Lymphocytes

Lymphocytes are a type of defense cell in the body, also known as white blood cells, which are produced in greater quantities when there is an infection, and are therefore a good indicator of the patient's health status.

Normally, the number of lymphocytes can be assessed by blood test, and when they are increased, it is usually a sign of an infection and, therefore, it is recommended to consult a general practitioner to diagnose the problem and initiate appropriate treatment.

Altered lymphocytes

The normal reference values ​​for lymphocytes are between 1000 to 5000 lymphocytes per mm³ of blood, which represents 20 to 50% in the relative count, and may vary according to the laboratory where the test is performed. When the values ​​are above or below the reference value, a picture of lymphocytosis or lymphopenia is characterized, respectively.

1. High lymphocytes

The number of lymphocytes above the reference values ​​is called lymphocytosis and is usually related to infectious processes. Thus, the main causes of high lymphocytes are:

• Acute infections, such as mononucleosis, polio, measles, rubella, dengue or whooping cough, for example; Chronic infections, such as tuberculosis, malaria; Viral hepatitis; Hyperthyroidism; Pernicious anemia, which is characterized by folic acid and vitamin B12 deficiency; Benzene poisoning and heavy metals; Diabetes; Obesity; Allergy.

In addition, the increase in the number of lymphocytes can also happen due to physiological situations, such as pregnant women and infants, in addition to nutritional deficiencies, such as vitamin C, D or calcium deficiency.

2. Low lymphocytes

The number of lymphocytes below the reference values ​​is called lymphopenia and is usually related to situations involving the bone marrow, such as aplastic anemia or leukemia, for example. In addition, lymphopenia can also be a sign of autoimmune diseases, in which the body itself acts against the immune defense system, such as systemic lupus erythematosus, for example (SLE).

Lymphopenia can still happen due to AIDS, immunosuppressive drug therapy or chemotherapy or radiotherapy treatment, rare genetic diseases, or be a consequence of stressful situations, such as postoperative and body overload, for example.

Types of lymphocytes

There are 2 main types of lymphocytes in the body, B lymphocytes, which are immature cells produced in the bone marrow and released into the bloodstream to produce antibodies against bacteria, viruses and fungi, and T lymphocytes, which are produced in the bone marrow. but then they are developed in the thymus until they are divided into 3 groups:

• CD4 T lymphocytes: help B lymphocytes to eliminate infections, being the first alert of the immune system. These are usually the first cells to be affected by the HIV virus, and in infected patients the blood test indicates a value below 100 / mm³. CD8 T lymphocytes: decrease the activity of other types of lymphocytes and, therefore, are increased in cases of HIV; Cytotoxic T lymphocytes: destroy abnormal cells and infected by viruses or bacteria.

However, tests of the type of lymphocytes, especially of the type CD4 or CD8, must always be interpreted by a doctor to evaluate if there is risk of having HIV, for example, since other diseases can also cause the same type of alterations.

So, if there is any doubt about being infected with HIV, it is advisable to do the laboratory test that looks for the virus within the body's cells. Learn more about HIV testing.

What are atypical lymphocytes?

Atypical lymphocytes are lymphocytes that present a varied form and that normally appear when there are infections, mainly viral infections, such as mononucleosis, herpes, AIDS, rubella and chickenpox. In addition to the appearance in viral infections, atypical lymphocytes can be identified in the blood count when there is a bacterial infection, such as tuberculosis and syphilis, infection by protozoa, such as toxoplasmosis, when there is hypersensitivity to drugs or in autoimmune diseases, as in lupus.

Usually the number of these lymphocytes returns to normal (reference value for atypical lymphocytes is 0%) when the agent causing the infection is eliminated.

These lymphocytes are considered to be activated T lymphocytes that are produced in response to infected type B lymphocytes and perform the same functions as typical lymphocytes in the immune response. Atypical lymphocytes are generally larger than normal lymphocytes and vary in shape.