Immunology of cutaneous lupus erythematosus.

The cause and effect between ultraviolet light and cutaneous lupus erythematosus (CLE) is clear. In LE patients indeed, photosensitivity is one of the major diagnostic criteria of the systemic form of lupus erythematosus. This strong clinical association has led to the postulate that abnormal photosensitivity participates in the pathogenesis of cutaneous lesions in LE. What is not clear is how the ultraviolet radiation (UVR) induces cutaneous lesions in susceptible individuals despite the fact that profound effects of UVR on the cellular components of the skin have been extensively studied. The whole scenario is complicated by the relationship between sunlight and the cutaneous immune system. Pronounced effects of UVR on the cutaneous immune response further complicate the understanding of photosensitivity in LE. In addition, the network of cutaneous cytokines, chemokines, and adhesion molecules has become increasingly intricate, thus contributing to the genetic substrate of each individual, and to the tremendous complexity of the pathogenesis of CLE.