Lymphocytes are special cells in the body of a living creature. They are responsible for its protection against external stimuli, infections, viruses. But the very concept of "lymphocytes" is quite extensive and general. Inside themselves, these cells will be divided into several groups. In the article we will get acquainted in detail with one of them - T-lymphocytes. Functions, types of cells, their normal indicators, deviations from the norm in human blood - all these topics will be discussed later.
Cell origin
Where do T lymphocytes form? Although the main place of their "residence" is the bloodstream (lymphocytes also live in other tissues), they are formed far from there. The place of their "birth" is bone marrow. It is known as the hematopoietic tissue of the body. That is, in addition to lymphocytes, red blood cells, white blood cells (neutrophils, white blood cells, monocytes) will also form here.
The "precursors" of our lymphocytes are stem cells. At the same time, some of the lymphocytes will be "born" not only in the red bone marrow, but also in other immune organs - the thymus gland (thymus). Here, their basis is already lymphoid tissue.
The structure of lymphocytes
T-lymphocytes, the functions of which we will consider later, are not visible to the naked eye - only under a special powerful microscope. Their size is relatively small compared to other blood cells (only 7-10 microns in diameter).
The “anatomical” features are as follows:
- The large core is round or oval.
- In the cytoplasm (the contents of the cell itself) there will be no granularity.
- If the cytoplasm in the cell is small, it is called narrow plasma, if a lot - wide plasma.
In their structure, the lymphocytes that inhabit the blood will be slightly different from their counterparts who settled in other tissues. And this is normal. Moreover, cells "living" in one place will also have some external differences between themselves.
Types of lymphocytes
In addition to the types of T-lymphocytes, there are various groups of these cells in general. Let's look at them.
The first classification is by size:
The second classification is based on the functions performed:
- B lymphocytes. They can recognize foreign particles and produce killer antibodies against them. In other words, they are responsible for humoral immunity.
- T lymphocytes. The main function is the responsibility for cellular immunity. Make contact with alien bodies and destroy them.
- NK cells. Natural killers that can recognize cancerous, defective cells and destroy them. Responsible for maintaining the cellular normal composition of the whole organism.
Types of T-lymphocytes
This group of lymphocytes within itself will be divided into several types:
- T-killers.
- T-helpers.
- T-suppressors.
- Memory T cells.
- Amplifiers-lymphocytes.
Next, we analyze each of these groups in detail. Consider the function of T-lymphocytes. Each species has its own purpose.
T-killers: what type
These are the most famous representatives of the T-lymphocyte group. Their main task is the destruction of defective, defective body cells. Another group name is cytotoxic T-lymphocytes. In other words, responsible for the elimination of cells ("cyto"), which have a toxic effect on the whole body.
The main function of T-killers is immune surveillance. Cells aggressively act on a foreign protein. It is this useful function that is harmful when transplanting organs to a person. T-killers seek to quickly destroy the "alien", not realizing that it is he who is able to save the body. Therefore, the patient for some time after organ transplantation takes medications that inhibit the immune system. Drugs reduce the percentage of T-killers in the blood, disrupt their interaction. Due to this, the transplanted organ takes root, and the patient is not threatened with complications and death.
The mechanism of action of this type of lymphocyte on a foreign element is very interesting. Phagocytes, for example, aggressively "attack" the "alien" for his subsequent devouring and digestion. T-killers against their background are “noble killers”. They touch the object with their processes, then break the contact and are removed. Only after such a “deadly kiss” does a foreign microorganism die. Why so?
During contact, T-killers leave a piece of their membrane on the surface of the body. It possesses properties that allow it to corrode the surface of the object of attack - up to the formation of through holes. Potassium ions leave the microorganism through these holes, and their place is occupied by water and sodium ions. The cell barrier is broken; there is no longer a border between the internal and external environment. The microorganism is inflated by the water entering it, the proteins of the cytoplasm and organelles are destroyed. The remains of the "stranger" then devour the phagocytes.
Helpers
The main function of these T-lymphocyte cells is to help. Hence their name, derived from the English word translated in the same way.
But to whom or what do these T-lymphocytes come to the rescue of? They are designed to induce and stimulate the immune response. It is under the influence of T-helpers that T-killers, with whom we have already met, will activate their work.
Helpers will transmit data on the presence of a foreign protein in the body. And this is valuable information for B-lymphocytes - they, in turn, begin to secrete certain protective antibodies against it.
Also, T-helpers stimulate the work of another variety of "protective" cells - phagocytes. In particular, they interact tightly with monocytes.
Suppressors
This term in itself means "suppression." From here, the function of T-suppressors becomes clear to us. Helpers in our body will activate protective, immune function, and these T-lymphocytes, on the contrary, will suppress it.
Do not think that this has any negative effect on the system. T-suppressors are responsible for the regulation of the immune response. Indeed, somewhere it is necessary to react to a certain stimulus with restraint and moderation, and somewhere - to accumulate all available forces against it.
Amplifiers
We now turn to the functions of T-lymphocytes of this group. After one or another aggressor enters the body, the lymphocyte content immediately rises in the blood and tissues of a living creature. For example, in just a few hours, their volume can double!
What is the reason for such a rapid growth of the army of defensive cells? Maybe the fact is that in the body somewhere for the time being they are "hidden" in reserve?
It really is. In the thymus and spleen there is a mass of mature full-fledged lymphocytes. Only until a certain moment, these cells are "not determined" with their purpose, function. They will be called amplifiers. If necessary, these cells turn into one or another type of T-lymphocytes.
Memory cells
Experience, as you know, is the main weapon. Therefore, having coped with any threat, our T-lymphocytes remember it. In turn, the body produces special cells that will store this information until a new “battle” with this alien element. These elements will be the memory T cells.
The secondary aggressor (the kind that the immune system has already resisted) penetrates the body. The memory T-cell recognizes him. Then this particle begins to multiply actively in order to give a foreign organism a worthy immune response.
Normal T-cell counts in human blood
In this category it is impossible to imagine any specific figure - normal values will vary depending on the person’s age. This is due to the peculiarities of the development of its immune system. The thymus volume will decrease with age. Therefore, if lymphocytes predominate in the blood in childhood, then with adulthood they pass the leading position to neutrophils.
The level of blood T-lymphocytes helps to determine the general clinical blood test. Normal indicators here are:
- (50.4 ± 3.14) * 0.6-2.5 thousand
- 50-70%.
- The ratio of "helpers / suppressors" is 1.5-2.
What are the increased and decreased indicators?
The increased content of T-lymphocytes in the blood may indicate the following:
- Chronic or acute lymphocytic leukemia.
- Hyperactive immunity.
- Cesari's Syndrome.
And, on the contrary, a low content of T-elements indicates the following pathologies and diseases:
- Chronic infections - purulent processes, HIV, tuberculosis.
- Decreased lymphocyte production.
- Genetic diseases causing immunodeficiency.
- Tumors of lymphoid tissue.
- Renal and heart failure observed in the last stage.
- T cell lymphoma.
- Patient taking medications that destroy lymphocytes.
- The consequence of radiation therapy.
We met with T-lymphocytes - the cells that protect our body. Each of the species performs its own special function.