CD1a and Lipids as Mediators of T Cell Activation in the Skin.

Despite increasing insights in cytokine pathways involved in T cell-mediated inflammatory skin diseases, the upstream T cell triggering events through antigen-presenting molecules and antigens often remain incompletely understood. Recent studies have proposed an immunopathogenic role for T cells that are activated through CD1a, a lipid antigen-presenting molecule abundantly expressed on antigen-presenting cells in human skin. These CD1a-restricted T cells are thought to play a role in psoriasis, atopic dermatitis, and allergic contact dermatitis. In this review, we discuss modes of T cell activation by CD1a proteins and lipid antigens and bacteria as well as recent insights in local and systemic functions of CD1a-restricted T cells in inflammatory skin disease.