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and migration across the endothelium, intercellular antibody.1990). Under conditions of blood flow these classes of receptors function sequentially to co-ordinate leukocyte margination and extravasation. The initial interaction is between a group of molecules with lectin-like properties (the selectins) and their carbohydrate ligands. This slows the passage of circulating leukocytes and initiates a pattern of rolling along the vessel wall (McEver, 1992; Bevilacqua, 1993; Albelda et al., 1994). Once associated with the endothelial surface there is an increased potential for the leukocytes to be exposed to an array of pro-inflammatory molecules. Thus, chemokines such as IL-8, MCP-1 and RANTES, bound to surface glycosaminoglycans (Tanaka et al., 1993), or lipid integrins, for example, mediates the firm adhesion o leukocytes to the endothelial lining of the microvasculature a sites of inflammation (Springer, 1990). Leukocyt