S100A7 and psoriasis: The exact role of IL-19 is not clear, but it has been suggested, in synergy with IL-20 and IL-24 that share the same receptor, to enhance the epidermal hyperplastic process, promote keratinocyte migration and drive production of several factors by keratinocytes or fibroblasts, such as anti-microbial peptides like S100A7 that are found in psoriasis as well as keratinocyte growth factor65, 66, 67.