Association of Non-HLA Genes With Type 1 Diabetes Autoimmunity

Approximately 50% of the genetic risk for type 1 diabetes is attributable to the HLA region. We evaluated associations between candidate genes outside the HLA region-INS, cytotoxic T-lymphocyte-associated antigen (CTLA)-4, interleukin (IL)-4, IL-4R, and IL-13 and islet autoimmunity among children participating in the Diabetes Autoimmunity Study in the Young (DAISY). Children with persistent islet autoantibody positivity (n = 102, 38 of whom have already developed diabetes) and control subjects (n = 198) were genotyped for single nucleotide polymorphisms (SNPs) in the candidate genes. The INS-23Hph1 polymorphism was significantly associated with both type 1 diabetes (OR = 0.30; 95% CI 0.13-0.69) and persistent islet autoimmunity but in the latter, only in children with the HLA-DR3/4 genotype (0.40; 0.18-0.89). CTLA-4 promoter SNP was significantly associated with type 1 diabetes (3.52; 1.22-10.17) but not with persistent islet autoimmunity. Several SNPs in the IL-4 regulatory pathway appeared to have a predisposing effect for type 1 diabetes. Associations were found between both IL-4R haplotypes and IL-4-IL-13 haplotypes and persistent islet autoimmunity and type 1 diabetes. This study confirms the association between the INS and CTLA-4 loci and type 1 diabetes. Genes involved in the IL-4 regulatory pathway (IL-4, IL-4R, IL-13) may confer susceptibility or protection to type 1 diabetes depending on individual SNPs or specific haplotypes.