Figure 8. Multiple bonding of neutrophil tethers to a P-selectin–coated surface. (a) A single tether was pulled and displayed a kink because of a local attachment to the sur- face (arrow at t 5 2.133 s). This attachment was subse- quently broken (t 5 3.467 s) while the tether continued to grow for over 8 s. The arrow at t 5 8.600 s points to the for- mation of a beaded structure as the tether becomes elon- gated. (b) Multiple points of neutrophil tether attachment to the P-selectin–coated sur- face are formed and broken at a wall shear rate of 150 s21. The kinked tether at t 5 0 s detaches at point 1 and, rather than fully snapping back, remains attached at points 2 and 3 (t 5 0.033 s). The kink in the tether at point 3 remains as the tether grows until t 5 1.033 s, at which point the tether detaches from point 3, yet remains bonded at point 2. multiple bonding, the poor loading of the most distal bonds, and the opportunity to form new bonds in the tether contact area. Tether Dragging, Multiple Tethering, Tether Beading, and Neutrophil String Formation on P-selectin One unique feature of these tethers was, at times when the tether detached from the surface, it did not always snap back fully to the neutrophil body, but would drag along the surface and become reattached similar to the function of a grapple hook to bring the cell to arrest (data not shown). In addition, two or three elongated tethers that were pulled from a single neutrophil were occasionally ob- served (data not shown). Although most tethers snapped back, inspection of the P-selectin–coated surface after neutrophils rolled on the surface demonstrated the exist- ence of detached tethers that often had a beaded appear- ance (Fig. 9 a). This is a flow-dependent mechanism of neutrophil microparticle formation and an example of cel- lular detachment by the failure of the membrane in which receptors are embedded. Fig. 9 b, which shows a single The Journal of Cell Biology, Volume 149, 2000 726