The granulocyte macrophage–colony-stimulating factor receptor (GM-CSF-R) is a heterodimer composed of 2 subunits,αand ?, and ligand binding to the high-affinity receptor leads to signalling for the multiple actions of GM-CSF on target cells. The GM-CSF receptors are found on the surface of myeloid precursors, granulocytes, mononuclear phagocyte, and also frequently present on the myeloid malignancies. The GM-CSF-R-alpha transduces a signal that results in the proliferation, differentiation, and functional activation of hematopoietic cells.