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Immuno-electron microscopic analysis of the distribution of ICAM-1 in human inflammatory tissue
K A Brown1, M E Perry, Y Mustapha
1Division of Immunology, United Medical School St Thomas' Hospital Campus, London, UK.
Insights
Intercellular Adhesion Molecule-1 (ICAM-1) is primarily found on high endothelial venules (HEV) in tonsils and rheumatoid arthritis synovia. This molecule likely facilitates lymphocyte interaction with endothelial cells in inflamed tissues.
Area of Science:
- Immunology
- Cell Biology
- Rheumatology
Background:
- Intercellular Adhesion Molecule-1 (ICAM-1) plays a role in immune cell trafficking.
- Understanding ICAM-1 expression is crucial for studying inflammatory conditions like rheumatoid arthritis.
Purpose of the Study:
- To investigate the expression patterns of ICAM-1 on vascular endothelium in human tonsils and rheumatoid arthritis synovia.
- To elucidate the role of ICAM-1 in lymphocyte interaction with endothelial cells in inflammatory environments.
Main Methods:
- Immuno-electron microscopy was employed to visualize ICAM-1 localization.
- Analysis was performed on human tonsil tissue and synovia from rheumatoid arthritis patients.
Main Results:
- ICAM-1 expression was concentrated on high endothelial venules (HEV) in parafollicular tonsils and synovial villi, areas rich in perivascular lymphocytes.
- Weak ICAM-1 expression was observed on the endothelium of capillaries, venules, and sinusoids.
- ICAM-1 was localized to the luminal and lateral surfaces of endothelial cells, not the abluminal surface.
Conclusions:
- ICAM-1 preferentially localizes to HEVs in inflammatory tissues, suggesting a role in lymphocyte adhesion.
- ICAM-1 may mediate the initial interaction of circulating lymphocytes with high endothelial cells.
- ICAM-1's role in lymphocyte transmigration through the entire vessel wall appears limited.
Abstract:
An immuno-electron microscopic analysis was undertaken to determine ICAM-1 expression on vascular endothelium in human tonsils and in synovia from patients with rheumatoid arthritis. ICAM-1 was preferentially expressed on high endothelial venules (HEV) located in the parafollicular regions of the tonsils and HEV located in the villous processes of the synovia. On both tissues, these areas contained the greatest number of perivascular lymphocytes. In contrast, ICAM-1 was only weakly expressed on the low endothelium lining capillaries, venules and sinusoids. In both tonsils and synovia, ICAM-1 was confined to the luminal and lateral surfaces of the endothelial cells and absent from the abluminal surfaces adjacent to the basement membrane. We propose that in inflammatory tissues, ICAM-1 mediates the interaction of circulating lymphocytes with the high endothelial cells, but may not have a major role in promoting their migration through the whole thickness of the blood vessel wall.
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