Effect of anti-TNFα, anti-IL-1, or anti-RANKL therapy on bone resorption markers. Effects of PEGylated soluble TNF receptor type I (TNFRI), IL-1 receptor antagonist (IL-1Ra) or osteoprotegerin (OPG)-Fc on serum levels of the bone resorption markers (a), (b) receptor activator of NF-κB ligand (RANKL) and (c), (d) tartrate-resistant acid phosphatase 5b (TRACP-5B) in (a), (c) adjuvant-induced arthritis (AIA) rats and in (b), (d) collagen-induced arthritis (CIA) rats. Values were determined on day 14 post onset, 10 days after the initiation of treatment. Data represent means ± standard error of the means, n = 8/group. cSignificantly different from control (nonarthritic) rats, P < 0.05. vSignificantly different from vehicle (Veh)-treated arthritic rats, P < 0.05. oSignificantly different from OPG-treated arthritic rats, P < 0.05.