
Rolling adhesion is the behaviour that white blood cells (WBC) exhibit as they passively roll along blood vessel walls under flow. It plays a critical role in capturing cells in the blood, guiding them toward inflammation sites. Rolling adhesion is mediated by catch-bond interactions between selectins expressed on blood vessels walls and PSGL-1 on WBC. Despite our understanding of individual components of this process, how biology utilize these molecular mechanical interaction remain experimentally unexplored. Here, we developed 2 methods that map the functional adhesion sites and their strength on a leukocyte surface. The first method relies on tracking the rotational angle of a single rolling cell, which confers advantages over standard methods that track the centre-of-mass alone. Constructing the adhesion map from the instantaneous angular velocity reveals that the adhesion profile along the rolling circumference is inhomogeneous. We corroborated these findings with a second method that allowed us to obtain a footprint of molecular adhesion events using DNA-based molecular force probes. Our results reveal that adhesion at the functional level is not uniformly distributed over the leukocyte surface as previously assumed, but is instead patchy. Lastly, I will discuss our recent work on the interpretation and future improvement of non-equilibrium molecular force sensors.

Rolling adhesion is the behaviour that white blood cells (WBC) exhibit as they passively roll along blood vessel walls under flow. It plays a critical role in capturing cells in the blood, guiding them toward inflammation sites. Rolling adhesion is mediated by catch-bond interactions between selectins expressed on blood vessels walls and PSGL-1 on WBC. Despite our understanding of individual components of this process, how biology utilize these molecular mechanical interaction remain experimentally unexplored. Here, we developed 2 methods that map the functional adhesion sites and their strength on a leukocyte surface. The first method relies on tracking the rotational angle of a single rolling cell, which confers advantages over standard methods that track the centre-of-mass alone. Constructing the adhesion map from the instantaneous angular velocity reveals that the adhesion profile along the rolling circumference is inhomogeneous. We corroborated these findings with a second method that allowed us to obtain a footprint of molecular adhesion events using DNA-based molecular force probes. Our results reveal that adhesion at the functional level is not uniformly distributed over the leukocyte surface as previously assumed, but is instead patchy. Lastly, I will discuss our recent work on the interpretation and future improvement of non-equilibrium molecular force sensors.