Histology of extravascular FIX distribution. Antibodies to FIX (A,D), Collagen IV (B), FX (C), and FVII (F) were used to stain human liver sections with 3,3′-diaminobenzidine. (E) No primary antibody; all no primary antibody controls lacked background noise. Notice that collagen IV in the sinusoids (B) is not stained with FIX, but that collagen IV and FIX staining generally coincide. The tissues stained with antibodies to FX and FVII differ noticeably from those stained for FIX. (G) A cluster of arteries sectioned in the human skeletal muscle stained for FIX. (H) An adjacent section stained for collagen IV. (I) No primary antibody control. Staining was visualized using a Vectastain ABC Elite Kit (Vector Labs PK-6100), followed by 3,3′-diaminobenzidine. The images were captured with a Nikon Optiphot-2 with a plan-apo lenses and an Olympus DP-70 camera.