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OBJECTIVE -- Autoimmune thyroid disease (ALT), celiac disease, and Addison's disease are characterized by the presence of autoantibodies: thyroid peroxidase antibody (TPOAb) and thyroglobulin antibody (TGAb) in AIT, tissue transglutaminase antibody (TTGAb) in celiac disease, and 21-hydroxylase antibody (21-OHAb) in Addison's disease. The objective of this study was to define the prevalence of these autoantibodies and clinical disease in a population with type 1 diabetes. RESEARCH DESIGN AND METHODS -- We screened 814 individuals with type 1 diabetes for TPOAb, TGAb, TTGAb, and 21-OHAb. Clinical disease was defined by chart review. Factors related to the presence of autoimmunity and clinical disease including age at onset of type 1 diabetes, duration of diabetes, age at screening, sex, and the presence of autoantibodies were reviewed. RESULTS -- The most common autoantibodies expressed were TPOAb and/or TGAb (29%), followed by TTGAb (10.1%) and 21-OHAb (1.6%). Specific HLA DR/DQ genotypes were associated with the highest risk for expression of 21-OHAb (DRB1(*)0404-DQ8, DR3-DQ2) and TTGAb (DR3-DQ2- DR3-DQ2). The expression of thyroid autoantibodies was related to 21-OHAb but not to TTGAb. The presence of autoantibodies was associated with and predictive of disease. CONCLUSIONS -- In this large cohort of individuals with type 1 diabetes, the expression of organ-specific autoantibodies was very high. The grouping of autoantibody expression suggests common factors contributing to the clustering. [ABSTRACT FROM AUTHOR]

Objective: The characterization of diverse subtypes of diabetes is a dynamic field of clinical research and an active area of discussion. The objective of this study was to identify new antigenic determinants in the neuroendocrine autoantigen IA-2 (ICA512) and assess whether circulating autoantibodies directed to new IA-2 epitopes identify autoimmune diabetes in young and adult populations with diabetes.Research Design and Methods: Clinically diagnosed patients with type 2 diabetes (n = 258; diabetes duration: 0.01-31 years) were evaluated using a new biomarker detecting autoantibodies directed to the extracellular domain of the neuroendocrine autoantigen IA-2 (IA-2ec). The proportion of IA-2ec autoantibodies was also evaluated in newly diagnosed patients with type 1 diabetes (n = 150; diabetes duration: 0.04-0.49 years). In addition, IA-2 (intracellular domain), GAD65, and zinc transporter 8 autoantibodies were assayed.Results: IA-2ec autoantibodies were detected in patients with type 1 diabetes and, surprisingly, in 5% of patients with type 2 diabetes without serologic responses to other IA-2 antigenic epitopes or other islet autoantigens. We also assessed the ability of IA-2ec-derived peptides to elicit CD4+ T-cell responses by stimulating peripheral blood mononuclear cells from patients with type 1 diabetes (n = 18) and HLA-matched healthy subjects (n = 13) with peptides and staining with the peptide/DQ8-specific tetramers, observing disease-associated responses to previously unreported epitopes within IA-2ec.Conclusions: We developed a new antibody biomarker identifying novel antigenic determinants within the N terminus of IA-2. IA-2ec autoantibodies can be detected in patients with type 1 diabetes and in a subgroup of adult autoimmune patients with type 2 diabetes phenotype negative for conventional islet autoantibody testing. These observations suggest that islet autoimmunity may be more common in clinically diagnosed type 2 diabetes than previously observed. [ABSTRACT FROM AUTHOR]