T-cell lines reactive to an immunodominant epitope of the tyrosine phosphatase-like autoantigen IA-2 in type 1 diabetes

Type 1 diabetes is the result of destruction of the insulin-secreting beta-cells of the pancreas by a process in which T-cells play a central role, A tyrosine phosphatase-like protein, IA-2, is a major target for autoantibodies and T-cells in the disease, In this study, we have further characterized the T-cell response to IA-2 by the generation and characterization of T-cell lines, T-cell lines responsive to IA-2 antigen were generated from 17 of 32 patients and 3 of 10 control subjects, Antigen specificity was confirmed in lines from six diabetic patients and one control individual by demonstration of responses to synthetic IA-2 peptides and epitope mapping, Five lines from diabetic patients responded to one of two peptides representing amino acids 831-850 and 841-860 of IA-2, The overlapping portion may therefore represent an immunodominant region of the molecule, The sixth patient-derived line responded to a peptide representing amino acids 751-770 of IA-2 presented by the DR 4 (DRB1 *0401) allele that confers susceptibility to type 1 diabetes, Primary T-cell responses to peptides of the immunodominant region were detected in 9 of 19 (47%) type 1 diabetic patients and 16 of 22 (73%) nondiabetic siblings, consistent with this region having immunostimulatory properties. The study reports for the first time T-cell lines reactive to IA-2 from diabetic patients and defines an immunodominant region of the molecule.