IL4 and psoriasis: What is striking is that genetic susceptibilities for psoriasis frequently involve genes that encode innate immune components including IL-23 signalling (IL23R, IL12B, TRAF3IP2, IL23A, TYK2), IFN signalling (IL28RA, IFIH1, TYK2, RNF114, SOCS1), NF-κB signalling (REL, TNIP1, TRAF3IP2, TNFAIP3, NFKBIA, FBXL19, CARD14, CARM1), IL-4/IL-13 signalling (IL4, IL13), and bacterial or viral responsiveness (NOS2, IL28RA, DDX58, ELMO1) [263–266].