Background. Autoimmune insulitis leading to insulin dependent diabetes mellitus (IDDM, Type 1 Diabetes) is accompanied by autoantibodies as its invaluable markers. The aim of the study was to determine the frequency of autoantibodies against GAD65, IA2 and insulin in Czech diabetic children at the disease onset. Methods and Results. Sera of 105 newly diagnosed children with IDDM drawn within 24 hours after the first insulin dose were investigated for anti-GAD65, anti-IA2 and insulin autoantibodies (IAA) using RIA methods. The cut-off normal levels were determined as the 99th percentile of 105 non-diabetic children. At given 99 % specificity, the sensitivity was 71 % for anti-GAD65, 73 % for anti-IA2, and 46 % for IAA. 29 % diabetic children were positive for all three autoantibodies, 25 % had anti-GAD65 and anti-IA2 (IAA negative), 5,7 % anti-GAD65 and IAA (anti-IA2 negative), 7,6 % anti-IA2 and IAA (anti-GAD65 negative). As the only positive autoantibody, anti-GAD65 was found in 12 %, anti-IA2 in 11 %, and IAA in 3,8 % children. In 5,7 % children, none of the investigated autoantibodies was positive. Diabetic children diagnosed before the age of 5 years had significantly higher prevalence of IAA than the older ones. Conclusions. We have determined normal levels in healthy children, and prevalence at childhood IDDM onset of autoantibodies against three main molecular-defined autoantigens.

        Key words: IDDM, childhood, autoantibodies, prevalence, IAA, GAD65, IA2.