IL-19 is member of the so-called IL-10 family of cytokines. This family also contains IL-10, an anti-inflammatory cytokine known of for a very long time, and six other mediators: IL-20, IL-22, IL-24, IL-26, IL-28A, IL-28B and IL-29. The members of the IL-10 family have the following features: clustering of their encoding genes, similar genomic structures, similar primary and secondary protein structures and use of similar receptor complexes. In fact, these nine proteins are encoded by genes that are found in the human genome in three clusters and have similar exon–intron structures. Interleukin- (IL-) 19, part of the IL-10 family, contributes to a range of diseases and disorders, such as asthma, endotoxic shock, uremia, psoriasis, and rheumatoid arthritis. IL-19 is expressed in several types of tumor cells, especially in squamous cell carcinoma of the skin, tongue, esophagus, and lung and invasive duct carcinoma of the breast.