IL18 and Splenomegaly: Our data suggest that, whilst the NLRP3 inflammasome is responsible for increased blood circulation levels of IL-18 in MAS, it is not responsible for the development of other features of MAS pathogenesis in CpG-induced MAS, such as hyperferritinaemia and splenomegaly, and therefore, indicate that alternative mechanisms are responsible for the splenomegaly, hypercytokinaemia and organ dysfunction in MAS.