Interleukin-20 (IL-20), a cytokine belonging to the IL-10 family. IL-20 signals through two heterodimeric receptor complexes: IL-20R1/IL-20R2 and IL-22R1/IL-20R2. These receptors are predominantly expressed on non-hematopoietic cells, particularly keratinocytes, synovial fibroblasts, and osteoblasts, rather than on immune cells.