TNF and rheumatoid arthritis: Theseresults suggest that this model couldbe a relevant model for evaluation ofpannus formation in patients with RA.Both PDE4 inhibitors, KF66490 and SB207499,showed an effect comparable to those ofantirheumatic drugs in this model; andalso, PDE4 inhibitors inhibitedlipopolysaccharide-induced TNF-α and IL-12production from thioglycolate-inducedmurine peritoneal macrophages and theproliferation of rat synovialfibroblasts.