ICAM-1 expression facilitates enhanced neutrophil effector functions. Whole blood from WT or ICAM-1 KO mice was incubated (4 hours at 37°C) with IL-1β (50 ng/mL), LTB₄ (30 nM), KC (30 nM), fMLP (1 µM), LPS (300 ng/mL), or TNF (100 ng/mL). Fluorescent ZymTR particles (10 µg/mL) or DHR (1 µM) were added to samples for 15 minutes before RBC lysis and labeling with DAPI and fluorescent antibodies against CD45 and Ly6G. Samples were analyzed by flow cytometry. (A) Representative histogram illustrating the detection of ZymTR-associated neutrophils. (B) Percentage of ZymTR^pos neutrophils in unstimulated and LPS-stimulated WT and ICAM-1 KO samples. (C) Percentage of DHR positive (DHR^pos) neutrophils, in LPS-stimulated as compared with LPS-unstimulated controls was quantified in WT and ICAM-1 KO samples. (D) Frequency of DHR positive neutrophils within the ICAM-1 positive (pos) or negative (neg) populations in LPS-stimulated blood. Data are expressed as mean ± SEM of n = 4 to 24 animals/group. (E) Percentage of DHR^pos neutrophils in WT neutrophils stimulated as shown. Statistically significant (t test) differences between treatment groups: **P < .01, ***P < .001; differences between WT and ICAM-1 KO: #P < .05, ###P < .001.