IL22 and psoriasis: For example, in rheumatoid arthritis, patients who responded to treatment showed reductions in plasma IL‐22 levels, indicating that plasma IL‐22 might play a detrimental role in this disease.10 In psoriasis, IL‐22 downregulates Cx43 expression, which could lead to keratinocyte hyperproliferation.11 Interestingly, in some diseases, IL‐22 plays a dual role.