Where do leukocytes form in humans?

Our body is an amazing thing. It is capable of producing all the substances necessary for life, coping with a multitude of viruses and bacteria, and finally, providing us with a normal life.

Where do leukocytes form in humans?

Human blood consists of uniform elements and plasma. Leukocytes are one of these uniform elements along with red blood cells and platelets. They are colorless, have a core and can move independently. They can be seen under a microscope only after preliminary staining. Of the organs that make up the immune system of a person, where leukocytes are formed, they exit into the bloodstream and tissues of the body. They can also freely move from vessels to adjacent tissues.

Leukocytes move in the following way. Fixed on the wall of the vessel, the leukocyte forms a pseudopodia (pseudopod), which it pushes through this wall and clings to it outside the tissue. Then he squeezes through the formed gap and actively moves among other cells of the body, leading a "sedentary" lifestyle. Their movement resembles the movement of an amoeba (a microscopic unicellular organism from a protozoan discharge).

The main functions of leukocytes

Despite the similarity of leukocytes with amoebas, they perform the most complicated functions. Their main tasks are protecting the body from various viruses and bacteria, destroying malignant cells. Leukocytes chase bacteria, envelop them and destroy them. This process is called phagocytosis, which in Latin means "devouring something with cells." It is more difficult to destroy a virus. With the disease, the viruses settle inside the cells of the human body. Therefore, to reach them, white blood cells need to destroy cells with viruses. Malignant cells also destroy leukocytes.

Where are the leukocytes formed and how many live?

In the performance of their functions, many leukocytes die, so the body constantly reproduces them. Leukocytes are formed in the organs entering the human immune system: in the thymus gland, bone marrow, lymph nodes, tonsils, spleen and in lymphoid formations of the intestine (in Peyer's patches). These organs are located in different parts of the body. The bone marrow is also the place where leukocytes, platelets, erythrocytes are formed. It is believed that leukocytes live about 12 days. However, some of them die very quickly, which happens when they fight with a lot of aggressive bacteria. Deceased leukocytes can be seen if pus appears, representing their congestion. To replace them from the organs relating to the immune system, where leukocytes are formed, new cells come out and continue to destroy bacteria.

Along with this among T-lymphocytes there are cells of immunological memory that live for decades. There was a lymphocyte, for example, with a monster like the Ebola fever virus - he will remember it for life. When re-encountering this virus, lymphocytes are transformed into large lymphoblasts, which have the ability to multiply rapidly. Then they become lymphocyte killers (killer cells), which block access to the body of a familiar dangerous virus. This indicates the existing immunity to this disease.

How do leukocytes learn about the introduction of the virus into the body?

In the cells of each person there is a system of interferon, which is part of the innate immunity. When the virus is introduced into the body, an interferon is produced - a protein substance that protects cells that are not yet infected from penetration of viruses into them. Simultaneously, interferon activates lymphocytes, killers, which are one of the types of leukocytes. From the bone marrow, where leukocytes are formed, they go to the infected cells and destroy them. In this case, some viruses and their fragments fall out of the destroyed cells. The dropped viruses try to penetrate the cells that are not yet infected, but interferon protects these cells from their introduction. Viruses that are outside cells are not viable and quickly die.

Fighting viruses with interferon system

In the course of evolution, the viruses have learned to suppress the interferon system, which is too dangerous for them. A strong suppressive effect on her have influenza viruses. Even more depresses this system of human immunodeficiency virus (HIV). However, all records broke the Ebola virus, which practically blocks the interferon system, leaving the body almost defenseless in front of a huge number of viruses and bacteria. From the spleen, lymph nodes and other organs belonging to the immune system, where leukocytes are formed, new cells are emerging. But, not having received a signal about the destruction of the virus, they are inactive. In this case, the human body begins to decompose alive, many toxic substances are formed, blood vessels are torn, and the person bleeds. Death usually occurs in the second week of the disease.

And when there is an immunity?

If a person has recovered from one or another disease and recovered, then he has acquired a stable acquired immunity, which is provided by leukocytes belonging to the groups of T-lymphocytes and B-lymphocytes. These leukocytes are formed in the bone marrow from progenitor cells. Acquired immunity develops after vaccination. These lymphocytes are well aware of the virus that has been in the body, so their killing effect is purposeful. The virus practically can not overcome this powerful barrier.

How do killer lymphocytes kill cells that have become dangerous?

Before you kill a dangerous cage, you need to find it. Lymphocyte killers tirelessly search for these cells. They are guided by the so-called histocompatibility antigens (tissue compatibility antigens) located on cell membranes. The fact is that if a virus has entered the cell, then this cell for self-preservation of the organism condemns itself to death and as it throws out the "black flag", signaling the introduction of the virus into it. This "black flag" is information about the introduced virus, which in the form of a group of molecules is located next to the histocompatibility antigens. This information is "seen" by the lymphocyte killer. This ability he acquires after training in the thymus gland. Control over learning outcomes is very tough. If the lymphocyte has not learned to distinguish a healthy cell from a patient, it itself is inevitably subject to destruction. With such a rigorous approach, only about 2% of the killer lymphocytes survive, which subsequently leave the thymus gland to protect the body from dangerous cells. When the lymphocyte precisely establishes that the cell is infected, it makes it "lethal injection", and the cell dies.

Thus, leukocytes play a huge role in protecting the body from pathogens and malignant cells. These are small indefatigable warriors of the basic defenses of the body - the system of interferon and immunity. They are massively killed in the fight, but from the spleen, lymph nodes, bone marrow, tonsils and other immune system organs, where leukocytes form in humans, they are replaced by a number of newly formed cells ready, like their predecessors, to sacrifice their lives in the name of Saving the human body. Leukocytes provide our survival in an environment filled with a huge number of different bacteria and viruses.