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Differential adhesion of granulocytes to five distinct phenotypes of cultured microvascular endothelial cells
K Ley1, P Gaehtgens, K Spanel-Borowski
1Department of Physiology, Freie Universität Berlin, Germany.
Abstract:
Adhesion of isolated human polymorphonuclear granulocytes (PMNs) to five different phenotypes of cultured microvascular endothelial cells derived from bovine corpora lutea was investigated by measuring the myeloperoxidase content of cell lysates. Untreated and interleukin 1 (IL-1) -pretreated confluent monolayers were overlaid with unstimulated and phorbol ester (PMA)-stimulated PMNs in the absence and presence of the monoclonal antibody IB4 recognizing and functionally blocking beta 2 (CD18) of the leukocyte integrins. Unstimulated PMN adhesion was highest on type 4, followed by type 3 and 5 endothelial cells. This adhesion was not inhibited by treatment with IB4. IL-1 pretreatment of endothelial cells resulted in a significant increase of PMN adhesion on types 1, 2, and 4, most of which was also beta 2 integrin-independent. PMA-stimulation of PMNs increased adhesion to maximal values on cell types 1 and 5, which was largely blocked by IB4. Type 2 endothelial cells supported significantly less PMA-stimulated PMN adhesion than all other types. In the presence of IB4, adhesion of PMNs to untreated and IL-1-pretreated type 3 and 4 endothelial cells was significantly reduced by PMA. This reduction of beta 2 integrin-independent adhesion by PMA stimulation is compatible with possible shedding of the lectin-like leukocyte adhesion molecule, L-selectin, from PMNs. Differential PMN adhesion may reflect distinctive expression of endothelial adhesion molecules in different phenotypes of microvascular endothelial cells. Endothelial specialization within the microcirculation may have important functional consequences for the inflammatory response in vivo.
Insights
Human white blood cells (PMNs) show varied adhesion to different bovine endothelial cell types. Interleukin-1 and PMA stimulation alter adhesion, with beta 2 integrin playing a key role in some interactions.
Area of Science:
- Immunology
- Cell Biology
- Endothelial Cell Biology
Background:
- Polymorphonuclear granulocytes (PMNs) are key immune cells involved in inflammation.
- Microvascular endothelial cells form the inner lining of blood vessels and play a critical role in regulating immune cell trafficking.
- Endothelial cell phenotypes can differ in their expression of adhesion molecules, influencing immune cell interactions.
Purpose of the Study:
- To investigate the adhesion patterns of human PMNs to distinct phenotypes of bovine microvascular endothelial cells.
- To determine the role of beta 2 integrins and stimulation with Interleukin-1 (IL-1) and phorbol ester (PMA) in PMN-endothelial cell adhesion.
Main Methods:
- Cultured bovine microvascular endothelial cells of five different phenotypes were used.
- Human PMNs were isolated and adhered to endothelial cell monolayers.
- Myeloperoxidase content of cell lysates measured PMN adhesion.
- Monoclonal antibody IB4, targeting beta 2 (CD18) integrins, was used to assess integrin-dependent adhesion.
- Endothelial cells were pretreated with IL-1, and PMNs were stimulated with PMA.
Main Results:
- Unstimulated PMN adhesion varied significantly among endothelial cell types, with highest adhesion on type 4.
- IL-1 pretreatment increased PMN adhesion on types 1, 2, and 4, largely independent of beta 2 integrins.
- PMA stimulation increased PMN adhesion on types 1 and 5, which was mostly blocked by IB4 (beta 2 integrin-dependent).
- Type 2 endothelial cells showed significantly less PMA-stimulated PMN adhesion.
- PMA reduced beta 2 integrin-independent adhesion on types 3 and 4, suggesting L-selectin shedding.
Conclusions:
- Differential adhesion of PMNs to various endothelial cell phenotypes suggests specialized expression of adhesion molecules.
- Endothelial cell specialization within the microcirculation may significantly impact in vivo inflammatory responses.
- Beta 2 integrins and other adhesion molecules contribute differentially to PMN adhesion under various stimulation conditions.