GENETIC AND IMMUNOLOGICAL MARKERS OF INSULIN-DEPENDENT DIABETES IN BLACK-AMERICANS

ICA and GAD65 autoantibody profiles and HLA-DR and DQ analysis were pe rformed on 43 Black juvenile onset IDDM patients and 34 unrelated Blac k controls from Tennessee, USA. 75% of patients were positive for GAD6 5 autoantibodies but only 53% had ICA; 39% both ICA and GAD65 antibodi es. The strongest HLA association was with the DR3 haplotype DRB103 D QA10501 DQB1*0201 (63% of patients v 12% of controls RR = 13.0, p < 0 .00002). DRB104 DQA1*0301 DQB1*0302, associated with IDDM in Caucasia ns but rare in Negroids, occurred in 27% of patients and 6% of control s (RR = 5.9, p < 0.04). All patients carried DQB10302 or DQB1*0201. D QB10602 was significantly reduced in patients (2.4% v 41%, RR = 0.036 , p < 0.008) and DRB11501 was absent in patients (0% v 35%). The freq uency of GAD65 autoantibodies in Black American IDDM patients is compa rable to that in Caucasians; however ICA positivity is reduced. GAD65 antibodies may therefore be a more sensitive serological test to ident ify individuals in the Black American general population for markers a ssociated with increased risk of developing IDDM. Current screening me thods for predicting preclinical IDDM in Caucasians relies on a combin ation of immune and HLA markers of IDDM; studies of these markers in t he Black Americans will make it possible to extend these options to ad ditional genetically diverse populations.