Effect of anti-TNFα, anti-IL-1, or anti-RANKL therapy on hind paw swelling. Effect of PEGylated soluble TNF receptor type I (TNFRI), IL-1 receptor antagonist (IL-1Ra) or osteoprotegerin (OPG)-Fc on hind paw swelling. (a) Hind paw swelling was assessed on day 4 post onset, prior to the beginning of therapies. Swelling was assessed in adjuvant-induced arthritis (AIA) rats by measuring average hind paw volume via water plethysmography, and in collagen-induced arthritis (CIA) rats by precision caliper measurements of paw diameter. (b), (c) Percentage changes in paw swelling in AIA and CIA rats, as measured from the time of treatment initiation (day 4) to day 14. 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 osteoprotegerin-treated arthritic rats, P < 0.05.