the effectiveness between these systems for processing large quantity of cells' purification for clinical use is few, but high purity (more than 90%) CD34+ cells were collected when CliniMACS system that was designed for large quantity of cells was used. Using CliniMACS had no any harm to cells and had nearly 60% of cell recovery rate. Its function is similar to corresponding laboratory type equipment, MiniMACS.
Autologous transplantation needs lower dose of stem/progenitor cells for hematopoietic reconstitution. The hematopoietic function was reconstituted in 3 patients in our study by transplant of 1.4-4.2×105/Kg of purified CD34+ cells. 3.8×106/Kg of CD34+ cells in average are enough for hematopoietic reconstitution in clinic because of the high recovery rate of CliniMACS system. In haploidentical transplantation, basing on strong immunological conditioning regimen, higher dose of stem/progenitor cells, generally 10×106/Kg of CD34+ cells is needed to overcome immune barrier, to engraft and to have hematopietic reconstitution. Such a high dose (per Kg) of stem/progenitor cells can be more easily obtained from small children(3，4)；For adult or the children with big bodyweight, in our study of the limited cases, 5.9×106/Kg of purified CD34+ cells were obtained, however, that was only enough to make part of the patients to establish a complete and sustained hematopoitic reconstitution. It is obvious that more effective PBSPC mobilization, more effective harvest method and purification system are needed.
Most of tumor cells including CML in blast(BC), multiphe myeloma(MM), Non-Hodgking's lymphoma( NHL), Hodgking's disease(HD), etc. don't express CD34 antigen except for leukemia and the tumor come from endothelial cells. CD34+ selection can deplete 3 to 6 log tumor cells in the graft(5，6). Although it has been reported that the contamination of tumor cells in the graft can cause the relapse, and CD34+ selection may be more effective in purging than that of negative selection, no clinical data are available now to prove whether CD34+ selection can reduce the relapse in autologous transplantation. The follow-up of this study is too short to make a conclusion. CD34+ selection can deplete T/B lymphocytes and NK cells and it was demonstrated that deplete CD3+ 3.9, CD8+ 4.2 above, CD19+ 2.7 above、CD56+ 3.2 log of cells in this study. 104/Kg of CD3+, CD8+ and CD56+ cells were transfused to HLA haploidentical patients and this number is generally considered to be lower than the threshold value that can cause GVHD. Serious GVHD was not observed in these three patients. The results are in accordance with Handgretinger et al 's work(4). It can be concluded that CD34+ selection can effectively prevent GVHD. T lymphocytes play an important role in autoimmune diseases. Autologous PBSPC transplantation provides a new approach to kill memory T cells that plus B cells may cause relapse after transplantation. Removing of T and B cells can reduce relapse. Now 3 patients have survived for 2 to 5 months without sign of relapse. This study is to be continued.
So, such conclusion was made that CliniMACS is a highly effective CD34+ cell purification system. Autologous transplant of CD34+ cell purified by CliniMACS is safe and can result in rapid hematopoietic reconstitution. The method should be improved for adult HLA haploidentical transplant. The transplant of purified CD34+ cells can effectively prevent GVHD and purge tumor cells or autoimmune disease cells in the graft.
(陈虎)
|
