HLA-DRB1 and rheumatoid arthritis: Cluster analyses indicated a significant spatial component in A*D interaction for HLA-B*08 × RA, HLA-DRB1*03 × RA, HLA-B*08 × MS (P < 0.01), and HLA-A*29 × CD (P < 0.05), which is represented in Fig. 5 (and in Additional file 8).