IL-18 blockade with a monoclonal anti–IL-18R antibody attenuates the severity of MAS in IL-18BP^−/−mice. Male IL-18BP^−/− mice received CpG injections on days 0, 2, and 4 and were either treated with an isotype control (n = 11) or a monoclonal anti–IL-18R (n = 12) antibody. All mice were killed on day 7. (A) Variations from baseline body weight are represented as mean ± SD in isotype and anti–IL-18R–treated mice. Circulating (Bi) white blood cell, (Bii) red blood cell, and (Biii) platelet counts and plasma levels of (C) ferritin and (D) ALT were measured before (baseline) and on day 7 after CpG injections (CpG) in isotype and anti–IL-18R antibody–treated IL-18BP^−/− mice. All data were pooled from 2 independent experiments. The Mann-Whitney U test was used to compare isotype control and anti–IL-18R antibody–treated mice at 1 time point. The Wilcoxon signed-rank test was used to compare baseline and day 7 values within each treatment group when data were paired. **P < .01; ***P < .005.