Distribution of endogenous HCII before and after injury. Frozen sections of carotid arteries harvested from HCII^+/+ mice before (A) or 30 minutes after (B) the onset of injury were stained with a polyclonal goat anti–HCII IgG. No HCII antigen was detected in the injured carotid artery of a control (HCII^−/−) mouse (C). Arrow indicates internal elastic lamina; arrowhead, external elastic lamina.