IL18 and systemic-onset juvenile idiopathic arthritis: In sJIA, uncontrolled activation of the innate immune system results in activation of monocytes/macrophages, neutrophils and immature (CD34 + CD33+) myelomonocytic precursors, and increased production of pro-inflammatory cytokines IL1β, IL6, IL18 and phagocyte-specific S100 proteins [16, 30, 31].