Effect of IL-4 or IL-4/prednisolone treatment on matrixproteoglycan loss. (a) Knee joint of a control naïve mouse. Thefully stained cartilage layers indicate no loss of proteoglycans. (b) Knee joint of an arthritic mouse treated with vehicle. Note the severe jointinflammation and complete loss of safranin O staining of the cartilage layers(indicated by arrows). (c) Mouse treated with IL-4 (1 μg/day).Loss of matrix proteoglycan can still be seen. (d) Knee joint of a mousetreated with IL-4/prednisolone (1 μg per day/0.05 mg per kg). Markedreduction in matrix proteoglycan depletion after combined treatment. Fordetails see Fig. 4. Safranin O staining, originalmagnification × 100.