Chimerism analysis by lineage-specific fluorescent polymerase chain reaction in secondary graft failure after allogeneic stem cell transplantation

Background Chimerism analysis is essential in understanding the etiology of graft failure occurring after allogeneic stem cell transplantation. The de tection of marrow and/or blood host cells suggests graft rejection, relapse of the underlying disease, or a state of stable mixed chimerism, However, complete donor chimerism may be observed in some cases. Our objective was t o characterize, by a sensitive process of chimerism analysis, six cases of graft failure occurring after transplant. Methods. Six cases of secondary graft failure, in which previous analysis h ad shown complete donor chimerism by standard polymerase chain reaction amp lification of variable number of tandem repeats, were studied. In order to detect a minority population of recipient cells, we increased the sensitivi ty of the process by using fluorescent polymerase chain reaction and analyz ing the origin of T, B, and natural killer lymphocytes at the time of graft failure. Results, The complete donor origin of mononuclear cells and lymphocytic pop ulations was confirmed with this method in five of six patients, In the rem aining patient, diagnosis of graft failure was clarified by the detection o f a previously undetected mixed chimerism, compatible with graft rejection. in the other five patients, graft rejection was thereby excluded and graft failure could be related to viral infection or to graft-versus-host diseas e. Conclusion. Our sensitive process of fluorescent lineage-specific chimerism analysis may help in distinguishing between graft rejection and other mech anisms of graft failure, which is essential for deciding appropriate therap y.