Phosphorylated ATF2 is expressed specifically in lesional endothelium. (A) Human donor tissue (iliac artery, male, age 43, died from subdural hematoma after fall) was probed for the presence of a continuous layer of endothelial cells by immunohistochemical CD31 staining. After confirmation of CD31 positivity, adjacent sections were stained for Thr71-phosphorylated ATF2 (pATF2). The left part of the panel shows an overview of the entire vessel, indicating the lesional and lesionfree areas that are enlarged in the composite images on the right, which show pATF2 or CD31 staining as red coloration. (B-E) Enlarged parts of lesional and lesionfree areas stained for pATF2 or CD31, taken from panel A as indicated by the red-lined boxes. Similar enlargements are shown for 2 other vascular specimens, obtained from human donor ([F-I] iliac artery, female, age 35, died in falling accident) or human obduction tissue ([J-M] internal carotid artery, male, age 85, died from liver failure). All sections were counterstained for nuclei with hematoxylin. The enlargements in panels A and B were obtained using a magnification of × 63.