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4
7 INTEGRIN-DEPENDENT ADHESION OF LYMPHOCYTES TO MADCAM-1 UNDER SHEAR-FLOW
1 Liver Research Group, University of Birmingham, United Kingdom
2 Liver Research Group, University of Birmingham, Edgbaston, BIRMINGHAM, United Kingdom
3 Liver Research Group, University of Birmingham, Birmingham, west mids, United Kingdom
4 Liver Research Group, University of Birmingham, United Kingdom; Liver Research Group, University of Birmingham, Birmingham, west mids, United Kingdom
* To whom correspondence should be addressed. E-mail: d.h.adams{at}bham.ac.uk.
Inflammatory bowel disease is characterised by the recruitment of lymphocytes to the gut via mucosal vessels. Chemokines are believed to trigger
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1 and
4
7 integrin-mediated adhesion to vascular cell adhesion molecule-1 (VCAM-1) and mucosal addressin cell adhesion molecule-1 (MADCAM-1) on mucosal vessels although the contribution of each pathway and the chemokines involved are not well-characterised. These interactions occur under conditions of hemodynamic shear which is critical in determining how lymphocytes integrate chemokine signals to promote transmigration. To define the role of specific chemokines in mediating lymphocyte adhesion to VCAM-1 and MADCAM-1 we studied the effect of immobilised chemokines to activate adhesion of human lymphocytes in a flow-based adhesion assay. Adhesion to immobilised MAdCAM-1 was
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7 dependent with no contribution from
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1, whereas
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1 mediated rolling and static adhesion on VCAM-1. We show that immobilised CCL25 and CCL28 can both trigger
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7-dependent lymphocyte arrest on MADCAM-1 under shear, highlighting a potential role for these chemokines in the arrest of lymphocytes on post-capillary venules in the gut. Neither had any effect on adhesion to VCAM-1 suggesting they selectively trigger
4
7-mediated adhesion. Immobilised CCL21, CCL25, CCL28 and CXCL12 all converted rolling adhesion to static arrest on MAdCAM-1 by activating lymphocyte integrins, but only CCL21 and CXCL12 also triggered a motile phenotype characterized by lamelipodia and uropod formation. Thus
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1/VCAM-1 and
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7/MAdCAM-1 operate independently to support lymphocyte adhesion from flow and chemokines may act in concert with one chemokine triggering integrin-mediated arrest and a second chemokine promoting motility and transendothelial migration.
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