The Bw4 epitope spans the residues 77–83 but it has been described that changes at specific positions in the HLA-B molecule outside this epitope, in particular, position 97, affect the interaction of Bw4 with KIR3DL1 and, interestingly, the position 97 of HLA-B has been found strongly associated with susceptibility to BD (8–10). This evidence concerns the gene KIR3DL1 and Behcet disease.