Fig. 2.

Colony-forming cell assay. A, colony-forming units of P3, P15, P27 and P40 MDSCs were counted, which indicated that colony-forming rates de-creased but did not disappear with increasing passage number. a to d, colony-forming rates of P3, P15, P27 and P40, respectively; B, the bar chart of colony-forming rates for different passages of MDSCs.