T cells utilize lamellipodia and filopodia for optimal intraluminal path finding (P5097)

Abstract

Abstract Immune cells circulating in inflamed blood vessels undergo series of adhesion cascades to leave out of blood vessels to infiltrate into inflamed tissues. It has been shown that leukocytes crawl a considerable distance before they undergo transendothelial migration (TEM), but how they steer their crawling direction to find TEM sites is not well understood. To determine whether flow direction or EC orientation has predominant roles on the direction of T cell crawling, we fabricated well-aligned EC layers by culturing ECs on nanogrooved surfaces and applied shear flow either parallel or perpendicular to the direction of EC orientation. Regardless of flow direction, T cells crawled along the EC orientation. Then, we further identified guiding cues on ECs and found out that T cells tend to crawl along the valleys of topographical landscapes of EC layers while avoiding nuclei of ECs. By using pharmacological inhibitors for Arp 2/3, which nucleate actin filament branching to form lamellipodia, and cdc42, a small GTPase regulating filopodia formation, we found out that T cells utilize lamellipodia to sense topography of EC layers and filopodia to sense nuclei of ECs. Importantly, inhibitor-treated T cells crawled much longer distances than untreated T cells before they underwent TEM, suggesting that lamellipodia and filopodia of T cells are critical for optimal intraluminal path finding.