Phenotypic, molecular, and functional characterization of human peripheral blood CD34(+)/Thy1(+) cells

A subset of mobilized CD34(+) cells present in patient aphereses expresses Thy1 (CDw90). This population contains most long-term culture initiating cells, as assayed with a murine stromal cell line. It also contains a significant proportion of colony-forming unit granulocyte macrophage, but very few burst-forming unit erythroid. The limited differentiation towards the erythroid lineage is further confirmed by the absence of GATA-1 mRNA in the CD34(+)/Thy1(+) subset, and by the low level of c-kit expression. The CD34(+)/Thy1(+) subset appears phenotypically and functionally heterogeneous, a finding consistent with its high representation, compared to phenotypes such as CD34(+)/CD38(-). Therefore, while at least some of CD34(+)/Thy1(+) cells may be infectable by retroviral vectors, as shown by the presence of a transcript for the receptor for murine amphotropic retroviruses, the use of this selection strategy to specifically target human stem cells appears questionable. (C) 1996 by The American Society of Hematology.