Cytokines in rheumatoid arthritis.

An ever-growing number of cytokines that play a critical role as soluble mediators of immune and inflammatory responses are being described. Not surprisingly, most of them have been detected in SF or serum of patients with RA. However, given the numerous interactions within the cytokine network--e.g., agonistic and antagonistic properties and natural inhibitors--one should beware of over-simplistic views, the most so as extrapolation from in vitro and animal models is always a challenge. From a clinical viewpoint, more work is required before measurements of cytokines in RA be used as activity indices and--more importantly--as prognostic marker.