White blood cell
The number of white blood cells increases when a person is fighting infection or disease and decrease when a person is healthy. The white blood cell is very important. Without them, a person would not be able to live.
Types of white blood cells [change]
Lymphocytes are round white blood cells a bit bigger than a red blood cell. Their center is round and they have little cytoplasm. Part of the lymphatic system, these target specific germs or poisons using their antibodies. There are three known types of lymphocytes, called T-cells, B-cells and natural killer cells.
Monocytes are reserve cells which turn into macrophages and dendritic cells, which work together in tissues to fight disease. Monocytes have a kidney bean shaped center and lots of cytoplasm. They may appear as macrophages in a non-round shape when they pass through tissue to eat germs, "junk" cells, and dead cells.
The next three types of white blood cells are referred to as granulocytes since they all contain rough, grain-like particles that assist in attacking viruses and bacteria. Granulocytes are also called polymorphonuclear leukocytes because of the shape of the nucleus, which has three segments.
Neutrophils are the most abundant type of white blood cells in mammals, 70% of leukocytes. They are an essential part of the immune system. They get to the site of an injury within minutes, and make up much of the content of pus. They have a short life-span of a couple of days.
The nucleus, which looks like a string of beads, does not take up stain strongly. Like phagocytes, they actually eat the bacteria and dead cells. They also release a bunch of proteins which work to damage the bacteria.
Basophils are rare granulocytes, making up only 0.1 to 0.3% of leukocytes. The nucleus is hidden by granules which turn dark blue in color when stained. Basophils carry histamine and heparin, and other protein chemicals. They appear at the sites of ectoparasite infection, or allergies. Exactly how they operate is not yet clear.
Eosinophils, or acidophils, are leukocytes. They are one of the immune system components which combat parasites and certain infections. As with mast cells and basophils, they part causes of allergy and asthma. Eosinophils are round cells with a lobed nucleus and granules which turn red when stained. These granules are packed with proteins that can be poured out to help destroy invaders.
Cell testing [change]
A test called a differential count shows how many white blood cells there are in a person's blood, and how many of each type are there.
- Janeway, Charles; Paul Travers, Mark Walport, and Mark Shlomchik (2001). Immunobiology; 5th ed. New York and London: Garland Science. ISBN 0-8153-4101-6. http://www.ncbi.nlm.nih.gov/books/bv.fcgi?call=bv.View..ShowTOC&rid=imm.TOC&depth=10..
- Abbas AK and Lichtman AH 2003. Cellular and molecular immunology. 5th ed, Saunders, Philadelphia. ISBN 0-7216-0008-5