P-selectin is a protein found on the surface of activated platelets and endothelial cells, which line blood vessels. It plays a crucial role in the process of inflammation and blood clotting by helping white blood cells adhere to the blood vessel walls. This adhesion is essential for the immune response, allowing white blood cells to reach sites of injury or infection. When P-selectin is activated, it binds to specific carbohydrates on the surface of white blood cells, facilitating their movement out of the bloodstream and into tissues. This interaction is vital for the body's defense mechanisms and helps regulate the healing process after injury.