Chapter 2 Biomechanics of Leukocyte and Endothelial Cell Surface

Abstract

Publisher Summary Human leukocytes—including neutrophils, lymphocytes, and monocytes—are the major immune cells within blood. Leukocytes travel around the human body through circulatory vessels that are lined with Endothelial cells (ECs). When they leave blood, leukocytes roll on ECs first. This is due, in part, to weak adhesive interactions mediated mainly by selectins on both leukocytes and ECs. This weak adhesion, coupled with the force and torque imposed on the leukocyte by blood flow, yields a consecutive series of jerky motion of the leukocyte, often coined “rolling.” Neutrophil and lymphocyte rolling are essential for their immunological functions, whereas monocyte rolling is critical for its arrest on the vascular wall and invasion into the aortic intima. Leukocyte rolling on the endothelium is the first critical step of leukocyte migration to sites of infection, injury, or atherosclerotic lesions. Unstable rolling impairs effective neutrophil and lymphocyte recruitment to infected tissues and renders human beings defenseless against invading microorganisms, resulting in immunological diseases, such as leukocyte adhesion deficiency syndrome. On the other hand, stable rolling is critical for monocyte infiltration into the aortic intima that initiates and exacerbates cardiovascular diseases, such as atherosclerosis. Elucidating the mechanisms that underlie leukocyte rolling can pave the way toward therapeutic amelioration of such maladies. However, the rolling of leukocytes is a complex dynamic process that is mediated concertedly by adhesion molecules expressed on leukocytes and ECs, shear stress due to blood flow, and mechanical properties of leukocytes and ECs. A complete understanding of leukocyte rolling requires thorough knowledge in all these areas. This chapter discusses the recent advances gained in biomechanics of leukocyte and endothelial cell surface, as well as their impact on leukocyte rolling.