1 TNFα but not IL-17 is critical in the pathogenesis of rheumatoid arthritis spontaneously occurring in a unique FcγRIIB-deficient mouse model Hideki Okazaki 1,2 , Qingshun Lin 1 , Keiko Nishikawa 1 , Naomi Ohtsuji 1 , Hiromichi Tsurui 1 , Mareki Ohtsuji 3 , Hirofumi Amano 4 , Norihiro Tada 5 , Katsuko Sudo 6 , Hiroyuki Nishimura 3 , Toshikazu Shirai 1 , and Sachiko Hirose 1 1 Department of Pathology, 4 Department of Internal Medicine, 5 Atopy Research Center, Juntendo University School of Medicine, Tokyo 113-8421, Japan 2 Health and Life Science, Musashigaoka Junior College, Saitama 355-0154, Japan 3 Toin Human Science and Technology Center, Department of Biomedical Engineering, Toin University of Yokohama, Yokohama 225-8502, Japan 6 Animal Research Center, Tokyo Medical University, Tokyo 160-8402, Japan Number of text pages: 33 Numbers of tables and figures: 2 tables and 4 figures (2 color [Figs.1 and 2] and 2 black-and-white [Figs.3 and 4]) Key words: FcγRIIB, monocytosis, osteoclastogenesis, RANKL, OPG Address correspondence and reprint requests to Sachiko Hirose, MD, PhD, Department of Pathology, Juntendo University School of Medicine, 2-1-1 Hongo, Bunkyo-ku, Tokyo 113-8421, Japan. Phone: +81-3-5802-1671, Fax: +81-3-3813-3164, E-mail address: sacchi@juntendo.ac.jp