Colony-stimulating factor

Colony-stimulating factors (CSFs) are secreted glycoproteins which bind to receptor proteins on the surfaces of hemopoietic stem cells and thereby activate intracellular signaling pathways which can cause the cells to proliferate and differentiate into a specific kind of blood cell (usually white blood cells, for red blood cell formation see erythropoietin).

Etymology
The name "colony-stimulating factors" comes from the method by which they were discovered.

Hemopoietic stem cells were cultured (see cell culture) on a so-called semi solid matrix which prevents cells from moving around, so that if a single cell starts proliferating, all of the cells derived from it will remain clustered around the spot in the matrix where the first cell was originally located, and these are referred to as "colonies." It was therefore possible to add various substances to cultures of hemopoietic stem cells and then examine which kinds of colonies (if any) were "stimulated" by them.

The substance which was found to stimulate formation of colonies of macrophages, for instance, was called macrophage colony-stimulating factor, and so on.

Examples
Colony-stimulating factors include:
 * - macrophage colony-stimulating factor
 * - Granulocyte macrophage colony-stimulating factors (also called GM-CSF and sargramostim)
 * - Granulocyte colony-stimulating factors (also called G-CSF and filgrastim)
 * Synthetic - Promegapoietin