Fig. 3. In vitro progression of hematopoietic and endothelial cell lineages. (A) FLK1⁺CD4^- and FLK1^-CD4^- cells were FACS-sorted from day 2.5 EBs and further cultured in vitro. The cells were then analyzed for FLK1 and CD4 expression for up to 20 hours. The cells at 0 hour indicate the starting cell population after sorting. (B) FLK1⁺CD4⁺ and FLK1⁺CD4^- cells were FACS-sorted from day 4 EBs and further subjected to in vitro culture as in A. The cells were analyzed for FLK1 and CD4 expression for up to 20 hours. The cells at 0 hours show the sorting purity.