Zinc transporter 8 (ZnT8) is a pancreatic β-cell secretory granule membrane protein that has been  identified as a target of humoral immunity in type 1 diabetes. Autoantibodies to ZnT8 (ZnT8As) constitute an additional marker of autoimmune diabetes, which complement the established antibodies to insulin (IAAs), glutamic acid decarboxylase ,GAD (GADAs), and protein tyrosine IA-2 (IA-2As) . 

Unit4,

Reference: Lampasona V, Petrone A, Tiberti C, et al. Zinc transporter 8 antibodies complement GAD and IA-2 antibodies in the identification and characterization of adult-onset autoimmune diabetes: Non Insulin Requiring Autoimmune Diabetes (NIRAD) 4. Diabetes Care. 2010;33(1):104-108. doi:10.2337/dc08-2305