1. From the Medical Research Council Centre for Transplantation, King's College London, King's Health Partners, Guy's Hospital, Great Maze Pond, London, United Kingdom (D.C., S.S., L.M., E.-L.T., R.I.L., A.D.); Department of Immunology, Imperial College London, Hammersmith Hospital, London, United Kingdom (S.S., J.A., J.D.C., D.S.); Thrombosis Research Institute, London, United Kingdom (J.H.M.).