New strategies for the manipulation of adaptive immune responses.

The maintenance of peripheral tolerance is largely based on thymus-derived CD4(+)CD25(+) naturally occurring regulatory T cells (Tregs). While on the one hand being indispensable for the perpetuation of tolerance to self-antigens, the immune suppressive properties of Tregs contribute to cancer pathogenesis and progression. Thus, modulation of Treg function represents a promising strategy to support tumor eradication in immunotherapy of cancer. Here, we discuss potential therapeutic applications of our observation that Tregs contain high concentrations of the second messenger cyclic adenosine monophosphate, which is transferred from Tregs via gap junctions to suppress the function of T cells and dendritic cells.