Regulatory T cells (TREG) comprise a subset of CD4+ T cells that maintain immunological tolerance by suppressing immune activation in a dominant manner. TREG helps shaping the immune responses to autoantigens, alloantigens, tumors, pathogens and allergens, and are thus considered a therapeutical target in a large variety of diseases. One aspect of TREG biology that remains poorly understood is what molecular program(s) are induced in cells that are being actively suppressed by TREG. The specific aims described below are designed to provide a better understanding of the molecular changes that occur as a result of TREG-mediated suppression and determine if the biochemical pathways altered by TREG-mediated suppression can be exploited for therapeutical purposes.1. Characterize the molecular changes that occur in CD4+ T cells and dendritic cells that are being suppressed by TREG using gene profiling and cell signaling experimental approaches.2. Evaluate the importance and therapeutical potential of genes with an expressionprofile altered by TREG-mediated suppression in animal models of human diseases.