Activity of thalidomide and CC-4047 on development of early-stage erythroid progenitor cells. (A) A total of 6 × 10⁵ CD34⁺ cells were cultured with SCF plus IL-3 plus hyper–IL-6 to yield SI2 cells as indicated in Figure 2A in the presence of thalidomide (10 μM), CC-4047 (10 μM), CC-5013 (10 μM), or 0.1% DMSO (control). At day 7 in culture, cells were analyzed for surface antigen expression by flow cytometry. The open area indicates staining with isotype control antibody. (B) The growth kinetics of cells from panel A are shown as cumulative cell numbers. ○ indicates thalidomide; •, CC-4047; and × with dotted line, control. Data represent means ± standard deviation.