Blood & Laboratory Values

Lymphocytes – Function & Diseases


As a subgroup of leukocytes (white blood cells), lymphocytes play a central role in the immune defense against foreign substances, especially infectious agents, as well as pathogen cells of the human organism such as tumor cells. An increased or decreased concentration of lymphocytes in the blood usually indicates a disease.

What are lymphocytes?

Lymphocytes are the smallest representatives of leukocytes and represent the most important carriers of the adaptive (acquired) immune system of the human organism. In addition to blood plasma, human blood consists of about 45 percent blood cells, which are divided into leukocytes (white blood cells), erythrocytes (red blood cells) and thrombocytes (blood platelets).

In general, a differentiation is made between B and T lymphocytes and NK cells. In an adult human, 1000-2900 lymphocytes per µl of blood or 17-47 percent of the proportion of white blood cells is considered normal.

The largest proportion of lymphocytes does not circulate in the bloodstream, but is located in the bone marrow and in the organs of the lymphatic system (thymus, tonsils, spleen, Peyer’s patches of the intestinal tract, lymph nodes ). An increased or decreased number of lymphocytes can indicate different diseases.

Medical & Health Functions, Tasks & Meanings

Depending on the type of maturation, the lymphocytes are divided into B and T lymphocytes and NK cells. The B cells (derived from English bone marrow for bone marrow or the Bursa Fabricii in birds, in which the B lymphocytes were first discovered), which begin their process of maturation in the bone marrow, are able to produce antibodies (defence substances) to produce and secrete, which neutralize specially soluble antigens classified as foreign to the body (including bacteria, released toxins). 

For this purpose, the inactive B lymphocytes circulate in the lymphatic system or bloodstream and are activated as soon as an antigen docks onto the immunoglobulins on the surface, the antigen receptors of the B cells. The B cell takes up the antigen, breaks it down and expresses it as a protein complex that is identified by the T helper cells (a subgroup of T lymphocytes). In addition, the T helper cells synthesize cytokines that activate the B lymphocytes, which then proliferate (divide) in the lymph nodes or spleen.

In addition, a smaller proportion of B lymphocytes differentiate into long-lived memory B cells, which store antigen information to ensure a timely and effective immune response upon further exposure to the specific antigen.

The T-lymphocytes, which mature in the thymus, identify foreign particles (including antigens such as viruses , intracellular bacteria , cells modified by mutations) that can have a damaging effect on the organism and prepare the corresponding cells for the immune system to ensure a quick and targeted defense against the identified pathogens.

The NK cells, the natural killer cells, primarily recognize modified endogenous cells such as virus-infected cells or tumor cells and trigger apoptosis, i.e. programmed cell death, in these cells.

Illnesses, Ailments & Disorders

A pathological increase (lymphocytosis) or decrease (lymphopenia) in the number of lymphocytes can be attributed to various causes. A reduced or increased number of lymphocytes , which is determined as part of a differential blood count with determination of all subtypes of leukocytes in the blood, indicates a possible disease. 

An increase in lymphocytes and leukocytes in the blood usually correlates with inflammation or infection. Viral droplet infections (including influenza , measles , rubella , mumps , chickenpox ), contact and smear infections (herpes simplex, diarrhea, hepatitis A and E, polio , Ebola, ]]yellow fever]], HIV, cytomegaly ), bacterial infections (brucellosis, tuberculosis , typhoid, pertussis or whooping cough) and various tumor diseases (leukemia, lymphoma) are associated with an increased concentration of lymphocytes in the blood.

Likewise, hyperthyroidism ( overactive thyroid gland ), Guillain-Barré syndrome (progressive impairment of the nervous system) or sarcoidosis or Boeck’s disease, an inflammatory disease and granulomatosis (focal accumulation of granulomas), which mainly affects the lungs, can lead to an increased lymphocyte create value.

On the other hand, chemotherapeutic and/or radiotherapeutic measures, cortisone, cytostatic therapy or treatment with immunosuppressants as well as an increased cortisol concentration (hypercortisolism), for example as a result of Cushing’s syndrome, can cause a reduced lymphocyte value in the blood.

In addition, autoimmune diseases (e.g. pronounced systemic lupus erythematosus or myasthenia gravis), various cancers (including Hodgkin’s disease or lymph node cancer), uremia (urinary poisoning in the end stage of kidney failure) and AIDS can result in a reduced concentration of lymphocytes in the blood.

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Hello! I am Lisa Newlon, and I am a medical writer and researcher with over 10 years of experience in the healthcare industry. I have a Master’s degree in Medicine, and my deep understanding of medical terminology, practices, and procedures has made me a trusted source of information in the medical world.