COLL 428 |
| Scott I. Simon, Biomedical Engineering, Biomedical Engineering, University of Cal, Davis, One Shields Ave, 1228 Bainer Hall, Davis, CA 95616 |
| Adhesion of leukocytes is in general maintained at a low level until cell recruitment is triggered during acute inflammation. Leukocytes detect low levels of tissue activation by signaling via G-protein linked chemotactic receptors that in turn activate b2-integrin adhesion receptors (CD18) and capture to ICAM-1, its counter-receptor upregulated on inflamed endothelium. This is deemed a critical step in facilitating cell arrest under the shear force of blood flow. Where and when leukocyte recruitment takes place in the vasculature appears to be a highly controlled process and a prime target for development of anti-inflammatory therapeutics. An allosteric shift in CD18 conformation regulates the affinity of CD18 for ICAM-1. We examined the efficiency of cell capture as a function of the dynamics of chemotactic receptor stimulation, the accompanying increase in CD18 affinity, and correlated this with the membrane distribution of the active conformation of CD18. A fluorescence flow cytometric based assay was developed to detect binding of beads derivitized with recombinant ICAM-1 while fluorescence microscopy was applied to detect receptor topography. We provide evidence that the efficiency of neutrophil capture on ICAM-1 is tightly regulated by the level of chemotactic receptor binding and the topography and lifetime of high affinity CD18 |
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Adamson Award Symposium Honoring Dave Allara and Ralph Nuzzo
Division of Colloid and Surface Chemistry |