Neutrophils, the immune system’s EMTs, spend most of their lives racing through the bloodstream constantly on the lookout for bacteria and other foreign invaders. Once they arrive at infiltrated tissues, they halt on a dime and slip through the vessel wall to reach the site of infection.
Alex Marki and his colleagues developed a sophisticated intra-vital imaging method that allowed them to watch in real time how neutrophils control their speed as they roll along the walls of blood vessels. The dramatic, real-time footage shows in great detail how neutrophils throw out tube-like tethers to anchor themselves to avoid being swept away by blood rushing by at high speed. As neutrophils gently roll along, tether after tether is peeled loose and slung forward like a lasso to gain new leverage, slowing them down enough to exit the blood vessel.