Abstract

Skin represents the first line of defense against various stresses including pathogens and injuries.
Cutaneous homeostasis is maintained by permanent cross-talk among dermal fibroblasts, epidermal keratinocytes, and cells of the immune system residing in the skin or infiltrated through the production of cytokines. In this review, we discuss current knowledge about the effects of different cytokine families on keratinocytes, and more particularly theirinvolvement in skin inflammation and in the development of inflammatory skin diseases such as psoriasis.
We highlight the origin of cytokines in the epidermis, in particular those derived from Th1 (IFNγ) Th2 (IL-4, IL-13), and the recently described Th17 pro-inflammatory T cell subset producing IL-17 and IL-22. We review their mechanism of action as well as their involvement in structure, metabolism, differentiation, chemotaxis, antibacterial activity, innate immunity, and tissue remodeling of epidermis (skin inflammation).
We discuss potential new therapeutic strategies focused on more specific and downstream targets, i.e. keratinocytes, rather than on modulating producing cells by immunosuppression, thus suggesting approaches aiming either to inhibit or to enhance the action of cytokines in epidermis.