Fig. 7. Expression of PrP^C, PECAM-1 and VLA-4 by U937 human monocytic cells. U937 cells were incubated with anti-PrP^C (SAF32), anti-PECAM-1 (HEC-7) or anti-VLA-4 antibodies (2 µg/ml) for 10 minutes at 25°C, then with FITC-conjugated anti-mouse antibodies. Samples were analyzed by flow cytometry and at least 5000 cells were counted. Black areas represent staining profiles with the indicated antibodies, gray areas represent staining profiles with first antibodies omitted as negative control.