The effects induced by LPS on HSCs and neutrophils are abrogated in a TLR4-null phenotype. (A) C57BL/6J CD45.2 mice were injected intraperitoneally with LPS from P aeruginosa (0.8 mg/kg) or PBS. BM was harvested at 24 hours from injection, and Lin⁻ cells were purified and stained with c-Kit, Sca1, and TLR4/MD2 antibodies. Histograms show TLR4 expression on LSK cells (black line) superimposed to TLR4 expression on LK cells (Lin⁻Kit⁺ Sca⁻; gray filled curve) in PBS control (left panel) and in LPS-challenged mice (right panel). TLR4 expression on LK cells was at limit of detection and superimposed with IgGs control. (B) C3H/OuJ(TLR4^wt) and C3H/HeJ (TLR4⁻) mice were injected intraperitoneally with LPS from P aeruginosa (0.8 mg/kg) or PBS. BM was harvested at 24 hours, stained with monoclonal antibodies necessary to identify the indicated subsets, and analyzed by multicolor flow cytometric analysis. (B) Average percentage of LSK on the Lin⁻ cells. TLR4^WT: PBS versus LPS; *P = .045. (C) Average percentage of Gr1⁺/Mac1⁺ neutrophils in the total BM population. TLR4^WT: PBS versus LPS *P < .001. (D) Average percentage of CMPs in the Lin⁻ population. TLR4^WT: PBS versus LPS; *P < .001. (E) Average percentage of GMPs in the Lin⁻ population. TLR4^WT: PBS versus LPS; *P < .001. In all graphs, values are average of 6 mice from 2 independent experiments. Error bars show SD.