PHENOTYPIC, MOLECULAR, AND FUNCTIONAL-CHARACTERIZATION OF HUMAN PERIPHERAL-BLOOD CD34(+) THY1(+) CELLS/

A subset of mobilized CD34(+) cells present in patient aphereses expre sses Thy1 (CDw90). This population contains most long-term culture ini tiating cells, as assayed with a murine stromal cell line. It also con tains a significant proportion of colony-forming unit granulocyte macr ophage, but very few burst-forming unit erythroid. The limited differe ntiation towards the erythroid lineage is further confirmed by the abs ence of GATA-1 mRNA in the CD34(+)/Thy1(+) subset, and by the low leve l of c-kit expression. The CD34(+)/Thy1(+) subset appears phenotypical ly and functionally heterogeneous, a finding consistent with its high representation, compared to phenotypes such as CD34(+)/CD38(-). Theref ore, 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 selectio n strategy to specifically target human stem cells appears questionabl e. (C) 1996 by The American Society of Hematology.