Like other blood cells, white blood cells are produced by the bone marrow. White blood cells are far less numerous than red blood cells as there are about 700 red blood cells to every white blood cell in circulation. The biological roles of white blood cells are complicated and diverse. Understanding the functions of white blood cells is important to describing and treating a number of diseases.
Kill and Eat Bacteria and Fungi
Neutrophils are the most abundant type of white blood cells. The Merck Manual explains how neutrophils serve to protect the body from invading bacteria as well as fungi. When neutrophils encounter an invading bacterium, they can release toxic chemicals that kill bacteria. Neutrophils can also eat bacteria through the process of phagocytosis. Monocytes, another type of white blood cell, can also scavenge the body for invading microorganisms and similarly eat or eliminate them through the process of phagocytosis.
Protect Against Viral Infection
T lymphocytes are white blood cells that act to destroy virally infected cells. The University of South Carolina Medical School illustrates how T lymphocytes recognize virally infected cells through proteins that are expressed on the surface of infected cells. When a T lymphocyte recognizes such a cell, it causes the infected cell to commit cellular suicide through a process known as apoptosis.
Destroy Cancer Cells
In addition to recognizing and killing virally infected cells, T lymphocytes can also target and kill tumor cells or abnormal cells that may represent the early beginnings of a tumor.
Remove Dead or Damaged Cells
In addition to eating up invading bacteria, monocytes and macrophages also find, recognize and ingest dead cells and foreign particles that do not belong in the body.
Develop Antibodies
White blood cells play many important roles in the immune response. The University of Florida explains how B lymphocytes produce antibodies. B lymphocytes are able to recognize self vs. non-self entities, or antigens, in the blood, can generate a near infinite diversity of antibodies and retain a memory of which foreign antigens have been encountered in the past.
Allergic Response
The roles of basophils in the allergic response are described by the University of Western Australia. Basophils are recruited to local areas of inflammation and infection where they release heparin and histamine to increase blood flow to sites of injury. Increased blood flow then allows other white cells and factors involved in inflammation to come to damaged or inflamed issues. Heparin makes the blood thinner so it flows more freely. Histamine is a vasodilator that increases blood vessel diameter to maximize blood flow.
References
- Merck Manual: Components of Blood
- University of South Carolina School of Medicine: CELLS INVOLVED IN IMMUNE RESPONSES AND ANTIGEN RECOGNITION
- Duquesne University: Dendritic Cells and Macrophages
- University of Florida: Immune System Basics: Acquired Immunity
- The University of Western Australia - School of Anatomy and Human Biology: Blue Histology - Blood
