CD4+ CD25+ T-regulatory cells in psoriasis. Correlation between their numbers and biologics-induced clinical improvement.

Background: Regulatory T-cells (T-reg) play a central role in the immunopathogenesis of psoriasis. T-reg cells are both functionally and numerically impaired in psoriasis and they are up-regulated by drug therapy. Objective: To analyse the circulating CD4+CD25 bright FOXP3+ subset in 14 patients with vulgaris/arthropathic psoriasis treated with biological drugs and to investigate their relationship with the clinical response. Methods: The CD4+ CD25 bright FOXP3+ expression was determined in peripheral blood by flow cytometry at baseline and during treatment. Results: A response was obtained in 10/14 patients with increased CD4+ CD25 bright FOXP3+ (T-reg) in peripheral blood after the first month and then 4 months after therapy with biological drugs. This increase is associated with the achievement of a clinical response and with a reduction in the Psoriasis Activity and Severity Index (PASI) score. 2/14 patients showed a decrease in T-reg after drug therapy and this decrease correlated with a worsening of the clinical skin. Conclusion: Biological drugs induce circulating T-reg up-regulation in psoriatic patients; such an increase is an early predictive marker of clinical response.