Regulatory T cells in autoimmune skin diseases

CD4⁺ Foxp3⁺ regulatory T cells (Tregs) are suppressors of immune activation and play a crucial role in the maintenance of peripheral tolerance. Mutations of Foxp3 result in fatal autoimmunity in multiple organs, including the skin, in both humans and mice. Many studies have demonstrated the altered frequency and functions of Tregs, changes in cytokine and chemokine levels related to Tregs and the differences in genetic background regarding Tregs in autoimmune skin disorders. Recent studies have extended our knowledge of certain properties of Tregs, especially skin-resident Tregs. In addition, some novel therapies have been performed by modulating the number and the function of Tregs. This review focuses on the role of Tregs in some autoimmune skin disorders, including alopecia areata, vitiligo, pemphigoid and pemphigus, and systemic sclerosis, and discusses questions that remain to be addressed.