DETECTION OF CHIMERISM AND EARLY ENGRAFTMENT AFTER ALLOGENEIC PERIPHERAL-BLOOD STEM-CELL OR BONE-MARROW TRANSPLANTATION BY SHORT TANDEM REPEATS

Chimerism can be monitored after HLA-matched allogeneic bone marrow tr ansplantation (BMT) or allogeneic peripheral blood stem cell transplan tation (PBSCT) by detecting polymorphisms in short tandem repeats (STR ). The purpose of our study was to document early complete chimerism i n BMT and PBSCT recipients using STR, and to determine whether the ini tial WBC recovery correlated with the days required to attain complete chimerism. A total of 5 patients (2 PBSCT and 3 BMT) were followed by STR after transplantation. Peripheral blood obtained prior to transpl antation was used to determine the 2 most informative SIR probes for e ach donor/recipient pair. STR were amplified by polymerase chain react ion (PCR) with 8 commercial probes, and PCR products were visualized w ith silver staining. Peripheral blood was evaluated daily post-transpl antation for WBC counts and to identify the presence of mixed or full chimerism by STR. The sensitivity of the STR technique varied from 0.0 5 to 1%, depending on the probe. Full chimerism was documented between day 9 and 14 in PBSCT recipients and on day 14 and 16 in BMT recipien ts. The initial rise in WBC occurred within 3 days of the onset of ful l chimerism, indicating that full chimerism is a more sensitive indica tor of early engraftment. Periodic recipient monitoring using STR afte r complete chimerism identifies those patients who revert to mixed chi meras. The STR method may be useful in future studies to determine the significance of early engraftment and the clinical implications of su stained complete chimerism or mixed chimerism. (C) 1996 Wiley-Liss, In c.