Immunological and Molecular Mechanisms of Photoallergic Contact Dermatitis

Yoshiki TOKURA
2003 Journal of UOEH  
The UOEHAssociation ofHealthSciences J UOEH25 (4): 387-395(2003) 387 (Review] Abstvact: Photocontact dermatitis is one of the major occupational skin diseases and an undesirable adverse effect produced by chemicals and drugs in our environment. This dermatitis is caused by skin application of photosensitive agents plus ultraviolet light irradiation. There exist both primary irritant and allergic mechanisms in this dermatosis. While the fbrmer is induced by the phototoxic reactions, the latter
more » ... lergic type is mediated by Langerhans cells, T cells, various cytokines and chemokines, and thus occurs via a well-orchestrated and wellelucidated immunological mechanism. The photoallergic type has a higher incidence and more severe skin eruptions than the primary irritation. Photocoajugation of epidermal cells with a photohaptenic halogenated chemical is the mitial step, and Langerhans cells serve as antigen-presenting cells. Causative photohaptens are bound to MHC class II molecules/self peptide on Langerhans cells upon exposure to UVA. The photomodified Langerhans cells sensitize and elicit antigen-specific T cells that mediate photoallergy. Thus, this photoallergy is induced by well-orchestrated photochemical and immunological mechanisms. [1]. Among these occupationai skin disorders, contact dermatitis is the major skin disorder, and photocontact dermatitis is a specialized form of this skin disease [2] . Photocontact dermatitis is divided into two subtypes: phototoxic and photoallergic contact dermatitis, with the latter being clinically more common than the former. It is sometimes difflicult to diagnose this photosensitivity, although its incidence is NII-Electronic
doi:10.7888/juoeh.25.387 pmid:14692341 fatcat:qltf6daz6rg5tcfr6ed7iu3hgm