Role of leukocyte integrins and their ligands in regulation of cell adhesion

• Main Authors: Ming-Yi Tsai, 蔡明怡
• Other Authors: Chi-Chang Shieh
• Format: Others
• Language: zh-TW
• Published: 2005
• Online Access: http://ndltd.ncl.edu.tw/handle/30982517591140388641

碩士 === 國立成功大學 === 微生物及免疫學研究所 === 94 === 　Leukocytes adhere to endothelium then transmigrate through blood vessels and traffic to different tissues. This process is important for host defense mechanisms and inflammatory response. The adhesion between leukocyte and endothelium is mediated by several cell surface receptors, including selectins, integrins, and immunoglobulin (Ig) superfamily cell-adhesion molecules (CAMs). Intercellular adhesion molecule-1 (ICAM-1) is an immunoglobulin (Ig) superfamily molecule which contains five Ig-like domains. Many inflammatory mediators activate endothelial cell expression of ICAM-1, which serves as a ligand for the integrin, LFA-1. The regulation mechanisms of leukocyte adhesion and transmigration in the inflamed endothelium mediated by integrein-Ig superfamily molecule thus are critical for immune responses. We previously prepared two monoclonal antibodies, EN2 and I9, which bind to ICAM-1. We found that human umbilical vein endothelial cells (HUVECs) treated with EN2 or I9 have enhanced adhesion between leukocytes and HUVECs. We also found that EN2 and I9 decrease leukocyte transmigration through HUVEC monolayers. We thus hypothesized that the adhesion ability changed by EN2 or I9 is involved in the regulation of cell transmigraton in inflammatory tissues. Based on the hypothesis that EN2 and I9 may bind to different epitopes on ICAM-1, we prepared six truncated forms of ICAM-1 (ICAM-1 five domains and ICAM-1 lacking domain 1, domain 1-2, domain 1-3, domain 4-5, domain 5) to map the binding sites of EN2 and I9 on ICAM-1. A flow-chamber assay system was established to test the adhesion function of leukocytes which may be modulated by these recombinant ICAM-1 molecules. 　We also investigated the modulation of integrins in inflammation. Recent studies showed that conformational changes cause activation or deactivation of integrins. Reactive oxygen species (ROS) can modulate the integrin activity by reversible redox reaction. We thus tested whether ROS change the adhesion states of leukocytes in flow chamber systems. In line with our previous studies, we found that H2O2 can modulate the interaction between VLA-4 and VCAM-1. We selected wall shear stress 1 dyne/cm2 to mimic normal physiological microvascular environments. In a lower concentration (10mM), H2O2 enhanced VLA-4 binding to VCAM-1, while in a higher concentration (250mM), H2O2 decreased VLA-4 binding to VCAM-1. These results support the hypothesis that ROS modulate the integrin-Ig superfamily molecule interactions and is critical for leukocyte trafficking in inflammatory tissues.