Alteration in regulatory T cells and programmed cell death 1-expressing regulatory T cells in active generalized vitiligo and their clinical correlation.

BACKGROUND: Vitiligo is an autoimmune depigmentation disease, and defects in regulatory T cells (Tregs) have been proposed in the pathogenesis of generalized vitiligo (GV). However, the role of programmed cell death (PD)1(+) Tregs has not been studied.

OBJECTIVES: To investigate the status of Tregs, PD1(+) Tregs and associated parameters in active GV (aGV) during the first episode of disease attack and to establish the clinical correlation.

METHODS: The percentages of circulating Tregs, PD1(+) Tregs and CD3(+) CD4(+) PD1(+) T cells were evaluated in 50 patients with aGV and 51 controls. Expression levels of FOXP3, TGFB1, CTLA4 and genes for chemokine receptors (CCR4, CCR7) and their ligands (CCL21, CCL22) were quantified in peripheral blood and in lesional, perilesional, nonlesional and normal skin sections. The corresponding proteins were immunolocalized in tissue of aGV.

RESULTS: The percentage of Tregs was decreased (P = 0·001) and that of PD1(+) Tregs increased (P = 0·001) in peripheral blood of patients with aGV compared with controls. The abundance of TGFB1 and CCL21 mRNA was significantly decreased in the peripheral blood of patients with aGV. Significant differences in forkhead box P3, transforming growth factor-β and CCL21 protein expression were found in skin sections.

CONCLUSIONS: Deficiency in Treg frequency and decreased expression of Treg-associated parameters (TGFB and CCL21) suggested a possible defect in Tregs that may alter their suppression function and skin homing in aGV. The increased PD1(+) Tregs suggests that the PD1/PD ligand pathway may be involved in aGV and may have a role in Treg exhaustion. Further study is required to delineate the effect of PD1 in regulating Treg function in aGV.