These mice spontaneously developed characteristic hallmarks of human psoriasis, including acanthosis (hyperplasia of the epidermis), increases in dermal CD4+ T cells, infiltrating epidermal CD8+ T cells, dermal dendritic cells and macrophages, and increased expression of cytokines and chemokines associated with psoriasis (IFN-γ, TNF-α, IL-1α, IL-6, IL-12, IL-22, IL-23, and IL-17). This evidence concerns the gene IL17A and psoriasis.