Scientists at Weizmann Institute have shown that white blood cells move like millipedes in order to get to the site of infection or injury.
Professor Ronen Alon and his research student Ziv Shulman, who led the study, say that their finding contrasts the current opinion about the movement of the immune system "soldiers", according to which they advance like inchworms.
The researcher say that rather than sticking front and back, folding and extending to push itself forward, the immune cell creates numerous tiny 'legs' no more than a micron in length-adhesion points, rich in adhesion molecules (named LFA-1) that bind to partner adhesion molecules present on the surface of the blood vessels.
They say that tens of these legs attach and detach in sequence within seconds, allowing them to move rapidly while keeping a good grip on the vessels' sides.
Using scanning and transmission electron microscopes, the researcher produced images that showed that upon attaching to the blood vessel wall, the white blood cell legs "dig" themselves into the endothelium, pressing down on its surface.
The researchers found that the shear force created by the blood flow was necessary for the legs to embed themselves. Without the thrust of the rushing blood, the white blood cells couldn't sense the exit signals or get to the site of the injury.
According to them, the results of the current study explain previous findings that the blood's shear force is essential for the white blood cells to exit the blood vessel wall.
The present study suggests that shear forces cause their adhesion molecules to enter highly active states.
In future studies, the scientists plan to check whether it is possible to regulate aggressive immune reactions, such as in autoimmune diseases, by interrupting the "digging" of immune cell legs into the endothelium.
They will also study whether cancerous blood cells metastasise through the blood stream using similar mechanisms in order to exit the blood vessels and enter different tissues.