Experimental studies of membrane tethers formed from human neutrophils.

Membrane tethers (thin, cylindrical pieces of membrane) have been implicated in the rolling of neutrophils along the endothelium. In our studies, these tethers were formed from passive, stimulated (0.1 microM fMLP), and osmotically swollen (170-180 mOsm) human neutrophils; as well as neutrophils treated with 0.3 microM latrunculin A to disrupt the cytoskeleton. This tether formation was accomplished by micropipette suction of latex beads coated with antibodies to proteins on the neutrophil membrane surface. From plots of force versus velocity for the tether formation process, we calculated adhesion energies per unit area of the lipid membrane to the cytoskeleton and the viscous resistance (effective viscosity) that occurs during the formation of these tethers at finite velocity. Most of the properties of the neutrophil were altered once it had been treated as described above. We were also able to show mechanical reversibility of membrane tethers, as well as an unexpected formation rate at "high" tether forces. Since membrane tethers have been implicated in the rolling of neutrophils, then the changes in tether formation may ultimately alter how these cells roll.