Synovial fluid neutrophil expression of interleukin-8 in rheumatoid arthritis

Most of the infiltrating leukocytes in the synovial fluid (SF) of patients with rheumatoid arthritis (RA) are neutrophils, and rheumatoid SF contains many cytokines which may be produced by monocytes and synoviocytes. In the present study, we investigated the contribution of SF neutrophils to augmented concentrations of interleukin (IL)-8, seen in RA SF. Neutrophils in RA SF contained large amounts of IL-8 protein and its transcript as compared with either peripheral blood neutrophils of RA patients or of normal individuals. Moreover, the amount of SF neutrophil-associated IL-8 correlated with the disease activity of RA. In addition, membrane expression of tumor necrosis factor receptor (type I and II) or superoxide generation was increased in RA SF neutrophils These results suggest that SF neutrophil-associated IL-8 and the activated state of SF neutrophils may be considered as an indicator for local and also systemic inflammation of RA, and this C-X-C chemokine may contribute to the recruitment of neutrophils from the bloodstream into synovial joints.