TGF-beta is a pleiotropic cytokine with powerful immunosuppressive functions. Mice deficient for TGF-beta 1 show a dramatic phenotype with severe multiorgan inflammation and die shortly after birth. Recent investigations have highlighted the role of TGF-beta in suppression of T cell mediated autoimmunne inflammation and anti-tumor immunity. In addition to its direct anti-inflammatory effects on T cells, TGF-beta has been implicated as central regulator of regulatory T cells. TGF-beta not only mediates the suppression of effector T cells by Tregs, recent evidence also reveals a role for TGF-beta along with TCR stimulation in the peripheral induction of regulatory T cells from naive CD4+CD25- cells. (c) 2005 Elsevier Ltd. All rights reserved.