– Interleukin 15 Receptor alpha (IL-15Rα) is a transmembrane glycoprotein that plays a pleiotropic role in immune development and function, including the positive maintenance of lymphocyte homeostasis. IL-15Rα chain can bind soluble IL-15 and “transpresent” cytokine to the cells, allowing them to respond to IL-15. Soluble IL-15Rα can function as a specific high-affinity IL-15 antagonist. The soluble IL-15/IL-15Rα complexes exhibit a strong agonistic activity which is mediated through membrane-bound IL-15 receptor β and γ heterodimers and enables signaling to cells.