IL-18 receptor (IL-18R) is a type I membrane protein present in lung, leukocytes, spleen, liver, thymus, prostate, small intestine, colon, placenta and heart, and absent from brain, skeletal muscle, pancreas and kidney. IL-18R is present in Hodgkin's disease cell lines, and does not bind IL-1(alpha) or IL-1(beta). The association of IL-18 to IL-18R leads to activation of NFkB. At present two subunits of IL-18R have been characterized: IL-18R(alpha) and IL-18R(beta). IL-18R(alpha) has been described as the ligand-binding chain and IL-18R(beta) as the signal-transduction chain.