Evaluation of chimerism after bone marrow transplantation with single locus minisatellite DNA probes

The origin of cells in almost all allogeneic donor-recipient pairs can be determined through the use of highly polymorphic minisatellite DNA probes. Single-locus probes were cloned from hypervariable fragments in a human DNA fingerprint detected with a multi-locus probe. While each probe is highly polymorphic and locus specific, they all contain repetitive sequences. The properties of single-locus probes have improved the sensitivity of detecting mixed chimerism in comparison with multi-locus probes. The use of single-locus probes permitted detection of mixed chimerism (MC) at levels as low as 0.625%, approaching that obtained by PCR methods. In the present study, five patients who received allogeneic BMT for hematologic malignancies were analyzed. Two patients exhibited MC after BMT. One developed acute GVHD and chronic GVHD and remained in CR while the second patient who had no signs of GVHD suffered a relapse.