Confocal immunofluorescence of TF and GPIbα in nonstimulated PBMC preparations. Unstimulated, fresh, nonpermeabilized suspensions of PBMCs were examined by contrast microscopy, Hoechst staining, and TF and GPIbα immunolabeling. No TF label is observed in leukocytes, whereas 1 platelet stained strongly for TF and GPIbα, with extensive colocalization of both glycoproteins. The other platelet is identified only by expression of the GPIbα label. Vis is phase contrast; arrows in Vis show platelets expressing GPIbα label.