Chemokines, but not selectins, cooperatively use Rap1 and PI3Kγ to trigger β2 integrin activation. (A) Rolling velocities of human neutrophils treated with the Rap1 inhibitor GGTI-298 and/or the PI3Kγ inhibitor AS-605240 on P-selectin with or without co-immobilized ICAM-1 in the presence or absence of anti-ICAM-1 mAb. (B) Percentages of human neutrophils treated with the indicated inhibitor rolling, arrested and round, or arrested and spread on co-immobilized P-selectin, ICAM-1, and IL-8 (10 μg/mL). (C) Rolling velocities of human neutrophils treated with the indicated inhibitor on P-selectin with co-immobilized ICAM-1 and low-dose IL-8 (1 μg/mL) in the presence or absence of anti-ICAM-1 mAb. (D) Percentages of human neutrophils treated with the indicated inhibitor rolling, arrested and round, or arrested and spread on co-immobilized P-selectin, ICAM-1, and low dose IL-8 (1 μg/mL). (E) Percentages of human neutrophils treated with the indicated inhibitor rolling or arrested on P-selectin co-immobilized with control IgG, KIM127, or MEM148 with or without IL-8 (10 μg/mL). The data represent the mean ± SEM from 5 experiments. *P < .05 for rolling velocity; #P < .05 for percentage of rolling cells compared with that in WT, as determined by unpaired Student t test.