Background Regulatory T cells (Tregs) have an essential role in tolerance and immune regulation. However, few and controversial data have been published to date on the role and number of these cells in atopic dermatitis (AD).
Objectives To investigate the number of CD4+CD25+FOXP3+ Tregs and interleukin 10-producing T regulatory type 1 (Tr1) cells in patients with AD.
Methods Peripheral blood and skin biopsy samples from atopy patch test (APT)-positive patients with acute- and chronic-phase AD were investigated. Immunohistochemistry was applied to identify CD4+CD25+FOXP3+ Tregs in the skin, while flow cytometry was used to detect CD4+CD25highFOXP3+ Tregs and Tr1 cells in the peripheral blood.
Results In the peripheral blood samples of patients with AD significantly elevated numbers of Tr1 cells were found. Although neither the absolute number nor the percentage of CD4+CD25highFOXP3+ Tregs showed significant alteration in the peripheral blood of patients, increased numbers of FOXP3+ Tregs were detected in skin biopsy specimens. All of the APT-positive skin samples showed epidermal dendritic cell aggregates, morphologically consistent with so-called Langerhans cell microgranulomas, which also contained intermingled FOXP3+ Tregs.
Conclusions Tr1 cell numbers were elevated in the peripheral blood and increased numbers of CD4+CD25highFOXP3+ Tregs were detected in the skin of patients with AD. The epidermal dendritic cell clusters in APT-positive lesional skin showed a close connection to the FOXP3+ Tregs.