IL17A and psoriasis: Because of the role of IL-17A in psoriasis and its effects on gene expression in primary normal human epidermal keratinocytes (NHEKs)16,17, we tested whether IL-17A affected the differentiation of keratinocytes in organotypic 3D skin equivalents (3D models) using keratinocytes and fibroblasts derived from skin biopsis of healthy individuals.