Lymphocytes are cells that play an essential role in the immune system. A high or too low level during a blood test can reveal anemia, an infection or (more rarely) cancer.
Lymphocytes represent between 20 and 40% of white blood cells circulating. They are small in size and come from the lymphoid organs, which are themselves separated into two groups: the primary lymphoid organs, which are the thymus and the bone marrow, and the secondary lymphoid organs, which are the spleen and the lymph nodes. It exists three groups of lymphocytes. THE two main ones are B and T lymphocytesthe third being represented by the NK group lymphocytes. The role of lymphocytes in defense against infectious attack is predominant.
What is the normal level of lymphocytes in the blood?
On the complete blood count (NFS)the normal rate of lymphocytes should be between 1500 and 4000/mm3 i.e. between 20 and 40% of the total number of white blood cells. In children, it can rise, normally, up to 7000/mm3. Standards vary by lab. The number of lymphocytes varies rapidly in the same individual and is always higher in chronic smokers.
What causes low lymphocyte count (lymphopenia)?
The lymphocyte count is low when it is less than 1500/mm3. This phenomenon called “lymphopenia” leads to an immune deficiency and it can be the consequence of:
- blood diseases such as leukemias
- viral infections such as AIDS, which directly affects the lymphocyte immune system, “HIV infection causes one of the most serious lymphocyte damage. Even if, today, the evolution of treatments makes it possible to ensure an extended lifespan, the protection of sexual relations with condoms remains the best way prevent this infection” recalls Dr Anne-Christine Della Valle, general practitioner.
- certain cancers also causing a drop in lymphocytes.
- administration of medications such as immunosuppressants or fall within chemotherapy used against certain cancers.
Cancer treatments, which are sometimes heavy, can cause a Myelosuppression, that is, the bone marrow no longer makes blood cells. The subjects, then at very high risk of infectious pathology, are placed in isolation. A fever associated with a low lymphocyte count should be an emergency alert.
What causes high lymphocyte count (lymphocytosis)?
Hyper-lymphocytosis or “lymphocytosis” corresponds to a lymphocyte count greater than 8000 to 9000 /mm3. Elevated lymphocytes are the sign of an infectious attack, most often viral. It may be a infection of the ENT sphere (mononucleosis, angina), bronchitis or any other infectious disease. Lymphocytes can also rise in cancer or lymphoma. They are also often higher in smokers.
What test measures the lymphocyte count?
Lymphocyte count is calculated from the complete blood count, by a simple blood test. This is either a routine examination or an examination guided by infectious signs.
When to consult?
It is necessary to consult when the level of lymphocytes is too high or too low, to find the cause. If no cause is found, a control is necessary a few days later. Additional examinations may be indicated such as a chest x-ray, a bone marrow puncture or viral serologies, such as HIV for example.
On our health forum, your questions about lymphocytes
To remember
► Lymphocytes represent between 20 and 40% of circulating white blood cells.
► T lymphocytes are responsible for so-called “cellular” immunity.
► The normal rate of lymphocytes must be between 1500 and 4000/mm3.
► In children, the lymphocyte count can normally rise to 7000/mm3.
► Elevated lymphocytes are a sign of infectious disease, most often viral.