Adhesion receptors cluster into adhesive platforms (small box) on the surface of endothelial cells before engaging leukocytes at the docking structure (large box).

As leukocytes rush by in the blood, the cells of the vessel wall are ready with a convenient handhold in the form of tetraspanin-enriched membrane microdomains, say Barreiro et al.

To fight infection, circulating leukocytes must exit the bloodstream, a process known to involve tetraspanins, membrane proteins that bring together other membrane proteins such as adhesion receptors.

To discover how tetraspanins assist leukocytes out of the blood, the team visualized them in live vascular endothelial cells by FRET-FLIM. Even in the absence of leukocytes, tetraspanins interacted with each other and with adhesion receptors such as VCAM-1 and ICAM-1 to form sticky nanoplatforms. The nanoplatforms then coalesced into larger structures, which presented the leukocytes with a plethora of adhesion receptors to grab onto. The platforms likely increase efficiency of leukocyte adhesion and bloodstream exit in the face of the high shear stress within the bloodstream, says author Francisco Sánchez-Madrid.

Barreiro, O., et al.
J. Cell Biol.