Cebpb^−/− mice lack Ly6C⁻monocytes. (A) Cebpb mRNA expression in purified hematopoietic populations (n = 3). (B) Expression of CD115 and CD135 in BM cells among c-kit⁺ lineage marker (CD11b, Gr-1, CD11c, Ter119, IL-7R, CD3, CD19, and NK1.1)⁻ cells. The frequencies of MDPs (CD115⁺ CD135⁺) and cMoPs (CD115⁺ CD135⁻) among lineage⁻ BM cells are shown in the right panel (n = 5). Data were pooled from 4 independent experiments. (C,E) Gating strategy to define Ly6C⁺ and Ly6C⁻ monocytes in the BM (C) and PB (E). Lineage marker (Ly6G, B220, CD4, CD8, and NK1.1) ⁻ CD11b⁺ CD115⁺ monocytes were subdivided on the basis of Ly6C expression. (D,F) Frequencies of Ly6C⁺ and Ly6C⁻ monocytes in the BM (D) and PB (F) of WT or Cebpb^−/− mice (n = 10 for BM and n = 19 for PB). Data were pooled from 7 independent experiments and are presented as the mean ± standard deviation (SD). **P < .01, ***P < .001. Numbers indicate the percentage of cells in the adjacent boxed area. FSC, forward scatter; Lin, lineage.