Direct head-to-head competitive repopulation of STAT5ab^-/- and c-Mpl^-/- BM grafts. (A) Because each STAT5ab^-/- BM graft was equally competitive as shown in Figure 3, the HW80 background STAT5ab^-/- BM graft was competed 1:1 with c-Mpl^-/- BM in 3 separate competitive repopulation experiments. The results of 3 experiments are shown, with each experiment being initiated by using bone marrow cells from one donor STAT5ab^-/- and one donor c-Mpl^-/- mouse. Mice received transplants and were analyzed 13, 12, and 12 weeks later, respectively, for the relative contribution of Hb_d and Hb_s in circulating peripheral red blood cells. (B) Experiment 3 also included a second competitive repopulation of c-Mpl^-/- BM with wild-type BM as was also shown in Figure 3. (C) Experiment 3 was also extended further by doing a secondary transplantation into lethally irradiated recipients and analysis of engraftment by hemoglobin electrophoresis 17 weeks later. Shown on the right of all sets of gels are positive controls for the Hb_s and Hb_d bands. The %Hb_s for each individual mouse is shown below each lane.