Recruitment of neutrophils into the tissue during inflammation is a crucial component of the immune response. This study aimed to further understand the role of intercellular adhesion molecule-2 (ICAM-2) in this process. Endothelial cell (EC) ICAM-2 has been implicated in neutrophil extravasation however, its precise role in this process is largely unknown. To address this, the current investigation examined the expression and functional role of ICAM-2 in neutrophil-EC interactions in vivo. Analysis of EC ICAM-2 expression was performed in the mouse cremaster muscle using immunofluorescent staining and confocal microscopy. A high EC body expression of ICAM-2 relative to that of EC junctions in post-capillary venules was observed. It was therefore hypothesised that ICAM-2 could potentially be involved in both luminal neutrophil-EC and junctional interactions. This hypothesis was analysed using confocal intravital microscopy (IVM) of cremaster muscles from WT or ICAM-2 KO Lys-eGFP-ki mice (express fluorescent neutrophils) in conjunction with fluorescent labelling of ECs. Neutrophil crawling and transendothelial migration (TEM) dynamics in IL-1β-stimulated post-capillary venules was analysed. A role for ICAM-2 in supporting speed and continuity of crawling and the initiation of TEM was demonstrated. Using functional blocking mAb to MAC-1 in WT and ICAM-2 KOs, the role of ICAM-2 in neutrophil crawling was demonstrated to be governed through a potential interaction with neutrophil MAC-1. It is therefore possible that non-junctional EC ICAM-2 has important roles in regulating neutrophil polarisation during crawling whilst junctional ICAM-2 mediates the opening of EC junctions and/or influencing the site of ‘preferred’ TEM. This study provides the first in vivo evidence for the ability of ICAM-2 to support neutrophil crawling and the initiation of TEM in IL-1β-induced neutrophil extravasation. To extend the above findings in a complex vascular injury model, a cremasteric Shwartzman Reaction, amenable to IVM analysis, was also developed as part of this project.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:667124 |
| Date | January 2013 |
| Creators | Halai, Krishma |
| Publisher | Queen Mary, University of London |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://qmro.qmul.ac.uk/xmlui/handle/123456789/8475 |
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