Interleukin-20 (IL20) binds a heterodimeric receptor complex that consists of Interleukin-20 receptor subunit alpha (IL20RA), which is associated with Tyrosine-protein kinase JAK1 (JAK1) and Interleukin-20 receptor subunit beta (IL20RB) (Blumberg et al. 2001, Parrish-Novak et al. 2002, Logsdon et al. 2012, Rutz et al. 2014). Interleukin-20 receptor A (IL20RA) and Interleukin-20 receptor B (IL20RB) form a receptor complex for Interleukin-20 (IL20), Interleukin-19 (IL19) and Interleukin-24 (IL24) (Blumberg et al. 2001, Parrish-Novak et al. 2002, Logsdon et al. 2012, Rutz et al. 2014). IL20 can also bind a receptor complex that consists of Interleukin-22 receptor subunit alpha-1 (IL22RA1) and IL20RB (Kolumam et al. 2017). As it is not clear whether the dimeric receptor can form in the absence of ligand, formation of the receptor dimer is represented here as an uncertain black box event.