IL-15 is a member of the four alpha-helical bundle family of cytokines with a molecular weight of 14-15 kDa. Its in vitro activity is very similar to IL-2, except that IL-15 utilizes the IL-15 receptor alpha subunit for binding. IL-15 plays an important role in the growth and differentiation of T and B lymphocytes, natural killer cells, macrophages, and monocytes. It also activates a number of important intracellular signaling molecules. This implies that IL-15 could be essential for the immune responses, allograpt rejection, and the pathogenesis of autoimmune diseases.
