Different types of leukocytes form dynamic interfaces with other cells, within which leukocytes search and identify specific molecules. It is only recently that the mechanical aspects of these cell-cell interfaces have been investigated : focusing on the cellular scale, we have shown that T lymphocytes generate forces when they form an immune synapse with a model antigen-presenting cell1-3. These forces are mechanosensitive, in the sense that they adapt to the stiffness of their opposing target1, 3.
We develop micropipette-based setups to quantify single-cell mechanical properties and forces and monitor them during the first minutes of leukocyte activation3-5. Our micropipette force probe3 allows measuring forces generated by single cells; we also develop a single-cell rheometer that allows us to quantify how leukocytes get stiffer and more viscous while they get activated. We apply this approach to different types of leukocytes including T lymphocytes, phagocytes, and more recently B lymphocytes. These mechanical measurements shed a new light on how cell mechanical properties evolve over seconds, how they adapt to the stiffness of their environment, and how cytoskeleton remodeling and intracellular signaling is involved. A detailed characterization of early mechanical changes in leukocyte activation will help to better understand at the single-cell level the effect of specific molecules including antitumoral immunotherapies.