In this study we examined the importance of neutrophil adherence in neutrophil-mediated endothelial cell injury. Phorbol myristate acetate (PMA)-activated neutrophils from a patient with a congenital defect in neutrophil adherence (Gp-150 deficiency) and PMA-activated normal neutrophils pretreated with monoclonal antibody (MoAb) 60.3 were used. Both Gp-150-deficient and MoAb 60.3-treated normal neutrophils failed to adhere to cultured human umbilical vein endothelial cell (HEC) monolayers when activated by PMA (adherence less than 10% with patient and MoAb 60.3-treated cells compared with 53 +/- 3% with normal cells). The addition of PMA-activated normal neutrophils to 51Cr-labeled HEC monolayers failed to induce significant 51Cr release but did produce marked HEC detachment (percentage of detachment 50 +/- 3 at 6 hr). In marked contrast, PMA-activated Gp-150-deficient neutrophils failed to induce significant HEC detachment (percentage of detachment zero (0) at 6 hr). Moreover, the addition of MoAb 60.3 to normal neutrophils inhibited neutrophil-mediated HEC detachment in a time- and dose-dependent fashion. Non-lytic HEC detachment was determined to be largely oxygen radical independent, because PMA-activated chronic granulomatous disease neutrophils and PMA-activated normal neutrophils produced similar disruption of HEC monolayers. Soybean trypsin inhibitor, a chloromethylketone elastase inhibitor, and autologous serum all failed to inhibit neutrophil-mediated HEC detachment. From these studies there is no evidence that nonlytic HEC detachment by PMA-activated neutrophils is mediated by the neutrophil-derived proteases, elastase and cathepsin G. Neutrophil-mediated HEC detachment also required intact neutrophils, because postsecretory medium from PMA-activated normal neutrophils and a suspension of frozen-thawed PMA-activated normal neutrophils were without effect. These in vitro studies indicate that the neutrophil cell surface glycoprotein Gp-150 is required for nonlytic HEC detachment by intact PMA-activated neutrophils.