One of a group of related proteins made by leukocytes (white blood cells) and other cells in the body. IL-2 is made by a type of T lymphocyte. It increases the growth and activity of other T lymphocytes and B lymphocytes, and affects the development of the immune system. Aldesleukin (IL-2 made in the laboratory) is being used as a biological response modifier to boost the immune system in cancer therapy. IL-2 is a type of cytokine. Also called interleukin-2.