Expansion of FOXP3-positive CD4+CD25+ T cells associated with disease activity in atopic dermatitis

Background: FOXP3-positive CD4(+)CD25(+) T cells are known to have an immunoregulatory function by means of preventing T-cell reactivity to both self- and non-self-antigens. However, the role of these cells in the pathogenesis of allergic diseases is not clear. Objective: To evaluate the quantity and quality of circulating FOXP3-positive T cells in patients with atopic dermatitis (AD). Methods: Peripheral blood mononuclear cells were isolated from 35 AD patients (mean [SD] age, 27.1 [7.5] years) and 36 controls (mean [SD] age, 27.5 [10.0] years). Cellular FOXP3 expression was analyzed using flow cytometry. Characteristics of FOXP3-positive T cells were evaluated with respect to cytokine production capability and suppressive function. Results: Frequencies of circulating FOXP3(+)CD25(+) cells in the CD4(+) T-cell population of AD patients were significantly higher than those in controls (mean [SD], 7.4% [4.6%] vs 4.5% [1.3%]; P = .002) and correlated with their Scoring Atopic Dermatitis (SCORAD) scores (r = 0.74, P = .008) and peripheral blood eosinophil counts (r = 0.72, P < .001). In the patients whose samples were analyzed at intervals of 1 to 2 months, frequencies of FOXP3-positive T cells were decreased as their skin lesions improved, regardless of medicines used. FOXP3-positive CD4(+) T cells from patients, as well as those from controls, showed little capability to synthesize interferon gamma and interleukin 4. No differences were found in suppression abilities of CD4(+)CD25(+) T cells between AD patients and controls. Conclusions: Our data suggest that dynamic fluctuation in numbers of circulating FOXP3-positive regulatory T cells might contribute to the pathogenesis of AD. Ann Allergy Asthma Immunol. 2009; 103:160-165.