Description: Mouse interleukin-13 (IL-13), originally designated p600, is a 11.6 kDa protein secreted by activated T helper cells, CD8+ T cells, and NK cells. IL-13 was originally identified in 1989 through differential hybridization of cDNA libraries prepared from T helper 1 and T helper 2 cells. IL-13 contains four cysteine residues, which form two intramolecular disulfide bonds. IL-13 shares many activities with IL-4; this relates to a requirement for IL-4Rα chain for signal transduction. The biological activities of IL-13 include suppression of macrophage cytotoxic activity, upregulation of IL-1RA expression, and suppression of inflammatory cytokine expression. IL-13 induces CD23 expression on B cells and enhances CD72, and expression of class II MHC gene products. Mouse IL-13 does not display the activities on T cells and B cell stimulatory effects which IL-4 exhibits. Mouse IL-13 is active on human and mouse cells.