A neutrophil is a type of white blood cell that plays a crucial role in the immune system. These cells are the body's first line of defense against infections, particularly bacterial infections. Neutrophils are produced in the bone marrow and are characterized by their ability to engulf and destroy pathogens through a process called phagocytosis. Neutrophils are the most abundant type of white blood cells, making up about 50-70% of all leukocytes in the bloodstream. They have a short lifespan, typically living only a few hours to a few days, but they are essential for maintaining health by responding quickly to sites of infection or injury.