Allosteric inhibition of LFA-1 binding to ICAM-1. (A) Neutrophils were preincubated with Fc fragments (all samples), anti-Mac-1 (2LPM19c), and IC487475, as indicated. ICAM-1/IgG-Alexa-488 was then added to neutrophil suspensions and was followed immediately by activation with mAb 240Q. Cells were fixed and analyzed by flow cytometry. Fluorescence histograms are representative of the average population response from 4 separate experiments. (B) Data represent the mean ± standard error of the mean (SEM) from 4 separate experiments, as described in panel A. ^*Significance compared with mAb 240Q + anti-Mac-1 (P < .05). ^**Significance compared with mAb 240Q (P < .05). (C) Isolated human neutrophils were incubated over a dose range with IC487475 or TS1/22. Suspensions were then activated with IL-8 and immediately analyzed by FACScan flow cytometry for binding of ICAM-1/IgG-coated latex beads (approximately 25 sites/μm²). Data are representative of the average response from 4 separate experiments.