The 3-dimensional structure of HLA-DR. The 3-dimensional ribbon model of HLA-DR is based on Protein Data Bank entry 3PDO with the DR α chain shown in violet and the DR β chain in gray. Amino acid positions identified within the HLA-DRB1 protein by the association analysis are shown for positions 11 (black), 13 (blue), 14 (cyan), 25 (orange), 30 (brown), 57 (yellow), 60 (pink), 73 (red), 74 (green), and 78 (purple).