C-C and C-X-C chemokines trigger firm adhesion of monocytes to vascular endothelium under flow conditions.

In summary, our findings indicate that specific chemokines that are elaborated by endothelial cells after cytokine or endotoxin activation can play an essential role in monocyte recruitment beyond their chemoattractant activities. We show that this action is to translate initial monocyte tethering into firm adhesion via rapid leukocyte integrin activation. The in vitro model presented here provides a sensitive system for investigating the modulating ability of chemokines and reveals an important biological effect that is not predicted by results in simpler in vitro assays, such as measurement of calcium transients or chemotaxis. The surprising finding that the C-X-C chemokine IL-8 can trigger monocyte firm adhesion to vascular endothelium suggests a potential role for this chemokine in monocyte recruitment and underscores the biological complexity of the chemokine family.