IL18,is a proinflammatory cytokine involved in the development of Th1 cells and in immune response. It can stimulate the NK cells and certain T cells to release interferon gamma which plays an important role in activating the macrophages or other cells. IL18 has been demonstrated to have the potential to enhance Fas ligand-mediated cytotoxicity,which is increased in PE and regulates placental apoptosis. IL18 is synthesized as a 24 kDa precursor and then cleaved into a biologically activate 18 kDa form.