Background: Differences in the number of Foxp3+ regulatory T cells (Tregs) in lesional skin and peripheral blood and their functioning in plaque vs. guttate psoriasis have not been reported.
Objectives: To investigate whether there is a differential expression of Foxp3+ Tregs and a differential regulation of inflammatory cytokines in plaque vs. guttate psoriasis vulgaris.
Methods: The number and the percentage of Foxp3+ cells in different phases of skin lesions of patients with plaque and guttate psoriasis vulgaris were assessed by immunohistochemical staining. The expression of Foxp3 and interleukin (IL)-17 protein in CD4 populations was measured by flow cytometry. Inflammatory cytokine production by transforming growth factor-beta1-induced Foxp3+ Tregs was assessed in an in vitro study. The cytokines in supernatant and serum were determined by enzyme-linked immunosorbent assay.
Results: The percentage of Foxp3+ CD3+ cells in the papillary layer was higher than in the reticular layer of dermis and in epidermis (P < 0.05). The numbers of Foxp3+ Tregs in skin lesions and peripheral blood were higher in plaque than in guttate psoriasis, whereas the percentage of IL-17+ CD4+ cells was higher in guttate than in plaque psoriasis (P < 0.05). The numbers of Foxp3+ cells were positively correlated with the Psoriasis Severity Index score of skin lesions (P < 0.0001), and the percentages of Foxp3+ CD4+ cells in peripheral blood were positively correlated with the Psoriasis Area and Severity Index score of patients (P < 0.05). The inhibitory functions of Tregs to IL-17 and IL-6 in guttate psoriasis and to tumour necrosis factor-alpha in plaque psoriasis were deficient.
Conclusions: Differential expression and regulatory functioning for inflammatory cytokine production by Foxp3+ Tregs may imply a different immunopathogenesis for plaque and guttate psoriasis.