Regulatory T cell-mediated suppression: potential role of ICER

Abstract: How regulatory T (TR) cells dampen T cell responses remains unclear. Multiple modes of action have been proposed, including cell contact-dependent and/or cytokine-dependent mecha-nisms. Suppression may involve direct contact be-tween TR cells and responder T cells. Alternatively, TR cells may act on dendritic cells to reduce their ability to prime T cells by modulating costimula-tion, inducing the secretion of suppressive cyto-kines or the increase of tryptophan metabolism. Here, we review emerging, novel mechanisms in-volved in contact-dependent, TR-mediated sup-pression of IL-2 production in responder CD25 – T lymphocytes and the potential involvement of in-ducible cAMP early repressor in this suppression. Finally, cytokines such as TGF- and IL-10, pro-duced by TR cells or other cells, may exert local suppression, which can be conveyed by basic mechanism(s) acting in a similar manner as con-tact-dependent, TR-mediated suppression. J. Leu-koc. Biol. 81: 000–000; 2007. Key Words: transcriptional repressor inhibitory receptor im-mune regulatio