Long-term hematopoietic potential in culture of CD34⁺ACE⁺ and CD34⁺ACE⁻ fetal liver- and BM-derived precursors. Sorted CD34⁺ACE⁺ and CD34⁺ACE⁻ cells were cultivated on MS-5 stromal cells. Proliferating hematopoietic cells were harvested from culture wells, stained with anti–CD19-PE, anti–CD15-FITC, anti–CD56-Cy-PE, and anti–CD34-FITC Abs and analyzed by flow cytometry. (A) Sort regions used for isolation of CD34⁺ACE⁺ cells in a 14-week liver (i) and BM (ii). (B) Bar plots indicate the percentages of CD34 progenitors harvested each week from the culture of CD34⁺ACE⁺ cells sorted from human fetal liver (i) and BM (ii) at different stages of development. Each bar represents the mean of several wells analyzed at the same time of culture. In panel B, the error bar shows the standard error obtained when more than 1 liver sample at the same stage of development was analyzed after the same time in culture. (C) B-lymphoid CD19⁺ cells and CD34⁺ progenitors in the culture of CD34⁺ACE⁺ and CD34⁺ACE⁻ cells sorted from a 14-week fetal liver. Analysis was performed at day 19 of culture. (D) Representative example displaying flow cytometric analysis after 83 days in culture of CD34⁺ACE⁺ cells sorted from a 14-week fetal liver. CD34⁺ cells represent 28% and B cells (CD19⁺) represent 19% of total harvested cells. (E) T-lymphoid CD4⁺CD8⁺ cells generated in the culture of CD34⁺ACE⁺ cells sorted from a 14-week fetal liver. Analysis was performed at day 14 of culture. GW indicates gestation weeks.