Interleukin-18 binding protein, also known as IL-18BP and tadekinig-alfa, is a secreted glycoprotein that contains an Ig-like C2-type domain. IL-18BP is a cytokine receptor that belongs to the interleukin 1 receptor family. IL18BP shares many characteristics with soluble cytokine receptors of the IL1 family in that the protein exhibits specificity for IL18, belongs to the immunoglobulin-like class of receptors and has limited amino acid sequences with those of the IL1 receptor type II. According to the other study, IL1R9 is evolutionarily related to IL18BP and may function as an IL-18 receptor. Plasma il-18 /IL18BP levels increase during disease activity, suggesting that it may play a role in the pathogenesis of ITP.