Relationships among 64k Autoantibodies, Pancreatic β-cell Function, HLA-DR Antigens and HLA-DQ Genes in Patients with Insulin-Dependent Diabetes Mellitus in Korea

OBJECTIVES: Among autoantibodies detected in patients with insulin-dependent diabetes mellitus(IDDM), antibodies to 64,000Mr islet protein(64k), now recognized as glutamic acid decarboxy lase(GAD), appear to be an even more predictive marker of IDDM than islet cytoplasmic antibody(ICA) or insulin autoantibody(IAA). We examined the relationships among 64k autoantibodies, pancreatic β-cell function, HLA-DR antigens and HLA-DQ genes in patients with IDDM in Korea. METHODS: To identify the 64k autoantibody, the immunoprecipitation method was performed for 35 patients with IDDM and 10 normal controls. In patients with IDDM, serum C-peptide levels were measured and HLA-DR typings and HLA-DQA1 and DQB1 gene typings were performed. RESULTS: 12 of 35(34%) patients with IDDM were positive for 64k autoantibody in contrast to none of 10(0%) normal controls. There were no differences in residual pancreatic β-cell function between 64k autoantibody positive and negative groups. 64k autoantibody was detected more frequently in patients with recent(duration< 6 months, 10/25[40%]) and young -aged(age< 15 years, 7/18[39%]) onset of IDDM. All of 3(100%) patients with HLA-DR3/DR4 heterotypes were positive in 64k autoantibody, in contrast to 1 of 7(14%) patients without HLA-DR3 nor DR4. The frequencies of HLA-DQA1*0301, HLA-DQB1*0201, DQB1*0302 and DQB1*0303 gene types were higher in patients with 64k autoantibody (12/12[100%]) vs. without 64k autoantibody 18/22[81%], 5/11[45%] vs. without 64k autoantibody 5/22[23%], 5/11[45%] vs. without 64k autoantibody 8/22[36%] and 6/11[55%] vs. without 64k autoantibody 9/22[41%]. CONCLUSIONS: There results suggest that 64k autoantibodies have some relationship with HLA-DR, DQA1 and DQB1 genes, but not with residual pancreatic β-cell function in Korean patients with IDDM.