Normal lymphocyte count in the blood

Each laboratory must establish its own normal ranges for the lymphocyte count in the blood. These ranges depend on the makeup of the local population, the technologies used and the accuracy of the measurement. There may be also slight differences in the normal levels, according to age, gender, race or ethnic origin, geographic region, diet, type of sample and other relevant status.

Your doctor will study the results along with your medical record, screenings, physical condition, symptoms and any other relevant information about your situation.

Lymphocytes are a type of WBCs (White Blood Cells) that are of great importance in the immune system. They protect the body against invading bacteria, viruses, and toxins. They also provide immunity for future invasions by producing antibodies, which have memory against such antigens.

There are three main types of lymphocytes:

• T lymphocytes: They provide mediated cellular immunity (60-80% of total lymphocytes)
  • CD4+ (T helper cells) – They are around 60-80% of T lymphocytes
  • CD8+ (Cytotoxic T lymphocyte) - They are around 30-40% of T lymphocytes
• B lymphocytes: They are responsible of humoral immunity (10-20% of total lymphocytes)
• NK (natural killer) lymphocytes: represent the first line of defense against virally infected cells and tumor cells (5-10% of total lymphocytes).

The main part of lymphocytes are produced by the bone marrow. Some of them enter into the bloodstream, but most of them are present in the lymphatic system in the lymphoid organs such as the tonsils, adenoids, spleen or thymus.

A high lymphocyte count in the blood is called lymphocytosis and it may be a first sign of infection. It may be due to viral infection (mononuclesosis, cytomegalovirus) or bacterial infection (whooping cough). In children, it may be a consequence of mumps, measles, chicken pox, etc. and in elderly people due to chronic lymphoblastic leukemia, a type of blood cancer.

A high lymphocyte count during the convalescence phase of an infection is usually a predictor of a good prognosis.

A low lymphocyte count in a blood test is called lymphocytopenia or lymphopenia and it may be related to autoimmune diseases like lupus or rheumatoid arthritis. It may be seen also in case of HIV infection or in some types of lymphomas (Hodgkin lymphoma).

Anyway, one of the main reasons of lymphocytopenia is medication. Corticosteroids have a profound effect in the reduction of lymphocyte count. Other reasons are drugs used in chemotherapy, the radiotherapy or a zinc deficit on diet.

The following values are considered to be normal values:

IMPORTANT: These levels are expressed in number of thousands/µl (microliter). They are an example of a healthy white woman of about 45 years old with no known disease and not taking any medication. The ranges can be different depending on the laboratory or on your personal circumstances.