Hematopoietic cytokines promote hematopoietic differentiation from hESCs prior to hematopoietic emergence. (A) Schematic diagram of stage I and stage II of human EB differentiation in the context of hematopoietic lineage emergence and experimental design for detecting the period of action of hematopoietic cytokines. Stage I is the period prior to the emergence of hematopoiesis as detected by lack of CD45 expression and hematopoietic progenitors. Stage II is the period during the emergence of the first CD45⁺ cells and hematopoietic progenitors. Proportion of (B) CD45⁺ cells and (C) CD45⁺ CD34⁺ cells within cytokine/control (+/-)–treated EBs at day 12.5 relative to control EBs not treated with cytokines (-/-). Proportion of (D) CD45⁺ cells and (E) CD45⁺ CD34⁺ cells within cytokine/control (+/-)–treated EBs at day 15 relative to control EBs not treated with cytokines (-/-) (n = 3). Error bars depict SEMs. (F-G) Representative analysis of CD45 and CD34 coexpressing cells within treated EBs at day 15.