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 rateof clearance from the surface. The aim of this study was to establishhow these factors depend on the chemokine and the tissue of originof the endothelium. Human lung and dermal microvascular endothelium,saphenous and umbilical vein endothelium, and a bone marrow endothelial linewere assayed in vitro. Chemokine expression, localizationand transport was measured by immunoassay and confocal microscopy.All endothelia bound CCL3 (MIP-1 alpha), CCL5 (RANTES) and CXCL10(IP-10). CCL3 and CCL5 bound at high levels, and CXCL10 bound lessstrongly. However, the profile of chemokine expression varied betweenendothelia, and different chemokines were shown to bind to the endothelialsurface by distinct mechanisms. The half-life of CCL3 and CCL5 atthe cell surface was approximately 30 min and chemokineswere cleared primarily by endocytosis into caveolae. Endotheliafrom different tissues synthesize distinctive sets of chemokines, butthe profile of surface-expressed chemokines also depends on thedistinctive characteristics of each endothelia. These two mechanismsmay contribute to the differential recruitment of leucocyte subsetsto different tissues.