CD8⁺ T cells dominate the lymphocyte population insynovial fluid in chronic inflammatory arthritis. It is known that theseCD8⁺ T cells are often clonally or oligoclonally expanded, but theirspecificity and their relevance to the pathogenesis of joint disease hasremained unclear. We found that as many as 15.5% of synovial CD8⁺ Tcells may be specific for a single epitope from an Epstein-Barr virus lyticcycle protein. The virus-specific T cells within the joint showed increasedexpression of markers of activation and differentiation compared with those inthe periphery, and retained their functional capacity to secreteproinflammatory cytokines on stimulation. These activated, virus-specificCD8⁺ T cells could therefore interact with synoviocytes, either bycell-cell contact or by a cytokine network, and play a 'bystander'role in the maintenance of inflammation in patients with arthritis.