GAD2 and diabetes mellitus: As an alternative approach to understanding autoantigen–HLA interactions, The Environmental Determinants of Diabetes in the Young (TEDDY) study has investigated the natural history of the emergence of autoantibodies on specific HLA backgrounds, revealing that in HLA-DR3-DQ2 individuals GAD65 tends to be the first of the studied islet antigens against which autoantibodies are formed, while in HLA-DR4-DQ8 individuals it is insulin [8, 9].