Monocytes marginate in the pulmonary vasculature. (A) A representative GFP⁺ monocyte (arrowhead) alters its morphology through pulmonary capillaries. Bar, 15 µm (time, h:mm:ss; green, CX₃CR1⁺ cells; red, TRITC-dextran). Results are representative of one out of three independent experiments. (B and C) Monocyte mean velocity (B) and duration of adherence (C) after indicated treatments. Results are pooled from three independent experiments per treatment and are expressed as mean ± SEM. ns, not significant; **, P < 0.01; ***, P < 0.001; **** P < 0.0001 (one-way ANOVA). (D) LPS-induced fold-increase in lung Ly6C^hi (left) and Ly6C^lo (right) monocytes 1 h after treatment. Results expressed as mean ± SEM (n = 4–7). ns, not significant; *, P < 0.05; ***, P < 0.001 (one-way ANOVA). (E) Snapshots of GFP⁺ monocytes in the lung of a Cx3cr1^gfp/+ reporter mouse, before (top) and after (bottom) i.v. administration of a Ly6B.2-PE antibody (4 µg). A representative GFP⁺ monocyte is depicted migrating through pulmonary capillaries (white track), becomes PE⁺ after antibody administration Bar, 15 µm (time, h:mm:ss; green, CX3CR1⁺ cells; red, Ly6B.2⁺ cells; blue, Evans blue). Results are representative of one out of three independent experiments. (F) FACS plots of lungs from Cx3cr1^gfp/+ mice i.v. injected with Ly6B.2-PE. Ly6C^hi (red), Ly6C^lo monocytes (orange), and neutrophils (green) were plotted in relation to Ly6B.2 expression. Results are representative of one out of three independent experiments.