Colony stimulating factor 1 (CSF1) is a homodimeric glycoprotein growth factor that regulates proliferation and differentiation of myeloid hematopoietic progenitor cells to mononuclear phagocytic cell lineages, including monocytes, macrophages, and osteoclasts. CSF1 is a crucial factor for the development of tissue-resident macrophages in most tissues. It is required for the maturation and activation of monocytes and macrophages, and regulates inflammatory responses in conjunction with other stimuli such as IFN-γ, LPS, and IL-4. CSF1 is also required for bone resorption by osteoclasts, and is involved in the development and regulation of the placenta, mammary gland, and brain.
