Figure 2.

A micrograph showing an anti-CD45-coated bead about to be touched by a human neutrophil. At the beginning of every experiment for a neutrophil-bead pair, a known suction pressure is applied inside the pipette on the left. Then a positive pressure is superimposed so that the neutrophil can move toward the bead. After the cell and the bead make contact, the positive pressure is released. If the cell does not adhere to the bead, the cell will move away freely under the suction pressure; if the cell adheres to the bead, the cell will stay close to the bead or it will move away at a smaller velocity than its free motion velocity. After the cell detaches from the bead, the positive pressure is superimposed again and the same procedure is repeated.