Selectins are a type of cell adhesion molecule that play a crucial role in the immune system. They help white blood cells adhere to the walls of blood vessels, allowing them to exit the bloodstream and reach sites of inflammation or injury. There are three main types of selectins: E-selectin, P-selectin, and L-selectin, each with specific functions and locations in the body. These molecules are essential for the process of leukocyte rolling, which is the initial step in the immune response. By binding to carbohydrates on the surface of leukocytes, selectins facilitate their movement toward areas where they are needed, contributing to the body's defense against infections and promoting healing.