Macrophage Colony Stimulating Factor (M-CSF) is produced by various cell types, including fibroblasts, microphages, and endothelial cells. M-CSF is involved in both the development and function of monocytes/microphages. The recombinant M-CSF is a disulfide-linked homodimer composed of two 18.2 kDa subunits of 156 amino acid residues.