Macrophage Colony Stimulating Factor (M-CSF) is a hematopoietic growth factor produced by a wide variety of cells. MCSF is known to stimulate differentiation of hematopoietic stem cells to monocyte-macrophage cell populations in culture. M-CSF acts through the CSF receptor 1. Although M-CSF shows activity on cells, CSF shows no activity on cells. Recombinant M-CSF is a disulfide linked homodimer, containing two 159 amino acid chains, with a total molecular weight of 36.8 kDa.