Photomicrographs of cross-sections of murine aortas.

Samples were obtained 2 minutes after the injection of human factor IX (K5A, K5R, and wild type), and detected with anti-human factor IX IgG. K5A, K5R, and WT: identify the injected protein. Color was developed by AEC. Control: artery was isolated from a factor IX knockout mouse that had not received any factor IX. Down arrows indicate factor IX K5R and wild-type binding at the endothelial surface. Up arrows indicate factor IX in the region beneath the endothelium. Bar = 20 μm.