Adhesion of polymorphonuclear cells to human endothelial cells. Adhesion-molecule-dependent, and Fc receptor-mediated adhesion-molecule-independent mechanisms.

Activation of human umbilical vein endothelial (HUVE) cells with the inflammatory mediators tumour necrosis factor-alpha (TNF), interleukin-1 (IL-1), lipopolysaccharide (LPS) and phorbol esters enhanced their adhesiveness for leucocytes. The appearance of an activation antigen ELAM-1, recognized by a monoclonal antibody (MoAb) ENA1, parallels the kinetics of the enhanced adherence of leucocytes to endothelial cells. Adhesion of polymorphonuclear cells (PMN) to activated HUVE cells could be blocked by F(ab')2 fragments of MoAb ENA1 up to 60%. An additive inhibition of the adhesion was established by pre-incubation of the PMN with anti-CD18 MoAb and/or leucocyte adhesion inhibitor (LAI), produced by endothelial cells. An opposite reaction, however, was observed when HUVE cells were pre-incubated with intact MoAb ENA1, resulting in an enhancement of the adhesion up to 200%. Apparently, the blocking effect of MoAb ENA1 could be bypassed by the strong interaction of the Fc part of the MoAb with the Fc receptor (FcR) on the PMN. Similarly, anti-CD18 MoAb and/or LAI reduced the adhesion observed if intact ENA1 were used, and Fc-FcR interaction took place. The results presented in this study indicate that adhesion via ELAM-1, the CD18 antigen and via the receptor for LAI are different mechanisms. These mechanisms may act in concert to strengthen the binding of PMN to HUVE cells. Moreover, a strong adhesion could be established via the Fc part of MoAbs directed against HUVE cells with the FcR on the PMN. The phenomenon described may play a role in graft rejection and in diseases where antibodies directed against endothelium are involved.