Compared with WT CIA mice, body size was decreased; however, cumulative arthritis scores from 1 to 9 weeks after primary immunization, paw thickness, levels of rheumatoid factors (RFs) and C-reactive protein (C-RP) from serum increased significantly in vehicle-treated CYP27B1−/− CIA mice (Figures 1a–f). The gene discussed is CYP27B1; the disease is arthritic joint disease.