Genetic predisposition and IDDM in Greece.

Serological typing of HLA-DR antigens was performed on 116 patients with IDDM and 380 healthy controls. As expected a high incidence of HLA-DR3 and DR4 antigens was observed in patients with IDDM. However, the HLA-DR2 antigen, which rarely occurs in IDDM and is considered to confer protection against IDDM, was found in equal distribution (35%) in both patients and controls. HLA-DQ genotype analysis in 10 children with IDDM and 13 controls, all with the HLA-DR2 haplotype, showed that the great majority of affected children and normal controls carry the DR2 (16) or AZH-DQA1 *0102, DQB *0502 subtype. The high incidence of this subtype in normal individuals possibly explains why the DR2 antigen does not offer protection against IDDM in Greeks.