Early establishment of hematopoietic chimerism following allogeneic peripheral blood stem cell transplantation in comparison with allogeneic bone marrow transplantation

To characterize the process of the establishment of complete chimerism afte r allogeneic peripheral blood stem cell transplantation (allo-PBSCT), we de termined the origin of leukocytes in peripheral blood (PB) obtained from 23 patients in the very early period after allo-PBSCT using amplification of mini- or microsatellite regions of genomic DNA. Donor-specific alleles were amplified from the PB obtained at day 8 post-transplant for 19 allo-PBSCT patients. Among the 19 patients, 12 showed only donor-specific alleles (com plete chimerism) while 7 did both donor and host-specific alleles (mixed ch imerism). Although donor specific alleles were amplified in 10 of 12 patien ts who received allogeneic bone marrow transplantation (allo-BMT) similarly to allo-PBSCT, all of these ten showed mixed chimerism. When the chimeric state was examined in PB samples obtained serially at 23-day intervals post -transplant, host-specific alleles in allo-PBSCT patients were not detectab le in the PB much earlier than those in allo-BMT patients. These findings i ndicate that the appearance of donor-derived cells associated with the disa ppearance of host-derived cells in the circulation occurs earlier after all o-PBSCT as compared with allo-BMT, leading to the rapid establishment of co mplete chimerism.