Regulatory T Cells (Tregs) in Polymorphic Light Eruption

PLE patients will be recruited through the Photodermatology Unit of the Department of Dermatology, Medical University of Graz, Graz, Austria. Eligible patients will be identified through diagnosis-related computer-assisted search in the electronic patient chart system of the Unit. The diagnosis of PLE will be verified by patient's history, clinical symptoms, histologic findings, laboratory studies and/or phototesting procedures.

The levels and function of Tregs, memory T cells, neutrophils, mast cells, Langerhans cells, cytokine and chemokine profiles, vitamin D levels in the blood and/or skin will be studied in PLE patients compared to control groups. Volunteers of four groups will be enrolled in this study: i) patients with PLE undergoing preventive medical UV photohardening in spring; ii) PLE patients not undergoing preventive UV photohardening; iii) healthy control subjects; and iv) patients with other diseases (including psoriasis, atopic dermatitis, and other conditions) undergoing therapeutic phototherapy.

Blood will be taken by venous puncture (mainly of a cubital vein) from the individual study participants at four defined time points during the year: (i) spring (March to April) (before medical photohardening in PLE patients); (ii) spring/early summer (April to June) (immediately after medical photohardening of PLE patients); (iii) late summer (August to September); and (iv) late fall (November to December). In addition, optional skin biopsies will be taken to study the parameters listed above. The statistical power analysis (alpha 0.05; power 0.8; assumed difference in Treg level/function of 30% among groups; based on the data by Myara et al., 2005) revealed that 23 patients (21+2 expected drop-outs) need to be enrolled per patient group. All patients of the non-PLE groups will be sex- and age (plus/minus 5 years)-matched to the PLE subjects.