This is a type of cell in your immune system — the collection of cells in your body that fight off infections. Neutrophils are the most abundant immune cells in the body. They form in the bone marrow and circulate in the blood. Each neutrophil lives only a few days, but while they are alive they are on constant patrol.
Neutrophils are one of the first cell types to arrive when an infection takes hold. When a cell in the body is infected with a harmful microbe, the cell sends out a chemical distress signal. When neutrophils detect this signal, they crawl toward the infected cell. Once they arrive, they release cytokines — chemicals that serve as an additional alarm call. These chemicals summon more immune cells to the scene.
But neutrophils don’t stop there. They can engulf microbes and digest them. Neutrophils can also spew out antimicrobial chemicals to kill bigger invaders. They can even release a web of fibers that trap and kill invading microbes.