Immunological heterogeneity in Type I diabetes: presence of distinct autoantibody patterns in patients with acute onset and slowly progressive disease

Summary Type I diabetes mellitus may represent a heterogeneous disorder with a distinct pathogenesis in patients with young and adult onset of the disease. To investigate whether serological markers directed to different autoantigens have the potential to distinguish acute onset from slowly progressive Type I diabetes we analysed antibodies to tyrosine phosphatases IA-2/ICA512 (IA-2A) and IA-2β/phogrin (IA2βA), antibodies to GAD65 (GADA) and cytoplasmic islet cell antibodies (ICA) in a non-selected group of diabetic patients clinically classified as having Type I or Type II diabetes at diagnosis. Both IA-2A and IA-2βA were found to be positively associated with onset before the age of 20 years and the presentation of classical features of Type I diabetes. In Type I diabetes 56 % (112/200) of patients were positive for IA-2A and 38 % (76/200) for IA-2βA. In contrast, only 1 of 785 (0.1 %) patients with Type II diabetes had IA-2A and all of them were negative for IA-2βA (p < 0.001). Among the patients with Type II diabetes 7.6 % (n = 60) were ICA positive and 2.8 % (n = 22) had GADA suggesting the presence of slowly progressive Type I diabetes. GADA were found in 8 of 60 (13.3 %) ICA positive subjects which was lower than the percentage detected in patients with acute onset of diabetes (115/157 73.2 %) (p < 0.001). Blocking of double antibody positive sera showed that only 3 of 8 (37.5 %) patients with slowly progressive diabetes had ICA restricted to GAD or IA-2 whereas ICA were completely inhibited in 12 of 20 (60.0 %) patients with Type I diabetes. Among 193 patients with Type II diabetes available for follow-up, 35 % of ICA positives, 58 % of GADA positives and 60 % of those positive for both markers required insulin by 3 years. However, using strict criteria for the switch to insulin treatment the corresponding sensitivity of each marker was only low (9 %, 10 % and 5 %). We show that clinical subtypes of Type I diabetes are associated with distinct humoral autoimmunity. IA-2A and GADA were associated with classical features of Type I diabetes whereas GADA and an uncharacterized ICA subspecificity indicate slowly progressive disease. [Diabetologia (1998) 41: 891–897] Received: 15 January 1998 and in revised form: 10 April 1998     

Autoantibodies associated with Type I diabetes mellitus persist after diagnosis in children

Summary To study the persistence of Type I (insulin-dependent) diabetes mellitus associated autoantibodies and their relation to genetic risk markers and clinical characteristics of the disease after clinical manifestation, serum samples were obtained from 90 children and adolescents at diagnosis and 2, 5 and 10 years later. The samples were analysed for islet cell antibodies (ICA) by immunofluorescence and for antibodies to glutamic acid decarboxylase (GADA), intracellular portion of the protein tyrosine phosphatase related IA-2 antigen (IA-2A) and insulin autoantibodies by specific radiobinding assays. Of the subjects tested 79 % were positive for IA-2A at diagnosis, 62 % for GADA, 81 % for ICA and 28 % for insulin autoantibodies, but the prevalence of IA-2A, GADA and ICA decreased substantially as a function of increasing duration of the disease (p < 0.05 or less), their levels following the same pattern (p < 0.001 for all three autoantibodies). Two thirds of the subjects still tested positive for at least one autoantibody specificity after the first 10 years of the disease and 42 % had two or three antibodies detectable. An increase over the initial antibody concentrations after the diagnosis was seen more often for GADA than for ICA (p < 0.001) or IA-2A (p < 0.05). In conclusion, autoantibodies associated with Type I diabetes appear to persist longer than expected after manifestation of the clinical disease, possibly due to small scale continuous beta-cell regeneration after diagnosis or to structural and/or functional mimicry between exogenous proteins and beta-cell antigens or both. [Diabetologia (1998) 41: 1293–1297] Received: 9 March 1998 and in revised form: 24 June 1998     

Relationship between serum insulin autoantibodies,islet cell antibodies and Coxsackie-B4 and mumps virus-specific antibodies at the clinical manifestation of Type 1 (insulin-dependent) diabetes

Summary In order to elucidate the possible relationship between insulin autoantibodies (IAA), conventional (ICA-IgG) and complement-fixing (CF-ICA) islet cell antibodies and Coxsackie-B4 and mumps virus-specific antibodies (IgG, IgM and IgA classes), we studied 194 children and adolescents with newly diagnosed Type 1 (insulin-dependent) diabetes. Sixty-one (31.4%) of the subjects were IAA-positive at diagnosis and 73.8% (45/61) of these also had ICA-IgG compared to 51.1% (68/113, p<0.01) of IAA-negative children. CF-ICA showed no significant association with IAA. The levels of IAA were significantly higher in the patients with ICA-IgG compared to those without [5.9±1.6% (SEM) vs 2.5±0.3%, p<0.01]. The patients positive for IAA were younger at diagnosis than the IAA-negative ones; (7.1±0.5 vs 9.3±0.3 years, p<0.001) and this was also true for ICA-IgG-positive children (8.1±0.4 vs 9.4±0.5 years, p<0.05) in comparison to ICA-IgG-negative subjects. No significant associations were found between IAA or ICA on the one hand and a positive family history of Type 1 diabetes or metabolic derangements at diagnosis on the other. Subjects negative for ICA were more frequently positive for mumps virus specific IgG antibodies than the ICA-positive patients (50/80 vs 53/111, p<0.05), and Coxsackie-B4 virus-specific IgA antibodies were more common in the CF-ICA-negative than the CF-ICA-positive children (53/111 vs 29/80, p<0.05). There was no association between the IAA levels and Coxsackie-B4 or mumps virus specific antibodies. However, patients with serological evidence of a recent mumps infection (n=13) had higher IAA levels than the other children (4.4±7.7% vs 2.8±1.4%, p<0.02). Our data suggest a positive association between IAA and ICA-IgG, supporting the view that IAA are like ICA serological markers of autoimmune B cell damage. The inverse associations between autoantibodies and age and between ICA and viral antibodies support the hypothesis that autoimmune mechanisms may play a more crucial role in younger patients contracting Type 1 diabetes while environmental factors may be more important in older ones.     

Karlsburg Type I diabetes risk study of a general population: frequencies and interactions of the four major Type I diabetes-associated autoantibodies studied in 9419 schoolchildren

Aims/hypothesis. The Karlsburg Type I (insulin-dependent) diabetes risk study on schoolchildren aims to evaluate the predictive diagnostic value of diabetes-associated autoantibodies in the general population. Methods. We took capillary serum from 9419 schoolchildren, aged 6–17 years, for testing of autoantibodies (AAbs) to glutamic acid decarboxylase (GADA), protein tyrosine phosphatase (IA2A) and insulin (IAA) by 125I-antigen binding. We also tested for autoantibodies to cytoplasmic islet cell antigens (ICA) immunohistochemically. Results. By testing of 9419 sera for the four AAbs at cut-off at or greater than the 98th centile for the radioassayed AAbs and at or greater than 10 Juvenile Diabetes Foundation (JDF) units for ICA, 8.1 % of schoolchildren had at least one AAb. We found that 3.04, 2.97, 2.35, and 0.86 % had IAA, GADA, IA2A or ICA, respectively. 7.3 % had only one AAb and 0.8 % (75) had two or more AAbs, reflecting a risk to develop diabetes. Thus, by primary screening by combined testing of GADA and IA2A, 98.7 % (74/75) would be identified. At high AAb levels, cut-off at or greater than the 99.8th centile and at or greater than 40 JDF units for ICA, 0.23 % (22/9419) of schoolchildren, similar to the disease prevalence of 0.3 %, had two or more AAbs. Ten of 17 children tested had reduced (p < 0.001) first-phase insulin secretion by intravenous glucose tolerance test. Six of 22 subjects developed Type I diabetes within a follow-up of 19 ± 10 months. Conclusion/interpretation. For children older than 5 years the combined anti-GAD/IA2 test with cut-off at or greater than the 98th centile should be used for primary screening followed by testing for IAA and ICA. Subjects at risk for diabetes have two or more AAbs at or greater than the 98th centile. Subjects at risk for rapid progression to Type I diabetes have two or more AAbs at or greater than the 99.8th centile. [Diabetologia (1999) 42: 661–670] Received: 3 September 1998 and in final revised form: 20 January 1999     

Gastric parietal cell antibodies are associated with glutamic acid decarboxylase-65 antibodies and the HLA DQA1*0501-DQB1*0301 haplotype in Type 1 diabetes mellitus. Belgian Diabetes Registry.

AIMS: To assess the prevalence of thyrogastric autoimmunity in relation to age, sex, beta-cell antibody status and HLA DQ haplotypes in Type 1 diabetes mellitus. METHODS: One hundred and seventy-one patients with Type 1 diabetes mellitus were studied (male/female 86/85; mean age 19 +/- 11 years; duration of diabetes 5 +/- 4 years). Islet cell antibodies (ICA) and parietal cell antibodies (PCA) were measured using indirect immunofluorescence; glutamic acid decarboxylase-65 antibodies (GADA) by radiobinding assay and thyroid peroxidase antibodies (TPO) with an immunoradiometric assay (IRMA). RESULTS: The majority of subjects (81.3%) showed one or more autoantibodies. The prevalence rates were: GADA 64.9%, ICA 46.2%, PCA 19.9% and TPO 19.3%. Patients with ICA+ > or = 3 years after diagnosis had a higher prevalence of GADA (P = 0.03, odds ratio (OR) 2.66) and thyrogastric antibodies (P = 0.05, OR 2.23) than subjects ICA- after 3 years. PCA+ patients were older (P = 0.04), had a higher prevalence of GADA (P = 0.005, OR 3.89) and TPO (P = 0.05, OR 2.50) than PCA- subjects. Logistic regression analysis showed that PCA status was determined by the HLA DQA1*0501-DQB1*0301 haplotype (beta = 2.94, P = 0.04) and GADA status (beta = 2.44, P = 0.041). CONCLUSIONS: Thyrogastric antibodies are highly prevalent in Type 1 diabetes mellitus, especially in patients with persisting ICA. Screening for gastric autoimmunity is particularly advised in patients who are positive for GADA and for the HLA DQA1*0501-DQB1*0301 haplotype.     

Combined screening for autoantibodies to IA-2 and antibodies to glutamic acid decarboxylase in first degree relatives of patients with IDDM

Summary To determine the value of antibodies to the intracytoplasmic domain of the tyrosine phosphatase IA-2 (anti-IA-2 ic) and glutamic acid decarboxylase (GADA) for identification of subjects at risk for insulin-dependent diabetes mellitus (IDDM) we investigated 1238 first degree relatives of patients with IDDM for the presence of anti-IA-2 ic and GADA and compared the results with cytoplasmic islet cell antibodies (ICA). Anti-IA-2 ic were observed in 54 (4.4 %) first degree relatives, in 51 of 86 (59.3 %) ICA positive relatives and in 3 of 4 individuals who developed overt IDDM within a follow-up period of 1 to 28 months. GADA were found in 78 of 1238 (6.3 %) first degree relatives. They were detected in 22 of 35 (62.9 %) sera with ICA alone and in 1 of 3 subjects with anti-IA-2 ic in the absence of ICA. Of the 1238 subjects 37 (3.0 %) sera were positive for all three antibodies. Both anti-IA-2 ic and GADA were positively correlated with high levels of ICA. Anti-IA-2 ic and GADA were detected in 39.1 and 47.8 % of subjects with ICA of less than 20 Juvenile Diabetes Foundation units (JDF-U) but in 66.7 and 76.2 % of individuals with ICA of 20 JDF-U or more, respectively (p < 0.05). The levels of ICA and GADA in first degree relatives with at least one additional marker were significantly higher than in subjects with ICA alone (p < 0.005) or GADA alone (p < 0.03). The combination of anti-IA-2 ic and GADA identified 84.9 % of all ICA positive subjects and 93.7 % of individuals with high level ICA (≥ 20 IDF-U). All 4 individuals who progressed to IDDM had either IA-2 ic or GADA. Our data indicate that primary screening for anti-IA-2 ic and GADA provides a powerful approach with which to identify subjects at risk for IDDM in large-scale population studies which may represent the basis for the design of new intervention strategies. [Diabetologia (1996) 39: 1351–1356] Received: 8 March 1996 and in revised form: 29 May 1996     

Islet autoantibodies in the prediction of diabetes in school children

In 1987 serum was collected from 1031 non-diabetic schoolchildren in the Southeast area of Sweden with the aim of evaluating islet autoantibody status (ICA, GADA and IA2-ab) in the prediction of diabetes in schoolchildren. The clinical development of Type 1 diabetes in the children was assessed in 1994 and 1997. The combination of ICA, GADA and IA2-ab were found in four subjects whereas six had two and 35 children one of these antibodies. After 10 years, six of the 1031 children had developed clinical diabetes and five of these six children were positive for islet antibodies. Two were positive for all three antibodies, two were positive for ICA and GADA, and one was positive for GADA. Among the individual autoantibodies, ICA showed the highest positive predictive value (29%) whereas the predictive value for the combination of two autoantibodies was highest for GADA and ICA (40%). Thus, GADA and ICA measurements may be a rational approach to detect schoolchildren at risk for developing diabetes.     

IA-2 antibodies – a sensitive marker of IDDM with clinical onset in childhood and adolescence

Summary To study the relationship of IA-2 antibodies (IA-2A) to other autoantibodies and genetic risk markers in insulin-dependent diabetes mellitus (IDDM), 758 children and adolescents younger than 15 years of age (mean age 8.4 years) with newly diagnosed diabetes were analysed for IA-2A, GAD antibodies (GADA) and insulin autoantibodies (IAA) with radiobinding assays, for islet cell antibodies (ICA) with immunofluorescence and for HLA DR alleles by serology. IA-2A were detected in 85.9 % of cases with no association with gender or age. An overwhelming majority of the patients (71.3 %) tested positive for three or more antibodies, and 90.7 % for at least two. Fifty-four subjects (7.1 %) had one antibody detectable, whereas only 2.1 % of the patients tested negative for all four. A higher proportion of patients was positive for IA-2A and/or GADA than for ICA alone (95.5 vs 84.2 %, p < 0.001). The prevalence and level of IA-2A were increased in cases carrying HLA DR4/non-DR3 compared with other DR combinations. The results indicate that almost all patients with newly diagnosed childhood IDDM can be identified by screening with these four autoantibodies. The combination of IA-2A and/or GADA had a higher sensitivity for IDDM than ICA alone. The close association between IA-2A and HLA DR4, the strongest single allele predisposing to IDDM, suggests that IA-2A may be a more specific marker of beta-cell destruction than GADA, which have been shown to associate with the DR3 allele and thyroid autoimmunity. [Diabetologia (1998) 41: 424–429] Received: 20 August 1997 and in final revised form: 13 November 1997     

Analysis of pathogenesis of juvenile new-onset diabetes

Background: Measurement of anti‐islet autoantibodies at the time of disease onset contributes greatly to the differentiation of Type 1A diabetes with HLA Class II subtyping also contributing. Methods: Blood samples were obtained from 900 patients with age from 1 month to 25 years (median age 11.1 years) within 2 weeks of diabetes onset to test anti‐islet autoantibodies to insulin (IAA), glutamic acid decarboxylase (GADA), insulinoma antigen (IA‐2AA), the zinc transporter‐8 (ZnT8AA), and islet‐cell antibodies (ICA). Polymorphisms of the HLA Class II gene were typed in 547 randomly selected patients. Results: Of the 900 subjects analyzed, 145 (16.1%) were negative for all five anti‐islet autoantibodies, and autoantibody negativity significantly increased with age: 10.2% (38/372) among children <10 years of age, 14.2% (46/325) in those 10–14 years of age, and 30.1% (61/203) in those >14 years of age (P < 0.001). The prevalence of IA‐2AA was the highest among young children. The prevalence of GADA increased with age while the prevalence of IAA was inversely correlated with age. At diagnosis, the subjects with negative antibodies had a higher body mass index (P < 0.001) and less high risk HLA genotype DR3‐DQ2/DR4‐DQ8 (P < 0.01). Conclusion: A large percentage of children and youths negative for all anti‐islet autoantibodies at the onset of diabetes are likely to have the non‐immune form, especially those without DR3/DR4 and obese patients. Among autoantibody‐positive Type 1A patients, IAA and GADA showed a reciprocal prevalence, suggesting differential disease pathogenesis.     

Islet autoantibodies in cord blood from children who developed Type I (insulin-dependent) diabetes mellitus before 15 years of age

Summary Islet autoantibodies are early markers for Type I (insulin-dependent) diabetes mellitus. The aim of this study was to establish whether islet autoantibodies were present at birth in children who developed Type I diabetes before 15 years of age. Cord blood sera from 81 children who developed Type I diabetes between 10 months and 14.9 years of age were tested for glutamic acid decarboxylase autoantibodies (GAD65Ab), islet cell antigen 512 autoantibodies (ICA512Ab), insulin autoantibodies (IAA) all by quantitative radioligand binding assays and islet cell autoantibodies (ICA) by indirect immunofluorescence. Cord blood sera from 320 randomly selected matched children were controls. The children who developed Type I diabetes had an increased frequency of cord blood islet autoantibodies compared with control subjects: Glutamic acid decarboxylase autoantibodies were detected in 6 % (5/81) patients and 2 % (5/320) control subjects (p = 0.03); islet cell antigen 512 autoantibodies in 5 % (4/73) patients and 1 % (4/288) control subjects (p = 0.06); insulin autoantibodies (IAA) in 0 % (0/79) patients and 0.3 % (1/320) control subjects (p = 0.36); and islet cell autoantibodies in 10 % (8/81) patients compared with 0.6 % (2/320) control subjects (p = 0.0001). Taken together, 17 % (14/81) patients had one or more islet autoantibody compared with 4 % (12/320) control subjects (p = 0.0001). Whereas none of the control children had more than one antibody, 4 % (3/81) children who later developed Type I diabetes were double positive (p = 0.002). Although glutamic acid decarboxylase autoantibodies' concentrations in cordblood correlated to those in the mothers' blood at the time of delivery, no corresponding correlation was found for the other two types of autoantibodies. The increased frequency of cord blood islet autoantibodies suggests that the Type I diabetes process could already be initiated in utero. [Diabetologia (1999) 42: 181–187] Received: 20 August 1998 and in revised form: 16 October 1998     

The cation efflux transporter ZnT8 (Slc30A8) is a major autoantigen in human type 1 diabetes

Type 1 diabetes (T1D) results from progressive loss of pancreatic islet mass through autoimmunity targeted at a diverse, yet limited, series of molecules that are expressed in the pancreatic beta cell. Identification of these molecular targets provides insight into the pathogenic process, diagnostic assays, and potential therapeutic agents. Autoantigen candidates were identified from microarray expression profiling of human and rodent pancreas and islet cells and screened with radioimmunoprecipitation assays using new-onset T1D and prediabetic sera. A high-ranking candidate, the zinc transporter ZnT8 (Slc30A8), was targeted by autoantibodies in 60-80% of new-onset T1D compared with <2% of controls and <3% type 2 diabetic and in up to 30% of patients with other autoimmune disorders with a T1D association. ZnT8 antibodies (ZnTA) were found in 26% of T1D subjects classified as autoantibody-negative on the basis of existing markers [glutamate decarboxylase (GADA), protein tyrosine phosphatase IA2 (IA2A), antibodies to insulin (IAA), and islet cytoplasmic autoantibodies (ICA)]. Individuals followed from birth to T1D showed ZnT8A as early as 2 years of age and increasing levels and prevalence persisting to disease onset. ZnT8A generally emerged later than GADA and IAA in prediabetes, although not in a strict order. The combined measurement of ZnT8A, GADA, IA2A, and IAA raised autoimmunity detection rates to 98% at disease onset, a level that approaches that needed to detect prediabetes in a general pediatric population. The combination of bioinformatics and molecular engineering used here will potentially generate other diabetes autoimmunity markers and is also broadly applicable to other autoimmune disorders.     

Ketoacidosis in young adults is not related to the islet antibodies at the diagnosis of Type 1 diabetes mellitus--a nationwide study.

AIMS: To test the hypothesis that there is lower prevalence of islet antibodies in subjects with newly diagnosed Type 1 diabetes mellitus in young adulthood than in children is associated with less severe diabetes at time of diagnosis. METHODS: This investigation was based on a nationwide study (Diabetes Incidence Study in Sweden) of 15-34-year-old newly diagnosed diabetic subjects. During 1992-1993, all diabetic subjects (excluding secondary and gestational diabetes) were reported on standardized forms, with information about clinical characteristics at diagnosis. The study examined islet cell antibodies (ICA) by indirect immunofluorescence, and autoantibodies to glutamic acid decarboxylase (GADA), tyrosine phosphatase-like antigen (IA-2A) and insulin (IAA) as well as C-peptide by radioimmunoassay. RESULTS: Blood samples were available from 78 patients with diabetic ketoacidosis (DKA) and 517 non-acidotic patients. The prevalence of ICA (63% vs. 57%), GADA (63% vs. 66%), IA-2A (35% vs. 44%) and IAA (20% vs. 15%) were very similar in patients with or without DKA. The median levels of the four autoantibodies did not differ between the two groups. High blood glucose (P < 0.001) and low C-peptide levels (P < 0.001) were the only parameters found to be related to DKA. CONCLUSIONS: The similarities in findings of newly diagnosed diabetic patients with or without DKA regarding ICA, GADA, IA-2A and IAA suggest that there is no relationship between the expression of antigenicity and the severity of beta-cell dysfunction. The lower prevalence of the four autoantibodies in 15-34-year-old diabetic subjects compared with previous findings in children is not explained by misclassification of diabetes type.     

IA-2 autoantibodies predict impending type I diabetes in siblings of patients

AIMS/HYPOTHESIS: Multiple islet autoantibody positivity is currently believed to best predict progression to Type I (insulin-dependent) diabetes mellitus. We compared its predictive value with that of positivity for a particular type of islet autoantibody, directed against the IA-2 antigen. METHODS: Autoantibodies against islet cell cytoplasm (ICA), insulin (IAA), GAD (GADA) and IA-2 (IA-2A) were measured at initial sampling in 1724 non-diabetic siblings (median age [range]:16 [0-39] years) of Type I diabetic patients with a median follow-up of 50 months. RESULTS: On initial sampling 11% of siblings were positive for one antibody type or more and 2.1% for three of more types. During follow-up, 27 antibody-positive siblings developed diabetes. Using survival analysis, the risk for clinical onset within 5 years was 34% in subjects positive for three or more types compared with 13% in those with one type or more. Progression to diabetes amounted to 12% within 5 years among siblings positive for IAA, 20% for ICA, 19% for GADA but 59% for IA-2A (p<0.001 vs absence of the respective antibody). IA-2A were detected in 1.7% of all siblings and in 56% of the prediabetic subjects on first sampling. Initial positivity for two or three antibody markers was associated with a higher progression rate in IA-2A positive as compared to IA-2A negative siblings (p=0.001). In absence of IA-2A initial positivity for another antibody (IAA, ICA or GADA) conferred a low (<10% within 5 years) risk of diabetes compared to subjects lacking this antibody. CONCLUSIONS/INTERPRETATION: In siblings of Type I diabetic patients, IA-2A positivity is a more direct predictor of impending clinical onset than multiple antibody positivity per se. Assessment of IA-2A status allows us to select subjects with homogeneously high risk of diabetes for participation in prevention trials.     

Autoantibodies to Glutamic Acid Decarboxylase and Insulin in Islet Cell Antibody Positive Presymptomatic Type 1 Diabetes Mellitus: Frequency and Segregation by Age and Gender

The frequency of antibodies to glutamic acid decarboxylase (GAD) and insulin (IAA) in presymptomatic Type 1 diabetes mellitus with a positive test for antibodies to islet cell antigen (ICA) was examined. Thirty-two persons positive for ICA (> 10 JDF units) were tested 2 to 48 months before their ascertained onset of Type 1 diabetes. ICA was quantitated by immunofluorescence as JDF units, anti-GAD by radioimmunoprecipitation and anti-insulin by radioimmunoassay. There was a positive test for anti-GAD in 25 (78%), and for IAA in 23 (72%), of the 32 prediabetic ICA-positive subjects. Stratification according to age at the onset of diabetes showed differing frequencies of anti-GAD and IAA in the prediabetic stage. Thus the positivity rate for anti-GAD for 18 subjects older than 10 years at onset of diabetes was 83%, and for 14 aged 10 or younger at onset was 71%; conversely, the rate for IAA for 18 subjects older than 10 at onset was 56% and for 14 aged 10 or less at time of onset was 93% (p = 0.01). The frequency of anti-GAD was higher in females (88%) than males (71%) whereas the frequency of IAA was higher in males (82%) than in females (60%). Since autoantibodies to GAD and insulin occur in presymptomatic Type 1 diabetes with differences in frequencies by age and gender, the stimuli to autoimmunity may operate differently at different ages, and may also be gender-related.     

Pancreatic autoantibodies in Italian patients with newly diagnosed type 1 diabetes mellitus over the age of 20 years

Abstract The aim was to estimate the prevalence of the serological markers of pancreatic autoimmunity in a cohort of Italian patients with type 1 diabetes mellitus occurring after 20 years of age in order to determine the prevalence of autoimmune diabetes and the most sensitive autoantibody combination to be employed for the diagnosis. We investigated 57 patients (31 males and 26 females) at clinical diagnosis of type 1 diabetes. 35 patients were 21–40 years and 22 were 41–72 years of age. Autoantibodies to islet-cells (ICA) were detected by indirect immunofluorescence, while those against glutamic acid decarboxylase (GADA), tyrosine-phosphatase (IA2A) and insulin (IAA) were detected by radiobinding assays. A positive test for at least one of the pancreatic autoantibodies was found in 45 of the 57 patients (78.9%). Coupling two antibody tests, GADA and/or IAA were found in 73.7%, ICA and/or GADA in 71.9%, while GADA and/or IA2A were found in 70.2% of the patients. The most frequently positive test was for GADA (66.7%). In general, the frequency of diabetes-related antibodies was higher in the 21–40-year-old group compared to the 41–72-year-old group and in females than males. Based on the detection of pancreatic autoantibodies determination, the great majority of the adult patients with recent onset type 1 diabetes were found to be autoimmune in nature. The best cost/benefit combination is provided by coupling the detection of GADA and ICA.     

Combined positivity for HLA DQ2/DQ8 and IA-2 antibodies defines population at high risk of developing type 1 diabetes

Aims/hypothesis Prevention trials in first-degree relatives of type 1 diabetic patients are hampered by large interindividual differences in progression rate to diabetes. We investigated whether specific combinations of immune and genetic markers can identify subgroups with more homogeneous progression to clinical onset.Methods Antibodies against islet cell cytoplasm (ICA), insulin (IAA), glutamate decarboxylase (GADA) and IA-2 protein (IA-2A) were measured in 790 non-diabetic control subjects and 4,589 first-degree relatives under age 40.Results On first sampling, 11.1% of the siblings presented at least one antibody type (p<0.001 vs other relatives). During follow-up (median 52 months) 43 subjects developed type 1 diabetes (31 siblings, ten offspring of a diabetic father, two offspring of a diabetic mother). Using Kaplan–Meier survival analysis and Cox regression, IA-2A conferred the highest 5-year diabetes risk (>50%) irrespective of the number of antibodies present. In initially IA-2A-positive relatives (n=58) progression to hyperglycaemia depended more on HLA DQ status than on type of kinship (84% progression in the presence of DQ2/DQ8 vs 32% in its absence; p<0.003). In IA-2A-negative relatives (n=4,531) 5-year progression to diabetes increased with the number of other antibodies (ICA, GADA and/or IAA) (p<0.001) but overall did not exceed 10% even for two or more antibodies. Among relatives initially positive for one or more antibody type other than IA-2A (n=315), there was significantly more progression to diabetes (overall still <10%) in carriers of DQ2 (p<0.001 vs no DQ2), regardless of DQ8 status.Conclusions/interpretation These observations suggest that the HLA-DQ-inferred risk of diabetes can proceed through two distinct pathways distinguished by IA-2A status. Combined positivity for DQ2/DQ8 and IA-2A defines a more homogeneous high-risk population for prevention trials than those used so far.Presented in part at the 38th Annual Meeting of the European Association for the Study of Diabetes, September 1–5, 2002, Budapest, Hungary.K. Decochez and I. Truyen contributed equally to the present work.     

Combined analysis of islet cell antibodies which cross-react with mouse pancreas,antibodies to the Mr 64,000 islet protein,and antibodies to glutamate decarboxylase in subjects at risk for IDDM

Summary With regard to progression to diabetes, ICA cross-reactive with mouse pancreas, antibodies to the M_r 64,000 islet antigen (64K), antibodies immunotrapping brain GAD activity, and IAA were analysed in 53 ICA-positive first-degree relatives of IDDM patients and 18 ICA-positive schoolchildren without a family history of diabetes. Sera from 29 (55 %) relatives did not bind to mouse pancreas, whereas 24 (45 %) displayed cross-species reaction. ICA titres on human and mouse pancreas were weakly correlated in the overall population (p <0.05) but more strongly (p <0.01) in only those subjects who displayed antibodies on tissues from both species. GAD and 64K antibodies were detected in 31 % and 35 % of relatives. In schoolchildren, the frequencies of cross-species reactive ICA (22 %), GAD antibodies (6 %), 64K antibodies (22 %), and IAA (6 %), were lower (p <0.05) than in relatives. A strong correlation (p <0.0001) was observed between GAD and 64K antibodies. GAD or 64K antibodies were strongly correlated with ICA on human pancreas (p <0.0001) but poorly with ICA on mouse pancreas (p =0.05). After pre-incubation of sera with brain homogenate, ICA titres were unaffected on mouse pancreas but reduced on human pancreas. ICA-positive subjects who displayed neither cross-species reactive ICA nor GAD or 64K antibodies were more frequent (p <0.05) among schoolchildren than relatives, whereas subjects who displayed all antibody specificities were more numerous (p <0.04) in relatives. All relatives with ICA binding only to human pancreas, as well as all schoolchildren, permanently displayed an AIRG higher than the first control percentile and remained non-diabetic. Five of ten relatives with cross-species reactive ICA, GAD and 64K antibodies at the same time displayed acute insulin response to glucose which fell below the first control percentile and developed the disease. The cross-species heterogeneity of ICA was thus confirmed in a large series of relatives and revealed in the general population. Detection of cross-species reactive ICA, GAD antibodies, or 64K antibodies enhances the prognostic significance after conventional ICA screening. The combination of these antibodies is more indicative of diabetes development than any antibody alone. Correlations between tests and absorption experiments indicate that GAD 64 is an ICA antigen on human but not on mouse pancreas, and that ICA which recognize GAD 64K coexist with others which react with mouse pancreas but not with GAD. A third ICA subset might have been revealed by high-titred ICA without either cross-species reactivity or GAD or 64K antibodies. This latter state was more frequent in the general population than in relatives and might typify an early immune response which may or may not progress. [Diabetologia (1994) 37: 491–499] Received: 29 July 1993 and in revised form: 25 November 1993     

High levels of antigen-specific islet antibodies predict future beta-cell failure in patients with onset of diabetes in adult age.

It is unclear whether high levels of antigen-specific islet antibodies [GADA (glutamic acid decarboxylase 65 antibodies) and IA2-ab (protein tyrosine phosphatase-like protein antibodies)] predict beta-cell failure in patients with onset of diabetes in adult age. Therefore, GADA and IA2-ab levels at the diagnosis of diabetes were related to fasting plasma C-peptide levels 5 yr later in 148 patients with diabetes onset in adult age (age at onset, 20-77 yr; median, 57 yr). Classical islet cell antibodies (ICA) were also determined. Complete beta-cell failure (undetectable fasting plasma C-peptide) was only present in 4 patients at diagnosis of diabetes, but in 21 patients 5 yr thereafter. At diagnosis, ICA were detected in 20 of 21 (95%) patients with beta-cell failure after 5 yr and in only 7 of 127 (5%) without, whereas GADA and/or IA2-ab (>97.5 percentile of healthy controls) were detected in all 21 (100%) with but also in 23 of 127 (18%) patients without beta-cell failure after 5 yr. Thus, ICA had a higher positive predictive value (74%) than GADA and/or IA2-ab (47%; P < 0.05). With high cutoff values for GADA and IA2-ab, however, GADA and/or IA2-ab were detected in 19 of 21 (90%) patients with beta-cell failure vs. only in 5 of 127 (4%) without, giving a positive predictive value of 79%. Slightly elevated GADA levels in IA2-ab-negative patients were associated with progressive but not complete beta-cell failure within the study period. Hence, high GADA and/or IA2-ab levels predict a future complete beta-cell failure, whereas low GADA levels predict slowly progressive beta-cell insufficiency.     

Islet antibodies associated with pancreatic B-cell dysfunction at and 3 years after diagnosis of diabetes in subjects aged 35-64 years old: degree of impairment less severe than in those aged 0-34 years old.

AIMS: To determine differences in pancreatic B-cell function in relation to islet antibodies at diagnosis of diabetes and 3 years later in subjects aged 35-64 years old compared with those aged 0-34 years. METHODS: From a population-based diabetes register, 46 (0-34 years old) and 323 (35-64 years old) incident diabetic patients were investigated at diagnosis and 3 years later. Islet cell antibodies (ICA, GADA and IA-2A) and fasting plasma C-peptide were measured. RESULTS: Islet antibodies were found in 80% of the subjects aged 0-34 years and in 11% of those aged 35-64 years at diagnosis. ICA and GADA was the only combination of two islet antibodies detected in those aged 35-64 years and was, with or without IA-2A, associated with significantly lower median fasting C-peptide values than in those without or with only one antibody [0.35 nmol/l, interquartile range (IQR) 0.63 vs. 0.85 nmol/l, IQR 0.49; P = 0.0004]. However, fasting C-peptide in subjects aged 35-64 years old with multiple islet antibodies was higher than in those aged 0-34 years with islet antibodies (median 0 nmol/l, IQR 0.16, P = 0.0019). After 3 years' follow-up, fasting C-peptide was even lower in subjects aged 35-64 years old with three islet antibodies (median 0.14 nmol/l, IQR 0.27; P = 0.05). CONCLUSIONS: Islet antibodies were common in adults at diagnosis of diabetes. The combination of ICA and GADA indicates impaired B-cell function at diagnosis of diabetes in those aged 35-64 years old.     

Evaluation of the importance of antibodies against islet cells (ICA) and Glutamate Decarboxylase(anti-GAD) for determining prognosis of diabetes type 1 in the Polish population--5 year observation

It was recently shown that there are significant differences between the frequencies of antibodies against pancreatic islet cell antigens (ICA, GADA) in the first degree relatives of IDDM patients in different regions of Poland. There are however no published studies concerning their predictive value in the development of IDDM in the Polish population. The aim of the present study was to evaluate the PPV (positive predictive value) of ICA and GADA antibodies and to analyse diabetes-free survival in association with titre, antibodies co-existence and relatives age in the Polish population. The study was performed in 225 first degree relatives of IDDM patients with ICA and/or GADA and 100 relatives without antibodies, in whom ICA and/or GADA were performed in 1993-1994. We have observed significantly lower percentages of diabetes-free survival in subjects with ICA > 20 JDF in comparison to relatives without ICA or with ICA < 20 JDF. The highest predictive value for diabetes type 1 development was associated with the ICA > 80 JDF and with the co-existence of ICA--20-79 JDF and GADA (+). There was also a statistically lower diabetes-free survival in first degree relatives (with ICA > 20 JDF) older than 20 years of age in comparison to the younger subjects. Detection of 2 antibodies: ICA and GADA made it possible to identify 80% of first degree relatives who have developed diabetes type 1 in the following 5-6 years, this suggests that the combined measurement of ICA and GADA could be a useful marker in screening for diabetes type 1 in first degree relatives of IDDM subjects in the Polish population. For the diabetes type 1 risk assessment in relatives with ICA > 20 JDF the age of the studied subjects should be taken into consideration.