THE EFFECT OF ULTRAVIOLET-RADIATION ON INFECTIOUS-DISEASES

Exposure to ultraviolet light (UV) has a number of adverse effects on biological systems, including suppression of selected immune responses . There is evidence that the function of antigen-presenting cells is i mpaired by the irradiation, and that a T helper 2 (Th2) pattern of cyt okines is promoted with anergy of Th1 cytokine production, Three human infections, namely, those caused by herpes simplex virus, papillomavi rus and human immunodeficiency virus, are affected by sunlight. A limi ted number of rodent models of infection with a variety of microorgani sms have been studied in the context of UV irradiation and, in general , in cases where a Th1 response is protective, exposure leads to decre ased ability to clear the agent and/or to suppressed antigen-specific immune responses. The impact of UV on most natural infections is not c lear at the present time but is of concern, particularly as environmen tal UV radiation is likely to increase in the future, with unknown con sequences for human health.