IL-2 (Interleukin-2) is 153 amino acid protein. IL-2 produced by T cells in response to antigenic or mitogenic stimulation. This protein is required for T cell proliferation and other activities crucial to regulation of the immune response. IL-2 can stimulate B-cells, monocytes, lymphokine-activated killer cells, natural killer cells, and glioma cells. Three different IL-2 dependent signal transduction pathways have been identified: the c-Fos/c-Jun induction pathway mediated by Src family protein-tyrosine kinases; the c-Myc induction pathway; and the Rapamycin-sensitive pathway.