Short tandem repeat analysis to monitor chimerism after allogeneic stem cell transplantation

Chimerism can be monitored after HLA-matched allogeneic stem cell transplantation by detecting short tandem repeat (STR) polymorphisms replacing the restriction fragment length procedure (RFLP). STR polymorphisms were analysed on ABI Sequencer 310 after co-amplification of nine STRs D3S1358/vWA/FGA, D8S1179/D21S11/D18S51 and D5S818/D13S317/D7S820 plus the Amelogenin gene with the AmpFISTR Profilerplus Kit, Fa. PE-ABI Weiterstadt. In addition cell samples of related individuals were mixed experimentally to evaluate the sensitivity of the multiplex system. 44 allogeneic stem cell recipients have been monitored by this method. In all cases (unrelated or related and of the same sex) different allele patterns were detected in at least two of the nine STR systems. Complete donor chimerism was consistent with long-term disease-free survival A complete recipient profile or a mixed chimeric state was observed in cases of graft failure or a relapse of the underlying malignancy. In samples with mixed chimerism the percentage of donor/recipient cells was assessed to distinguish between a low-level mixed chimerism and a progressive mixed chimerism in order to define patients who are at a high risk of leukaemia relapse.