Detection of High-Affinity α4-Integrin Upon Leukocyte Stimulation by Chemoattractants or Chemokines

TL;DRAbstract

On circulating leukocytes, including monocytes and lymphocytes, α4-integrins are expressed in a low-affinity conformation. Low-affinity interactions with its ligand, vascular cell adhesion molecule-1 (VCAM-1), result in leukocyte tethering and rolling under flow (,), whereas high-affinity interactions mediate leukocyte arrest (). Rapid triggering of integrin-mediated arrest occurs upon leukocyte stimulation with chemoattractants and chemokines (,). In monocytes, α4-integrin affinity is rapidly upregulated and mediates arrest (). Changes in affinity may be monitored by binding of a soluble ligand because high-affinity α4-integrins form stable interactions with a soluble ligand, unlike low-affinity α4-integrins (). In this protocol, binding of recombinant chimeric human VCAM-1 is used to identify high-affinity α4-integrins by flow cytometry. In addition, a recently reported method for monitoring α4-integrin affinity in real time using a ligand-mimetic peptide, which contains the leucine,

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