Fig. 5. Localization of `activated' <sub>v</sub>ß<sub>3</sub> in resorbing OC. Primary human OCs were plated onto bone slices in the presence of 10% FBS and stained by double immunofluorescence with the anti-ß<sub>3</sub> mAb AP5, which recognizes only the `activated' integrin conformation, followed by cyanine-3-conjugated rabbit anti-mouse IgG (A,C,E) and by fluorescein-tagged phalloidin (B,D,F). Microscopic images show the three different axial sections indicated in Fig. 3A: at the level of the sealing zone (SZ), the `activated' ß<sub>3</sub> (A) only partially colocalizes with the actin ring (B) and displays a discrete pattern. In the ruffled border area (RB) the `activated' ß₃ (C) is very abundant with a punctuate distribution similar to that of the actin microfilaments of D. In the optical yz-plane, note the presence of the actin in the sealing zone SZ (F) as a line at the edge of the cell that only partially colocalizes with the integrin detected by AP5 (E). By contrast, the `activated' receptor and the actin are both present in the ruffled border area RB. Bar, 5 µm.