Neutrophil adhesion to 24-hour IL-1-stimulated endothelial cells under flow conditions

In this study, we examine neutrophil adhesion under flow conditions to cultured HUVEC stimulated for 4 or 24 h with IL-1. Interactions are measured using videomicroscopy and a parallel-plate flow system which is capable of distinguishing primary adhesion and rolling from secondary (firm) adhesion. We find that after 24 h, E-selectin does not contribute to primary adhesion, in contrast to a significant contribution after 4 h. Endothelial cell P-selectin does not contribute at either time point. Blocking or removing L-selectin from the neutrophil surface decreases adhesion 50 to 70% at either time point, and neuraminidase treatment of neutrophils decreases adhesion by 85%. These results suggest that after a 24-h stimulation, primary adhesion depends on a distinct selectin-like interaction in which a HUVEC receptor binds carbohydrates on neutrophil glycoproteins, including L-selectin. We also find that secondary adhesion in this system can be inhibited 90% with Ab blockade of CD18/ICAM-1 interactions after a 24-h stimulation, and that a combination of IL-1 and IL-4 selectively down-regulates the pathway for primary adhesion at 24 h. These results demonstrate that neutrophils adhere using different receptor pathways following 4- and 24-h stimulations, and provide experimental data characterizing some properties of the receptors involved. One of the pathways that is evident at 24 h appears to be a novel selectin-like interaction.