IL-31 which produced by activated Th2-type T cells. IL-31 signals through a receptor composed of IL-31 receptor A and oncostatin M receptor. IL-31 activates STAT3 and possibly STAT1 and STAT5 through the IL-31 heterodimeric receptor composed of IL31RA and OSMR. IL-31 has also been identified as a major player in a number of chronic inflammatory diseases, including atopic dermatitis. Patients with atopic dermatitis, chronic spontaneous urticaria, allergic contact dermatitis, prurigo nodularis, primary cutaneous lymphoma and mastocytosis exhibit increased serum levels of IL-31 protein and elevated IL-31 mRNA in the skin.