the demonstration and specificity of autoreactive tlymphocytes in type1 diabetes background and objective type 1 diabetes is characterised by a chronic autoimmune process predominantly transmitted by tcells yet current knowledge about autoimmune reactions in type 1 diabetes transmitted by antigenspecific tcells is very limited in this study we investigated tcell reactivity to potential autoantigens and their immunodominant epitopes in patients with type 1 diabetes and in control groupspatients and methods using 3hthymidine incorporation in peripheral blood lymphocytes in patients with type 1 group 1 or type 2 group 2 diabetes healthy controls group 3 and healthy twins of type 1 diabetics group 4 cell reactivity was measured to the proteins insulin and glutamate decarboxylase gad 65 and against the peptides of insulin gad 65 heat shock protein hsp and bovine serum albumin bsaresults patients with type 1 diabetes had a significantly higher stimulation of peripheral tlymphocytes by gad 65 and a mixture of selected gad 65 peptides than healthy controls there was no significant difference between the groups with regard to the stimulation of peripheral blood lymphocytes by insulin individual gad peptides or insulin hsp and bsapeptidesconclusions autoantigenspecific tlymphocytes can be demonstrated in blood of type 1 diabetics the necessary tests for this are at present relatively cumbersome and therefore limited to special research laboratories but in the future their identification in autoimmune diseases such as type 1 diabetes will be a valuable addition to the demonstration of antibodies in which even in the prediabetic phase possibly protective and cytotoxic immune reactions can be distinguished