The resistance to flow of individual human neutrophils in glass capillary tubes with diameters between 4.65 and 7.75 μm

Objective: The resistance to flow of individual human neutrophils flowing through smooth-walled glass capillary tubes at velocities ranging between 0 and 30 μm/s is measured for six different capillary tube diameters between 4.65 and 7.75 μm. Methods: The experiments were performed with a micropipet manipulation system. The velocity of individual human neutrophils was measured under different constant pressures and compared to the velocity of the cell-free fluid in the same tube. With the aid of a theory that describes the motion of a concentric, smooth-walled, sausage-shaped body in a tube, the experimental measurements are used to calculate an apparent gap width between the cell and the capillary wall. Results: The maximum calculated gap width in the larger capillary tubes was on the order of 0.1 μm, whereas the minimum gap width in the smaller capillaries was about 0.015 μm. These small gap widths mean that even one neutrophil can cause a significant increase in the apparent viscosity when a cell flows through 100- to 200-μm-long capillary tubes. The neutrophils often exhibited a small static friction that tended to increase as the capillary diameter decreased. Maximum values for the adhesive force caused by the static friction were on the order of 80 pN. Conclusions: Even a single white cell entirely within a capillary can cause a significant increase in the resistance of flow.