Pain in collagenase-induced arthritis is GM-CSF dependent. C57BL/6 mice were treated prophylactically (from day -4) with anti-GM-CSF or isotype control monoclonal antibody. (A) Change in weight distribution (pain) (Methods) over time. (B) Quantification of arthritis development (histology) at day 42. Results are expressed as the mean ± standard error of the mean; n = 10 to 15 mice per group (from two independent experiments). *P <0.05, **P <0.01, ***P <0.001, control versus anti-GM-CSF. GM-CSF: granulocyte-macrophage colony-stimulating factor; LF: lateral femur; LT: lateral tibia; MF: medial femur; MT: medial tibia.