LTR-mediated NGFR transgene expression in progeny of transduced CFC. Sorted NGFR-expressing, CD34⁺Lin⁻ cells transduced with either the LINGFR (LINGFR⁺) or MINGFR (MINGFR⁺) vectors (see Fig 3) were assayed for CFC activity. After 14 days CFC numbers were enumerated (shown in Table 1), and total cells were obtained and stained for lineage markers and NGFR transgene expression. Fifty-two percent and 88% of erythroid cells (glycophorin A⁺), and 71% and 91% of granulocytes (CD15⁺) derived from LINGFR⁺ and MINGFR⁺ CFC, respectively, retained the NGFR reporter on cell surface.