Interleukin 18 (IL-18), also known as interferonγinducible factor, is a proinflammatory cytokine that in humans is encoded by the IL18 gene.IL-18 belongs to the IL-1 superfamily, which is secreted and produced by macrophages and other cells.Upon stimulation by IL-18, natural killer (NK) cells and certain T cells release another important cytokine & mdash;interferonγ or type II interferon, which in turn activates macrophages or other cells.IL-18 induces a severe inflammatory response and likewise increases the production of β-amyloid (associated with Alzheimer’s disease) in human neurons.