CD97 monoclonal antibody (mAb) treatment protects against proteoglycan depletion. Mice were treated with NaCl, 0.5 mg control immunoglobulin (cIg), or 0.5 mg anti-CD97 mAb. Paws were stained with safranin O (n = 8 to 12 per group). (a) Representative examples of joints with normal (left) and depleted (right) proteoglycan derived from mice treated from day 21 on with 0.5 mg CD97 mAb or cIg, respectively. (b,c) Staining scores of mice treated from day 21 (b) or day 35 (c) on. Values are mean ± standard error of the mean.