GAD2 and type 1 diabetes mellitus: Type 1 diabetes is an autoimmune disease caused by the activation of CD8+ and CD4+ T cells targeted to a group of autoantigens released from β-cells: (Pre)proinsulin, glutamic acid decarboxylase of 65 KD (GAD65), tyrosine phosphatase IA2, and the zinc transporter ZnT8.