Detection of hematopoietic stem cells by flow cytometry.

Various studies have been conducted to identify hematopoietic stem cells (HSCs) using flow cytometry. The technique is primarily based on fluorochrome-conjugated antibodies against cell surface markers of HSCs and the physiological properties of HSCs such as high-efflux activity of certain fluorescent dyes. The surface marker schemes are based on using c-Kit, Sca-1, and Lineage markers, resulting in "KSL" population. Markers in KLS scheme can be used to further subfractionate this KLS population to distinguish HSCs from differentiating progenitors. The "signaling lymphocyte activation molecule" (SLAM) family of proteins can also be used to enhance the KLS enrichment scheme. The other strategy is to identify HSCs based on their high efflux ability of fluorescent dyes. This chapter describes the method used for identifying the side population (SP) in combination with surface markers to isolate HSCs from murine bone marrow and to discuss the advantages and pitfalls of this method.