CD97 monoclonal antibody (mAb) treatment reduces bone damage when initiated at the onset of arthritis. Mice were treated with NaCl, 0.5 mg control immunoglobulin (cIg), or 0.25 mg or 0.5 mg anti-CD97 mAb. X-rays of hind paws (n = 8 to 20 mice per group) were analysed for erosions. (a) Representative x-rays of paws showing no bone or joint abnormalities (left) and complete bone destruction (right) derived from mice treated from day 21 on with 0.5 mg CD97 mAb or cIg, respectively. (b-d) Radiological scores of mice treated from day 21 (b,c) or day 35 (d) on, corresponding with the experiments 1, 2, and 3, respectively (Figures 1 and 2). Values are mean ± standard error of the mean. *P < 0.05.