Inflammatory diseases are a major cause of morbidity and mortality in the United States. Rapid recruitment of inflammatory cells is a hallmark of inflammation and requires the concerted action of chemoattractants, cytokines and adhesion molecules. Previous research has identified four major sets of adhesion molecules: integrins, immunoglobulin- like molecules, selectins, and carbohydrates serving as selectin ligands. Selectin-mediated adhesion causes leukocytes to roll along the endothelium and is required for recruitment of leukocytes from the blood stream. Three known selectins have been cloned and sequenced in the human and important experimental animal systems, L (leukocyte)-, P (platelet and endothelial cell)- and E (endothelial cell)-selectin. Although the specific functions of L-, P- and E-selectin have been investigated using in vitro model systems, data about the role of individual selectins during the inflammatory process in vivo is sparse and partially controversial. Leukocyte rolling is modulated by the biomechanical properties of leukocytes and the distribution of adhesion receptors on the cell surface. The proposed research will investigate the importance of L-,P- and E-selectins for leukocyte rolling in vivo in a comprehensive and definitive way. The investigator postulates that the selectins are involved sequentially in leukocyte rolling, that rolling requires clustering of L-selectin molecules on the cell surface, and that leukocyte deformability is an important determinant of rolling.
The specific aims are to (1) determine the role of L-selectin in trauma- and cytokine induced leukocyte rolling, (2) identify P- and/or E-selectin mediated leukocyte rolling and to correlate function with expression of these selectins on endothelial cells, (3) assess the effect of surface distribution of L- selectin on rolling and (4) determine the extent and importance of transient leukocyte deformation during rolling in vivo. The investigations will be made using the method of intravital microscopy on two novel strains of gene knockout mice deficient for expression of L- and P-selectin, respectively. To further distinguish between the contribution of L-selectin and vascular E- and P-selectins, cell lines transfected with L-selectin, function-blocking monoclonal antibodies, and cell lines bearing ligand(s) for E- and P-selectin will be used in mice and rats. The knowledge gained will improve the understanding of the inflammatory process and provide significant information pertinent to potential anti-inflammatory therapies for future clinical use in patients.
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