Single administration of lesion-limited high-dose (TURBO) ultraviolet B using the excimer laser: clinical clearing in association with apoptosis of epidermal and dermal T cell subsets in psoriasis
Conflicts of interest:
Dr Kevin D. Cooper, M.D., Department of Dermatology, University Hospitals Case Medical Center, 11100 Euclid Avenue, Lakeside, Mailstop 5028, Cleveland, OH 44106-5028, USA.
Development of effective therapy for psoriasis is confounded by numerous factors contributing to disease pathogenesis, including pathogenic immunocytes which appear to drive epidermal keratinocyte hyperproliferation. Our objective was to study clinical and biomarker effects of a single dose of TURBO laser UVB (308 nm) applied directly to psoriatic plaques.
Eighteen patients with chronic plaque psoriasis received a single dose of 10 minimal erythema dose (MED) UVB and were followed for 8 weeks. Keratome and punch biopsies were assessed for T cell depletion and apoptosis following a single 308-nm dose of UVB.
Patients demonstrated clinical improvement as indicated by decreased global Psoriasis Area and Severity Index scores and reduced numbers of pathogenic memory/effector T cells infiltrating lesional epidermis and dermis. Consistent with apoptosis induction, caspase activation increased in lesional T cells after treatment.
We conclude that a single 10 MED dose of TURBO UVB is effective at reducing the severity and extent of psoriatic lesions. We hypothesize that the reason a single treatment is sufficient to clear a psoriatic plaque is that the 10 MED dose is able to deliver sufficient photons to a microanatomic area of the lesion where susceptible pathogenic T cell mechanisms are operative.