Cell-surface IL-7 receptor expression facilitates the purification of FOXP3(+) regulatory T cells.

FOXP3+ regulatory T (Treg) cells have crucial roles in maintaining self-tolerance and modulating adaptive immune responses. Functional studies of Treg cells have been hampered by a lack of suitable cell-surface markers that specifically enable their purification without contamination by non-regulatory CD25+ effector T cells. Two recent studies have demonstrated that downregulation of the interleukin-7 receptor (CD127) distinguishes Treg cells from activated T cells, facilitating both Treg-cell purification and their functional characterization in human diseases. CD127 uniquely enables the purification of FOXP3+ Treg cells and, potentially, also "adaptive" regulatory T-cell subsets from the CD4+CD25- T-cell population.