Endothelial cell–intrinsic MYD88 signaling is required to stimulate accelerated neutrophil production, myeloid progenitor lineage skewing toward granulocyte-macrophage progenitors (GMPs), and increased CFU-G activity in vivo. (A) Graphical scheme depicting experimental outline to induce LPS-induced emergency granulopoiesis and to assess BrdU incorporation. (B) Representative FACS profile showing BrdU incorporation in in BM CD11b⁺Gr1^high mature and BM CD11b⁺Gr1^low immature neutrophils in control Myd88^fl/fl, and Tie2-Cre;Myd88^fl/fl mice during steady-state and LPS-induced emergency granulopoiesis. (C) Frequencies of BrdU⁺ BM CD11b⁺Gr1^high mature and (D) BrdU⁺ BM CD11b⁺Gr1^low immature neutrophils in PBS- or LPS-injected Myd88^fl/fl and Tie2-Cre;Myd88^fl/fl mice. (E) Representative FACS profile showing myeloerythroid progenitors in control Myd88^fl/fl, and Tie2-Cre;Myd88^fl/fl mice during steady-state and LPS-induced emergency granulopoiesis. (F) Frequencies of Lin⁻cKit⁺Sca1⁻FcgR⁺CD34⁺ GMPs in PBS- or LPS-injected Myd88^fl/fl and Tie2-Cre;Myd88^fl/fl mice. (G) Absolute CFU numbers per 1 hind leg in control Myd88^fl/fl and Tie2-Cre;Myd88^fl/fl mice during steady-state and LPS-induced emergency granulopoiesis (CFU-G, CFU granulocyte; CFU-M, CFU macrophage; CFU-GM, CFU granulocyte/macrophage; CFU-GEMM, CFU granulocyte/erythrocyte/macrophage/megakaryocyte; BFU-E, burst-forming unit erythrocyte). Black squares, PBS-injected mice; red squares, LPS-injected mice. Data from 2 independent experiments are shown. Two-tailed Student t tests were used to assess statistical significance (*P < .05, ***P < .001).