Many newly generated CD45R⁺ cells lack c-kit . Lin⁻c-kit^Hi, Lin⁻c-kit^Lo, and Lin⁻c-kit⁻ cells were sorted from BM and placed in stromal cell free culture containing IL-7, FL, SCF, and stromal cell conditioned medium. Cells were harvested at days 1 to 3 and percentages of CD45R⁺ CD19⁻ cells expressing c-kit at each time point generated from each starting population are represented in the bar graph. (CD45R⁺cells were found to express c-kit at low levels.) Data reflect means±SE from three independent experiments with pooled marrow from 8 or 10 mice. The asterisks indicate that no B-lineage cells were generated before day 3 in cultures initiated with c-kit⁺cells.