leukocyte
Meaning of leukocyte: Which type is raised matters more than the total, since neutrophils, lymphocytes and eosinophils each point somewhere different.
Definition of leukocyte
A leukocyte is a white blood cell, one of the circulating cells that defend the body against infection, clear damaged tissue and drive inflammation. Leukocytes arise from stem cells in the bone marrow and travel in the blood and lymph, but most do their real work after leaving the vessels and entering tissue. The name covers several very different cell types.
How leukocyte is built
- leuk/o Combining form · Greek white
- -cyte Suffix · Greek cell
A medical term is read from its ending backwards: the suffix first, then the prefix, then the root. See all 223 word parts.
What are the different types?
| Type | Main job |
|---|---|
| Neutrophil | The most numerous in adults; arrives first and engulfs bacteria and fungi |
| Lymphocyte | T cells, B cells and natural killer cells; targeted defense, antibody production, memory |
| Monocyte | Leaves the blood and matures into a macrophage that clears debris and alerts lymphocytes |
| Eosinophil | Acts against parasites and takes part in allergic inflammation |
| Basophil | Releases histamine and other mediators during allergic reactions |
The first three arise in the bone marrow and finish developing there, while lymphocytes begin there and mature elsewhere, T cells in the thymus and B cells in marrow and lymph tissue. Most leukocytes spend only hours to days in the bloodstream. The blood is a transport route rather than a destination, and the numbers a laboratory measures are a sample of cells in transit, not the whole workforce of the immune system.
Why does the differential count matter more than the total?
A blood cell count reports one total, but a differential breaks that total down by type, and the pattern carries most of the information. A rise driven by neutrophils suggests bacterial infection, tissue damage or inflammation, and also follows steroid treatment and physical stress. A rise driven by lymphocytes fits many viral illnesses and certain leukemias. A rise in eosinophils points toward allergy, parasites or a drug reaction. Immature cells appearing in the blood, which normally stay in the marrow, suggest either a marrow under heavy demand or a marrow disease.
What drives the count down?
A low count is often the more urgent finding. Chemotherapy and radiation suppress marrow production, and neutrophils fall first because they are consumed and replaced fastest. Diseases of the marrow itself, some medicines and viral infections, and severe overwhelming infection that outpaces production all lower it too. The consequence of a very low neutrophil count is that the usual outward signs of infection depend on those same cells, so pus, swelling and redness may be muted, and fever can become the only visible sign that something serious is under way.
Also known as
Used in a sentence
The complete blood count showed an elevated leukocyte count consistent with an active infection.
Good to know
An elevated total leukocyte count only indicates that white blood cells are increased overall, while a differential count identifying which specific type is elevated often carries more diagnostic weight, such as a rise in neutrophils pointing toward bacterial infection.
Word origin
Where “leukocyte” comes from
Formed from Greek leukos, meaning white, and kytos, meaning cell.