Figure 3

Interleukin (IL)-7 increases osteoclast activity in collagen-induced arthritis. Mice were injected with either phosphate-buffered saline (PBS) or IL-7. Osteoclast activity indicated by cathepsin K expression (brown) was graded for each ankle with a scoring index from 0 to 3. Representative cathepsin K staining with hematoxylin & eosin (H&E) counterstains from arthritic mice of each treatment group demonstrate bone erosion associated with high numbers of active osteoclasts (A; ×40 magnification of tibial tarsal joints). Osteoclast activity, indicated by cathepsin K expression, was significantly increased in IL-7-treated mice as compared with PBS-treated mice (B) (1.4 ± 0.2 versus 2.4 ± 0.2). Values are expressed as mean ± SEM of 15 mice per group. ***Statistical differences with PBS group of P < 0.005.