Neutrophils are blood cells that are produced in the marrow, or core of the bones.
Neutrophils are very important because they fight infection. When bacteria invade the body, a chemical signal is sent out and the neutrophils, like fire fighters responding to a blaze, rush to the site of infection. The bone marrow also responds by speeding up its production of neutrophils to replace those involved in fighting the infection. If, however, production of new neutrophils is suppressed or slowed down, a shortage may develop, and any infection can overwhelm the few neutrophils available. Therefore, a person with only a few neutrophils is at particular risk for developing a serious bacterial infection.