Peripheral Vascular Surgery Society

#5. CYTOTOXIC MOLECULE EXPRESSING T-CELLS IN ABDOMINAL AORTIC ANEURYSM (AAA) WALL.

A. Hewitt, BSc, K. MacLennan, MD, FRCS, R.W. Soames, PhD, R. Macadam, FRCS, and D.J.A. Scott, MD, FRCS

St. James's Hospital, Leeds, United Kingdom

Aims: Marked inflammatory infiltrates within AAA are associated with increased matrix metalloproteinase expression and subsequent extracellular degradation. Previous investigators have identified cell mediate immunity as an important factor in the pathogenesis of AAA. The aim of this study is to identify the inflammatory cells present in AAA tissue.

Methods: Immunohistochemistry using T-cell markers was carried out on 33 samples of formalin fixed, paraffin-embedded aortic walls obtained at the time of elective AAA surgery. Sections were stained with hemotoxylin and eosin, and monoclonal antibodies to CD3, CD4 and CD8. Activated cytotoxic cells were detected with monoclonal antibodies to CD57, present on natural killer (NK) cells and TIA-1, a membrane protein present in cytotoxic T lymphocytes and NK cells. Sections were scored on the medial infiltrate by a consultant hematologist (KM) and the degree of staining graded as absent, mild, moderate or strong.

Results: An inflammatory infiltrate was present in 94% of patients (31/33) and all infiltrates contained mature CD3 + T-lymphocytes. 79% of AAA walls contained CD4 +T-lymphocytes and 91% contained CD8 +T-lymphocytes. The numbers of CD4+ and CD8+ T-lymphocytes in each infiltrate were broadly similar. CD57+ NK cells were detected in 39% (13/33) of aneurysms, demonstrating a mild infiltrate only. However, 91% (30/33) of AAA walls demonstrated TIA-1 positive cells, which in 65% (19/33) of cases were moderate or strong infiltrates, indicating the presence of activated cells with cytotoxic potential.

Conclusions: These results demonstrate that cytotoxic molecule expressing T-cells are frequently present in the media of AAA and may therefore contribute to arterial wall injury and disease progression.

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Last Updated 5/28/99