Recruitment of immune cells, innate immunity. This illustration shows the phenomenon of diapedesis. This phenomenon corresponds to the passage of immune cells into tissues from the bloodstream. It takes place in several phases. The first phase is the capture phase. The immune cell in the blood vessel comes close to the endothelial cells (endothelium of the blood vessel). The second phase is the adhesion and rolling phase. It activates immune cells. It expresses in an increased manner the adhesion molecules expressed by the immune cells and those presented on the surface of the endothelium. Then the third phase is the adhesion phase. The cell adheres strongly to the endothelium thanks to the numerous adhesion molecules. Finally, the fourth phase is the migration phase. The recruited cell crosses the endothelium to the site of inflammation. Then the immune cell will activate and produce cytokines. Therefore the production of cytokines maintains or amplifies the inflammatory response at the site of infection.