IL22 and dermatitis: In psoriasis, the significantly elevated plasma IL-22 levels are correlated with the disease severity, and skin-infiltrated T and natural killer cells are the sources of IL-22 in psoriasis,[27] while ultraviolet B facilitates skin inflammation by increasing keratinocyte’s responsiveness to IL-22,[28] IL-22 aggravates lupus nephritis by promoting macrophage infiltration.[29] The elevated expression of IL-22 is also involved in the occurrence and development of malignant tumors.