PTPRN and Autoimmunity: In T1D, autoantibodies to islet antigens–insulin (IAA), glutamic acid decarboxylase 65 (GAD), islet cell cytoplasmic antigens (ICA), zinc transporter 8 (ZnT8), and protein tyrosine phosphatase-like protein (IA-2/ICA512) [5] are validated biomarkers of autoimmunity.