One of the cells the body makes to help fight infections. There are several types of white blood cells (leukocytes). The two most common types are the lymphocytes and neutrophils (also called polymorphonuclear leukocytes, PMNs, or “polys”).
Lymphocytes are made in lymphoid tissue in the spleen, lymph nodes, and thymus gland. There are different kinds of lymphocytes. Lymphocytes identify foreign substances from germs (bacteria or viruses) in the body and produce antibodies and cells that specifically target them. It takes from several days to weeks for lymphocytes to recognize and attack a new foreign substance.
Neutrophils are also major players in the body’s defense against bacterial infections. Neutrophils are made in the bone marrow and circulate in the bloodstream. Neutrophils move out of the blood vessels into the infected tissue to attack the bacteria. The pus in a boil (an abscess) is made up largely of neutrophils. Normally a serious bacterial infection causes the body to produce an increased number of neutrophils, resulting in a higher than normal white blood cell count (WBC). When the WBC is low, there may not be enough neutrophils to defend against bacterial infections.
The white blood cell count is done by counting the number of white blood cells in a sample of blood. A normal WBC is in the range of 4,000 to 11,000 cells per microliter. A low WBC is called leukopenia. A high WBC is termed leukocytosis.
A normal absolute neutrophil count (ANC) is in the range of 1,500 to 8,000 cells per microliter. If the ANC is below 500 for an extended period of time, the risk of serious bacterial infection may increase significantly. A low neutrophil count is called neutropenia.
- White blood cell count
The number of white blood cells (WBCs) in the blood. The WBC is usually measured as part of the CBC (complete blood count). White blood cells are the infection-fighting cells in the blood and are distinct from the red (oxygen-carrying) blood cells known as erythrocytes. There are different types of white blood cells, including neutrophils […]
- White cell differential, automated
A machine-generated percentage of the different types of white blood cells, usually split into granulocytes, lymphocytes, monocytes, eosinophils, and basophils.
- White coat hypertension
A transient increase in blood pressure (hypertension) that is triggered by the sight of medical personnel in white coats (or other attire). Ideally, people so affected should do their best to relax when in the medical office.
- White matter
The part of the brain that contains myelinated nerve fibers. The white matter is white because it is the color of myelin, the insulation that covers nerve fibers.
- White phosphorus
A waxy solid which burns easily and is used in chemical manufacturing and smoke munitions. It is also used by industry to produce phosphoric acid and other chemicals for use in fertilizers, food additives, and cleaning compounds. Small amounts of white phosphorus were used in the past in pesticides and fireworks. Breathing white phosphorus for […]