What are CD4 lymphocytes and why their number is so important, every HIV-positive patient knows. For most of us, this concept is unknown. In the article we will talk about white blood cells, CD4 and CD8 lymphocytes, their meaning and normal values.
Our main defenders
Lymphocytes are one of the varieties of white blood cells and our most important immune cells that protect the body from viral, bacterial, fungal infections, produce antibodies, fight cancer cells and coordinate the work of other agents of the immune response.
There are 3 types of lymphocytes:
- B-lymphocytes are the "spies" of the immune system. They, having once met with the pathogen, remember it. It is thanks to them that we develop immunity to those diseases that we have had. They are about 10-15%.
- NK-lymphocytes are the "KGB" of our body. They track "traitors" - infected cells of the body or cancerous ones. They are about 5-10%.
- T-lymphocytes are the "soldiers" of our immunity. There are many of them - about 80%, they detect and destroypathogens that enter our body.
General characteristics
All lymphocytes are 15 to 20 microns in diameter. The volume of the cytoplasm is large, and the nucleus is irregular in shape with light chromatin. T-lymphocytes and B-lymphocytes can only be distinguished using immunomorphological methods.
All of them are capable of phagocytosis and can penetrate through blood vessels into intercellular and interstitial fluids.
Protein receptors are located on the surface of T-lymphocyte membranes, which are associated with molecules of the human major histocompatibility complex. It is these co-receptors that determine the functions and tasks that various types of leukocytes solve.
Their average life expectancy is 3-5 days, they die either at the site of the inflammatory process, or in the liver and spleen. And everything is formed in the bone marrow from hematopoietic precursors.
T-lymphocytes: directions of protection
This large army is working for our benefit in several ways:
- T-killers directly destroy viruses, bacteria, fungi that have entered the body. On their membrane there are special CD8 co-receptor proteins.
- T-helpers enhance the body's defense response and transmit information about a foreign agent to B-lymphocytes so that they produce the necessary antibodies. On the surface of their membranes is the glycoprotein CD4.
- T-suppressors regulate the strength of the body's immune response.
We are interested in work andthe value of T-lymphocytes of CD4 helpers. It is about the specifics of these helpers that we will talk in detail.
A little more about lymphocytes
All lymphocytes are formed in the bone marrow from specific hematopoietic stem cells (hematopoietic stem cell, from the Greek words haima - blood, poiesis - creation). B-lymphocytes undergo maturation in the bone marrow, but T-lymphocytes in the thymus gland or thymus, which is why they got their name.
The abbreviation CD stands for cluster of differentiation. These are specific proteins on the surface of cell membranes, of which there are several dozen types. But CD4 and CD8 are most often examined, since they are of significant diagnostic value.
HIV and CD4 cells
It is T-helpers that are the target for the attack of the human immunodeficiency virus. The virus invades these cells of the immune system and inserts its DNA into the DNA of the lymphocyte. The cd4 lymphocyte dies and gives a signal to increase the production of new T-helpers. This is exactly what the virus needs - it immediately penetrates young lymphocytes. As a result, we have a vicious circle that our immunity cannot cope with, like all modern medicine.
Norm and tasks
With data on the number of CD4 T-lymphocytes in the patient's blood, one can draw a conclusion about the he alth of the immune system. If there are few of them, the immune system is not in order.
The normal number of CD4 lymphocytes in a cubic millimeter of blood is from 500 to 1500 units. Counting them is especially important for HIV-positive people. Precisely according tothe number of CD4 lymphocytes in the patient's blood, the doctor decides on the start of antiretroviral therapy.
In patients with HIV, in the absence of treatment, the number of helpers in the blood decreases by 50-100 cells per year. When the number of CD4 lymphocytes in the blood is less than 200 units, patients begin to develop AIDS-related diseases (for example, pneumocystis pneumonia).
Proportion of helpers in blood tests
For an ordinary person, it is not the number of these cells that matters more, but their proportion in the blood, and it is this column that is more often found in the results of a blood test. In a he althy person, the proportion of CD4 lymphocytes in the blood is 32-68% of the total number of all leukocytes.
It is the indicator of the proportion of T-helpers that is often more accurate than their direct count. For example, the number of helpers in the blood can vary over several months from 200 to 400, but their share is 21%. And as long as this indicator does not change, we can assume that the immune system is normal.
If the proportion of CD4 T-lymphocytes decreases to 13%, regardless of their number, this means that significant damage has appeared in the work of the human immune system.
Immune status
In the results of the analysis, the ratio of T-helpers to T-killers - CD4 + / CD8 + (the number of CD4 lymphocytes divided by the number of cd8 lymphocytes) can also be indicated. HIV-positive people are characterized by a low CD4 count and a high CD8 count, and, accordingly, their ratio will below. Moreover, if this indicator increases during treatment, this indicates that drug therapy is working.
The ratio of CD4 to CD8 lymphocytes from 0.9 to 1.9 is considered normal in a person's complete blood count.
Clinical diagnostic value
Determination of the number and content of the main groups and subpopulations of lymphocytes in the patient's blood is important in immunodeficiency states, lymphoproliferative pathologies and HIV infection.
CD4 counts may increase with other immune activations such as infections or transplant rejection.
Data on the number and ratios of these lymphocyte subpopulations are used to confirm or refute the diagnosis, to monitor the functioning of the immune system, to predict the severity and duration of the disease, and to evaluate the effectiveness of therapy.
When analysis is needed?
The main indications for a CD4 count blood test are:
- Infectious diseases that have a chronic and protracted course, frequent relapses.
- Suspicion of congenital or acquired immunodeficiency.
- Autoimmune diseases.
- Oncological pathologies.
- Allergic diseases.
- Examinations before and after transplants.
- Examination of patients before major abdominal surgery.
- Complications in the postoperative period.
- Monitoring of antiretroviral therapy, effectivenesscytostatics, immunosuppressants and immunomodulators.
Preparation and analysis
Biomaterial for clinical diagnostic analysis - patient's venous blood. Before donating blood for the determination of CD4 + / CD8 +, it is necessary to exclude smoking and physical activity. Blood is taken on an empty stomach, the last meal is at least 8 hours before the analysis.
Children under five years of age and patients who are contraindicated in fasting are allowed to eat light food two hours before the analysis.
Interpreting the result
The CD4+/CD8+ ratio is higher than normal in diseases such as lymphocytic leukemia, thymoma, Wegener's disease and Cesari's syndrome. An increase in the number of cells can indicate a significant viral load and autoimmune reactions.
This figure increases with mononucleosis, which is caused by the Epstein-Barr virus, chronic lymphocytic leukemia, myasthenia gravis, multiple sclerosis, HIV infection.
Ratios in the region of three are often observed during the acute phase of various infectious diseases. In the middle of the inflammatory process, a decrease in the number of T-helpers and an increase in the number of T-suppressors are more often observed.
Reducing this indicator due to an increase in the number of suppressors is characteristic of some tumors (Kaposi's sarcoma) and systemic lupus erythematosus (a congenital defect of the immune system).
