Lymphocytes are white blood cells. White blood cells are an important part of the human immune system. They protect the body from attacks of bacteria, viruses, and parasites. Bone marrow produces five different types of white blood cells, one of which is the lymphocyte.
Lymphocytes make up an average of 20–30% of all white blood cells. They are involved in the identification and destruction of microorganisms, foreign molecules, and cancer cells, and are especially activated in chronic infections.
How do lymphocytes work in the body?
Lymphocytes are formed in the bone marrow and about 25% of them remain in the bone marrow to mature and become B lymphocytes. The other 75% travel to the mature in the thymus, thus turning into T lymphocytes.
After maturation, the lymphocytes travel in the blood to the secondary lymphatic organs, i.e. the spleen, lymph nodes, and the lymphatic tissues of the body’s mucous membranes in the intestine, tonsils, and adenoids, as well as to the walls of the airways and the urinary tract. There they divide and activate, after which they can participate in specific immune defence.
Specific immunity, or so-called acquired immunity, begins to develop after birth. When the body encounters a new pathogen, information about it is stored in a specialised memory cell.
Each lymphocyte accurately identifies its target and specialises in destroying only these certain types of pathogens. Because of this specialization, there may be thousands of different types of lymphocytes in the body.
B lymphocytes and T lymphocytes work together to fight infection.
What are B lymphocytes?
B lymphocytes maintain immunological memory. Some of the B lymphocytes are converted into special memory cells. They recognise a previously encountered antigen and specialise in plasma cells that produce immunoglobulin, an antibody against the antigen.
What are T lymphocytes?
T lymphocytes are divided into three categories:
Killer T cells
Helper T cells
Suppressor T cells
Killer T cells destroy cells infected with antigens. They can also destroy cancer cells as well as foreign cells, such as transplanted organs.
Helper T cells control the immune response of B cells and other T cells. They produce cytokines, or signaling proteins, that increase the division and differentiation of lymphocytes and enhance phagocytosis.
Suppressor T cells keep the immune system in balance. They make sure that the T-cell response stops when the antigen that caused the immune reaction is destroyed.
What is the B-Ly reference value?
The reference value for lymphocytes in adult men and women is 1.3–3.6 xE9/l. The B-Ly value indicates the number of lymphocytes per litre of blood.
What is the reference value for lymphocytes (L-Ly%)?
The reference value for lymphocytes (L-Ly%) in adult men and women is 20–45%. The L-Ly% value indicates the relative proportion of lymphocytes in all leukocytes.
The B-Ly and L-Ly% values are calculated in connection with the leukocyte differential (B-Diffi) test in a complete blood count. B-Diffi should be done when the number of leukocytes in the blood is elevated.
What is lymphocytopenia (low lymphocyte count)?
Lymphocytopenia, a lower than normal lymphocyte count, is rarely associated with any specific disease. It can be caused by acute or chronic infections or temporary immune deficiency. Common cold, for example, can cause a decrease in lymphocyte levels.
What are the possible causes of lymphocytopenia?
In addition to the common cold, other possible causes of lymphocytopenia include:
malnutrition
HIV and AIDS
influenza
autoimmune diseases, such as lupus
some cancers, such as lymphocytic anaemia, lymphoma, and Hodgkin’s disease
use of steroids
radiation therapy
certain medicines, such as chemotherapeutic medicines
certain hereditary diseases, such as Wiskott-Aldrich syndrome and DiGeorge syndrome
As a low lymphocyte count in the blood makes the person susceptible to infections, it should not be ignored.
What is lymphocytosis (high lymphocyte count)?
Lymphocytosis, a higher than normal lymphocyte count, is usually associated with chronic infections. Lymphocyte counts can also be elevated after a recent infection.
What causes lymphocytosis?
Possible causes of lymphocytosis include:
viral infections such as measles, mumps, and mononucleosis
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