Review: Skin and the Immune System

Elizabeth R. Mann, Kathryn

Abstract

The skin immune system comprises a complex network of cells, functioning both in immunity against invading pathogens but also tolerogenic mechanisms to ensure maintenance of immune homeostasis. The nature of antigens present and interplay between the cutaneous innate and adaptive immune systems determine the type of immune response generated. Dendritic cells are the key players in bridging innate and adaptive immune responses due to their inherent plasticity, direct roles in both type of immune responses, and cross-talk with other immune cells. This review dissects the functional roles of components of both innate and adaptive immune systems in the skin, with a special focus on cutaneous dendritic cells as the only cells capable of inducing primary immune responses, their ability to generate either immunogenic or tolerogenic immune responses, and ability to direct effector cells back to the skin via imprinting of skin-homing properties on T-cells. Finally the reciprocal interactions between the skin microbiota and immune system and their role in host defence and disease have been discussed.