The Biology of CSF-1 and Its Receptor

The constant renewal of blood cells in vertebrate species depends on the proliferation and differentiation of hematopoietic stem cells in the bone marrow (Harrison et al. 1988). These cells in turn give rise to progenitor cells which are committed to more restricted pathways of differentiation. The survival, proliferation, and differentiation of these progenitor cells are regulated by the colony stimulating factors (CSFs), so named because of their ability to promote the in vitro proliferation and differentiation of single progenitor cells into macroscopic colonies with discernible differentiated cell types (Pluznik and Sachs 1965; Bradley and Metcalf 1966; Ichikawa et al. 1966). This group of hematopoietic growth factors includes interleukin-3 (IL-3), granulocyte-macrophage colony stimulating factor (GM-CSF), granulocyte colony stimulating factor (G-CSF), interleukin-5 (IL-5), and colony stimulating factor-1 (CSF-1) (reviewed in STANLEY and JUBINSKY 1984; METCALF 1986).