Effects of infliximab treatment on rheumatoid synovial tissue.

Several studies have shown decreased synovial inflammation after treatment of patients with rheumatoid arthritis (RA) with infliximab. Recent data indicate that these effects can be detected as soon as 48 hours after first infusion. Although there are strong indications that infliximab exerts its effects in patients with Crohn's disease by induction of apoptosis in the gut, there are as yet no studies that convincingly show the same mechanism of action in RA. Conceivably, neutralization of tumor necrosis factor-alpha may be sufficient to induce clinical improvement in RA, even without induction of apoptosis at the site of inflammation. This hypothesis could explain the observation that both infliximab and etanercept are effective in RA, whereas apoptosis induction by infliximab might be required in Crohn's disease. Future studies should focus on the evaluation of apoptosis within the first 48 hours after initiation of therapy in RA to exclude the possibility that the effects occur very early after infliximab infusion.