Bone destruction is prevented by interleukin (IL)-4 andIL-4/prednisolone treatment. (a) Severe bone destruction in patella andfemur in knee joint of vehicle-treated animal. (b) Almost no bonedegradation was noted after treatment with IL-4/prednisolone (1 μg perday/0.05 mg per kg). (c) Bone destruction in femur of a vehicle-treatedanimal at higher magnification. Osteoclasts, large multinuclear cells, locatedat the site of bone destruction (arrows). (d) No osteoclast-like cellswere found in IL-4 (1 μg/day) treated animals. For treatment details seeFig. 4. S, synovium; B, bone; BM, bone marrow. Originalmagnifications × 200 (a, b), × 400 (c, d).