Endotoxemia promotes monocyte retention in the pulmonary circulation. (A) Blood Ly6C^hi (top) and Ly6C^lo (bottom) monocyte counts after i.v. treatment with 10 ng LPS. Results are expressed as mean ± SEM (n = 4) and representative of one out of three independent experiments. ns, not significant; *, P < 0.05; **, P < 0.01; ****, P < 0.0001 (one-way ANOVA). (B) Illustration showing the intravascular labeling of leukocytes with anti-CD45 antibodies. (C) Representative flow cytometry plots showing the extravascular and intravascular localization of lung immune cells of one out of three independent experiments. (D and E) Quantification of Ly6C^hi (left) and Ly6C^lo (right) monocytes in blood (D) and lung tissues (E) from LPS-treated mice. Results are expressed as mean ± SEM (n = 4) and representative of one out of four experiments. ns, not significant; *, P < 0.05; **, P < 0.01; ***, P < 0.001; ****, P < 0.0001 (one-way ANOVA). (F) WT and Tlr4^−/− chimeric mice were analyzed for Ly6C^hi monocyte numbers after 1 h of LPS administration. Each data point represents one individual mouse and results are representative of two individual experiments. ns, not significant; **, P < 0.01 (one-way ANOVA).