GAD2 and type 1 diabetes mellitus: Islet autoimmunity is serologically confirmed by the presence of at least one of the major T1DM-related autoantibodies (AAbs) in humans, i.e., insulin AAbs, glutamate decarboxylase 65 (65 kDa isoform) (designated as GAD65) AAbs, protein tyrosine phosphatase islet antigen 2 AAbS, and zinc transporter 8 AAbS (So et al. 2021).