We examined the role of the neutrophil membrane antigen complex designated CDw18 (LFA-1/Mac-1/p150, 95) in human peripheral blood neutrophil adherence to cultured human umbilical vein endothelial cells (HEC) pretreated with lipopolysaccharide (LPS), interleukin 1 (IL 1), or recombinant tumor necrosis factor-alpha (rTNF-alpha). Pretreatment of HEC with LPS produced a dose-and time-dependent increase in subsequent neutrophil adherence (7 +/- 1% adherence to untreated HEC vs 38 +/- 3% adherence to HEC pretreated for 4 hr with LPS 150 ng/ml; mean +/- SE of 22 experiments: p less than 0.001). This effect was observed in primary and passaged HEC, but not in bovine aortic endothelial cells or human dermal fibroblasts. The LPS-induced activity appeared to be associated with the HEC surface, since it was not removed by washing and was not detected in the supernatant medium. Inhibition of RNA or protein synthesis during pretreatment of HEC with LPS prevented induction of the adherence-promoting activity. Pretreatment of HEC with IL 1 and rTNF-alpha produced a similar protein synthesis-dependent increase in neutrophil adherence to HEC. Coincubation of neutrophils with murine monoclonal antibody (MoAb) 60.3, an antibody directed to the CDw18 complex, produced a 70 +/- 4% inhibition of neutrophil adherence to LPS-pretreated HEC, 59 +/- 5% inhibition of adherence to IL 1-pretreated HEC, and 65 +/- 11% inhibition of adherence to rTNF-alpha-pretreated HEC (means +/- SE of 18, seven, and five experiments, respectively). Notably, MoAb 60.3 did not completely inhibit neutrophil adherence to pretreated HEC, although it completely inhibited adherence to untreated HEC when neutrophils were activated directly with phorbol ester. Similarly, the adherence of neutrophils from a patient with an inherited deficiency of the CDw18 complex to LPS-, IL 1-, and rTNF-alpha-pretreated HEC was markedly reduced compared with normal neutrophils (5 to 11% adherence with CDw18-deficient neutrophils vs 43 to 54% adherence with normal neutrophils), but adherence to pretreated HEC was still significantly greater than adherence to HEC that were not pretreated (2% adherence). We conclude that LPS, IL 1, and rTNF-alpha induce synthesis of an endothelial cell-surface factor(s) that promotes neutrophil adherence primarily by a mechanism involving the CDw18 complex. It thus appears that the CDw18 complex is important for augmented neutrophil adherence to endothelium in vitro whether the is stimulated directly by inflammatory mediators or indirectly by endothelial-dependent mechanisms.