The adventitia of atherosclerotic coronary arteries frequently contains Chlamydia pneumoniae

The presence of Chlamydia pneumoniae in the human arterial system has mainl y been determined in atherosclerotic plaque, whereas the adventitia has rem ained relatively unexplored. We assessed the presence of C. pneumoniae in a ll three vessel wall layers of coronary (n = 72) and brachial (n = 48) arte ries in relation to local atherosclerosis. Immunohistochemical staining of C. pneumoniae was observed in plaque and adventitia. Cells stained for C. p neumoniae were detected in the same areas as cells stained for macrophages in adjacent sections. C. pneumoniae staining in the adventitia was associat ed with the extent and severity of atherosclerosis. Coronary sections with C. pneumoniae staining in both adventitia and plaque more often contained a dvanced atherosclerosis than sections with staining only in the adventitia. Staining was observed more often in the coronary artery than in the brachi al artery (24/72 vs. 5/48 and 51/72 vs. 8/48 for plaque and adventitia. res pectively, P = 0.004 and P < 0.001). PCR confirmed the presence of C. pneum oniae DNA in the adventitia. In summary, the adventitia of atherosclerotic coronary arteries frequently contains C. pneumoniae that seems to be locate d within macrophages. These results might indicate a possible route fur inf ected circulating macrophages to home into atherosclerotic lesions in the a rtery via vasa vasorum. (C) 2001 Elsevier Science Ireland Ltd. All rights r eserved.