Integrins are a large family of molecules that are expressed on the surface of cells. Their role is to bind with other complimentary molecules expressed by other cells. A sub-group of integrins, called b2 integrins, are exclusively expressed by white blood cells (leukocytes).
Integrins, together with other families of molecules, including selectins, ICAM and VCAM, are known as adhesion molecules.
B2 integrins are important in the summoning of leukocytes to the site of an infection. Leukocytes already present on the scene secrete signalling molecules called cytokines. These are detected by the cells on the inner layer of blood vessels (endothial cells) which in turn express adhesion molecules, especially a group called selectins. These selectins stick to the integrins on the surface of leukocytes passing through the blood vessel. The leukocytes then squeeze through the endothelium and follow the gradient of chemokines to the site of the infection.
Hospital Practice: Integrins: The Molecular Glue of Life
The Integrin Page