Effect of anti-GM-CSF treatment post-onset on joint histopathology of hind-limb distal interphalangeal joints with CIA. (a), (b) Normal joint; (c), (d) joint from a control mAb-treated mouse; and (e), (f) joint from an anti-GM-CSF mAb-treated mouse. For control and anti-GM-CSF mAb-treated mice, both limbs had a clinical score of 1 at onset. The control mAb-treated mouse limb progressed to a score of 3, whereas the anti-GM-CSF mAb-treated mouse limb showed no change over the course of treatment. These results are representative for each treatment group. (c) Severe inflammation and joint destruction is shown compared with (a). (e) Only mild infiltration and damage is evident with the architecture of the joint remaining intact. This is also reflected in (d), where there is loss of proteoglycan staining (arrowheads) compared with (b), while (f) shows intermediate staining. (a), (c) and (e) H & E staining; (b), (d) and (f) Safranin O, fast green staining. Magnification, x 125. B, Bone; C, cartilage; CIA, collagen-induced arthritis; GM-CSF, granulocyte macrophage-colony stimulating factor; J, joint space; M, bone marrow; mAb, monoclonal antibody.