Interleukin-3 (IL-3), also known as MCGF, Multi-CSF, HCGF and P-cell stimulation factor, belongs tothe α-helixfamily of hematopoietic cytokines. It is produced by activated T-cells, mast cells and natural killer cells. IL-3 binds to the IL-3 receptor alpha subunit and recruits the signal-transducing common beta chain. IL-3induced signal transduction results in the survival, differentiation and proliferation of a variety of immune cells, such as macrophages, neutrophils, megakaryocytes, mast cells and hematopoietic stem cells. IL-3 often acts synergistically with other cytokines, such as IL-7, EPO, GM-CSF and IL-6, to exert its simulative function.