Structure of the immune system

Specific immune systemThe structure of the immune system is very complex, just like the tasks it does: it protects our body from disease-causing pathogens, while making it immune to its influence. This is because the immune system differentiates between foreign and own ones.

Immunity is subclassified in the innate part and is present from birth (nonspecific or innate immune system). In part, the human being acquires immunity through a learning process, in which the Immunsystem develops molecules that can recognize a certain type of proteins of another type, these are the specific antigens (specific or acquired immune system).

A wide variety of organs and systems of cells are part of the structure of the immune system and therefore of its formation. The organs belonging to the immune system are subdivided as follows:

Primary lymphatic organs

Among them are the bone marrow and thymus, a large organ; in the childhood; Located in the upper chest area. These organs are responsible for the formation of lymphocytes, which reach the peripheral lymphatic organs through the blood. There begins the immune response of the acquired immune system.

Immune system

Secondary or peripheral lymphatic organs

 Lymph nodes, spleen and lymphatic tissue of the gastrointestinal tract (adenoids, intestine, etc.), lungs and mucous membranes.

The innate (nonspecific) and acquired (specific) immune systems are very similar in their functioning system. Most pathogens are detected within a few hours and destroyed by mechanisms of the nonspecific immune system.

Since the innate immune response is not specialized in the antigens, it does not need a long initial phase. When the first defense of the body fails to eliminate the pathogens, after a period of four to seven days the specific or acquired immune response occurs. Then, antigenic cells are formed, which are designed to fight against each pathogen specifically.

Structure of the immune system – Nonspecific immune system

The nonspecific immune system is not only composed of humoral and cellular mechanisms, there are also other factors that make up the structure of the non-specific immune system: in this way, healthy skin presents a natural protection that prevents the penetration of pathogens.

Gastric juices destroy bacteria thanks to their high acidity. Pathogens that reach the airways through the air we breathe are trapped in mucous membranes of the respiratory system in the mucosa.

The structure of the immune system is divided into two systems with different defense mechanisms: nonspecific and specific immune systems. The nonspecific immune system attempts to neutralize foreign bodies and many other pathogens on first contact. Hence it is also called the innate immune system. The innate immune system is primarily responsible for fighting bacterial infections. The non-specific immune system encompasses cellular and non-cellular (humoral) mechanisms:

Cellular factors

The defense cells of the non-specific immune system are white blood cells that absorb and digest the pathogen or foreign body: phagocytes. The granulocytes, neutrophils and eosinophils, macrophages and monocytes (macrophage precursors) are phagocytes. It is true that sometimes engulf strange particles, but do not digest them, but they expel them to the interstice where the real macrophages eliminate them.

Humoral factors

These specific immune system factors dissolved in body fluids are bactericidal substances. To this group belongs the enzyme lysozyme, which is found in different body fluids such as tears and saliva and attacks the cell wall of numerous bacteria.

At the same time, the non-specific immune system includes the so-called complement system, an enzyme system produced by the liver, which consists of a group of about 20 proteins and leads to the dissolution of foreign cells. They also belong to the nonspecific humoral immune system called interferons, which are mainly responsible for viruses.

Structure of the immune system – Specific immune system

Unlike the nonspecific (innate) immune system, the structure of the specific system is created throughout life. The specific immune system develops for the first time after direct contact with a particular pathogen. Hence it is also called an acquired or adapted immune system.

Specific immune system is formed after the first contact with a pathogen, special defense mechanisms are developed, which are designed to deal with certain pathogens in the learning process. The memory cells that have formed during the immune response protect against a new attack of the same pathogen. In addition, the specific immune system is able to identify and eliminate the diseased cells of the body itself as the tumor cells.

The cells of the immune system or lymphocytes are cells capable of giving an immune response. These manage the specific immune system. Lymphocytes are the smallest white blood cells. These represent a quarter of the total white blood cells. However, 98% of the lymphocytes are not found in the blood, but in the lymphatic organs (lymph nodes, lymphatic vessels, spleen) and bone marrow.

The body continually deposits a small part of these lymphocyte cells into the blood. The life of a lymphocyte rises from ten days to several years. First, they develop in the bone marrow and thymus, that is, in the primary organs of the immune system, which play a decisive role in the development of the structure of the immune system. Then, they colonize the secondary organs of the immune system such as the lymphatic tissue and the spleen. There are several types of lymphocytes:


These white blood cells are characterized by their ability to distinguish between their own and strange structures. Its development takes place in the thymus a bilobular organ that are behind the sternum. T lymphocytes constitute approximately 70-80% of the total blood lymphocytes. They belong to the specific cellular immune system. Upon contact with a foreign body they become effector T lymphocytes, which produce or reinforce various immune responses or memory T lymphocytes, which are able to recognize the same foreign body after re-penetrating the body years later and produce a response Immune system.

Effector T lymphocytes are divided into two groups: the so-called helper T lymphocytes, which activate B lymphocytes and macrophages and T killer lymphocytes, which by lysis (disintegration) kill the infected cell. In addition, there are also suppressor T lymphocytes (regulatory T lymphocytes), whose function consists in the suppression of the activation of the immune system and the inhibition of the immune response to the body’s own tissues. So healthy organisms take care that the immune system does not attack their own cells. This prevents the onset of autoimmune diseases.

B lymphocytes

These type of lymphocytes mature in the bone marrow and constitute approximately 15% of the total lymphocytes in the blood. B lymphocytes belong to the specific humoral immune system.

Upon contact with foreign bodies, a part of the B lymphocyte is transformed into the so-called plasma cells, which form the antibodies (immunoglobulins, Ig) that confront these foreign bodies. Plasma cells live for two to three days. On the other hand, when they make contact with the foreign body, they become B memory cells. B memory cells can continue to produce the same antibody even when it is no longer in our body.

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