Selectins are a family of "sticky" molecules (adhesion molecules) that are expressed on the surface of the cells lining the inside of blood and lymph vessels (endothelial calls). Selectins and other adhesion molecules act as hooks to capture white blood cells (leukocytes) and bring them to the site of an infection.
Endothelial cells express selectins and other adhesion molecules in reponse to receiving chemical signals (cytokines) from white blood cells already present at the site of an infection in the bodily tissue surrounding the blood vessel. Once captured, a leukocyte is rolled along from the selectin to selectin until it reaches the edge of the endothelial cell. Once there, other adhesion molecules, such as ICAM and PECAM-1, take over and manipulate it through the gap between the endothelial cells from where it follows the gradient of cytokines to the infection site.
Overview of Selectins
Adhesion Molecules: Selectins