Bath-PUVA therapy improves impaired resting regulatory T cells and increases circulating activated regulatory T cells in psoriasis

Abstract

Bath-PUVA therapy is applied for the treatment of psoriasis due to its efficacy, safety profile, and low cost. The pathogenesis of psoriasis might be an imbalance of Th17 cells and regulatory T cells (Treg). We previously evaluated the effects of bath-PUVA therapy on Th17/Treg balance in peripheral blood obtained from patients with psoriasis. Bath- PUVA therapy significantly reduces the number of Th17 cells. The Treg Functional Ratio (%), defined as %suppression of responder cell proliferation by Treg, is significantly lower in patients (72.1 ± 24.8% n = 15) than in controls (94.4 ± 4.3% n = 9, p = 0.015). The Treg Functional Ratio is significantly increased, and Treg function is restored to almost normal levels. The Treg Functional Ratio is inversely correlated with the Psoriasis Area and Severity Index score (r = −0.407, p = 0.084). These findings confirm that Treg are dysfunctional in psoriasis patients, and that bath-PUVA therapy restores Treg function in most patients. In the present study, we examined three distinct Treg subsets: activated Treg (aTreg), resting Treg (rTreg), and cytokine-secreting non-suppressive Treg (non- Treg). aTreg is considered to have the strongest suppressive activity among the three subsets. We examined these subsets from the peripheral blood before and at each of the 5 sessions of bath-PUVA therapy in 10 psoriasis patients. aTreg levels were significantly increased in the early sessions of bath-PUVA therapy and later diminished afterward. The psoriasis lesions improved concomitantly with the increase in aTreg. The improvement was negatively correlated with the Psoriasis Area and Severity Score. Bath-PUVA therapy resolves the Th17 and Treg imbalance in patients with psoriasis and induces aTreg.