Interleukin 34 (IL-34), also known as uncharacterized protein C16 or f77 homolog, is a secreted cytokine that belongs to unknown cytokine family. IL-34 protein is expressed in various tissues, including heart, brain, lung, liver, kidney, spleen, thymus, testes, ovary, small intestine, prostate and colon, and most abundant in the spleen. The colony-stimulating factor 1 receptor (CSF-1R) is identified as the receptor for IL-34. IL-34 increases growth or survival of immune cells known as monocytes. In addition, IL-34 promoted the formation of the colony-forming unit-macrophage (CFU-M), a macrophage progenitor, in human bone marrow cultures.
- Lin H, et al. (2008) Discovery of a cytokine and its receptor by functional screening of the extracellular proteome. Science. 320(5877): 807-11.