GCG and type 1 diabetes mellitus: Collectively, these results suggest that (i) in T1D donors, human pancreatic islets show a higher proportion of α- and β-cells expressing MDA5 with respect to nondiabetic controls or T1D-LS donors; (ii) in T1D, both α- and β-cells drive the increase in MDA5-positive cells in human pancreatic islets; (iii) such an increase is more pronounced in T1D-RO with respect to T1D-LS; and (iv) in T1D-RO donors, we uncovered the existence of MDA5-expressing islet-like structures, which were positive for chromogranin A but negative for islet main hormones (insulin, glucagon, and somatostatin).