Peripheral blood microchimerism in human liver and renal transplant recipients : Rejection despite donor-specific chimerism

Development of donor-specific microchimerism (DSM) has been proposed as one of the possible mechanisms for induction and maintenance of allograft tolerance. The aim of this study was to determine: (1) the state of DSM in liver transplant (LTx) and renal transplant (RTx) recipients, (2) whether the persistent presence of an allograft is a requirement for maintenance of chimerism, and (3) whether donor-specific blood transfusions (DST) facilitate chimerism development in RTx recipients and whether this correlates with allograft function. Qualitative and quantitative analysis of DSM in peripheral blood of LTx and RTx recipients was assessed by polymerase chain reaction and competitive polymerase chain reaction using HLA-DR probes for mismatched antigens between the donor and recipient. LTx recipients (11 of 12) who had or were having rejection were positive for DSM in circulation compared with 4 of 11 with normal allograft function (P