Granulocyte-macrophage colony-stimulating factor (GM-CSF) is a potent species-specific stimulator of granulocyte-macrophage, eosinophil, megakaryocyte and erythroid progenitors. GM-CSF has also been reported to have a functional role on non-hematopoietic cells including endothelial cells. Additionally, GM-CSF can stimulate the proliferation of a number of tumor-derived cell lines, such as osteogenic sarcoma, carcinoma and adenocarcinoma. GM-CSF binds to a heterodimeric receptor formed by the GM-CSFRα/CD116 binding chain and the signal transducing common β chain (CD131), which is also a component of the high affinity IL-3 and IL-5 receptors. Recombinant mouse GM-CSF contains 125 amino acids and has a predicted molecular mass of approximately 14.8 kDa.