IL-1 epsilon is an actively secreted member of the IL-1 family of cytokines. It is mainly expressed in tissues with epithelial cells and in psoriatic plaques, as well as by monocytes, B cells and T cells. IL-1 epsilon has been shown to signal through the IL-Rrp2 receptor which is primarily expressed on certain denditic cells, and to act as an agonist of NF-kappaB which then stimulates the inflammatory response in bronchial epithelial cells.