Interleukin (IL-15) is a pleiotropic cytokine that plays a pivotal role in both innate and adaptive immunity. IL-15 is unique among cytokines due to its participation in a trans signaling mechanism in which IL-15 receptor alpha (IL-15R alpha) from one subset of cells presents IL-15 to neighboring IL-2R beta/gamma(c)-expressing cells. This newly discovered cytokine is produced by a wide variety of cells and tissues and like IL-2, stimulates the proliferation of T-lymphocytes and induces the generation of cytotoxic T-lymphocytes (CTLs) and lymphokine-activated killer (LAK) cells