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Genes Immun. 2011 Sep;12(6):415-27. doi: 10.1038/gene.2011.24. Epub 2011 May 12.

Functional consequences of HLA-DQ8 homozygosity versus heterozygosity for islet autoimmunity in type 1 diabetes.

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Department of Immunohaematology and Blood Transfusion, Leiden University Medical Center, Leiden, The Netherlands.


Human leukocyte antigen (HLA) class II haplotypes are established risk factors in type 1 diabetes (T1D). The heterozygous DQ2/8 genotype confers the highest risk, whereas the DQ6/8 genotype is protective. We hypothesized that DQ2/8 trans-molecules composed of α and β chains from DQ2 and DQ8 express unique β-cell epitopes, whereas DQ6 may interfere with peptide binding to DQ8. Here we show that a single insulin epitope (InsB13-21) within the T1D prototype antigenic InsB6-22 peptide can bind to both cis- and trans-dimers, although these molecules display different peptide binding patterns. DQ6 binds a distinct insulin epitope (InsB6-14). The phenotype of DQ8-restricted T cells from a T1D patient changed from proinflammatory to anti-inflammatory in the presence of DQ6. Our data provide new insights into both susceptible and protective mechanism of DQ, where protecting HLA molecules bind autoantigens in a different (competing) binding register leading to 'epitope stealing', thereby inducing a regulatory, rather than a pathogenic immune response.

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