GRANULOCYTE ENDOTHELIUM INITIAL ADHESION - ANALYSIS OF TRANSIENT BINDING EVENTS MEDIATED BY E-SELECTIN IN A LAMINAR SHEAR-FLOW

The adhesion of moving cells to receptor-bearing surfaces is a key ste p to many important biological processes. Attachment was subjected to extensive modeling. However, the numerical values of kinetic bonding p arameters relevant to realistic models of cell adhesion remain poorly known. In this report, we describe the motion of human granulocytes to interleukin-1-activated endothelial cells in presence of a low hydrod ynamic drag (a few piconewtons) estimated to be much weaker than a sta ndard ligand-receptor bond. It was thus expected to visualize the form ation and rupture of individual bonds. We observed multiple short-time cell arrests with a median duration of 2.43 s. Stop frequency, not du ration, was significantly inhibited by anti-E-selectin antibodies. Bin ding efficiency exhibited an almost linear relationship with the inver se of cell velocity. The distribution of arrest duration was determine d: results were consistent with the view that these arrests reflected the formation/dissociation of single ligand-receptor bonds with a spon taneous dissociation rate of 0.5 s-1. The rate of bond formation was o n the order of 0.04 s-1 when cells were freely rolling (mean velocity: 19 mum/s) and it exhibited an approximately 10-fold increase after th e formation of a first adhesion.