ENVIRONMENTAL TRIGGERS OF AUTOIMMUNE DISEASE
Environmental factors can trigger autoimmune disease in susceptible hosts, as illustrated by the initiation of disease by sun exposure in a subset of lupus patients. The wavelengths most likely to induce lupus fall in the UV range: UVC (200-290 nm), UVB (290-320 nm), UVA (320-400 nm). UVB irradiation is mostly absorbed in the upper layers of the epidermis, whereas the longer wavelength UVA is able to reach the dermis. UV exposure can induce apoptosis and release of immune mediators and activation of resident dendritic cells and T cells. Expression of certain self-antigens, such as Ro60/Ro52, on the surface of the apoptotic cells may lead to antibody-mediated inflammatory responses that could play a role in the pathogenesis of skin rashes in lupus.