Effect of infliximab on circulating IL-1ra in patients treated with a single infusion of infliximab or placebo on Day 0. Infliximab 1 mg/kg (closed triangle ▲), infliximab 10 mg/kg (closed square ■), and placebo (open circle ○). *P < 0.05, **P < 0.01, ***P < 0.001 compared with placebo. Adapted with permission from Charles et al. . Copyright 1999. The American Association of Immunologists.