GAD2 and type 1 diabetes mellitus: Interest in recent immunologic response serology in T1D resulted in the identification of four major molecularly characterized islet specific autoantigens as immunological markers of disease progression: the secreted hormone insulin; the Mr 65,000 isoform of glutamate decarboxylase or glutamic acid decarboxylase (GAD65); islet protein tyrosine phosphatase-like molecule (IA-2) or islet cell autoantigen 512 (ICA512); and the novel T1D autoimmunity target zinc transporter 8 (ZnT8) [5], [21]–[31].