FIGURE 2.

Bead displacements when (a) no tethers, (b) single tethers, or (c) double tethers were extracted from a PMA-treated lymphocyte under the aspiration pressure (Δp) of 5 pN/μm². Different bead translation velocities are separated by dashed lines and marked as (1) approaching the cell, (2) making contact with the cell, (3) moving away freely from the cell, (4) extracting a single tether, and (5) extracting double tethers. Here, the free motion velocity of the bead (U_f) is ∼9.5 μm/s (a–c), the growth velocity of the single tether is ∼5.7 μm/s (b and c), and the growth velocity of the double tether is ∼3.9 μm/s (c). In c, after one tether was broken, the other grew at a velocity that was almost the same as the velocity when only one tether was initially extracted as in b. The adhesion lifetime is defined as follows: τ₁ is the adhesion lifetime of single tethers, τ₂ is the adhesion lifetime of double tethers when both tethers are present, and τ₃ is the adhesion lifetime of double tethers when at least one tether is present.