Aetiology and pathogenesis of reactive arthritis: role of non-antigen-presenting effects of HLA-B27

Spondyloarthropathies are inflammatory diseases closely associated with human leukocyte antigen (HLA)-B27 by unknown mechanisms. One of these diseases is reactive arthritis (ReA), which is typically triggered by Gram-negative bacteria, which have lipopolysaccharide as an integral component of their outer membrane. Several findings in vivo and in vitro obtained from patients with ReA and from different model systems suggest that HLA-B27 modulates the interaction between ReA-triggering bacteria and immune cells by a mechanism unrelated to the antigen presentation function of HLA-B27. In this review we piece together a jigsaw puzzle from the new information obtained from the non-antigen-presenting effects of HLA-B27.