A model of leukocytes (White Blood Cells) Aggregation

Cell-cell interactions and cell-extracellular matrix (ECM) interactions affect immune regulation such as leukocyte trafficking via blood and lymphatic vascular system. The leukocytes has numerous folds which probably allows cell deformation without a change in surface area and volume. Leukocytes stiffness rigidity is largely determined by the cytoskeleton of actins and actins-binding protein and its degree of cross linking. White blood cells have a larger volume than red cells leading to the resistance imposed by a single white cell in capillaries is much larger than that of a single red cell. As large number of leukocytes move at a wide range of speeds, collisions occur. These collisions result in abrupt changes in the motion and appearance of leukocytes. The formation of adhesive bonds depends on local velocity and shear forces to the captured cells. Migration of leukocytes in blood flow and collision with vessel wall depends on the direct hemodynamic interaction of leukocytes with erythrocytes results in pushing leukocytes against the endothelium. A collision model between leukocyte and erythrocyte is presented where leukocyte being adhered to endothelium as shear stress and surface energy increases.