E-selectin is a type of protein found on the surface of endothelial cells, which line blood vessels. It plays a crucial role in the immune response by helping white blood cells adhere to the blood vessel walls. This adhesion is essential for the movement of these cells to sites of inflammation or injury. When inflammation occurs, E-selectin is expressed in response to signals from the immune system. It binds to specific carbohydrates on the surface of white blood cells, facilitating their migration out of the bloodstream and into tissues where they are needed to fight infection or heal damage.