Purified M40^−/− HSCs exhibit enhanced repopulation and self-renewal ability. (A) Fifty CD34⁻CD150⁺CD48⁻LSK cells from WT and M40^−/− mice were mixed with 0.4 × 10⁶ Sca1-depleted competitor BM cells and transplanted. Donor percent reconstitutions in the blood 16 weeks post-BMT are shown. (B) At the end of primary transplant, 3000 donor-derived LSK cells from each primary recipient were sorted and individually transplanted into 1 to 4 secondary recipients. Donor chimerisms in peripheral blood of secondary recipient mice are shown. Each symbol represents an individual mouse; horizontal lines are the mean values in each group. P values were calculated using the 2-tailed Student t test.