OBJECTIVETo analyze the kinetics of hematopoietic cell chimerism in the early period after non-myeloablative stem cell transplantation (NAST) and to investigate the correlation between molecular and hematologic assessment of engraftment or rejection.

METHODShort tandem repeat-polymerase chain reaction (STR-PCR) analysis of chimerism status was carried out in 6 patients who received NAST from HLA-matched sibling donors.

RESULTSIn 5/6 patients, the peripheral blood samples collected on the first day after allograft infusion displayed the presence of mixed chimerism. STR-PCR analysis revealed a gradual increase of the donor-specific allelic signal which became dominant over the recipient-specific allele by day +7. On day +14, hematologic chimerisms were completely donor origin. Their molecular engraftments (ME) were detected at a median time of 6 days, preceding hematologic engraftment by a median of 5 days (P > 0.05). But the sixth patient showed more than 50% host residual cells on day +7 and had no signs of ME on day +14.

CONCLUSIONIt suggested that molecular monitoring of the early dynamics of chimerism after NAST could be useful in predicting engraftment, or rejection. If the engraftment was less than 50% on day +7 and failed to get ME on day +14, the graft rejection would occur.