Leukemia is a disease of the white blood cells, specifically an overproduction of white blood cells. In fact, the word "leukemia" comes from two Greek words meaning "white blood": leukos, meaning white, and haima, blood. Understanding normal white blood cells, or leukocytes, makes it easier to understand the results of the white blood cell (WBC) count laboratory test. The types of white cells found in peripheral (or circulating) blood and profiled in the results of the WBC count are neutrophils, eosinophils, basophils, monocytes, and lymphocytes.
These five types of WBCs can be further divided into two groups, granulocytes (also known as polymorphonuclear leukeocytes) and mononuclear leukocytes. Neutrophils, eosinophils, and basophils are granulocytes, and have cytoplasm which has a grainy appearance (the reason they are called "granulocytes") and they have nuclei that are elongated and have several rounded portions called lobes when viewed under a microscope. The lobed nuclei are the reason these cells are called polymorphonuclear; the lobes are connected only by thin threads, and so it almost looks like many nuclei instead of just one.
By contrast, mononuclear leukocytes may have nuclei that are indented, but not so deeply divided that they appear to have multiple nuclei. Mononuclear leukocytes are also called "non-granulocytes." Each type of leukocyte, or WBC, has its own function in supporting the immune system, and elevated numbers of WBCs in the blood can be one of the first indicators of leukemia.
Neutrophils:
Neutrophils are the most plentiful leukocytes in the bloodstream, and take their name ("neutro" meaning neutral, and "phil" from philia, meaning "loving") from the way they can be stained with dye for viewing under a microscope. Neutrophils don't show a special affinity (love) for either acidic or basic stains, and can be stained by either type of stain. The main function of neutrophils is to break down bacterial cells in the body with enzymes stored in the grains in the neutrophils' cytoplasm.
Eosinophils:
Eosinophils are so called because they stain red when microscopic slides of them are dyed with acidic stains like eosin, and their size is similiar to that of the neutrophil. Scientists are not sure of the exact mechanism of eosinophils, but numbers of these cells in the blood increase in the presence of allergens (substances which cause allergies) or parasites.
Basophils:
Basophils are the least plentiful leukocytes in the bloodstream, and are named because they stain for viewing under the microscope when treated with basic stains. Basophils are similiar in size to neutrophils and eosinophils, and are involved in beginning the process of inflammation, one of the body's ways of responding to injury or irritation that's characterized by redness, warmth, swelling, and pain in one specific place. During this process, basophils can migrate from the bloodstream to the site of inflammation.
Monocytes:
Monocytes are mononuclear leukocytes that typically have a horseshoe or kidney-shaped nucleus, and are the largest type of white blood cell. Monocytes help devour microorganisms that don't belong in the body by surrounding them and digesting them. They also devour and digest body cells that have died or are old, and also help remove other unneeded cellular material from the body.
Lymphocytes:
Lympocyte are the second most plentiful type of leukocyte in the blood, and are smaller than other types of leukocytes. Lymphocytes use the blood to travel around the body, but can wander freely in other types of tissues and return to the blood using the
lymphatic channels, vessels that are part of the
lymphatic system. The lymphocyte takes its name from its unique method of travel within both the blood and the lymphatic system.
Source:
King, David. "SIU School of Medicine Histology Intro." 8 Oct 2007. Southern Illinois University School of Medicine. 2 June 2008.
