Effect of systemically delivered IFN-β at the onset of arthritis in mice with collagen-induced arthritis. (a) Clinical score (mean ± SEM) was assessed on a scale of 0 to 3.5 (as described in Materials and methods), and (b) hind paw swelling (mean ± SEM) of the first arthritic paw was monitored during the course of disease using calipers. On day 7 after the start of the treatment, differences between all treatment groups and the control group were statistically significant (P = 0.005) (Kruskal–Wallis test). Arrows mark the first day of treatment. *Statistically significant difference. SEM, standard error of the mean.