Endothelial cells from various organs express high levels of Myd88 and Tlr4, respond to LPS challenge with strong upregulation of VCAM-1 and G-csf in vivo, and exogenous G-CSF administration rescues emergency granulopoiesis in Tie2-Cre;Myd88^fl/fl mice. (A) Myd88 and (B) Tlr4 expression were assessed by quantitative reverse-transcription PCR in CD45⁻Ter119⁻CD31⁺ECs isolated from BM, heart, liver, kidney, spleen, and lung (gray bars) compared with spleen DCs (black bars), ie, pooled classical dendritic cells (CD3ε⁻CD19⁻NK1.1⁻CD11c^highCD45RA⁻MHCII⁺) and plasmacytoid dendritic cells (CD3ε⁻CD19⁻NK1.1⁻CD11c⁺CD45RA⁺MHCII^high). All cells were isolated from steady-state mice. (C) Graphical scheme depicting experimental outline to assess in vivo LPS responsiveness of ECs that were flow-cytometrically sorted from BM, heart, liver, kidney, spleen, and lung of PBS- and LPS-injected mice, respectively. (D) Comparative G-csf transcript levels normalized to Actb in ECs from BM, heart, liver, kidney, spleen, and lung of LPS-injected (red bars) vs PBS-injected (black bars) wild-type mice. (E) Representative FACS analysis depicting cell-surface expression of VCAM1 (red lines) on BM ECs in steady state as well as LPS-injected control Myd88^fl/fl and Tie2-Cre;Myd88^fl/fl mice. Isotype control shown as blue line. (F) Graphical scheme showing experimental outline to assess G-CSF effects in vivo. (G) Representative FACS profile showing characteristic G-CSF–induced changes 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. (H) Frequencies of BM CD11b⁺Gr1^high mature and (I) BM CD11b⁺Gr1^low immature neutrophils in PBS- and G-CSF–injected control Myd88^fl/fl and Tie2-Cre;Myd88^fl/fl mice. All data represent mean ± standard deviation from 2 or 3 independent experiments. Two-tailed Student t tests were used to assess statistical significance (**P < .01, ***P < .001).