Cytokines in bone and cartilage destruction and repair

It is widely recognized that tumor necrosis factor (TNF) is a major target in developing therapy for rheumatoid arthritis (RA). Many trials are in pro gress that are expected to show a benefit from blocking the production or i nhibiting the activity of this cytokine. Nevertheless, studies using a vari ety of animal models suggest that, although TNF is the key cytokine mediati ng joint swelling, it plays no direct role in tissue destruction. Conversel y, interleukin-1 (IL-1) does not play a significant role in the early infla mmation process but plays a pivotal role in erosive cartilage damage. The m echanisms of cartilage destruction are described, with particular attention given to the distinct roles of TNF and IL-1. It is concluded that IL-1 bet a may be an equally important or even more important target, and outcomes i n RA might be improved by therapies that address both of those cytokines.