GPIbα is required for the VWF effect on PMN recruitment. Mice were treated with adhesion-blocking anti-GPIbα Fab-fragments, anti-VWF antibodies, or a combination of both before peritonitis was induced with thioglycollate. After 2 hours, PMNs were collected and counted. The experiment was repeated 3 times with n ≥ 3 mice per group, giving similar results. Error bars show SEM. *P ≤ .05.