Expression of chemokines on the surface of different human endothelia.

Expression of chemokines at the endothelial surface depends on their rate of synthesis, the capacity of the endothelium to bind chemokines and the rate of clearance from the surface. The aim of this study was to establish how these factors depend on the chemokine and the tissue of origin of the endothelium. Human lung and dermal microvascular endothelium, saphenous and umbilical vein endothelium, and a bone marrow endothelial line were assayed in vitro. Chemokine expression, localization and transport was measured by immunoassay and confocal microscopy. All endothelia bound CCL3 (MIP-1alpha), CCL5 (RANTES) and CXCL10 (IP-10). CCL3 and CCL5 bound at high levels, and CXCL10 bound less strongly. However, the profile of chemokine expression varied between endothelia, and different chemokines were shown to bind to the endothelial surface by distinct mechanisms. The half-life of CCL3 and CCL5 at the cell surface was approximately 30 min and chemokines were cleared primarily by endocytosis into caveolae. Endothelia from different tissues synthesize distinctive sets of chemokines, but the profile of surface-expressed chemokines also depends on the distinctive characteristics of each endothelia. These two mechanisms may contribute to the differential recruitment of leucocyte subsets to different tissues.