CML leukapheresis products can be enriched for CD34+ cells and simultaneously depleted of CD15+ cells using a simple Ab cocktail.

BACKGROUND: CML progenitor-cell studies would be greatly facilitated if samples could be repeatedly accessed from a source of well-characterized cells. The present study was designed to develop a simple, inexpensive Ab cocktail that would provide subpopulations of cells enriched for CD34+ cells and simultaneously depleted of CD15+ mature myeloid cells. METHODS: Cells from leukapheresis products from CML patients at diagnosis were incubated with each of two Ab cocktails. The standard cocktail (debulking, DB), containing 11 Abs, is recommended for obtaining a highly enriched population of CD34+ cells. The efficacy of an alternative, simpler cocktail (CML custom, CC), containing only four Abs was tested. The recoveries of CD34+ cells, CD15+ cells, colony-forming unit granulocyte-macrophage, and LTCIC were monitored. The samples were then cryopreserved, thawed, and the recoveries remeasured. RESULTS: The purity of CD34+ cells was significantly superior using the DB cocktail than with the CC cocktail. Conversely, using the CC cocktail, the yield of CD34+ cells was significantly higher compared to the DB cocktail. These results were maintained even when the amount of Ab was reduced 10-fold. Both Ab cocktails consistently removed > 99% of the CD15+ cells. Consistent with the CD34+ cell-enrichment data, higher colony-forming cell (CFC) frequencies were obtained with the DB cocktail, although superior yields of CFC were obtained with the CC cocktail. After cryopreservation and thawing the yield of CD34+ cells remained high, and a further reduction in the number of CD15+ cells was obtained. DISCUSSION: A method is described that allows the rapid and efficient debulking of large CML samples. This strategy will provide a source of well-characterized CML stem/progenitor cells that can be repeatedly accessed.