Neutrophils are a type of phagocyte and are normally found in the bloodstream. During the beginning (acute) phase of inflammation, particularly as a result of bacterial infection, environmental exposure, and some cancers, neutrophils are one of the first responders of inflammatory cells to migrate toward the site of inflammation. They migrate through the blood vessels and then through interstitial tissue, following chemical signals such as Interleukin-8 (IL-8), C5a, fMLP, Leukotriene B4, and H2O2 in a process called chemotaxis. They are the predominant cells in pus, accounting for its whitish/yellowish appearance.