Granulocyte colony-stimulating factor (G-CSF), also referred to as CSF3, is a protective cytokine with anti-inflammatory effects. G-CSF is important in promoting survival of the granulocytic lineage cells and proliferation and migration of neutrophils as well as trophoblast cells. G-CSF acts by binding to its receptor G-CSFR (also called CSF3R), which after binding with G-CSF activates the canonical Janus kinase (Jak)/signal transducer, activator of transcription (STAT) and Ras/Raf/MAP kinase pathways. G-CSF potently stimulates the proliferation and release of peripheral blood progenitor cells into the bloodstream and is therefore used to treat neutropenia after chemotherapy. Furthermore, G-CSF levels are elevated upon intensive exercise leading to increased neutrophil counts, which are predominantly due to delayed neutrophil apoptosis.