Fig. 2. Force versus displacement traces of the interaction between 3A9 cells and immobilized ICAM-1. The measurements were carried out with a resting cell (first trace), a Mg²⁺-treated cell (second trace) and a PMA-stimulated cell (third trace). The measurements were acquired with a compression force of 200 pN, 5 seconds contact and a cantilever retraction speed of 2 µm/second. The fourth trace corresponds to a measurement acquired from a PMA-stimulated cell in the presence of LFA-1 (20 µg/ml FD441.8) and ICAM-1 (20 µg/ml BE29G1) function-blocking antibodies (inh. mAbs). The shaded area shows an estimate of the work of de-adhesion, and is the detachment force. Arrows point to breakage of LFA-1–ICAM-1 bond(s).