Immunohistochemical Colocalization of the Terminal Complex of Human Complement and Smooth Muscle Cell α-Actin in Early Atherosclerotic Lesions

Abstract

Abstract There is substantial evidence that activated components of the complement cascade are present in atherosclerotic lesions, and it was suggested some years ago that smooth muscle cells may be an important target of complement attack by the terminal components of the cascade, C5b-9, also called the membrane attack complex. Recent in vitro studies have shown that assembly of membrane attack complex on smooth muscle cells leads to the release of monocyte chemotactic protein-1, and, if this were to occur in vivo, then it could be responsible for the recruitment of monocytes into the lesion. In this study we have investigated the localization of C5b-9 in early atherosclerotic lesions of human coronary arteries, collected from autopsies, by immunohistochemical staining. C5b-9 was found to colocalize widely with smooth muscle cell α-actin, but not with intact macrophages, thus supporting the hypothesis that interaction of complement with smooth muscle cells may indeed be important in atherogenesis.