Intraluminal crawling of neutrophils to emigration sites: a molecularly distinct process from adhesion in the recruitment cascade

Abstract

The prevailing view is that the β2-integrins Mac-1 (αMβ2, CD11b/CD18) and LFA-1 (αLβ2, CD11a/CD18) serve similar biological functions, namely adhesion, in the leukocyte recruitment cascade. Using real-time and time-lapse intravital video-microscopy and confocal microscopy within inflamed microvessels, we systematically evaluated the function of Mac-1 and LFA-1 in the recruitment paradigm. The chemokine macrophage inflammatory protein-2 induced equivalent amounts of adhesion in wild-type and Mac-1−/− mice but very little adhesion in LFA-1−/− mice. Time-lapse video-microscopy within the postcapillary venules revealed that immediately upon adhesion, there is significant intraluminal crawling of all neutrophils to distant emigration sites in wild-type mice. In dramatic contrast, very few Mac-1−/− neutrophils crawled with a 10-fold decrease in displacement and a 95% reduction in velocity. Therefore, Mac-1−/− neutrophils initiated transmigration closer to the initial site of adhesion, which in turn led to delayed transmigration due to movement through nonoptimal emigration sites. Interestingly, the few LFA-1−/− cells that did adhere crawled similarly to wild-type neutrophils. Intercellular adhesion molecule-1 but not intercellular adhesion molecule-2 mediated the Mac-1–dependent crawling. These in vivo results clearly delineate two fundamentally different molecular mechanisms for LFA-1 and Mac-1 in vivo, i.e., LFA-1–dependent adhesion followed by Mac-1–dependent crawling, and both steps ultimately contribute to efficient emigration out of the vasculature.

The small GTPase Rap1b negatively regulates neutrophil chemotaxis and transcellular diapedesis by inhibiting Akt activation

“…9 F). Finally, we confirmed that transmigration is CD11b-dependent because CD11b / neutrophils exhibited defective transmigration (unpublished data; Phillipson et al, 2006;Zhang et al, 2006). Adoptive transfer of neutrophils further supported impaired CD11b / neutrophil emigration into lungs (Fig.…”

“…The neutrophil crawling and TEM steps are highly M 2 -integrin-dependent (Phillipson et al, 2006). Because Rap1b controls some adhesion-dependent cellular functions, including superoxide production (Fig.…”

“…After arrest, neutrophils undergo actin-dependent polarization and lateral migration or crawling on endothelial cells in search for permissive sites, before final diapedesis out of blood vessels (Phillipson et al, 2006;Muller, 2011). Diapedesis or transendothelial migration (TEM) is the least explored step and can occur by two distinct routes: either through junctions between endothelial cells (the paracellular route) or directly through individual endothelial cells (the transcellular route; Feng et al, 1998;Schenkel et al, 2004;Phillipson et al, 2006;Carman et al, 2007;Carman and Springer, 2008;Sage and Carman, 2009;Shulman et al, 2009;Muller, 2011). Once at the site of inflammation, neutrophils release reactive oxygen species, proinflammatory cytokines, and various proteases that all contribute to tissue injury when the neutrophilic response remains uncontrolled.…”

Coordinated RhoA signaling at the leading edge and uropod is required for T cell transendothelial migration

“…After the capture of leukocytes on blood vessel walls, they polarize and migrate on the endothelial cells (ECs) lining the vessels, which is thought to enable them to find optimal sites for transendothelial migration (TEM; Schenkel et al, 2004;Phillipson et al, 2006). Leukocytes transmigrate either at EC junctions (paracellular TEM) or through individual EC (transcellular TEM; Carman and Springer, 2004;Millán et al, 2006;Vestweber, 2007).…”

A computational mechanics approach to assess the link between cell morphology and forces during confined migration

“…1) generated between the cell frontal and rear adhesion surfaces and the underneath substrate. As in previous works (Phillipson et al 2006;Sakamoto et al 2011;Allena and Aubry 2012;Allena 2013), such forces are assumed to be viscous and may be distinguished into a frontal (f adh, f ) and a rear (f adh,r ) force as follows…”