IL18BP and macrophage activation syndrome: Similarly, inhibition of the IL-18 receptor is insufficient to alter CpG-induced MAS in young wild-type mice but does prevent the development of a more-severe MAS phenotype observed in IL-18BP-knockout mice (Girard-Guyonvarc'h et al., 2018), indicating that endogenous regulation of IL-18 is paramount for controlling disease severity (Weiss et al., 2018).