Psoriasis is a chronic inflammatory disease of the skin characterized by keratinocyte hyperplasia and dermal infiltration with inflammatory cells. Driving factors the epidermal hyperplasia in psoriasis are not fully understood, but there is evidence that T cell-derived cytokines can be involved. In this article, we focus on the recent data indicating a key role of interleukin-2I, a cytokine mostly made by activated CD4 + T cells, in promoting epidermal hyperplasia and expanding pathogenic Th cell responses in psoriasis.