Abstract
Immunosuppressants are powerful drugs, capable of triggering severe adverse effects. Hence, there is tremendous interest in replacing them with less‐toxic agents. Adoptive therapy with CD25^+^CD4^+^ T regulatory cells (Tregs) holds promise as an alternative to immunosuppressants. Tregs have been described as the most potent immunosuppressive cells in the human body. In a number of experimental models, they have been found to quench autoimmune diseases, maintain allogeneic transplants, and prevent allergic diseases. A major stumbling block in their clinical application is related to Treg phenotype and the very limited number of these cells in the periphery, not exceeding 1–5% of total CD4^+^ T cells. Recent progress in multicolor flow cytometry and cell sorting as well as cellular immunology has found ways of overcoming these obstacles, and has opened the doors to the clinical application of Tregs. In the review, we describe Treg sorting and expansion techniques that have been developed in recent years. In the experience of our laboratory, as well as some published reports, Treg adoptive therapy is a promising tool in immunosuppressive therapy, and should be considered for clinical trials. © 2008 International Society for Advancement of Cytometry