Description
Mouse IL-18BP is a circulating glycoprotein, which functions as an IL-18 antagonist by binding to IL-18 with high affinity and neutralizing its biological activity. IL-18BP has no amino acid sequence homology to IL-18 or IL-1 receptors. The gene for human IL-18BP encodes at least four isoforms by alternative splicing. The IL-18BP isoforms A and C each contain one immunoglobulin (Ig)-like C2-type domain while isoforms B and D lack the complete Ig domain. The complete Ig domain has been shown to be essential for IL-18BPs binding and neutralizing properties. Several poxviruses have been shown to encode proteins with sequence similarity to human and mouse IL-18BPs that also bind and inhibit IL-18 bioactivities. This could lead to viral modulation of host immune responses