Notably, we define a series of new histopathological correlates for the stage 1/2 pancreas (i.e., an enhanced immune cell burden as reflected in higher frequencies of islets with ≥ 1 associated immune cell[s]; early targeting of small, including “GCG-deficient” islets; a relative reduction of total ProINS/IAPP areas; and a pronounced collapse of islet cluster I magnitude) that position AAb subjects on the cusp of developing the very histopathological hallmarks that are distinctive for T1D. Here, GCG is linked to type 1 diabetes mellitus.