Flow Cytometric Immunophenotyping of Umbilical Cord and Peripheral Blood Haematopoietic Progenitor Cells by Different CD34 Epitopes, CD133, P-Glycoprotein Expression and Rhodamine-123 Efflux

The flow cytometric enumeration of CD34+ cells, comprising both haematopoietic stem (HSC) and progenitor cells (HPC) is currently widely used to assess suitability of stem cell transplants for transplantation. However, to ensure the long-term reconstruction in human recipients, the enumeration specifically of those HSC possessing self-renewing and differentiation potential would be preferable. In the present study we addressed a multiparametric flow cytometric profiling of haematopoietic stem cells of umbilical cord (CB) and peripheral blood (PB) using stem cells markers (epitope- specific CD34, CD133, rhodamine-123 (Rho123) efflux, p-glycoprotein) to assess their stem cell features. In contrast to CB, the CD34 class III compartment of PB did not include all CD34 class I- and class II-expressing cells. In CB and PB, there was no clear correlation between CD34 epitope and CD133 expression. Furthermore, we detected CD133+ CD34- cells (0.07% of mononuclear cells) in CB. The functional ability to exclude Rho123 was mainly restricted to CD34- and CD133-co-expressing cells. However, CB cells showed a higher activity. Functionally active cells were characterised by their expression of the verapamil-sensitive protein pump p-glycoprotein 170 using the monoclonal antibody MRK16. It is therefore possible to use multiparametric flow cytometry to estimate the numbers of immature stem cells as CD34+ CD133+ (Rhodull) MRK16+. This would allow a more precise assessment of transplant quality, especially with respect to their long-term engraftment potential, and supports haemotherapy of malignant diseases.