Triggering mechanisms and T-cell responses in the spondylarthropathies

Abstract The term spondylarthropathy (SpA) applies to a group of different, although closely related, diseases: ankylosing spondylitis (AS); reactive arthritis (ReA); a subset of psoriatic arthritis (PsA); arthritis/sacroiliitis in inflammatory bowel disease; and undifferentiated SpA. All these diseases have an HLA-B27 association, sacroiliitis, a characteristic type of peripheral joint involvement, enthesitis, and some extra-articular manifestations in common (Dougados et al. 1991a). Their pathogenesis is not clear, but the interaction of bacteria, T cells, and the HLA-B27 molecule seems to be important (Kingsley and Sieper 1993).