Interleukin-31 (IL-31) is an immunoregulatory cytokine that is mainly expressed by activated TH2 cells. IL-31 signals through the IL-31 Receptor (IL-31RA) and the oncostain receptor (OSMR), which are expressed on monocytes, epithelial cells, and ke inocytes. IL-31 has a role in inflammatory skin diseases. Recombinant IL-31 is a non-glycosylated Protein, containing 141 amino acids, with a molecular weight of 15.7 kDa.