Autoantibodies to GAD, IA-2 and insulin in ICA-positive first-degree relatives of children with type 1 diabetes: a comparison between parents and siblings.
BACKGROUND: Islet cell antibodies (ICA) represent a heterogenous group of autoantibodies to diabetes-associated antigens, including glutamic acid decarboxylase (GAD) and the IA-2 protein. The objectives of the present study were to compare the prevalence of autoantibodies to known biochemically characterized autoantigens between ICA-positive non-diabetic parents and siblings of children with type 1 diabetes and to evaluate how such antibodies explain ICA reactivity. METHODS: The presence and levels of GAD antibodies (GADA), IA-2 antibodies (IA-2A) and insulin autoantibodies (IAA) were analyzed in the sera of 184 ICA-positive first-degree relatives (79 parents and 105 siblings). RESULTS: The prevalences of GADA (61.9% in siblings vs 32.9% in parents), IA-2A (55.2% vs 15.2%) and IAA (41.0% vs 0%) were increased among ICA-positive siblings relative to ICA-positive parents (p