The chimerism status after allogeneic bone marrow transplantation (BMT) provides substantial information about the replacement of host cells with donor cells after the transplantation. We studied six Bulgarian patients after sex-mismatched allogeneic BMT by fluorescent in situ hybridization (FISH) with alternatively labeled X and Y probes and three male-to-male donor-recipient pairs by genotyping of microsattellite loci. Complete hematopoi­etic chimerism (CC) was found in one patient who did not experience graft failure. Near-complete chimerism (NCC) was detected in three patients who experienced an auto­logous recovery over several months followed by relapse and graft failure. In one patient, low-level mixed chime­rism (MC) that progressed to high-level MC, accompanied by full remission, was found. One patient showed low-level MC followed by complete loss of chimerism. In all patients the percentage of chimeric cells correlated with clinico-hematological data for remission or relapse. Of the three sex-matched BMT patients, one showed chimerism 3 months after BMT followed by recurrence, one died before the first monitoring, and in another patient, the markers produced no informative results. We conclude that dynamic changes in chimerism have clinical and predictive value for the hematological status of patients after BMT.
Key words: Bone marrow transplantation (BMT), Chimerism, Monitoring