What it means
A helper molecule made from the vitamin niacin. Cells use it to build fats and other molecules and to protect themselves from damage. White blood cells use an enzyme called NADPH oxidase to make the bursts of reactive oxygen that kill swallowed bacteria and fungi; children born without a working enzyme (chronic granulomatous disease) get repeated serious infections.
Related terms
immune system
The body's defense system of cells, tissues and organs that fights germs and other foreign substances.
immunodeficiency
A state in which the immune system is weaker than normal and cannot fight infection well.