Immature Reticulocyte Fraction in Guiding Stem Cell Harvest in Autologous Peripheral Blood Stem Cell Transplant

Peripheral blood (PB) CD34+ cells enumeration is currently the most reliable method to guide the timing of stem cell harvest. However, its usage is restricted by being technically challenging, costly, and time-consuming. Immature reticulocyte fraction (IRF) determination, which is simpler and cheaper and has a faster turn-around time, has been proposed for a similar purpose. The purpose of this study is to evaluate the value of IRF in guiding stem cell harvest and examine the correlation between IRF and PB CD34+ cells count. Daily pre-harvest tests, i.e. PB CD34+ cells and IRF from 21 patients scheduled for autologous PBSC transplant were assessed. Stem cells harvests were commenced when the PB CD34+ cell count were more than 10 cell/ul. A total of 205 pre-harvest tests were analysed. Following stem cell mobilisations, both the IRF and PB CD 34+ cell counts rose with a variable pattern. In this study, we observed that the IRF peaks preceded the PB CD34+ count by 2 days. On the day of stem cell harvest, all the peak IRF values were >0.3. The PB CD34+ cell counts correlated with the harvested stem cell yield, whereby r2 = 0.77, p 0.3 may be used as a cut-off value for the initiation of PB CD34+ quantifi cation prior to stem cell harvest.

Non-myeloablative conditioning for hemopoietic stem cell transplantation--does it work?

Allogeneic bone marrow or peripheral blood stem cell transplantation traditionally uses myeloablative regimen for conditioning to enable grafting of donor's stem cells. Animal experiments have shown that a milder non-myeloablative conditioning regimen does allow engraftment to occur. Nonmyeloablative conditioning regimens are low-intensity immunosuppressive treatment given to the recipient before infusion of donor's stem cells. It was reported to have decreased immediate procedural mortality, in particular those secondary to acute graft versus host reaction. However, it did give rise to higher risks of graft rejection, tumour tolerance and disease progression. Fortunately, appropriately administered donor lymphocyte infusion has been shown to establish full donor chimerism (complete donor stem cell grafting in the recipient's bone marrow) and potentiate antitumour effect (graft versus tumour reaction). The reduction of immediate transplant mortality allows the procedure to be carried out in older age groups, patients with concomitant diseases that otherwise would have made the patients unfit for the procedure, patients with non-malignant disorders such as congenital immune deficiencies, autoimmune disorders or thalassaemia majors. The regimen also allows transplantation of genetically manipulated haemopoietic stem cells (gene thrapy) to be carried out more readily in the immediate future. Lastly, the regimen may serve as a platform for immunotherapy using specific T cell clones for anti-tumour therapy with or without the knowledge of known tumour antigen.