In case of HIV infection, a blood test for CD4 cells is prescribed. According to the indicators of this test, one can judge the state of the human immune system. The test results also indicate the stage of the disease and the degree of damage to the body by the virus. What are the standards for this analysis? Does a low level of such cells always indicate acquired immunodeficiency syndrome? We will consider these issues in the article.
What is this
The most important cells of the human immune system are lymphocytes. They are divided into 3 groups:
- B-lymphocytes. They are able to remember and recognize pathogens that have previously entered the body. With repeated exposure to dangerous microorganisms, this type of lymphocyte produces antibodies - immunoglobulins. Thanks to these cells, a person develops immunity against certain infectious pathologies.
- NK-lymphocytes. Destroy their own body cells that have undergone infection and malignant transformation.
- T-lymphocytes. This is the largest groupprotective cells. They detect and destroy pathogens.
CD4 cells are a type of T-lymphocyte. Next, we will look at their functions in more detail.
Cell functions
In turn, T-lymphocytes are divided into several types that perform different functions in the body:
- T-killers. Kill pathogens.
- T-helpers. These are helper cells. They enhance the immune system's response to invading infectious agents.
- T-suppressors. This type of lymphocyte regulates the strength of the immune system's response to invading microbes.
On the surface of T-helpers are molecules of the glycoprotein CD4. They work as receptors that recognize the antigens of pathogens. Helper T cells are also called CD4 or CD4 T cells. They transmit information about the invasion of infectious agents into B lymphocytes. Next, the process of producing antibodies against foreign antigens starts.
This is how CD4 cells function in a he althy person. They serve to protect the body from pathogens. However, with HIV infection, there are serious malfunctions in the work of T-helpers. We will look at them further.
Acquired immunodeficiency
CD4 cells are the first to be affected by HIV. It is T-helpers that become the main target for the virus.
The causative agent of HIV penetrates into CD4 and replaces the normal genetic code of these cells with a pathological one. In the process of reproduction of T-helpers, more and more new andnew copies of the virus. This is how the infection spreads in the body.
In the initial stages of the disease, there is an increased production of T-helpers. This is the body's response to an invading virus. It is no coincidence that people with HIV-positive status note that in the early stages of infection, they rarely had colds.
However, the long stay of the virus in the body and its spread depletes the immune system. In the future, HIV-infected people experience a sharp drop in the level of CD4 cells. This indicates that a person has been infected with the immunodeficiency virus for quite a long time. With a low rate of these cells, the patient has practically no body resistance to dangerous microbes. The patient becomes extremely susceptible to any infectious diseases that occur in his severe form.
What test should I take
To find out the state of your immune system, you need to get tested for CD4 T-cells. Venous blood samples are taken. The test is carried out in the morning on an empty stomach. Before the study, you need to exclude physical and psycho-emotional stress, drinking alcohol and smoking.
Indications for the sample
A blood test for CD4 T cells is prescribed for patients with HIV-positive status. This test is carried out for the following purposes:
- to monitor the dynamics of the development of HIV infection;
- to determine the stage of pathology;
- to identify the need for drug therapy.
As already mentioned, the presence and spread of the HIV virus in the body is always accompanied by a sharp decrease in the body's resistance to pathogens. The analysis helps to assess the likelihood of a patient developing infectious pathologies and to conduct antiviral and prophylactic treatment in time.
Normal results
Consider acceptable CD4 cell counts. The norms depend on the age of the person, as well as on the unit of measurement. Most often, these cells are calculated as a percentage of the total number of lymphocytes. Some laboratories determine the concentration of T-helpers in 1 liter of blood.
What percentage of all types of lymphocytes are CD4 cells in a he althy person? The norm is considered to be from 30 to 60%. These are reference values for adult patients.
If the concentration of T-helpers in 1 liter of blood is estimated in the laboratory, then for adults values from 540 x 106 to 1460 x 106cells/l.
Normally, CD4 cells in a he althy child are produced in higher quantities than in adults. Reference T-helper values for children are shown in the table below:
| Age | Indicators in % of the total number of lymphocytes | Number of cells x 106 in 1 liter of blood |
| 1 - 3 months | 41 - 64 | 1460 - 5116 |
| 3 months - 1 year | 36 - 61 | 1690- 4600 |
| 2 - 6 years old | 35 - 51 | 900 - 2860 |
| 7 -16 years old | 33 -41 | 700 - 1100 |
Reason for increase
Usually, when conducting an analysis, not only T-helper indicators are evaluated, but also the number of T-suppressors (CD8 cells). Their ratio is of great diagnostic value. Very often, an increase in the concentration of T-helpers is accompanied by a decrease in the activity of suppressors. This leads to an excessive and inadequate immune response. In this case, lymphocytes can attack he althy body tissues. This is a sign of the following autoimmune pathologies:
- systemic lupus erythematosus;
- scleroderma;
- rheumatoid arthritis;
- autoimmune thyroiditis;
- dermatomyositis.
Elevated CD4 counts are also seen in patients with cirrhosis and hepatitis.
Reason for decline
The most common cause of falling CD4 counts is HIV infection. This indicates the progression of the disease and a high risk of infection with bacterial, viral and fungal pathologies. If these cells are low, doctors prescribe a course of preventive therapy.
In this case, attention is always paid to the number of T-suppressors. Their increase and decrease in the level of helper lymphocytes is noted in Kaposi's sarcoma. This severe complication often occurs in patients with advanced AIDS.
However, HIV is not the only reason for the decrease in the concentration of T-helpers. The number of these cells also decreases in the following diseases andstates:
- chronic protracted infectious pathologies (for example, with tuberculosis or leprosy);
- congenital disorders of the immune system;
- nutrition deficit;
- cancerous tumors;
- radiation sickness;
- after burns and injuries;
- in old age;
- with systematic stress.
Certain medications can also affect CD4 counts. Drugs that reduce the level of T-helpers include corticosteroid hormones, cytostatics, immunosuppressants. Therefore, before taking the test, it is recommended to exclude the use of such medications.
Doctors' recommendations
What to do if a person with HIV-positive status has shown a sharp decrease in CD4 count? Such test results indicate the spread of the virus and serious damage to the immune system. The patient needs to take prophylactic drugs.
In this case, the results of the T-helper test are taken into account along with the analysis data for the viral load. This study shows the number of copies of the HIV pathogen per unit of blood.
CD4 counts less than 350 x 106 cells/l are considered dangerous (no more than 14% of total lymphocytes). Such results suggest that HIV infection can move into the stage of active manifestations of AIDS. If at the same time the patient has a high viral load, then special treatment is necessary. It's called antiretroviral therapy. Patients are prescribed three or four types of drugs that inhibit reproductionpathogen at different stages of its development. Such treatment allows HIV-infected people to remain in remission.
There is also a concept - opportunistic infections. These are diseases that rarely occur in people with a normal immune system. However, such pathologies are quite common in HIV. The test shows the likelihood of such diseases:
- When cell counts are less than 200 x 106 the patient has an increased risk of fungal pneumonia (pneumocystosis).
- If CD4 falls below 100 x 106, toxoplasmosis and fungal meningitis (cryptococcosis) are more likely to occur.
- If T-helper levels fall below 75 x 106, then the patient has an increased risk of mycobacteriosis. This is a severe form of tuberculosis that occurs only with AIDS.
With such analysis data, the patient needs the prevention of opportunistic infections. The patient is prescribed a preventive course of antifungal and antibacterial drugs.
HIV-infected people are advised to take a CD4 test at least once every 3-4 months. This allows you to track the spread of the virus in time and prevent dangerous complications.
