Human and rhesus macaque hematopoietic stem cells cannot be purified based only on SLAM family markers

Various combinations of antibodies directed to cell surface markers have been used to isolate human and rhesus macaque hematopoietic stem cells (HSCs). These protocols result in poor enrichment or require multiple complex steps. Recently, a simple phenotype for HSCs based on cell surface markers from the signaling lymphocyte activation molecule (SLAM) family of receptors has been reported in the mouse. We examined the possibility of using the SLAM markers to facilitate the isolation of highly enriched populations of HSCs in humans and rhesus macaques. We isolated SLAM (CD150⁺CD48^-) and non-SLAM (not CD150⁺CD48^-) cells from human umbilical cord blood CD34⁺ cells as well as from human and rhesus macaque mobilized peripheral blood CD34⁺ cells and compared their ability to form colonies in vitro and reconstitute immune-deficient (nonobese diabetic/severe combined immunodeficiency/interleukin-2 γc receptor^null, NSG) mice. We found that the CD34⁺ SLAM population contributed equally or less to colony formation in vitro and to long-term reconstitution in NSG mice compared with the CD34⁺ non-SLAM population. Thus, SLAM family markers do not permit the same degree of HSC enrichment in humans and rhesus macaques as in mice.