Fig. 4. Histograms of breakage forces of LFA-1–ICAM-1 bond(s) from the force-displacement traces of (A) resting and (B) PMA-stimulated 3A9 cells. The breakage forces were derived from the magnitude of the force transitions acquired in measurements obtained with a compression force of 200 pN, 5 seconds contact and a cantilever retraction speed of 2 µm/second. The y-axis plots the number of force transitions detected.