CD4+CD25+ regulatory T cells in health and disease.

1. Over the past 5 years, tremendous progress has been made in understanding the suppressive mechanisms of T regulatory (Treg) cells. The Treg cells, a subpopulation of T cells, have been shown to play an important role in maintaining peripheral tolerance and the prevention of autoimmunity. 2. Various populations of Treg cells have been described, including thymically derived CD4(+)CD25(+) Treg cells. These naturally occurring Treg cells are present in the periphery and are capable of suppressing proliferation and effector T cell responses both in vitro and in vivo. 3. In addition, a second subset of Treg cells, type 1 T regulatoary (Tr1) and Th3 cells, exert their suppressive capacity via cytokines such as interleukin-10 and transforming growth factor-beta and are contact independent. 4. The present review summarizes the characteristics and molecular basis of CD4(+)CD25(+) Treg cells, as well as their therapeutic potential in modulating inflammatory diseases, such as inflammatory bowel disease and rheumatoid arthritis.