[1] Univ Cambridge, Addenbrookes Hosp, Dept Med, Cambridge CB2 1TN, England
[2] Papworth Hosp, Dept Transplantat, Cambridge CB3 8RE, England
[3] Papworth Hosp, Dept Pathol, Cambridge CB3 8RE, England
[4] Yale Univ, Sch Med, Dept Surg, New Haven, CT 06510 USA
[5] Yale Univ, Sch Med, Dept Pathol, New Haven, CT 06510 USA
[6] Yale Univ, Sch Med, Dept Immunobiol, New Haven, CT 06510 USA