HLA-DR has been linked to aberrant presentation of self-peptide to autoreactive T helper cells in the thymus22, and genetic polymorphisms in the HLA-DRB1 gene are associated with a range of autoimmune diseases, such as rheumatoid arthritis, diabetes mellitus type I or systemic lupus erythematosus23. Here, HLA-DRB1 is linked to type 1 diabetes mellitus.