Identification of Lesional CD4+ CD25+ Foxp3+ Regulatory T Cells in Psoriasis

<i>Background:</i> Depletion of CD4+ CD25+ Foxp3+ naturally occurring regulatory T cells (T_reg) induces autoimmune phenomena. These cells have not yet been fully characterized in the skin of psoriatic patients. <i>Objectives:</i> To prove that the Zenon immunofluorescent labeling technique is suitable for the demonstration of co-localization of T-cell markers and in particular to show the distribution of T_reg in psoriatic skin. <i>Methods:</i> In biopsies derived from normal and psoriatic skin, CD4+ CD25+, CD4+ CD45RO+, CD8+ CD25+, CD8+ CD45RO+ and CD4+ CD25+ Foxp3+ cells in the dermis and in the epidermis were immunophenotyped, using a quantitative immunofluorescent labeling technique (Zenon), analyzed and compared using image analysis. <i>Results:</i>The immunofluorescent labeling technique was shown to be an easy and reliable tool to demonstrate co-localization of T-cell markers. In psoriasis, all pathogenic T-cell subsets (CD4+ CD25+, CD4+ CD45RO+, CD8+ CD25+ and CD8+ CD45RO+ cells) were significantly increased in the dermis and in the epidermis, as compared to normal skin (all p < 0.05). Using this labeling technique we were able to reveal CD4+ CD25+ Foxp3+ T_reg in psoriatic dermis, but not in the dermis of normal skin (p < 0.0001). <i>Conclusions:</i>The Zenon immunofluorescence technique in combination with image analysis is suitable for the demonstration of co-localization of T-cell markers in tissue. Increased numbers of pathogenic T cells (CD4+ CD25+, CD4+ CD45RO+, CD8+ CD25+ and CD8+ CD45RO+) were shown in the dermis and epidermis, whereas CD4+ CD25+ Foxp3+ T_reg were identified in psoriatic skin with a predilection for the upper dermis.