Shinji Maeda, Tomoyo Maeda, Ayako Kobayashi, Taio Naniwa, Shinya Tamechika and Yoshihito Hayami
There is an increasing amount of evidence suggesting the importance of CD4+ T cells, particularly IL-17-producing helper T cells (Th17), in the pathology of rheumatoid diseases such as rheumatoid arthritis. In various mouse models, arthritis has been reported to be markedly decreased because of IL-17 deficiency. Genetic polymorphisms in Th17 and Th17-related cytokines have also been reported in association with human rheumatoid diseases. This review summarizes the role of Th17 in mouse and human joint pathology and discusses the role of Th17 cells in the pathology of rheumatoid arthritis, psoriasis, psoriatic arthritis, and Behcet’s disease. Th17 cells play a significant role in the main pathology of these diseases. They are involved in the onset of arthritis and articular bone destruction due to osteoclastogenesis in rheumatoid arthritis. They are also involved in acanthosis and parakeratosis of the skin in psoriasis and migration and activation of neutrophils in Behcet\'s disease. Therefore, Th17 cells may have significant potential to function as therapeutic targets for these diseases.