Skin Immunology and Immunotoxicity

The primary role of the skin, the largest organ of the body, is to provide barrier function. While preventing desiccation of our internal milieu is the primary task, evolution equipped our skin with additional mechanisms to deal with our environment. The immune function of the skin is an excellent example. Within the skin are the components needed to initiate the immune response. Moreover, environmental agents that interact with the skin can induce regulatory processes that affect distant immune reactions. A prominent example is the ultraviolet (UV) radiation present in sunlight. UV radiation is a complete carcinogen and the primary cause of nonmelanoma skin cancer, the most prevalent type of cancer found in the industrialized world. Furthermore, UV induces immune suppression and the immune suppression induced by UV radiation is a well-recognized risk factor for skin cancer induction. The focus of this chapter is to review the immune modulation that results after UV exposure of the skin, an immunotoxicant that all humans are exposed to on a daily basis. Moreover, this chapter attempts to illustrate other 'dermal immunotoxicants' that induce immune suppression via similar mechanisms.