Prevalence of chimerism after non-myeloablative hematopoietic stem cell transplantation.

Context And Objective: Non-myeloablative hematopoietic stem cell transplantation (NMA-HSCT) is performed in onco-hematological patients who cannot tolerate ablative conditioning because of older age or comorbidities. This approach does not completely eliminate host cells and initially results in mixed chimerism. Long-term persistence of mixed chimerism results in graft rejection and relapse. Involvement of graft-versus-host disease is concomitant with complete chimerism and graft-versus-tumor effect. The aim of this study was to evaluate the prevalence of chimerism in onco-hematological patients who underwent NMA-HSCT.

Design And Setting: Observational clinical study on chimerism status after human leukocyte antigen-identical NMA-HSCT at the Discipline of Hematology and Hemotherapy of Universidade Federal de São Paulo.

Methods: We sequentially analyzed the amplification of APO-B, D1S80, DxS52, FVW, 33.6, YNZ-2 and H-ras primers using variable number of tandem repeats (VNTR) on 17 pairs and fluorescent in situ hybridization (FISH) with the XY probe and SRY primer on 13 sex-unmatched pairs.

Results: The informativeness of the primers using VNTR was 60% for APO-B, 75% D1S80, 36% DxS52, 14% FVW, 40% YNZ-22 and 16% H-ras. The SRY primer was informative in female receptors with male donors. The XY-FISH method was informative in 100% of the sex-unmatched pairs.

Conclusion: These methods were sensitive and informative. In VNTR, the association of APO-B with D1S80 showed 88% informativeness. The quantitative FISH method was more sensitive, but had the disadvantage of only being used for sex-unmatched pairs.