Effect of macrophage depletion on cytokine and matrix metalloproteinase (MMP) production in osteoarthritis (OA) synovial cells. OA cultures of synovial cells were either left intact or macrophage-depleted, as described in Materials and methods. Cells were left to adhere for 24 hours before the supernatants were removed for enzyme-linked immunosorbent assay analysis of cytokines and MMPs. Data are expressed as the percentage of cytokine/MMP production in the depleted culture as compared with the undepleted one. The standard error of the mean is given (n = 7–9). IL, interleukin; MCP, monocyte chemoattractant protein; TNF, tumour necrosis factor.