IL1A and systemic-onset juvenile idiopathic arthritis: sJIA, previously thought to be an autoimmune disease, is now more commonly classified as an autoinflammatory disease, because the genetic abnormalities of the major histocompatibility complex (MHC) and the innate immune system (such as natural killer (NK) cells, polymorphonuclear neutrophils (PMNs), and macrophages (MP))—with the participation of interleukins 1 (IL-1), 6 (IL-6), and 18 (IL-18)—have been shown to be involved.