Adventitial infiltrates associated with advanced atherosclerotic plaques: structural organization suggests generation of local humoral immune responses

Advanced atherosclerotic lesions often contain adventitial lymphoid infiltr ates, which occasionally contain nodular aggregates resembling lymphoid fol licles, The structural organization suggests that local maturation of B cel ls may take place at these sites, as described for the mucosa-associated ly mphoid tissue (MALT). This concept was evaluated by studying the micro-anat omy and cellular composition of adventitial infiltrates associated with adv anced atherosclerosis of the aorta. Sections of 22 atherosclerotic aortas w ere stained immunohistochemically for cellular markers characteristic for l ymphoid follicles, such as HECA-452-positive endothelial cells, CD20-positi ve B cells, CD21-positive follicular dendritic cells, and CD68-positive mac rophages, Ki-67 was used as a proliferation marker. The TUNEL technique was used to study the presence of apoptotic cells. Specimens containing MALT s erved as comparison and positive controls. Seven of the 22 atherosclerotic aortas contained adventitial infiltrates resembling lymphoid follicles, The organized nodular centres were composed of CD45RA(+) B cells, follicular d endritic cells (CD21(+)), a few T lymphocytes (CD3(+)) and 'tingible body' macrophages (CD68(+)). A large number of cells were Ki-67-positive: apoptot ic bodies were numerous and phagocytosed by macrophages, The parafollicular area contained CD45RO-positive T cells and HECA-452-positive vessels. Vess els elsewhere were always HECA-452-negative. Specimens with MALT showed sim ilar features. This study reveals a close resemblance between adventitial l ymphoid infiltrates in advanced atherosclerotic aortic disease and MALT, su ggesting local generation of a humoral immune response, likely to be initia ted by antigens released during a process of longstanding tissue injury and inflammation as part of advanced atherosclerosis, Copyright (C) 2000 John Wiley & Sons, Ltd.