SLAM-Family Expression on Human Mobilized Peripheral Blood Progenitors.

Background and significance: A simple but precise method to identify hematopoietic stem cells within mobilized peripheral blood would be useful for transplantation. Our lab has recently identified a family of surface markers whose differential expression distinguishes mouse hematopoietic stem cells from other hematopoietic progenitors. The founding member of the signaling lymphocyte attractant molecule (SLAM) family, CD150, was expressed on all hematopoietic stem cells (HSCs) but not on other hematopoietic progenitors. Other SLAM-family members, including CD244 and CD48, were expressed by non-self-renewing multipotent progenitors and most colony-forming restricted progenitors, respectively. As a result, mouse stem cells can be highly purified as CD150⁺CD48⁻ cells, dramatically simplifying and improving the purification of mouse HSCs. To begin to test whether SLAM family markers can facilitate the identification and purification of human hematopoietic stem cells, we have assessed the frequency of CD150⁺CD48⁻ cells in mobilized peripheral blood and compared their distribution to that of CD34⁺CD38⁻ cells, which are known to be highly enriched for human hematopoietic stem cells.

Methods: Mobilized human peripheral blood samples were stained with anti-CD150 (conjugated to the FITC), anti-CD48 (PE), anti-CD41 (PE), anti-CD34 (APC), and anti-CD38 (PE-Cy5) antibodies. Samples were analyzed by flow-cytometry.

Results: We have identified a population of CD150+CD48⁻CD41⁻ cells within human mobilized peripheral blood that is present at a similar frequency as the same population in mobilized mouse peripheral blood (mean 0.039±0.11%). The CD34⁺CD38⁻ population was similarly infrequent. Interestingly, 16.3±19.5% of CD150⁺CD48⁻CD41⁻ cells were also CD34⁺ whereas only 1.13±3.45% of the CD34⁺CD38⁻ population was CD150⁺CD48⁻CD41⁻ raising the possibility that SLAM-family members may substantially improve the purity of human hematopoietic stem cells.

Conclusion: Murine and human hematopoietic tissues have a similar frequency of CD150⁺CD48⁻CD41⁻ cells. It is possible that the use of SLAM-family markers might enhance the identification and purification of human hematopoietic stem cells beyond what is possible using CD34 and CD38. We are currently performing reconstitution assays to test this functionally.

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Peripheral Blood Mononuclear Cells

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Peripheral Blood Mononuclear Cells

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