Appendix to Chapter 5 Human phagocytes: useful dealers of death and destruction

Abstract The production of O2• ™ and H202 by some types of white blood cell is one example of a useful role for these oxygen-derived species, but it can become a source of tissue damage if their production is too widespread or goes on for too long. Human blood contains large numbers of neutrophils (about 2.5 —7.5 million per ml in healthy subjects), amoeba-like white blood cells whose function is to recognize, engulf, and destroy foreign organisms, such as bacteria and viruses (Figure Al). This process of engulfment is called phagocytosis, and cells which can do it are often called phagocytes. Indeed, infection usually causes a rise in the ‘ white blood cell count’ (number of cells per ml of blood) as the body mobilizes more of these cells to fight the infection.