Kawahito and co-authors demonstrated that the synovial lining layer, fibroblasts, and endothelial cells show expression of PPARγ in patients with rheumatoid arthritis (RA) and suggested that PPARγ may be an essential immunoinflammatory mediator and its ligands, especially 15d-PGJ2, may be helpful in the treatment of RA [75]. The gene discussed is PPARG; the disease is rheumatoid arthritis.