Interleukin 18 (IL-18) is a cytokine that has been found to be involved in many different biological processes and is produced by dendritic cells, monocytes, macrophages, neutrophils and epithelial cells. IL-18 is unique in that it has two forms, mature IL-18 and pro IL-18. IL-18 is first present as proform 24kd precursor and lacks the signal sequence required for secretion1. However, it is the active form of IL-18 that is present in many different tissue types2. IL-18 is cleaved so it can be in its active form. ICE (IL-1β Converting Enzyme) or Caspase 1 cleaves Pro-IL-18 after Asp35, leading to the active form of IL-18, measuring at 18 kDa2. This activation has shown to be an important aspect of immune defense. MBL International was the first to offer IL-18 products and has since become the leader in trusted IL-18 research.