Interleukin 31 (IL-31) is a 24 kDa, short-chain member of the alpha-helical family of cytokines. It is mainly associated with activated T cells and preferentially expressed by Th2 rather than Th1 cells. The human IL-31 cDNA encodes a 164 amino acid (aa) precursor that contains a 23 aa signal peptide and a 141 aa mature protein. Human and mouse IL-31 share 24% aa sequence identity in the mature region.
IL-31 signals via a receptor complex that is composed of IL-31 receptor A (IL31RA) and oncostatin M receptor subunits. These receptor subunits are expressed in activated monocytes and in unstimulated epithelial cells. IL-31 signaling has been shown to involve the Jak/STAT pathway, the PI3 kinase/AKT cascade, and the MAP kinase pathway. In addition, IL-31 is believed to play a role in inflammation of the skin.