ICAM-1 is expressed on LPS-stimulated neutrophils in vivo. WT mice were injected with saline, LPS (300 ng IS or 1000 ng IP) or IL-1β (50 ng IP and IS). After a 4-hour in vivo test period, blood, lungs, peritoneal lavage, and cremaster muscles were collected. Cremaster muscles were fixed, permeabilized, and labeled with fluorescent antibodies against PECAM-1, the intracellular neutrophil marker S100a9, and ICAM-1 or an isotype control. Tissues were imaged by confocal microscopy and analyzed using Imaris. Following RBC lysis and enzymatic digestion of lung tissues, leukocytes from the blood, lung tissue digest, and peritoneal lavage were labeled with DAPI and fluorescent antibodies against CD45, Ly6G, ICAM-1, or an isotype control. (A) Representative images of unstimulated and stimulated cremaster muscles. (B-C) Quantification of extravasated neutrophils in saline and stimulated inflamed sites. (D) Representative images of ICAM-1 expression on extravasated neutrophils in LPS- and IL-β–stimulated cremaster muscles. (E-F) Quantification of ICAM-1 expression on extravasated neutrophils in inflamed tissues. (G) Percentage of Ly6G-positive neutrophils among CD45⁺ leukocytes in blood and digested lung tissue samples as quantified by flow cytometry. (H) Percentage of ICAM-1^pos neutrophils in blood of saline, IL-1β–, and LPS-stimulated animals. Data are expressed as mean ± SEM of n = 3 to 10 animals/group. Statistically significant (t test or ANOVA) differences between stimulated and unstimulated treatment groups: *P < .05, **P < .01, and ***P < .001; differences between stimuli: ##P < .01 and ###P < .001.