Granulocyte colony-stimulating factor (G-CSF) is a member of the CSF family of glycoproteins that regulate hematopoietic cell proliferation, differentiation, and function. It is a key cytokine involved in the production of neutrophils and the stimulation of granulocyte colony formation from hematopoietic progenitor cells (Metcalf & Nicola. J Cell Physiol, 1983). G-CSF causes a range of effects including a transient reduction of SDF-1 expression (Petit et al. Nat Immunol, 2002), the activation of metalloproteases that cleave VCAM-1 (Levesque et al. Blood, 2001), and the release of norepinephrine from the sympathetic nervous system (Katayama et al. Cell, 2006), leading to the release or mobilization of hematopoietic stem cells from the bone marrow into the periphery. The G-CSF receptor is expressed on a variety of hematopoietic cells, including myeloid-committed progenitor cells, neutrophils, granulocytes, and monocytes. In addition to hematopoietic cells, G-CSF is also expressed in cardiomyocytes, neuronal cells, mesothelial cells, and endothelial cells. Binding of G-CSF to its receptor leads to activation of the JAK/STAT, MAPK, PI3K, and AKT signal transduction pathways. At the carboxy terminus, Human Recombinant G-CSF (HEK293-expressed) contains a human IgG1 Fc tag.