TY - JOUR T1 - Downregulation of RCAS1 and Upregulation of Cytotoxic T Cells Affects Synovial Proliferation and Apoptosis in Rheumatoid Arthritis JF - The Journal of Rheumatology JO - J Rheumatol SP - 1716 LP - 1722 VL - 35 IS - 9 AU - SHIRO YOSHIDA AU - FUJIO HIGUCHI AU - YUMIKO ISHIBASHI AU - MASAFUMI GOTO AU - YASUO SUGITA AU - YUKO NOMURA AU - KENNOSUKE KARUBE AU - KEI SHIMIZU AU - RYOSUKE AOKI AU - HIDEKI KOMATANI AU - KEIKO HASHIKAWA AU - YOSHIZO KIMURA AU - MANABU NAKASHIMA AU - KENSEI NAGATA AU - KOICHI OHSHIMA Y1 - 2008/09/01 UR - http://www.jrheum.org/content/35/9/1716.abstract N2 - Objective The main histological change in rheumatoid arthritis (RA) is the villous proliferation of synovial lining cells. This seems to be the result of the proliferation and apoptosis induced by immune balance. We studied the involvement of RCAS1 and the infiltration of cytotoxic T lymphocytes (CTL), and examined the synovium immunohistochemically to determine the involvement of proliferation and apoptosis in synovial lining cells, and their relationship with the activity of RA Treg cells in the germinal center. Methods We used double-immunological staining of Ki-67 and caspase-3 to investigate proliferation and apoptosis. We analyzed CTL, regulatory T cells (Treg), and receptor-binding cancer antigen expressed on SiSo cells (RCAS1), recently recognized to play a role in immune evasion. Proliferation and apoptosis were more frequently encountered in synovial lining cells in RA than in those in osteoarthritis (OA) that were used as a control. Results High expression of RCAS1 was detected more frequently in the synovial lining cells of OA, but CTL infiltration into the synovium was rarely found. In RA, on the other hand, CTL were observed, while RCAS1 expression was lacking. We compared the presence of Foxp3-positive cells with the level of C-reactive protein (CRP) that served as an active inflammatory marker. Foxp3-positive cells in the germinal center and in CRP showed possible correlation in terms of the range of inflammatory states. Conclusion In RA, the lack of RCAS1 is thought to induce CTL infiltration through loss of the ability to evade immune attack, thus leading to apoptosis of the synovial lining cells. In addition, Treg cells may play a role in the downregulation of activated T cells. ER -