Early time course of BM reconstitution from the 38⁺34⁻ subset of PHSC after previous engraftment of 38⁻34⁺ cells.

(A) Lethally irradiated Ly5.2 mice were given transplants of 1000 38⁻34⁺ cells (carrying the Ly5.1 surface marker). Seven days later, each animal received an injection of 400 38⁺34⁻ cells (carrying both the Ly5.1 and the Ly5.2 surface markers). Engraftment of 38⁺34⁻and 38⁻34⁺ cells in the BM was examined 7 days later. (B) A representative FACS analysis of BM from a recipient mouse 7 days after the injection of 38⁺34⁻ cells; mean ± SE engraftment was 27.9% ± 6.9% for 38⁻34⁺ cells and 7.8% ± 1.5% for 38⁺34⁻ cells. Two independent experiments were performed using 5 to 8 mice per group in each experiment. The data suggest that the 38⁻34⁺ subset of PHSC supports early engraftment of 38⁺34⁻ cells because, as shown in Figure 5, engraftment of 38⁺34⁻ cells was undetectable 8 days after transplantation.