interleukin 34

{{Short description|Protein-coding gene in the species Homo sapiens}}

{{redirect|IL-34|the road|Illinois Route 34}}

{{Infobox_gene}}

Interleukin 34 (IL-34) is a protein belonging to a group of cytokines called interleukins. It was originally identified in humans, by large scale screening of secreted proteins; chimpanzee, murine, rat and chicken interleukin 34 orthologs have also been found. The protein is composed of 241 amino acids, 39 kilodaltons in mass, and forms homodimers. IL-34 increases growth or survival of immune cells known as monocytes; it elicits its activity by binding the Colony stimulating factor 1 receptor.

Messenger RNA (mRNA) expression of human IL-34 is most abundant in spleen but occurs in several other tissues: thymus, liver, small intestine, colon, prostate gland, lung, heart, brain, kidney, testes, and ovary. The discovery of IL-34 protein in the red pulp of the spleen suggests involvement in growth and development of myeloid cells, consistent with its activity on monocytes.

{{cite journal |vauthors=Lin H, Lee E, Hestir K, etal |title=Discovery of a cytokine and its receptor by functional screening of the extracellular proteome |journal=Science |volume=320 |issue=5877 |pages=807–11 |date=May 2008 |pmid=18467591 |doi=10.1126/science.1154370 |bibcode=2008Sci...320..807L |s2cid=44340470 }}