CD218a, an approximately 62 kDa type I transmembrane glycoprotein, is the alpha subunit of IL-18 receptor heterodimer. It is expressed in various immune cells, including lymphocytes, NK cells, and myeloid cells, as well as in heart, lung, liver, gut and another tissues. IL-18 is a proinflammatory cytokine, that promotes both Th1 and Th2 immune responses, induces IFN-gamma production and activates NK cells.