Hans Koenen is an immunologist who specialized in immune regulation of the immune system during his PhD and postdoctoral work, thereby focusing on human regulatory T cells. Now his research focuses on translational and fundamental aspects of immune regulation and immunotherapy in transplantation and inflammatory diseases, emphasizing on human regulatory T-cell(Treg) biology and their clinical application, as well as identifying immunomodulating compounds that facilitate Treg function. The research includes development of in vitro and ex vivo immunomonitoring tools for human Treg function and phenotype, including a pre-clinical humanized-mouse model. Collaborating with clinical research and industrial partners, we exploit this to dissect Treg-disease associations and support experimental clinical trials and personalized medicine. Current work focuses on: 1.) understanding Treg-stability and development of new immunotherapeutic strategies, 2.) biomarker characterization to monitor immune status in healthy individuals, transplant patients and patients with inflammatory diseases, 3.) immune monitoring of clinical trials and treatment efficacy in patients and experimental trials in healthy individuals.