Interleukin-3 (IL-3) is a type of biological signal (cytokine) which is encoded by the IL-3 gene located on chromosome 5 and produced primarily by activated T cells beside human thymic epithelial cells, activated murine mast cells, murine keratinocytes and neurons/astrocytes. The protein acts in hematopoiesis by controlling the production, differentiation, and function of 2 related white cell populations of the blood, the granulocytes and the monocytes-macrophages. In addition, it exerts its biological activities through binding to interleukin-3 receptors included α and β subunits. The Mouse IL-3 is different from human IL-3 and contains 140 amino acids residues. Specifically, mouse and human IL-3 share low homology and have not cross species activity.