Effect of infliximab on IL-6 concentrations. (a) Circulating IL-6 concentrations 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. (b) The relationship between the reduction in circulating IL-6 by Day 3 and the reduction in C-reactive protein (CRP) over the same period (r = 0.59, P < 0.002). Adapted with permission from Charles et al. . Copyright 1999. The American Association of Immunologists.