The severity of synovitis, evaluated by the synovial volume in H&E staining (Figures 4C, D; p= 0.0259), and osteoclastic resorption, indicated by TRAP staining (Figures 4C, E; p= 0.0089), were significantly exacerbated in TNF-tg x cKit-/-, resulting in a greater reduction in bone volume compared to their TNF-tg littermates (Figures 4A, B; p= 0.0023). This evidence concerns the gene ACP5 and synovitis.