lymphocyte
Meaning of lymphocyte: These are the cells that remember, which is why a second encounter with the same organism is dealt with far faster than the first.
Definition of lymphocyte
A lymphocyte is a white blood cell that carries out the targeted part of the immune response. Lymphocytes are produced in the bone marrow and circulate between the blood, the lymph nodes and the tissues. The main groups are B cells, which produce antibodies, T cells, which direct and destroy, and natural killer cells.
How lymphocyte is built
- lymph/o Combining form · Latin lymph, lymphatic tissue
- -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 do the different types do?
| Type | Role |
|---|---|
| B lymphocyte | Recognizes a specific target and matures into a plasma cell that pours out antibody against it |
| Helper T cell | Coordinates the response, signaling to B cells and to other immune cells and deciding how strong the reaction should be |
| Cytotoxic T cell | Kills the body's own cells once they are infected by a virus or have turned cancerous |
| Regulatory T cell | Restrains the response and helps prevent attack on healthy tissue |
| Natural killer cell | Destroys abnormal cells without needing prior exposure, working by a broader rule than the others |
B cells complete their development in the bone marrow, while immature T lymphocytes travel to the thymus, a gland behind the breastbone, where the ones that would attack the body's own tissue are weeded out before release.
Why does a second exposure go so much better?
Each lymphocyte carries a receptor for one particular molecular shape, and the body holds an enormous library of them, most of which are never used. When a matching target appears, that one cell multiplies rapidly into a large population all recognizing the same thing. The first response is slow because the search and the multiplication take days. Some of those cells then persist as memory cells, so a later encounter with the same organism meets a ready population rather than a search. Vaccination is that mechanism used deliberately, presenting the shape without the disease.
What does a lymphocyte count show?
A low count is common during and after many viral illnesses, with corticosteroid treatment, after chemotherapy or radiation, and in advanced HIV infection, where the loss of one helper T cell subset is what is tracked. A high count accompanies some viral infections, notably infectious mononucleosis, and can also reflect a leukemia or lymphoma arising from lymphocytes themselves. Since the types look nearly identical under an ordinary microscope, telling them apart requires laboratory methods that tag surface markers.
Used in a sentence
The blood count revealed a low lymphocyte count in the setting of the patient's recent viral illness.
Good to know
B lymphocytes and T lymphocytes cannot be distinguished from one another by appearance alone under a standard microscope and instead require specialized laboratory testing to differentiate.
Word origin
Where “lymphocyte” comes from
Formed from lymph-, from Latin lympha, meaning water, and -cyte, from Greek kytos, meaning cell.