IL-18 receptor is composed of an a and a b subunit that combine to form a high affinity receptor for IL-18. IL-18 receptor a chain, also known as CDw218a, is a 75-80 kD type I transmembrane protein. It is expressed on NK cells, neutrophils, endothelial cells, and subsets of T and B cells. The expression of CDw218a on lymphocytes is upregulated after activation. The interaction of IL-18 and IL-18 receptor has been reported to be implicated in promotion of Th1 cytokine production and atherogenesis.