Flow Cytometric Enumeration of Viable CD34(+) Hematopoietic Stem and Progenitor Cells

Flow cytometric enumeration of viable CD34(+) progenitor and stem cells has become a routine measurement in many laboratories and its accuracy is crucial for the assessment of the quality of stem cell products or to optimize the timing of collection following stem cell mobilization. Yet the complexity of the measurement and analysis is still a source of incorrect determinations of viable CD34(+) stem cell numbers which may lead to the failure of stem cell therapies and inflict severe clinical consequences for the patients. Besides the use of different reagents and protocols for the sample storage, preparation and the staining of the CD34 antigen expressed on stem cells the comprehension and correct use of the gating strategy for the identification of CD34(+) stem cells according to the ISHAGE guidelines is essential for a reliable and reproducible accurate enumeration of viable CD34(+) stem cells.