B-cell progenitors in myeloid colony formation assays. (A) Reanalyzing the sorted CD34⁺/CD19⁺ cells in each experiment for the presence of any CD34⁺/CD19^- cells that might form myeloid colonies showed that 100% of sorted cells expressed CD19. The percentage of each subpopulation relative to the total number of cells is shown. (B) Myeloid colony formation per 1000 cells. A significant fraction of CD34⁺/CD19⁺/CXCR4^- BM cells was able to form myeloid colonies containing granulocytes, macrophages, or erythrocytes (top) as compared to CD34⁺/CD19⁺/CXCR4⁺ cells (middle) and total CD34⁺ cells (bottom). □ indicates granulocyte-macrophage colony-forming units (CFU-GMs); ▦, BFU-E; and ▪, CFU-GEMM. Note the different scales showing the colony numbers between the graphs; n = 3 each performed in triplicate. Error bars indicate standard error (SE).