diagnosed patients randomized to cyclosporin A (CsA) or placebo plus subcutaneous insulin for 12 months; and 14 islet cell antibody-positive relatives receiving either intravenous and subcutaneous insulin prophylaxis or no treatment. At the onset of diabetes, the major subclass distributions of insulin autoantibodies (IAAs) were IgG1 and, to a lesser extent, IgG4. After insulin treatment in the 29 new-onset patients, IAs were initially of the IgG1 subclass. IgG4-IAs appeared later, but at 12 months, they were at higher levels than IgG1-IAs in 11 patients. Responses were higher in children compared with adults and were higher in subjects with IAAs (P < 0.001). Insulin prophylaxis in relatives showed a similar profile, with a decline in levels of IgG1-IAs after cessation of daily subcutaneous insulin. Patients treated with CsA took longer to develop IAs and showed suppressed levels of IgG4-IAs; however, their levels of high-titer IgG1-IAs persistently rebounded after completion of CsA therapy. Despite the presence of IgG4-IAs in most insulin-treated patients and relatives, a shift to IgG4-anti-GAD or IgG4-IA-2 was not found for up to 3 years after the initiation of insulin therapy. While our findings need to be correlated with T-cell cytokine responses, we suggest that the strong IgG4-IA response in insulin-treated patients is consistent with an enhancement of Th2 immunity, but there is no evidence of subsequent spreading of potentially Th2-associated IgG4 responses to other autoantigens.

Maturation of the humoral autoimmune response to epitopes of GAD in preclinical childhood type 1 diabetes

GAD is a major target of autoimmunity in preclinical type 1 diabetes. Here we examine the maturation of the humoral response to GAD epitopes sequentially from birth to diabetes onset or current follow-up in 29 GAD antibody (GADA)+ offspring of parents with diabetes from the BABYDIAB Study. Antibodies were measured against GAD65, GAD67, and GAD65/67 chimeras by radiobinding assay. In 28 of 29 offspring, the first GADAs contained reactivity against epitopes within GAD65 residues 96-444, suggesting that the middle GAD65 region is a primary target of GAD humoral autoimmunity. In 7 of these 28 offspring, initial antibody reactivity was against all epitope regions tested (middle GAD65, COOH-terminal GAD65 residues 445-585, NH2-terminal GAD65 residues 1-95, and GAD67); in 16 offspring, reactivity was to middle and COOH-terminal GAD65 epitopes, and in 5 offspring, reactivity was only to the middle GAD65 epitopes. The single offspring without middle GAD65 reactivity had antibodies to the NH2-terminal epitopes in the absence of all other islet autoimmunity. Subsequent GADA epitope spreading was frequent and seen in 10 of 15 offspring with informative follow-up samples. Spreading was mostly (eight cases) to NH2-terminal GAD65 epitopes. In two offspring, spreading to new epitopes was found when antibody titers to GAD65 and early epitopes were declining, suggesting determinant-specific regulation of the humoral response. None of the GADA reactivities nor any changes in reactivity over time were specifically associated with diabetes onset. The findings suggest that the humoral autoimmune response to GAD found in childhood is dynamic, is initially against epitopes within the middle portion of GAD65, and spreads to epitopes in other regions of GAD65 and GAD67.

Modulation of humoral islet autoimmunity by pancreas allotransplantation influences allograft outcome in patients with type 1 diabetes

Pancreas transplantation in patients with type 1 diabetes presents allogeneic beta-cell autoantigens to the immune system long after the initial beta-cell destruction that leads to diabetes has occurred. The aims of this study were to determine whether re-exposure to beta-cell autoantigen through transplantation affect the humoral autoimmune response and whether its modulation correlates with graft outcome. Antibodies to the major autoantigens GAD (GADA) and protein tyrosine phosphatase IA-2 (IA-2A) were measured before and after transplantation in patients with type 1 diabetes who received pancreas and kidney allografts. In the 110 cases studied, pancreas graft survival was not significantly associated with the presence of GADA or IA-2A before transplantation. In the 75 patients with sequential follow-up samples up to 11.2 years after transplantation, autoantibodies were persistently undetectable in 44 cases (59%) and remained at stable detectable levels in 13 cases (17%). Substantial changes in antibody levels were found in 18 cases (24%), of which 13 cases (17%) had declining levels and 5 cases (7%) had marked increments after transplantation. Rising GADA and IA-2A levels in these five patients were predominantly of the IgG1 subclass, with progressive spreading of epitope reactivity. Pancreas graft function was lost 0.7-2.3 years after rising autoantibody levels in four of these five patients, and a significantly lower pancreas graft survival was found in patients with major rises in either GADA or IA-2A levels (P < 0.0001 vs. the remainder) and in patients having persistently high levels of IA-2A (P = 0.002 vs. stable antibody-negative patients). Kidney graft survival was not associated with islet autoantibody status. In conclusion, a minority of patients receiving pancreas allografts under generalized immunosuppression show a stimulation of islet autoantibody reactivity characteristic of that found in preclinical type 1 diabetes, which is almost invariably followed by graft function failure and resumption of insulin therapy.

Cellular and humoral immunity against cow's milk proteins in type 1 diabetes

Cow's milk beta-casein has been proposed as a candidate trigger of autoimmunity associated with type 1 diabetes. In this study, cellular and humoral immunity against beta-casein was compared to that against other major cow's milk proteins in patients with recent onset type 1 diabetes and control subjects. T cell responses were found against alpha-casein, beta-casein, beta-lactoglobulin and bovine serum albumin in both patients with type 1 diabetes (stimulation index: 0.2-22.8, n=23) and control subjects (stimulation index: 0.1-18.2, n=22), with no significant differences between groups. Twelve (52%) patients and nine (41%) control subjects had stimulation indices >3 to at least one protein, including 9 (39%) patients and 4 (18%) control subjects against beta-casein, all but one of these also having elevated responses to alpha-casein. The highest responses (stimulation index >9) were against alpha- and beta-casein in some patients and control subjects who had the HLA DR3 allele. Antibody levels against alpha-casein, beta-casein and beta-lactoglobulin were low in both patients (n=59) and control subjects (n=52). Nevertheless, significantly higher IgG binding to both alpha-casein in ELISA (P=0.02) and beta-casein using ELISA (P=0.02) and RIA (P=0.04) was observed in patients aged <15 years compared to control subjects of similar age. No relationship was found between cellular and humoral immunity against individual antigens. These data show that immune responses to cow's milk are not limited to patients with diabetes and not solely against beta-casein.

Antibodies to tissue transglutaminase C in type I diabetes

AIMS/HYPOTHESIS

Silent coeliac disease is a gluten driven autoimmune disease which is relatively frequent in patients with Type I (insulin-dependent) diabetes mellitus. To determine the extent of gluten associated autoimmunity in Type I diabetes, autoantibodies to tissue transglutaminase C, a major autoantigen in coeliac disease, were measured in patients with new-onset Type I diabetes.

METHODS

We measured IgG and IgA tissue transglutaminase C autoantibodies using human recombinant antigen and radio-binding assays in a cohort of 287 patients with new-onset Type I diabetes, 119 with Type II (non-insulin-dependent) diabetes mellitus and in 213 control subjects.

RESULTS

We found IgA and IgG tissue transglutaminase C antibodies in 24 (8 %) patients with Type I diabetes; 97 (33 %) patients had IgG antibodies only and 1 IgA antibodies only. Antibody concentrations were highest in those with both IgA and IgG antibodies. Only 2 (2 %) patients with Type II diabetes and 2 (1 %) control subjects had either IgG or IgA tissue transglutaminase C antibodies. Patients with HLA DRB1(*)04 alleles had the highest prevalence of IgG tissue transglutaminase C antibodies.

CONCLUSION/INTERPRETATION

These data show that almost 10 % of patients have autoimmunity typical of coeliac disease and that another 30 % have low level tissue transglutaminase C antibody binding. This high prevalence suggests either involvement of the gut in the pathogenesis of Type I diabetes or that transglutaminase is a secondary autoantigen resulting from beta-cell destruction. [Diabetologia (1999) 42: 1195-1198]

Myoclonic encephalopathy and diabetes mellitus in a boy

We describe an 18-month-old boy with insulin-dependent diabetes mellitus who developed idiopathic myoclonic encephalopathy (dancing eye syndrome) at 26 months of age. The neurological symptomatology (multifocal myoclonus, opsoclonus, ataxia, behavioural disturbance) developed within 10 to 14 days after presentation. Biological, neuroradiological, and scintigraphic examination excluded CNS infectious diseases, intoxication, or tumours. At onset of diabetes mellitus, anti-glutamic-acid decarboxylase (GAD) antibodies were observed, and markedly increased in titre when myoclonic encephalopathy occurred. Corticosteroid treatment resulted in a decrease in anti-GAD autoantibody titres and the disappearance of neurological disturbances. As GAD is expressed both in pancreatic beta-cells and cerebellar Purkinje cells, it is possible that a common autoimmune disorder in this patient may account for both the diabetes and myoclonic encephalopathy.

Early autoantibody responses in prediabetes are IgG1 dominated and suggest antigen-specific regulation

The islet autoimmunity of preclinical type 1 diabetes remains poorly characterized in humans. In this paper, the IgG subclass response to the islet autoantigens insulin, glutamic acid decarboxylase, and IA-2 was studied sequentially from birth to diabetes onset or current follow-up in 26 autoantibody positive offspring of parents with diabetes. Islet autoantibody appearance was characterized by an early IgG1 peak response to one or more Ags, most commonly to insulin, at a median age of 2.2 yr (interquartile range, 2-2.9 yr). In five offspring, an acute fulminant beta-cell destruction and diabetes onset occurred during this initial Ab response. In the remainder, early Ab levels declined markedly, and Ab peaks against other beta cell Ags arose sequentially over several years suggesting regulation and spreading of autoimmunity. Second peak Ab responses to the same Ag were observed in only two offspring, both developing diabetes at this time. Two others developed diabetes with declining Ab levels. Abs of IgG1 subclass dominated against each Ag, and other subclasses, were usually only detected during peak IgG1 responses. The IgG4 response to insulin was exceptional, being dominant over IgG1 in four offspring and in five others appeared and/or persisted after IgG1 levels declined. These Th2-associated IgG4 responses were not correlated with protection from diabetes. The presence of IgG1-restricted responses to DA2 were associated with diabetes development. These findings suggest that type 1 diabetes has an early acute destructive phase of beta cell autoimmunity, which may be regulated and which spreads chronically until diabetes onset.

Low prevalence of islet autoimmunity in adult diabetes and low predictive value of islet autoantibodies in the general adult population of northern Italy

AIMS/HYPOTHESIS

To assess the prevalence of islet autoimmunity in adult-onset diabetes mellitus and the predictive value of islet autoantibodies in the general adult population of northern Italy.

METHODS

A sample of 2076 people aged 40 years or more participating in the population-based Cremona Study and classified in 1990 as having diabetes mellitus, impaired and normal glucose tolerance according to WHO criteria after an oral glucose tolerance test, were tested for antibodies to glutamic acid decarboxylase and IA-2.

RESULTS

Increased concentrations of glutamic acid decarboxylase antibodies were found in 4 (2.8 %) of 143 participants with known diabetes and none of 50 with previously unknown diabetes, 1 (0.65%) of 153 with impaired and 18 (1.0%) of 1718 with normal glucose tolerance. The increased prevalence of these antibodies in subjects with known diabetes was not statistically significant. Protein tyrosine phosphatase IA-2-antibodies were found in only four subjects, two of whom also had glutamic acid decarboxylase antibodies, all with normal glucose tolerance. After 8 years of follow-up, none of 21 non-diabetic subjects with either glutamic acid decarboxylase or IA-2-antibodies had developed diabetes and only a slight deterioration from normal to impaired fasting glucose was observed in 3 of 15 subjects with previous normal glucose tolerance.

CONCLUSION/INTERPRETATION

This study has shown that in northern Italy the prevalence of adult autoimmune diabetes in the general adult population is 0.19% (95 % CI 0.05-0.5); that autoimmune diabetes represents only a minority of all cases of adult diabetes; and that islet autoantibodies are not a high-risk factor for diabetes development in adults with normal glucose tolerance over 8 years of follow-up.

Immunoglobulin G insulin autoantibodies in BABYDIAB offspring appear postnatally: sensitive early detection using a protein A/G-based radiobinding assay

Insulin autoantibodies (IAA) are early sensitive markers of pre-diabetes in the young. The aim of this study was to assess whether, using IgG-specific measurement with a protein A/G assay, IAA are already present at birth, and whether this assay is suitable for early autoantibody screening. Cord blood and follow-up samples from offspring of parents with type 1 diabetes included in the BABYDIAB study were analyzed. Although insulin antibodies in cord blood from children of mothers with type 1 diabetes were readily detected and correlated well with levels in the maternal circulation, no insulin binding was detected in 247 cord blood samples from children of father probands. IgG IAA were detected at 2 yr in all 21 children who had multiple islet autoantibodies or who later developed type 1 diabetes, but were confirmed in only 6 of 58 with IAA by the conventional IAA assay in the absence of other islet autoantibodies. False positive IAAs in the conventional assay were often attributable to hemolysis. Hemolysis did not affect protein A/G IAA measurement, and results in whole capillary blood samples were comparable to those in corresponding serum samples (r2 = 0.99). These data show that IgG IAA appear early and after birth, and that the protein A/G IAA assay is sufficiently sensitive for early screening. The specificity of this assay requires further evaluation.

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.

Comparison of tissue transglutaminase-specific antibody assays with established antibody measurements for coeliac disease

Tissue transglutaminase C has recently been identified as one of the auto-antigens of endomysial antibodies found in coeliac disease. In this study we have cloned the human autoantigen and developed immunoassays measuring antibodies to transglutaminase in order to compare their diagnostic performance to that of established markers of the disease. A radiobinding assay using in vitro transcribed and translated 35S-methionine-labelled transglutaminase detected IgG antibodies in 110 and IgA antibodies in 109 of 112 patients at diagnosis of coeliac disease and in three and four of 92 control subjects, respectively. A radiobinding assay measuring both IgG and IgA transglutaminase antibodies identified 111 (99.1%) of the patients and 4 (4.3%) control subjects. Concordance of this assay with the IgA endomysial antibody test was found in 108 patients and 89 control subjects: two patients who had IgA deficiency and a third patient without IgA deficiency were only detected in the radiobinding assay; one patient had weak IgA endomysial antibodies only, and three of the control subjects with weak transglutaminase antibodies by radiobinding assay were undetectable in the IgA endomysial antibody assay. IgA and IgG ELISA using guinea pig transglutaminase and commercial ELISA measuring anti-gliadin antibodies had lower sensitivity and specificity than the radiobinding assays or the IgA endomysial antibody assay. This study confirms tissue transglutaminase C as a major autoantigen in coeliac disease and describes novel radiobinding assays for large scale testing to identify cases of coeliac disease.

Capillary whole blood measurement of islet autoantibodies

OBJECTIVE

Islet cell antibody (ICA) measurements in serum are used for large-scale screening to identify subjects who are at high risk of developing type 1 diabetes. The aim of this study was to adapt measurements to capillary whole blood samples to facilitate and reduce screening costs.

RESEARCH DESIGN AND METHODS

GAD65, IA-2, and combined GAD65/IA-2 antibody tests were performed on patients with type 1 diabetes, first-degree relatives of patients, and control subjects, and results from serum, plasma, whole venous blood, and capillary whole blood lysates were compared. Measurements obtained in serum and eluates from dried capillary blood spots from 36 ICA+ first-degree relatives were also compared.

RESULTS

GAD65, IA-2, and combined GAD65/IA-2 antibody levels were completely concordant with measurements obtained from serum, plasma, whole venous blood, and capillary whole blood lysates. Antibody levels obtained in eluates from dried capillary blood spots were lower than corresponding serum samples, and weak antibodies were not detected.

CONCLUSIONS

Initial screening for diabetes risk can be performed using one drop of capillary whole blood without further processing to separate serum. This method should be considered as a way to simplify and reduce costs of screening programs.

Early development and spreading of autoantibodies to epitopes of IA-2 and their association with progression to type 1 diabetes

Autoimmunity precedes clinical type 1 diabetes, and indicators of maturing autoimmune responses may be useful markers for disease prediction. To study this, epitope maturation of autoantibodies to the related protein tyrosine phosphatase (PTP)-like autoantigens IA-2 and IA-2beta was examined in sequential samples from birth in a cohort of 21 offspring developing multiple islet autoantibodies and a similar cohort of 48 relatives of patients with type 1 diabetes recruited at an older age. Initial reactivity in offspring was heterogeneous against the IA-2 juxtamembrane region (10/21) and PTP domains (13/21), and both specificity and extent of initial IA-2/IA-2beta autoantibodies were associated with HLA class II genotype. Intra-IA-2 epitope spreading and/or intermolecular spreading to IA-2beta epitopes were observed in seven offspring. In contrast, in older relatives, IA-2/IA-2beta Ab reactivity was stable and spreading rare. Development of diabetes in children was associated with the presence of Abs to the IA-2 juxtamembrane region (risk by age 5 yr, 52% vs 0% in those with PTP domain Abs only; p < 0.02), and 5 of 26 relatives who developed diabetes had IA-2 Abs only against the juxtamembrane region. The findings show that autoantibody reactivity to IA-2/IA-2beta is dynamic in the young, show that the juxtamembrane region of IA-2 is an early IA-2 autoantibody target, and suggest that these Abs are a risk factor for development of type 1 diabetes in infancy.