Integrins are a large family of heterodimeric receptors (consisting of an #alpha# and a #beta# chain) that mediate cell-cell and cell-extracellular matrix (ECM) recognition in nearly all cells. Many #alpha# and #beta# chains have been discovered, and most #beta# chains can associate with more than one #alpha# chain, creating a large repertoire of at least 22 receptor combinations. Integrins interact with the actin cytoskeleton via talin, #alpha#-actinin and vinculin and, thus, represent a mechanismfor plasma membrane-cytoskeleton association. The integrins expressed in leukocytes, their expression pattern, and ligand specificity have been reviewed(1). The #beta#_2 family of integrins are expressed exclusively on leukocytes and are a major class of integrins involved in regulating effector functions in lymphocytes and phagocytes. Integrins have the ability to mediate activation, adhesion, migration, and phagocytosis by interacting with ligands experessed in their environment. Cellular and matrixprotein ligands are primarily found in inflamed tissues, allowing leukocytes to sense an inflammatory locus.
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