We have known about the strong association between AS and the HLA-B*27 (B*27) gene for the past 40 years; however, the mechanism with which only some allomorphs of the HLA-B27 molecule, as well as some other HLA class I molecules, are involved in the occurrence of SpAs is still unclear [1]. In this issue of Rheumatology, Cauli et al. [2] present data that may aid our understanding of this mecha...
