Human abdominal aortic aneurysms. Immunophenotypic analysis suggesting an immune-mediated response

Area of Science:

• Immunology
• Vascular Biology
• Pathogenesis of Atherosclerosis

Background:

• Cellular immunity is implicated in atherosclerosis pathogenesis.
• The specific role of immune cells in abdominal aortic aneurysm (AAA) formation requires further elucidation.

Purpose of the Study:

• To investigate the role of cellular immunity in the development of abdominal aortic aneurysms.
• To differentiate immune cell infiltrates in normal aortas, occlusive atherosclerotic disease, abdominal aortic aneurysms, and inflammatory abdominal aneurysms.

Main Methods:

• Immunohistochemistry was used to analyze aortic tissues from 32 patients.
• Monoclonal antibodies against CD3 (T cells), CD19 (B cells), CD11c (macrophages), CD4 (T helper cells), and CD8 (T suppressor cells) were employed.
• Quantification of inflammatory cell infiltrates and their distribution within aortic layers was performed.

Main Results:

• Inflammatory cell infiltrate increased progressively from normal aortas to occlusive disease to AAAs and inflammatory aneurysms.
• CD3-positive T lymphocytes were predominantly found in the adventitia of AAAs and inflammatory aneurysms, unlike normal or occlusive aortas.
• A higher CD4:CD8 ratio was observed in AAAs and inflammatory aneurysms, with increased macrophages in inflammatory aneurysms.
• CD19-positive B lymphocytes were present in the adventitia of all pathological tissues.

Conclusions:

• Abdominal aortic aneurysm disease may progress from occlusive atherosclerosis.
• Aneurysmal disease is associated with increased chronic inflammatory cells and altered immune cell distribution.
• Aneurysmal disease is suggested to be an immune-mediated event.