Interleukin 20

Interleukin 20 (IL20) is a protein that is in humans encoded by the IL20 gene which is located in close proximity to the IL-10 gene on the 1q32 chromosome. IL-20 is a part of an IL-20 subfamily which is a part of a larger IL-10 family.

IL-20 subfamily also includes other cytokines, including IL-19, IL-20, IL-22, IL-24, and IL-26. Members of the cytokine IL-20 subfamily form an important link between the immune system and epithelial tissues due to the fact that receptors for these cytokines are highly expressed on epithelial cells and are almost exclusively produced by cells of the immune system.

IL-20 requires an IL-β-subunit receptor (IL-20RB) for signaling, which can form a functional heterodimeric receptor with either the α-subunit of the IL-20 receptor (IL-20RA) or the α1-subunit of the IL-22 receptor (IL-22RA1). Both of these receptor variants allow efficient IL-20 signaling. Receptors for IL-20 are expressed in the skin, lungs, ovary, testes, and placenta. IL-20 is mainly produced by myeloid cells such as monocytes, granulocytes, and dendritic cells but can also be produced by keratinocytes and fibroblasts. The expression of IL-20 is stimulated by IL-1β, IL-17, IL-22, TNF, and LPS. The main cellular targets of IL-20 are keratinocytes, endothelial cells, and adipocytes. IL-20 has been shown to transduce its signal through signal transducer and activator of transcription 3 (STAT3) in keratinocytes.