Which force triggers and dominates rolling of leukocytes?

Leukocyte recruitment towards and rolling at inflammatory regions on activated endothelial cells has been a subject of intensive experimental and computational investigations. The mechanism of rolling is commonly attributed to active formation and breakage of bonds between selectin adhesion molecules and their ligands. The induced cells first rotate with an angular velocity of about 25 sec-1, before they migrate towards the nearest wall where they roll, deform, adhere and migrate through the endothelial cells. The rolling process may take about 20 seconds during which leukocytes are exposed to chemoattractants. The rolling velocity can be as slow as 2.73 mm/s and as large as 60 mm/s in a typical venule in the rat muscle of 23.5 mm in diameter. Aiming at a better understanding of the complexity of the rolling process and of the influence of hydrodynamic forces, we present here updated experimental and simulation results conducted in collaboration with A. S. Silva and C. Saldanha of FML.