What are CD4 cells - features, properties and recommendations

In case of HIV infection, a blood test for CD4 cells is prescribed. By 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 norms of this analysis? Is a low level of such cells always indicative of acquired immunodeficiency syndrome? We will consider these issues in the article.

What it is

The most important cells of the human immune system are lymphocytes. They are divided into 3 groups:

1. B lymphocytes. They are able to remember and recognize the causative agents of the disease that have previously penetrated the body. With the repeated entry of dangerous microorganisms, this type of lymphocyte produces antibodies - immunoglobulins. Thanks to these cells, a person develops immunity against certain infectious pathologies.
2. NK lymphocytes. Destroy the body's own cells that have undergone infection and malignant degeneration.
3. T lymphocytes. This is the largest group of protective cells. They detect and destroy pathogens.

CD4 cells are a type of T-lymphocyte. Further we will consider in more detail their functions.

Cell function

In turn, T-lymphocytes are divided into several types that perform different functions in the body:

1. T-killers. Kill pathogens.
2. T-helpers. These are helper cells. They enhance the response of the immune system to the invasion of infectious agents.
3. T-suppressors. This type of lymphocyte regulates the response of the immune system to the penetration of microbes.

On the surface of T-helpers are molecules of CD4 glycoprotein. They work as receptors that recognize the antigens of pathogens. T-helpers are otherwise called CD4 or CD4 T. They transmit information about the invasion of infectious agents into B-lymphocytes. Next, the process of generating antibodies against foreign antigens is launched.

This is how CD4 cells function in a healthy person. They serve to protect the body from pathogens. However, HIV infection causes serious malfunctioning of T-helpers. We will consider them further.

Acquired immunodeficiency

In HIV, CD4 cells are affected first. It is the T-helpers that become the main target for the virus.

The causative agent of HIV enters 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 copies of the virus are created. So there is a spread of infection in the body.

In the initial stages of the disease, increased production of T-helpers is observed. This is the body's response to the invasion of the virus. It is no coincidence that people with HIV-positive status note that they rarely had colds in the early stages of infection.

However, the long stay of the virus in the body and its spread depletes the immune system. Subsequently, HIV-infected patients experience a sharp drop in the level of CD4 cells. This indicates that a person has been infected with the immunodeficiency virus for quite some time. With a low rate of these cells, the patient has practically no resistance to dangerous microbes. The patient becomes extremely susceptible to any infectious diseases that occur in his severe form.

What kind of analysis do you need to pass

To find out the state of your immune system, you need to take an analysis for CD4 T cells. Venous blood is taken for the sample. The test is carried out in the morning on an empty stomach. Before the study, physical and psycho-emotional stress, alcohol consumption and smoking should be excluded.

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 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 the patient developing infectious pathologies and timely conduct antiviral and preventive treatment.

Normal results

Consider permissible CD4 cell counts. Norms depend on the person’s age, as well as on the unit of measurement. Most often, these cells are calculated as a percentage of the total number of lymphocytes. In some laboratories, the concentration of T-helpers in 1 liter of blood is determined.

What percentage of all types of lymphocytes are CD4 cells in a healthy person? The norm is considered indicators from 30 to 60%. These are reference values ​​for adult patients.

If the laboratory evaluates the concentration of T-helpers in 1 liter of blood, then for adults, values ​​from 540 x 10 ⁶ to 1460 x 10 ⁶ cells / l are allowed.

Normally, CD4 cells in a healthy child are produced in higher quantities than in adults. Reference values ​​of T-helpers for children are shown in the table below:

Reasons for the increase

Typically, when analyzing, not only T-helper indices are evaluated, but also the number of T-suppressors (CD8 cells). Their ratio has important diagnostic value. Very often, an increase in the concentration of T-helpers is accompanied by a decrease in suppressor activity. This leads to an excessive and inadequate immune response. In this case, lymphocytes can attack healthy body tissues. This is a sign of the following autoimmune pathologies:

• systemic lupus erythematosus;
• scleroderma;
• rheumatoid arthritis;
• autoimmune thyroiditis;
• dermatomyositis.

An increase in CD4 concentration is also noted in patients with cirrhosis and hepatitis.

Reasons for the decline

The most common cause of a drop in CD4 levels is HIV infection. This indicates the progression of the disease and the high risk of infection with bacterial, viral and fungal pathologies. At low rates of these cells, doctors prescribe a course of preventive therapy.

This always pays attention to the number of T-suppressors. Their increase and decrease in the level of helper lymphocytes is noted with 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 with the following diseases and conditions:

• chronic protracted infectious pathologies (for example, with tuberculosis or leprosy);
• congenital disorders of the immune system;
• nutritional deficiencies;
• cancerous tumors;
• radiation sickness;
• after burns and injuries;
• in old age;
• with systematic stress.

Some medications may also affect CD4 counts. The 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 if a person with HIV-positive status showed a sharp decrease in CD4? 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 test for T-helpers are taken into account together with the analysis data for viral load. This study shows the number of copies of the HIV pathogen per unit of blood.

CD4 counts of less than 350 x 10 ⁶ cells / l (not more than 14% of total lymphocytes) are considered dangerous. These results suggest that HIV infection can go into the stage of active manifestations of AIDS. If the patient has a high viral load, then special treatment is necessary. It is called antiretroviral therapy. Patients are prescribed three or four types of drugs that inhibit the reproduction of the pathogen at different stages of its development. Such treatment allows HIV-infected people to remain in remission.

There is also the concept of opportunistic infections. These are diseases that rarely occur in people with a normal immune system. However, such pathologies are quite common with HIV. The test shows the likelihood of such diseases:

1. With cell indices of less than 200 x 10 ⁶ , the patient is at increased risk of developing pneumonia of fungal etiology (pneumocystosis).
2. If CD4 falls below a level of 100 x 10 ⁶ , then this is fraught with the occurrence of toxoplasmosis and meningitis caused by fungi (cryptococcosis).
3. If the indicators of T-helpers fall below 75 x 10 ⁶ , then the patient has an increased risk of mycobacteriosis. This is a severe form of tuberculosis that occurs only in 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 1 time every 3-4 months. This allows you to track the spread of the virus in time and prevent dangerous complications.