Relation of insulin-dependent diabetes mellitus (IDD) and the HLA-linked SB system.

This report deals with the question of the susceptibility for IDD association with the recently described HLA-linked SB system. The SB system is located centromeric of HLA-DR between HLA-DR and GLO. At present five specificities of the SB system, which behave as alleles, can be recognized. A total of 40 IDD patients and 96 normal controls were characterized for HLA-A, -B, -C, -DR and SB antigens. Our results confirmed the strong positive association of IDD with HLA-DR3 and -DR4 and the negative association of IDD with HLA-DR2. The genetic analysis of the SB system and IDD, however, demonstrated no significant association between alleles of SB and susceptibility for IDD. The analysis of association between alleles of HLA-DR and SB revealed no significant linkage disequilibrium in IDD patients and a significant linkage disequilibrium between SB1 and HLA-DR3 in the controls. These results suggest that the genes associated with susceptibility for IDD are primarily coded for telomeric of SB and tightly linked with HLA-DR.