The cellular components in our blood perform amazing functions. Red blood cells are an efficient and effective transport vessel for the delivery of oxygen to every cell and removal of cellular waste in the form of carbon dioxide. Without platelets to plug the holes and start the clotting cascade, we would bleed to death. But for a higher order of functionality, the white blood cells reign.
White blood cells, or WBCs, can follow internal signals directing them to areas of infection or to unwelcome foreign objects that find their way past our outer defenses.
Once on scene, the WBCs help rid us of these undesirable visitors. White blood cells can change their shape and become mobile, so they can leave the blood stream and maneuver through tissue to get at their intended target.
Certain WBCs produce antibodies that help fight infection and others can transform into killer cells. WBCs also perform the clean up, the removal of the dead bacteria or other pathogens or the disassembled foreign object and the WBCs that have died in the defense process1.
Discovery
The compound microscope was invented in the year 1590, allowing scientists to explore the microscopic world. Seventy years later, a scientist named Swammerdam was the first to describe red blood cells. And it took another 150 years for scientists to find white blood cells, first described in 18432.
Part of the problem with WBCs is that they aren’t really white. Without special stains, they are difficult to see under the microscope but once those stains became available, they revealed that all white blood cells are not the same.
Differential
White blood cells are also called leukocytes because ‘leuko’ is the Greek prefix for white. We can’t have just one name for something in our profession -- that would be too easy. There are five types of leukocytes, each with different functions.
These white blood cells are divided into two clans; those with multi-lobed nuclei and granules and those with a single nucleus and no granules3.
When these different WBC types are identified and counted under a microscope or by a machine, the number and type of white blood cell can point us to different disease processes such as infection, inflammation or leukemia.
Granulocyte clan
Granulocytes, or polymorphonuclear (many nuclei) leukocytes, include neutrophils, eosinophils and basophils. These are identified and named by the type and amount of dye they will absorb.
The suffix ‘phil’ means to like or attract, thus neutrophils are a neutral color because they don’t stain well and end up with a pale pink color. Eosinophils take up an eosin or red dye, and basophils prefer blue, ‘baso’ meaning blue or basic.
Photos provided by the New York State Department of Health
The neutrophil is the most common type of WBC and responds to bacterial infections along with participating in other inflammatory processes. Immature neutrophils or granulocytes are called bands and are a sign that the bone marrow has run out of mature neutrophils and now has to send the youngsters out to work.
The appearance of bands on the differential white blood cell count usually means there is an acute infection in progress.
Eosinophils may increase during allergic reactions, inflammatory diseases like rheumatoid arthritis and parasitic infections. One may find eosinophils in the nasal discharge of someone suffering with allergic rhinitis.
Basophils are the least common granulocyte type and are involved in the inflammatory and allergic processes in our body.
Mononuclear clan
These leukocytes or WBCs have a single nucleus and no granules, and include lymphocytes and monocytes.
Monocytes like to morph into larger cells, called macrophages or ‘big eaters,’ and help with the clean up at the sight of infection or inflammation. They also contribute to inflammatory and allergic activity.
Lymphocytes come in two varieties, B cells and T cells. B cell lymphocytes produce antibodies, which identify and destroy pathogens and other uninvited guests.
T cell lymphocytes provide attack cells that can kill and remove undesirables from our body, including cancer cells.
Unfortunately the B and T cells can also cause harm when they recognize certain cell types in our own body as a threat. This occurs with auto-immune diseases like rheumatoid arthritis.
In RA, the body thinks our joint cartilage is a non-native or abnormal cell type and a potential menace, and tries to destroy the cartilage. You can see and feel the resultant auto-destructive process with the typical hot, tender, swollen joints during an acute flare of rheumatoid arthritis.
Summary
When you look at the white blood cell section of a complete blood count or CBC, use the laboratory’s standard for the normal count range printed with the report to determine if the overall white blood cell count or a specific leukocyte number is increased or decreased.
The information provided may aid in understanding your patient’s disease process.
References
1. CBC: MedlinePlus Medical Encyclopedia. Available at http://www.nlm.nih.gov/medlineplus/ency/article/003642.htm Accessed January 15, 2012
2. Hajdu SI. A Note from History: The Discovery of Blood Cells. Annals of Clinical & Laboratory Science 2003;33:237-238.
3. Learn About White Blood Cells. Available at http://www.uwosh.edu/med_tech/teaching/ElementaryHemeWeb/LEARN%20ABOUT%20WBCS.htm Accessed January 17, 2012
