Mechanical adaptation of monocytes in model lung capillary networks

Significance Proper circulation of white blood cells (WBCs) in the pulmonary blood capillary network is crucial for a healthy immune watch. The remarkable mechanical properties of monocytes, a class of WBCs, allow them to gradually adapt their shape as they pass through the narrowest capillaries, ensuring a transition from a slow motion by hops at the entrance of the capillary network to a smooth and rapid circulation. The key parameters are a low cell cortical tension allowing adaptation of the cell shape, but high enough to prevent cell breakage when passing through the network bifurcations, and a high cell internal viscosity to maintain an elongated shape throughout the network.