Differential roles of adhesion receptors during neutrophil adhesion to endothelial cells under flow conditions
Gopalan, Priya Kadambi
Akin, John Edward.; McIntire, Larry V.
Doctor of Philosophy
Neutrophil emigration from the vasculature is an essential part of the primary immune response to infections. It is a multi-step process of cell interaction with the endothelium (capture, rolling, arrest and transmigration) that involves several classes of receptors. Neutrophils are captured (tethered) and then roll on the endothelial surface. This initial interaction is thought to involve the selectin family of cell adhesion molecules. Cell arrest (firm adhesion) follows neutrophil activation. Activated CD18 integrins and ICAM-1, a member of the immunoglobulin gene superfamily, mediate arrest. Finally, the neutrophils transmigrate beneath the endothelial cells, a process also thought to be dependent on the CD18 integrins and ICAM-1. We used a parallel plate flow chamber to simulate laminar flow along vessel walls in the vasculature. We demonstrate that L-selectin can activate the adhesive function the CD18 integrins. In this work, we show for the first time that L-selectin can activate LFA-1. We also show that two of the members of the CD18 integrin family, LFA-1 and Mac-1, are both sufficient to mediate neutrophil arrest and transmigration across endothelial cells stimulated for 4 hr with IL-$1\beta .$ We provide evidence for the existence of a pathway independent of the CD18 integrins that can mediate arrest and transmigration. Neutrophils utilizing this pathway are able to transmigrate with a rate comparable to CD18-dependent transmigration. We provide some preliminary data that demonstrates that PECAM-1 ligation does not activate neutrophil CD18 integrin-mediated arrest, in contrast to published reports. Finally, we report the results of some initial experiments that suggest that L-selectin and PSGL-1 mediate the capture of neutrophils by endothelial monolayers stimulated for 4 hr with IL-$1\beta ,$ while E-selectin and sialic acids are involved in rolling, but not in capture. Our results give insight into the interplay between laminar shear flow and adhesion receptor function which enable neutrophil emigration during inflammatory conditions.
Cell biology; Immunology; Biology; Health sciences