Interleukin 34

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

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