Arthritis can occur in any one of these diseases, but the role of Th17 cells and Th17-related cytokines in arthritis appears to differ according to disease. In RA, Th17 cells may play an important role in the initial development of arthritis and bone destruction caused by the induction of osteoclast formation, causing subsequent arthritis mutilans, which is characteristic of RA. In psoriasis, Th17 and Th22 cells promote the cutaneous pathophysiology of acanthosis and parakeratosis while inducing osteoclastogenesis in joints and progression to osteoclastic arthropathy. Meanwhile, in Behcet’s disease, Th17 and IL-23 abnormalities are involved in neutrophil migration and activation and form the basis of the various pathophysiologies observed in Behcet’s disease, which exhibits a principally neutrophilic pathophysiology and sometimes appears to cause the onset of arthritis.
Figure 2: The role of Th17 cells in rheumatoid arthritis (RA), psoriasis, and Behcet’s disease.