CSF and plasma IL-6 concentrations for 12 participants over 24 hours from the start of infusion. (a) CSF IL-6 and (b) plasma IL-6 concentrations. Solid symbols and lines represent patients that received IL-1Ra. Open symbols and dashed lines represent patients that received placebo. CSF, cerebrospinal fluid; IL, interleukin; IL-1Ra, interleukin-1 receptor antagonist.