IL-19,a member of the IL-10 cytokine family,is expressed in epithelial cells,endothelial cells,and macrophages. It can bind the interleukin-20 receptor complex IL-20R1/IL-20R2 and lead to the activation of the signal transducer and activator of transcription 3 (STAT3). IL-19 induces IL-6 and TNF-alpha production in monocytes. It also induces cell apoptosis and reactive oxygen species production in monocytes,which suggests a role of this cytokine in inflammatory responses. It is up-regulated in monocytes following stimulation with lipopolysaccharide (LPS),and granulocyte-macrophage colony-stimulating factor (GM-CSF). IL-19 alters the balance of Th1 and Th2 cells in favor of Th2 cells. IL-19 contributes to a range of diseases and disorders,such as breast cancer,squamous cell carcinoma of the skin,asthma,endotoxic shock,uremia,psoriasis,rheumatoid arthritis,and periodontal and vascular disease.