IL3, as known as interleukin 3, is a pleiotropic factor produced primarily by activated T cells that can stimulate the proliferation and differentiation of pluripotent hematopoietic stem cells as well as various lineage committed progenitors. Also, this protein affects the functional activity of mature mast cells, basophils, eosinophils and macrophages. Because of its multiple functions and targets, it was originally studied under different names, including mast cell growth factor, P-cell stimulation factor, burst promoting activity, multi-colony stimulating factor, thy-1 inducing factors and WEHI-3 growth factor. Recombinant human IL3, fused to His-tag at C-terminus, was expressed in insect cell and purified by using conventional chromatography techniques.