Abstract

The skin represents the first line defense against various stresses including pathogens and injuries. Cutaneous homeostasis and defenses are maintained by permanent cross talk among dermal fibroblasts, keratinocytes, and cells of the immune system residing in or recruited to skin, through the production of cytokines and chemokines. In this chapter, we discuss the biological effects of IL22 on keratinocytes and more particularly its position in skin inflammation and in the development of inflammatory skin diseases such as psoriasis.
Focused on in vitro human models, we present the mechanisms of action of IL22 as well as its involvement in structure, metabolism, differentiation, chemotaxis, antibacterial activity, innate immunity, and tissue remodeling of epidermis. Pertinence of these models is debated by confrontation to structural and molecular characteristic of psoriatic skin. IL22 belongs to cytokine milieu impregnating inflammatory skin. We attempt to delineate more precisely its unique position among other proinflammatory cytokines and in the synergistic effect of these cytokines. Finally, we consider the local cell sources of IL22 in the psoriatic skin.
We question potential new therapeutic strategies for psoriasis focused on more specific and downstream targets, i.e., keratinocyte-targeting cytokines, rather than on modulating producing cells by immunosuppression.