Figure 4. Time required for ATRA effects on B lymphopoiesis.

(A) Sorted LSK were treated with ATRA in stromal cell free culture for 1, 3, 5, or 7 days, and the treated cells were washed and put back in culture. All the cells were recovered on day 7 and flow cytometry was performed to examine B lineage lymphoid cell (CD19⁺B220⁺) production. (B) Sorted LSK cells were put in stromal cell free culture and ATRA was added at day 0, day 1, day 3 or day 5, and was kept in the culture until day 7. All of the cells were then recovered and flow cytometry was performed to examine the B lineage lymphoid cell (CD19⁺B220⁺) production. (C) Sorted LSK were put in stromal cell free culture and ATRA was added on day 0, day 1, day 3, day 5 or day 7, and was kept in the culture until day 11. All of the cells were recovered and flow cytometry was performed to examine the B lineage lymphoid cell (CD19⁺B220⁺) production. All data are reported as means ± S.D. for n= 3.*, p < 0.05, and **, p < 0.01 (Student's t-test). Different Y axis scales were used to reflect production of B lineage cells over time, and the results shown are representative of three independent experiments.