In the clinical part of the study the prevalence of genetic markers and disease-associated autoantibodies in Estonian patients with new-onset type 1 diabetes were determined, and the associations between genetic factors and autoantibodies were analysed. The experimental part of the study was carried out in RIP(rat insulin promoter)-B7.1 transgenic mice in whom the expression of the immunostimulatory B7.1 molecule in -cells increases the susceptibility of the mice to autoimmune diabetes. In the current study the main diabetogenic T cell population of this experimental model was characterised and the target epitope of the pathogenic T cell response against the insulin molecule was identified.