Deletion of Mcl-1 blocks the development of mature neutrophils and induces the accumulation of myeloid precursors. (A) Graph of the average number of BM cells from littermate control of Mcl-1^f/null plus LysM-Cre mice. ■ represents the total BM number from hind limbs; red bars, the total number of mature neutrophils (Mac-1⁺ Gr1^High). Graph represents average numbers of more than 5 mice analyzed, and error bars denote SEM. *P < .01 by 2-tailed t test when compared with littermate control population. (B) Representative flow cytometric analysis of BM from littermate control and Mcl-1–deleted mice stained for Mac-1 and Gr1. Top right quadrant contains mature neutrophils; bottom right quadrant, immature myeloid precursors. Numbers indicate the percentage of cells from the total BM. (C) Stained cytospins of BM aspirates from littermate control (Mcl-1^f/wt) and Mcl-1–deleted mice (Mcl-1^f/null plus LysM-Cre). Images taken with a 40× objective. (D) Flow cytometric analysis of BM from littermate control and Mcl-1–deleted mice stained for Gr1 and annexin-V to detect apoptotic cells. Top right quadrant contains myeloid lineage cells that are undergoing cell death. Numbers indicate the percentage of total BM cells.