Regulatory T cells (Treg) control numerous immune activities and non-immunological processes. Based on the observation that Treg regulate the postthrombotic inflammatory response we aim to systematically analyze their functional role in postthrombotic inflammation, thrombus resolution and repair. Working steps consist in depletion or activation of Treg prior and post deep vein thrombosis (DVT) induction to reveal their regulatory impact, gene expression profiling and functional evaluation of Treg pathways. Investigations are carried out in the inferior vena cava (IVC) ligation model, thrombotic tissue from chronic thromboembolic pulmonary hypertension (CTEPH) patients as well as murine and human EC and SMC cultures.