Description: IL-19 belongs to the IL-10 family, which includes IL-10, IL-19, IL-20, IL-22, IL-24, IL-26, and several virus-encoded cytokines (e.g, Y134R). Similar to IL-22, but unlike IL-10 which exists as a homodimer, IL-19 was found to be a monomer, based on protein crystal structure analysis. IL-19 gene transciption has been detected in resting monocytes and, at a lower level, in B cells; this is up-regulated in monocytes stimulated with LPS or GM-CSF. Priming monocytes with IL-4 or IL-13 (but not with IFN-γ) significantly increases the level of IL-19 mRNA induced by subsequent LPS treatment. IL-19 signals through a receptor complex that is also utilized by IL-20 and IL-24. The complex is composed of two chains, CRF2-8 (or IL-20R1) and CRF2-11 (or IL-20R2), belonging to the class II cytokine receptor family. Receptors from this family also form heterodimeric complexes for type I and type II interferons and for other IL-10-related cytokines. Binding of IL-19 to the receptor complex results in STAT3 phosphorylation. IL-19 induces IL-6 and TNF-α production in monocytes. It also induces cell apoptosis and reactive oxygen species production by monocytes. In vitro IL-19 induces IL-4, IL-5, IL-10, and IL-13 production by activated T cells, and might play an important role in the pathogenesis of asthma.
