IL-18 BP

Interleukin-18 binding protein (IL-18BP) is a constitutively secreted glycoprotein that acts as a natural antagonist for interleukin-18 (IL-18) by preventing interaction between IL-18 and its receptors. Through this binding, IL-18BP neutralizes the proinflammatory role of IL-18 in cell-mediated immune responses, resulting in reduced IFN-γ production by T helper type I cells and inhibition of allospecific cytotoxic T lymphocyte (CTL) activity through augmented natural killer (NK) cell cytotoxicity. As an inhibitor of IL-18 and an essential component of skin homeostasis, IL-18BP has been linked to a variety of diseases, including eczema, asthma, and the autoimmune condition, Crohn’s disease. The upregulation of IL-18BP by keratinocytes expressing the human papillomavirus (HPV) E7 oncoprotein has been shown to decrease IL-18-induced IFN-γ production and IL-18-mediated T cell activation. Elevated levels of IL-18 and IL-18BP, as well as proinflammatory cytokines IFN-γ, TNF-α, IL-1β and IL-8, have been linked to chronic inflammation and observed in macrophages (including Kupffer cells) isolated from lesions and intestinal tissues of Crohn’s disease patients. As a member of the immunoglobulin-like class of receptors, IL-18BP contains a single immunoglobulin (Ig) domain; although two (b and d) of the four identified human isoforms (a-d) contain incomplete domains that greatly reduce their binding affinity. The CHO cell-derived Recombinant Human IL-18BP Fc is a glycosylated, disulfide-linked homodimer of 792 amino-acid-residues whose monomer consists of a 163-amino-acid portion of secreted IL-18BP fused to the 231-amino-acid length Fc portion of human IgG by two glycine residues. The calculated molecular weight of monomeric CHO cell-derived Recombinant Human IL-18BP Fc is 43.6 kDa; however, due to glycosylation, it migrates at an apparent molecular weight of approximately 60-65 kDa by SDS-PAGE analysis under reducing conditions.