Factors that regulate naturally occurring T regulatory cell-mediated suppression

T regulatory (Treg) cells play a key role in the modulation of allergic and autoimmune responses. This review will discuss the factors that regulate naturally occurring Treg (nTreg) cell-mediated suppression. The involvement of cytokines, costimulatory molecules, and ligands on antigen-presenting cells in the inhibition of nTreg cell-mediated suppression in vitro is summarized. Understanding the events that control suppressive function of nTreg cells will allow manipulation of these cells to inhibit or enhance their functions in the development of novel therapies for autoimmune and allergic diseases.