PD1 regulates alloreactive donor T cells after liver transplantation in graft-versus-host-disease - Schuchmann, M; Meyer, RG; Gregor, S; Distler, E; Bender, K; von Stebuth, E; Huber, C; Galle, PR; Otto, G; Herr, W (Zeitschrift für Gastroenterologie, 2008)