Platelet derived HMGB1 promotes monocyte recruitment. (A-G) Left, Quantification of monocytes. Results are mean ± SEM. Right, Immunofluorescence staining for F4/80 (red) from cross-sections of the IVC. Nuclei are counterstained with DAPI (blue); arrowheads indicate individual monocytes at higher magnification; bar, 200 µm. Images representative of n = 3 experiments. (A) BoxA compared with control (n = 5 each). (B) Hmgb1^−/− (n = 3) fetal liver cell chimeras compared with Hmgb1^+/+ chimeras (n = 5). (C) Hmgb1^−/− chimeras compared with Hmgb1^−/− chimeras receiving wild-type platelets, Hmgb1^−/− platelets, or wild-type neutrophils. Dotted line indicates mean in Hmgb1^+/+ bone marrow chimeras (n = 3 each). (D) Tlr2^−/− compared with control (n = 4 each). (E) Tlr4^−/− compared with control (n = 4 each). (F) Rage^−/− compared with control (n = 5 each). (G) Myd88^−/− compared with control (n = 4 each). The Student t test was used to compare results between 2 groups, 1-way ANOVA followed by LSD–post hoc test for 3 groups.