Effects of steady shear flow on the deformation of leukocyte adhered to vascular endothelial surface.

OBJECTIVE: To investigate the effects of steady shear flow on the deformation properties of an adherent leukocyte and its nucleus.
METHOD: A compound drop model was developed to simulate the leukocyte adhered to the inner surface of a blood vessel, and a two dimensional computational fluid dynamics (CFD) was conducted to solve the model equations. RESULT: The results show: 1) The Reynolds number of the external shear flow plays a crucial role in leukocyte deformation. Leukocyte deformation increases with Reynolds number; 2) The nucleus deforms together with the leukocyte, and the deformation index of the leukocyte is greater than that of the nucleus. The leukocyte is more deformable while the nucleus is more capable of resisting external shear flow; 3) The leukocyte and the nucleus will not deform infinitely when the Reynolds number increases beyond a certain value where the deformation index reaches its maximum; 4) Pressure distribution over the surface demonstrated that there exists a region downstream of the cell, where is high pressure produced to retard continuous deformation and to provide a positive lift force on the cell.
CONCLUSION: The nucleus with high viscosity plays a particular role in leukocyte deformation under shear flow.