BIOLOGICAL EFFECTS OF NARROW-BAND (311 NM TL01) UVB IRRADIATION - A REVIEW

The narrow-band UVB (TL01) lamp (311 nm emission) was developed for us e in phototherapy, as an alternative to a broad-band UVB source and to photochemotherapy, both of which have significant side effects and ca rry a risk of carcinogenesis. This new lamp has proved to be particula rly effective at clearing psoriasis. It is now acknowledged that the T L01 lamp is probably 2-3 times more carcinogenic per minimum erythema dose than broad-band UVB, but the cumulative dose required in therapy is considerably less than when using broad-band UVB sources. In terms of irradiation dose, the TL01 lamp is about 5-10-fold less potent than broad-band UVB for erythema induction, hyperplasia, oedema, sunburn c ell formation and Langerhans cell depletion from skin. However, the br oad-band UVB to TL01 potency ratio for cis-urocanic acid formation in the skin is approximately unity. In addition, the TL01 lamp, as used i n phototherapy, has relatively more suppressive effects than broad-ban d UVB on systemic immune responses as judged by natural killer cell ac tivity, lymphoproliferation and cytokine responses. However, the TL01 lamp is less effective at reducing epidermal antigen presentation, ind ucing dendritic cell migration to lymph nodes draining irradiated site s and suppressing contact hypersensitivity at the doses tested. Theref ore the use of the TL01 lamp in phototherapy should be considered care fully after weighing up its diverse effects on the skin and immune sys tem. (C) 1997 Elsevier Science S.A.