one of a group of related proteins made by leukocytes (white blood cells) and other cells in the body. interleukin-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 (interleukin-2 made in the laboratory) is being used as a biological response modifier to boost the immune system in cancer therapy. interleukin-2 is a type of cytokine. also called il-2.