Expression of neutrophil activation markers and neutrophil adhesion to chondrocytes in rheumatoid arthritis patients: relationship with disease activity

Abstract

Neutrophil infiltration in synovial fluid is an important step in inflammation characterizing rheumatoid arthritis (RA). In this study, the activation and functional state of neutrophils in the blood and synovial fluid of patients with rheumatoid arthritis were compared: mean density of neutrophil activation markers CD11b, CD18 and L-selectin was measured with a flow cytometer, and adhesion to chondrocytes using a fluorimetric assay. No significant differences between control and patient peripheral blood neutrophils were observed. When comparing neutrophils of patient peripheral blood with paired synovial fluid, an increase in CD11b (p = 0.008) and a decrease in L-selectin (p = 0.008) were measured. For neutrophils of control and patient peripheral blood, fMet-Leu-Phe stimulation induced upregulation of CD11b (resp p = 0.007 and p = 0.008) and CD18 (resp p = 0.005 and p = 0.01). In the synovial fluid, no significant increase in CD11b and CD18 could be induced with fMet-Leu-Phe. Percentages of adherent neutrophils were comparable between controls and patients, both in peripheral blood and synovial fluid. Adhesion to chondrocytes of peripheral blood neutrophils of patients was correlated with clinical (Ritchie) and biological (erythrocyte sedimentation rate) parameters (resp r = 0.67, r = 0.73). In conclusion, these results demonstrate that peripheral blood neutrophil adhesion to chondrocytes was correlated with active disease, and that synovial fluid neutrophils were activated in vivo. These findings provide further evidence for the contributing role of neutrophils in articular destruction in RA.