Rolling dynamics of a neutrophil with redistributed L-selectin.

The most common white blood cell is the neutrophil, which slowly rolls along the walls of blood vessels due to the coordinated formation and breakage of chemical selectin-carbohydrate bonds. We show that L-selectin receptors are rapidly redistributed to form a cap at one end of the cell membrane during rolling via selectins or chemotactic stimulation. This topography significantly alters the adhesive dynamics as demonstrated by computer simulations of neutrophils rolling on a carbohydrate selectin-ligand substrate under flow. It was found that neutrophils with a redistributed L-selectin cap roll on sialyl Lewis-x with a quasi-periodic motion, as characterized by relatively low velocity intervals interspersed with regular jumps in the rolling velocity. On average, neutrophils with redistributed L-selectin rolled at a lower velocity when compared with cells having a uniform L-selectin distribution of equal average density. We speculate on the possible biological implications that these differences in adhesion dynamics will have during the inflammatory response.