CD4 and type 1 diabetes mellitus: HLA-DQ2 (DQA*05:01, DQB*02:01) is also present in about 1/3 T1D patients, and trans dimers can be formed where the beta alpha chain of DQ2 pairs with the beta chain of DQ8 (DQ8 trans: DQA*05:01, DQB*03:02), which may present unique epitopes to autoreactive CD4 T cells in T1D (53, 56, 57).