HLA Associations with Insulin‐Dependent Diabetes Mellitus in a Sample of the American Black Population*

It has been of considerable interest to determine if the HLA associations with insulin-dependent diabetes mellitus (IDDM) in blacks are the same as in whites in the United States. Seventy-nine black IDDM patients who were under the age of 40 at onset and 283 black controls were HLA typed for A, B and C specificities. This is the largest sample of black IDDM patients yet reported. Analysis of HLA antigen frequencies for these samples has revealed an increased frequency of HLA B8 (p<0.01), B13 (p<0.02) and B15 (p<0.006), and a decreased frequency of B14 (p<0.01). The estimate of relative risks for B8 and B15 was 2.6 and 4.4, respectively. Comparison of a subsample of the black patients (n= 61) and controls (n=137) revealed increased frequencies of DR3 (p<0.0004), DR4 (p<0.0002), and DR7 (p<0.03) in the IDDM patients. Both HLA DR2 and DR5 were decreased in the diabetic patients (p<0.0()01 and p<0.0002, respectively). All p values were uncorrected. The associations of HLA antigens with IDDM in our black American sample are essentially the same as those found in white IDDM patients. This suggests that the occurrence of IDDM in American blacks may be due to admixture of white genes.