Foxp3+ regulatory T cells and related cytokines differentially expressed in plaque vs. guttate psoriasis vulgaris

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‐β1‐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‐α 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.