IL-34

Interleukin 34 (IL-34) is a 39 kDa, secreted cytokine that belongs to no known cytokine family. Mouse IL-34 is synthesized as a 235 amino acid (aa) precursor with a 20 aa signal sequence and a 215 aa mature chain) . The mature chain contains two potential sites for N-linked glycosylation. There are three isoforms for IL-34. Mouse IL-34 is 71% identical to human IL-34 on the amino acid level. IL-34 is expressed in various tissues, including heart, brain, lung, liver, kidney, spleen, thymus, testes, ovary, small intestine, prostate, and colon, and it is most abundant in the spleen. The receptor for IL-34 is colony-stimulating factor 1 receptor (CSF-1R) . IL-34 stimulates monocyte viability. In functional studies, IL-34, like CSF-1, the other ligand for CSF-1R, stimulated phosphorylation of extracellular signal-regulated kinase-1 and -2 (ERK1/2) in human monocytes. In addition, IL-34 promoted the formation of the colony-forming unit-macrophage (CFU-M), a macrophage progenitor, in human bone marrow cultures.