Interleukin-15 (IL-15) is a pleiotropic cytokine that plays an important role in both innate and adaptive immunity. IL-15 is mainly produced by activated monocytes, macrophages and dendritic cells, and is structurally similar to IL-2 (PMID: 8178155; 12401478). These two cytokines share the same IL-2/15Rβ and common γ-chain receptor subunits. In addition, IL-2 and IL-15 have their own private α-chain receptor subunit, IL-2Rα and IL-15Rα, respectively (PMID: 7641685). The IL-15Rα chain is expressed by many cell types including monocytes, DCs, NK, T cells and fibroblasts. Several isoforms of IL-15Rα exist and are generated either by alternative splicing or by proteolytic cleavage (PMID: 10480910; 15265897).