α4β1 -expressing neutrophils were allowed to settle onto VCAM-1–transfected L cells and flow was initiated to 2 dyne/cm2. This force did not displace the neutrophils in the presence or absence of the anti-CD18 antibody, IB4 (A). Pretreatment of neutrophils with either the anti-β1 antibody (K20) or the anti-α4 integrin antibody (HP2/1) significantly reduced the number of adhering cells (A). These concentrations of HP2/1 or K20 were sufficient to displace Ramos cells from the VCAM-1–transfected L cells (B). For (A), (□) fMLP + DHCB, (▨) fMLP + DHCB + IB4 , (▧) fMLP + DHCB + IB4 + K20, or () fMLP + DHCB + IB4 + HP2/1. For (B), (□) no antibody, (▨) K20, or (▧) HP2/1. *P < .05 relative to FMLP + DHCB value. #P < .05 relative to the no antibody condition.
