P-selectin staining of 7E3-treated platelets adherent to collagen is confined to the granulomere, whereas staining of control murine antibody–treated platelets is distributed throughout the sheetlike mass of platelets.

Differential interference contrast microscopy images of normal human platelets in the presence of control murine antibody (A) or 7E3 (B) deposited on collagen for 1 hour at 22°C. Panels on the left are at lower magnification and panels on the right are at higher magnification. Panels C and D contain P-selectin immunofluorescence images of panel A and panel B, respectively. P-selectin staining of the control antibody–treated platelets is distributed throughout the sheetlike mass, including punctate staining near the edges of the spread platelets, whereas the staining of the 7E3-treated platelets was more distinct and better localized to the granulomere areas.