Effect of anti-GM-CSF treatment on cytokine levels in the joints. GM-CSF, TNFa and IL-1? levels were measured by enzyme-linked immunosorbent assay in washouts from ankle joints of arthritic mice for mice treated with anti-GM-CSF or control mAb every second day from days 21 to 31 post immunization. Results are expressed as the mean level ? SEM (pg/ml). *P = 0.02 and **P = 0.007 compared with control mAb-treated mice. GM-CSF, Granulocyte macrophage-colony stimulating factor; IL-1?, interleukin-1?; mAb, monoclonal antibody; TNFa, tumor necrosis factor-a.