Specificity of T cells in synovial fluid: high frequencies of CD8

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