The human leukocyte antigen class II gene has different contributions to autoimmune type 1 diabetes with or without autoimmune thyroid disease in the Japanese population.

AIM: Type 1 diabetes (T1D) is associated with autoimmune thyroid disease (AITD). The human leukocyte antigen (HLA) has been extensively studied in these diseases. We aimed to clarify the contribution of AITD on the susceptibility and resistance of the HLA subtype to autoimmune T1D in the Japanese population.

METHODS: The frequency of the HLA DR-DQ haplotype was compared between 56 autoimmune T1D patients with AITD and 71 autoimmune T1D patients without AITD, and control subjects.

RESULTS: The frequencies of DRB1 0405-DQB1 0401, DRB1 0802-DQB1 0302, and DRB1 0901-DQB1 0303 haplotypes were significantly higher in T1D patients with AITD than in control subjects. The frequencies of DRB1 0101-DQB1 0501, DRB1 0901-DQB1 0303, and DRB1 1302-DQB1 0604 haplotypes were significantly higher in T1D patients without AITD than in control subjects. The frequencies of DRB1 1101-DQB1 0301 and DRB1 1501-DQB1 0602 haplotypes were significantly lower in T1D patients with or without AITD than in control subjects.

CONCLUSIONS: Our results suggest that the susceptibility of the HLA subtype to autoimmune T1D differs between T1D with AITD and T1D without AITD, whereas there is no difference between the two groups with regard to HLA subtypes that confer protection against autoimmune T1D.