Interleukin 15 (IL-15)  cDNA clones from all three species encode a 162 amino acid (aa) residue precursor protein that contains a 48 aa leader sequence and a 114 aa mature IL-15 subunit. IL-15 is a cytokine with structural similarity to IL-2. Like IL-2, IL-15 binds to and signals through a complex composed of IL-2/IL-15 receptor beta chain (CD122) and the common gamma chain (gamma-C, CD132). IL-15 is secreted by mononuclear phagocytes (and some other cells) following infection by virus(es). This cytokine induces cell proliferation of natural killer cells; cells of the innate immune system whose principal role is to kill virally infected cells. Survival signals that maintain memory T cells in the absence of antigen are provided by IL-15. This cytokine is also implicated in NK cell development. In rodent lymphocytes, IL-15 prevents apoptosis by inducing an apoptosis inhibitor, BCL2L1/BCL-x(L). In humans with celiac disease IL-15 similarly suppresses apoptosis in T-lymphocytes by inducing Bcl-2 and/or Bcl-xL.
There have been recent studies suggesting that suppression of IL-15 may be a potential treatment for celiac disease and even presents the possibility of preventing its development. IL-15 has been shown to enhance the anti-tumor immunity of CD8 T cells in pre-clinical models.