WBC
Meaning of WBC: The total count says little on its own; which of the five types is raised or lowered is what points anywhere useful.
Definition of WBC
WBC is the abbreviation for white blood cell, or leukocyte, the class of blood cells that defends the body against infection and takes part in inflammation, allergy and tissue repair. The same abbreviation names the laboratory count of those cells in a sample of blood, reported as part of a complete blood count.
What are the five types?
| Type | What it does |
|---|---|
| Neutrophils | First responders to bacterial infection; the most numerous type |
| Lymphocytes | Targeted defense: B cells make antibodies, T cells kill infected cells and direct others |
| Monocytes | Become macrophages in tissue, clearing debris and organisms and presenting them to lymphocytes |
| Eosinophils | Act against parasites and take part in allergic disease |
| Basophils | Release histamine and other mediators in allergic and inflammatory responses |
The first, fourth and fifth are grouped as granulocytes because of the granules visible inside them. The breakdown by type is called the differential, and it is what turns a bare number into information about the immune system.
Where do they come from?
All of them descend from blood-forming stem cells in the bone marrow, which produces them continuously and can raise output sharply when demand rises. Neutrophils survive only hours to a few days in the circulation, so the marrow must replace them constantly, and this short lifespan is why marrow damage shows as a falling neutrophil count within about a week. Lymphocytes follow a different path: they mature in the thymus or in lymphoid tissue, recirculate between blood and lymph nodes, and some persist for years as memory cells. Most white cells spend little time in the blood itself, which is only the transport route to the tissue where they act.
What does a high or low count mean?
A raised count, leukocytosis, accompanies bacterial infection, inflammation, tissue injury, physical stress, steroid treatment, smoking and the leukemias. A low count, leukopenia, follows some viral infections, chemotherapy and other marrow-suppressing drugs, autoimmune destruction, overwhelming sepsis and certain deficiencies. Because the types move independently, the pattern matters: neutrophils up in bacterial infection, lymphocytes up in many viral illnesses, eosinophils up with parasites and allergy. A low neutrophil count in particular raises the risk of serious infection, which is why it is watched during cancer treatment. Any single result is interpreted against the person and the clinical picture rather than on its own.
Also known as
Used in a sentence
The complete blood count included a WBC measurement as part of the infection workup.
Good to know
A white cell count above or below the usual range prompts examination of the differential, since the specific cell types involved carry the information rather than the total count alone.