GAD1 and type 1 diabetes mellitus: We focused on PPI-reactive T cells, as these have been well characterized from the pancreatic islet infiltrates of T1D organ compared with T cells directed against GAD and IA-2A (12, 14, 19–22), despite finding specific Vβ genes early in life associated with a subset of cases that developed GAD and IA-2A autoantibodies.