INTEGRIN FUNCTION IN LEUKOCYTE-MEDIATED INFLAMMATION-ACTINOPATHIES IN IMMUNE DISEASES.

Integrins play a critical role in leukocyte recruitment and activation within inflamed tissues. These heterodimeric cell-surface receptors recognize ligands on vascular endothelium or extracellular matrix to initiate intracellular signals leading to leukocyte adhesion, migration, and activation. The best-described role for integrins is in the leukocyte adhesion cascade, which is the process by which leukocytes exit the blood vasculature and enter the tissues in response to infection or injury. During the adhesion cascade, integrin signaling is required for changes in leukocyte cytoskeletal structure required for firm adhesion to endothelial cells, followed by intravascular crawling and transmigration from the bloodstream into the tissues. During this process, integrin signaling augments leukocytes' inflammatory and antimicrobial functions. Mutations in the genes encoding integrins or their downstream signaling molecules result in immunodeficiency and altered tissue repair following injury. Many of these mutations occur in proteins involved in the reorganization of the actin cytoskeleton and have become known as actinopathies, the classic example being Wiskott-Aldrich syndrome. We describe a new actinopathy-type mutation in the integrin signaling molecule SKAP2, which is associated with autoimmunity and type 1 diabetes.