Regulatory T cells in health and disease

. The healthy host does not normally develop tissue destructive autoimmunity in part because of the presence of natural regulatory T cells. These cells are best identified by their expression of a unique transcription factor forkhead box transcription factor (Foxp3) that controls their regulatory function. Several other types of regulatory T cells also occur most of which are induced in response to antigen stimulation. Some of these express the Foxp3 transcription factor but many do not. The role of natural T‐regulatory cells as well as induceable regulatory cells in autoimmunity, cancer, allergy and infectious disease is described. The current status of therapeutic approaches that modulate regulatory T‐cell responses on the outcome of experimental animal and human disease is also discussed.