The pathogenesis of diabetes mellitus I is multifactorial. Both genetic predisposition and environmental factors are involved in the deregulation of immune system with subsequent breakage of self-tolerance. Autoantibodies against numerous autoantigens are raised during this long-term process but the principal pathogenic mechanism is cytotoxic killing of
cells of pancreas mediated predominantly by T cells. There could be the chance to interrupt this pathogenetic process by manipulation with immune system to achieve induction of tolerance. Such clinical trials are now under progress.

        Key words: Diabetes mellitus I - Immunopathogenesis - Autoantigens - Genetic predisposition - Environmental factors