What are white blood cells?
White blood cells (WBCs), also called leukocytes, are the cells of the immune system that protect the body against infectious disease, allergens, and other foreign invaders.
The number of white blood cells in the blood can often tell the health care provider if a disease is present. The normal number of white blood cells is usually between 4,000–11,000 cells per microliter of blood. Having more WBCs in the blood than normal is called leukocytosis, and having fewer WBCS than normal is called leukopenia.
There are many types of white blood cells, each with very specific jobs:
Neutrophils, are the most common WBC. Around 60-70% of circulating leukocytes are neutrophils. These cells defend the body against bacterial or fungal infection by digesting bacteria in a process called phagocytosis.
Eosinophils are fewer in number, but have an important role in allergic reactions and other functions. Only about 2-4% of WBCs are eosinophils, but that number rises in response to allergies, parasites, autoimmune diseases such as rheumatoid arthritis (RA), and in certain diseases of the spleen and central nervous system.
Basophils respond to allergens and other invaders by releasing two chemicals that aid in the body’s defenses: histamine and heparin. Histamine is responsible for widening blood vessels and increasing the flow of blood to injured tissue, whereas heparin is an anticoagulant that prevents blood clotting.
B cells make antibodies that can bind to pathogens, and enhance their destruction.
T cells come in 3 types: helper cells, cytotoxic cells and natural killer cells. Together, they help coordinate the immune response and maintain immune system integrity.
Monocytes not only share the infection-eating function of neutrophils, but also present pieces of disease-carrying bacteria and other organisms to T cells so that the they may be killed.
What are common white blood cell disorders?
Two major types of white blood cell disorders are proliferative disorders and leukopenias.
In the proliferative disorders, there is an increase in the number of white blood cells. This increase is comonly a reaction due to infection, but may, less commonly, be related to some types of cancer.
In leukopenias, there is a decrease in the number of white blood cells, which can be caused by cells being destroyed by an illness or by other conditions.
One particular kind of leukopenia is neutropenia, which means that there are fewer neutrophils in the blood. Outside causes of neutropenia include chemotherapy, medications, toxins, and viral illness. Disorders that can cause neutropenia within the body include defects in bone marrow (where all WBCs are created), or conditions in which a person is born with too few neutrophils.
Both leukopenia and neutropenia can dause deficiency in the immune system, which can increase risk of infection. Treatment of leukopenia and neutropenia are aimed at the underlying cause of the change in cell counts.
An increase in the number of white blood cells in circulation is called leukocytosis. Leukocytosis can be caused by inflammation and other disorders that result in increased bone marrow production (which leads to greater production of WBCS), too many WBCs being released from bone marrow all at once, or disorders that prevent WBCs from attaching to tissues and being absorbed by the body’s tissues.
Our approach to white blood cell disorders
All of the disorders discussed above have to do with the number of white blood cells. Other disorders include those in which the number of white blood cells is normal but the cells do not function normally. If white blood cells form abnormally, it can affect their ability to perform normal functions such as killing bacteria.
Specialized testing is available through our center to further determine what the treatment will be.