Fig. 2. Cytosolic free Ca²⁺ changes during ß2 integrin-mediated phagocytosis. The data show a typical experiment in which human neutrophils were presented with a DCDHF-labelled C3bi-opsonised particle for phagocytosis with simultaneous cytosolic free Ca²⁺ measurement. (a) The upper row shows the phase contrast images and the second row shows the accompanying Ca²⁺ images (fura2 ratio image pseudo-coloured to show changes in cytosolic free Ca²⁺ concentration as a change from blue to green), acquired at the times shown below. The images illustrate some of the key features of the phagocytic event. The first image shows the micropipette presenting the particle to the cell; the second, adhesion of the particle to the cell without Ca²⁺ signalling; the third, the formation of the phagocytic cup; the fourth, closure of the phagosome, and the fifth, completion of the event and the return of cytosolic free Ca²⁺ to baseline. (b) The complete time course of the cytosolic free Ca²⁺ data. This experiment was typical of at least 50 others.