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.