摘要：Antibodies to glutamic acid decarboxylase (GADab) is considered to be a marker for the autoimmune process against pancreatic β cells. Indeed, nearly 70% of patients with type 1 diabetes is repoted to be GAD ab＋. A subgroup of patients diagnosed as type 2 diabetes has GADab. Therefore, it is questioned whether GADab＋ patients with type 2 diabetes represent a late onset of type 1 diabetes or a unique disease entity. Fifty five GADab＋ patients with type 2 diabetes were compared with 137 GADab- patients. They were admitted to Abe Diabetes Clinic for the control of diabetes. The age at onset of these patients was ＞30 years, and did not require insulin therapy for at least 6 months from the disease onset. The GADab＋ patients had lower urinary C-peptide concentrations (uCPR) ［(47.8±48.9) μg/d vs (58.1±49.9) μg/d, P=0.034］ than the GADab- patients. The GAD＋ patients were assigned insulin therapy more often (81.8% vs 56.3%, P=0.0038) and earlier ［(8.5±7.5)years vs (10.1±7.3) years, P=3.3×10-12］ than the GAD- patients. The levels of uCPR were associated with the titers of GADab (r=0.32, P=0.038). Among the susceptible HLA alleles for type 1 diabetes, the frequencies of B54 and DRB1* 0405 alleles, but not B61 and DRB1*0901 alleles, were increased among GADab＋ patients. There data suggest that the GADab＋ type 2 diabetes has an autoimmune nature, although the extent of insulin dependency and the distribution of HLA susceptible alleles are different from type 1 diabetes.