Xenon chloride ultraviolet B laser is more effective in treating psoriasis and in inducing T cell apoptosis than narrow-band ultraviolet B

Earlier we reported that a 308-nm xenon chloride (XeCl) UVB laser is highly effective for treating psoriasis. As ultraviolet B light seems to cause T cell apoptosis, in the present study we studied the ability of the XeCl laser to induce T-cell apoptosis in vitro, and then compared the apoptosis-inducing capacities of narrow-band UVB (NB-UVB) light and the XeCl laser. The role of laser impulse frequency and intensity in the therapeutical and apoptosis-inducing efficacy of XeCl laser was also investigated. Both XeCl laser and NB-UVB induced T cell apoptosis, but quantitative induction was greater with XeCl laser. Changes in the frequency and intensity of impulses of XeCl laser did not influence its therapeutic and T cell apoptosis-inducing efficacy. These results suggest that the more effective induction of T cell apoptosis can be responsible for the greater clinical efficacy of XeCl laser compared to NB-UVB. Additionally, the optical properties of the XeCl laser (a monochromatic, coherent, pulse-mode laser; easier precise dosimetry, there are no 'contaminating' wavelengths) can make this laser light an ideal tool for studies of the mode of action of UVB light. (C) 2002 Elsevier Science BY. All rights reserved.