Variation in the velocity, deformation, and adhesion energy density of leukocytes rolling within venules.

Leukocyte rolling along the endothelium in inflammation is caused by continuous formation and breakage of bonds between selectin adhesion molecules and their ligands. We investigated trauma-induced leukocyte rolling in venules (diameter, 23 to 58 microns; wall shear stress, 1.2 to 35 dyne/cm2) of the exteriorized rat mesentery using high-resolution intravital microscopy. While rolling, the leukocytes deformed into a tear-droplike shape. Deformation continued to increase with shear stress up to the highest values observed (35 dyne/cm2). Successive leukocytes had similar rolling velocities at the same axial positions along each vessel, suggesting that heterogeneity of endothelial adhesiveness is responsible for velocity variation. Adhesion energy density varied inversely with instantaneous rolling velocity and directly with instantaneous deformation. Adhesion energy density reached a maximum of 0.36 dyne/cm, similar to values found for lymphocyte function-associated antigen-1-dependent adhesion of stimulated T cells to isolated intercellular adhesion molecule-1. We conclude that selectin-mediated adhesion during rolling produces adhesion energy densities comparable to those observed for integrin-mediated adhesion events in other experimental systems.