How do white blood cells – immune system “soldiers” – cross the blood vessel barrier to get to the site of infection or injury? Until recently, it was believed that these cells advanced like inchworms, sticking front and back, folding and extending to push themselves forward. Yet in research recently published in Immunity, Prof. Ronen Alon and his research student, Ziv Shulman, of the Immunology Department showed that the rapid movement of the white blood cells is more like that of millipedes.
The cell creates numerous tiny “legs” no more than a micron in length, rich in adhesion points that bind to partner adhesion molecules on the surface of the blood vessels. Tens of these legs attach and detach in sequence within seconds, enabling them to move rapidly while keeping a good grip on the vessels’ sides.
Images produced by scanning and transmission electron microscopes, taken by Drs. Eugenia Klein and Vera Shinder of the Institute’s Electron Microscopy Unit, 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 scientists believe that the tiny legs are trifunctional: used for gripping, moving and sensing distress signals from the damaged tissue.
In future studies, the scientists plan to check whether aggressive immune reactions (such as in autoimmune diseases) can be regulated by interrupting the digging of immune cell legs into the endothelium. They also plan to investigate whether cancerous blood cells metastasize through the blood stream using similar mechanisms.
Prof. Ronen Alon’s research is supported by the De Benedetti Foundation-Cherasco 1547. Prof. Alon is the incumbent of the Linda Jacobs Chair in Immune and Stem Cell Research.