Rethinking the molecular definition of regulatory T cells.

It has been postulated that expression of the transcription factor Foxp3 "specifically" identifies the regulatory T cell (Treg) lineage and it acts as its "master regulator" or "lineage specification factor". However, emerging evidence challenges these views and suggests that the Treg lineage may be determined by a higher-order regulatory process that ensures stable and high levels Foxp3 expression.