Progenitor analysis by multicolor flow cytometry. Populations of hematopoietic stem cells (HSCs), common myeloid progenitors (CMPs), granulocyte-macrophage progenitors (GMPs), and megakaryocyte-erythroid progenitors (MEPs) were identified by flow cytometry, as described in “Materials and methods.” Ly5.1 and Ly5.2 expression in each of the progenitor cell populations is shown for a single 9:1 (KO/WT) chimeric mouse. The percentage of KO and wild-type cells is shown in the corner of each individual plot. Data are representative of 4 mice analyzed. The KO/WT ratio for each population is reported in the text.