HLA and complement allotypes in Type 1 (insulin-dependent) diabetes.

A group of patients with Type 1 (insulin-dependent) diabetes mellitus was investigated for HLA-A, B and DR antigens as well as C4 and factor B polymorphism. A significant excess of DR3/DR4 heterozygotes was observed (27% versus 17% by Hardy-Weinberg expectation). The factor B allele BfF1 was present in 13% of patients with Type 1 diabetes (gene frequency of 0.08 versus 0.01 in control subjects). A rare C4 B allele, C4 B2.9, was found in 18% of patients with Type 1 diabetes (n = 63) compared with 1.1% of control subjects (n = 176). Total C4 deficiency at the C4 A locus (C4 AQ0,0) was present in 10% of patients with Type 1 diabetes compared with 0% of control subjects. Examination of HLA, C4 and Bf phenotypes in patients with Type 1 diabetes suggested that three high risk supratypes, HLA-A1 B8 BfS C4 AQ0 C4 B1 DR3; HLA-B18 BfF1 C4 A3 C4 BQ0 DR3; HLA-A2 CW3 BW62 BfS C4 A3 C4 B2.9 DR4 are markers for susceptibility alleles.