|Udo Bakowsky, H. Bakowsky, Gerd Bendas, Ulrich Rothe, Carsten Ehrhardt, Claus-Michael Lehr, and Dick Hoekstra
Saarland University, Biopharmaceutics and Pharmaceutical Technology, Geb. 8.1, Im Stadtwald, D-66123 Saarbrücken, Germany
The receptor-mediated recruitment of leukocytes to sites of injury or infection is essential for the development of an appropriate immune response. Leukocytes rolling along endothelial cells under shear force represent the first step in a sequence of adhesive interactions that lead to firm attachment and subsequent emigration. The selectins, a family of three adhesion molecules (P-, E-, L- selectin), are thought to mediate rolling by rapid association and dissociation with their ligands. E-and P-selectin are expressed on endothelial cells in response to inflammatory signals, and bind to carbohydrate moieties on subsets of leukocytes. All selectins can interact with sialylated and fucosylated polylactosaminoglycans presented by mucin-type glycoproteins, where sLex-epitopes are of key importance . Here, we investigated the influence of structure, density and lateral clustering of the selectin-ligands on ligand/receptor pair recognition. Different synthetic glycolipid ligands were incorporated at various concentrations into phospholipid model membranes at the air water interface. The glycolipids were either organized in defined clusters or homogeneously distributed within the lipid matrix by selection of suitable physico-chemical parameters. Using the Langmuir-Blodgett technique, we transferred the mixed glycolipids monolayers onto solid sensor surfaces. The lipid organisation in the transferred films was studied employing AFM. Carbohydrate specific binding of selectins and selectin-modified liposomes was quantified by quartz-crystal microbalance measurements, film balance studies and visualised by AFM.